Digitization and Workflow

#### **Chapter 5**

## Finite Element Analysis in Orthodontics

*Nandakishore Rajgopal*

#### **Abstract**

One of the governing ideologies in orthodontics is gradually imposing remodeling, which involves progressive and irreversible bone deformations using specific force systems on the teeth. Bone remodeling results in the movement of the teeth into new positions, with two tissues having a major influence along with it: the periodontal ligament and the alveolar bone. There is a definite connection between the mechanical, biological and physiological reactions to the orthodontic forces. The development of the Finite Element Analysis and administration of this new age computer-aided method in orthodontics applies to this chapter. Finite Element Analysis is a computational procedure to calculate the stress in an element, which can show a model solution. The FEM analyses the biomechanical effects of various treatment modalities and calculates the deformation and the stress distribution in the bodies exposed to the external forces. The ideology behind this particular chapter is to introduce this scientific approach to the orthodontist and to reinforce the effects and advantages to the ones who are already aware of the same. In this chapter there is a detail discussion and explanation systematically on Finite element analysis method and its application strictly in and around orthodontics without much deviation from the subject.

**Keywords:** FEM, Nodes, Voxels, PDL, Orthodontic tooth movement (OTM)

#### **1. Introduction**

Orthodontics is the specialty of dentistry which in brief deals with correcting the malaligned teeth with the application of force delivery system, which includes wires, brackets, elastics etc. It is just one branch of dentistry which is deeply interlinked with the engineering branch of mechanics. Application of force and its resultant effects are the key stones in orthodontics, hence the fundamentals of physics also applies to the physics such as the Newtonian physics. The intention of the Orthodontist is to make betterment in function and esthetics. The treatment is just not limited it and has intentions to correct things like a tooth implanted to the alveolar bone can lead to caries or other paraodontal infections or affect the oral hygeine), esthetics (of the dentition or the face), or prosthetic (orthodontic treatment preceding a prosthetic replacement/missing tooth or teeth) [1].

An Orthodontic treatment might be carried out with evidence based system or by a clinical experience or by a acquiring knowledge and experience from a postgraduate curriculum or even via specific trainings and hands on programmes. Orthodontics is a spectacular as well as brain buzzer branch in dentistry where the work undertaken by an orthodontist could be considered as solving a puzzle, when he or she treats each case. It is associated with logical reasoning and through knowledge about the basics of biomechanics and even common sense. Turner et al. in 1956 introduced Finite element analysis (FEA). From then it has been used in different sectors such as in building aircrafts to dams to bridges etc. The usage of computer software's for the stressful calculations are used in order to find the stress and its distribution within a body for a given load. It also sketches the displacement of the body before and after the application of the load as well [2]. It could be a different dimensional opening for the chapter readers who are not familiar as well as to reinforce the knowledge for the readers who are already aware of this topic, so the chapter is designed to extremely simplify the concept of FEM and to integrate it with orthodontics from the very basic levels [2].

The Finite Element Method was introduced in orthodontics as a powerful tool for analyzing the biomechanical effects of various treatment modalities and is an approximation method to represent both the deformation and the 3Dstress distribution in bodies that are exposed to stress. The Finite Element Method is used to study the stresses and strains in engineering, it can be used to evaluate the biomechanical component such as displacement, strains and stresses induced in living structures from various external forces, the biomechanical response of the bone to external forces are quite complex. The FEM analyses the biomechanical effects of various treatment modalities and calculates the deformation and the stress distribution in the bodies exposed to the external forces. It should also be understood that the stress and strain in living tissues are thought to be key factors in biologic change, it is important to understand that stress and strain to understand its relationship to bone remodeling, the belief is such that the pattern of the stress will affect the localized proliferation of cells and growth activities [3]. The chapter is discussed from the fundamentals of FEM and further notes its usage in dentistry and particularly in orthodontics, followed by stepwise procedure explanations in detail.

The chapter further takes a road from its aspects such as construction of the models, which is the soul step in the FEM, with the help of scans such as the CT scans and FEM's credibility is in question due to the complexity and accuracy of the model seems to represent from truth and reality in the oral cavity [4].

Many new concepts and terminologies are being introduced and explained to its best in this chapter. Keeping in mind that many of readers, being from a medical academic background, including Orthodontists and clinicians hesitate to understand and relate the formulas and equations which are quite natural, a few vital equations are presented with ease. Further the chapter goes in detail to bone remodeling concepts and the brief explanations of individual components of the dental organ and its reaction to force and the chapter sinks with the concepts of FEM and orthodontics in the body. Towards the end the advantages as well as the limitations of FEM is discussed with some insight. This chapter is well supported with scientific literature evidence for the assertion it implies and it credits each and every scientist for their contributions and valuable time in life they have devoted for the good of the mankind.

#### **2. Utility of finite element analysis**

Orthodontics is periodically changing from an opinion-based practice to an evidence-based practice. Currently, it is necessary to have a scientific approach for *Finite Element Analysis in Orthodontics DOI: http://dx.doi.org/10.5772/intechopen.100343*

any treatment modality and the evidence of tissue response to it [5]. Finite element analysis (FEA) has the ability of being applicable to solids of irregular geometry that contain heterogeneous material properties. It is therefore suited to evaluate the structural behavior of teeth. The use of FEM is wide seen in dentistry and in the field of orthodontics in the field of research in topics such as the geometry of the tooth, materials used, prosthetics etc. In the field of orthodontics, it's used to find the stress values or its distributions in appliances used in orthodontics etc. FEA could be wisely used to estimate the stress and strain patterns within the tooth structure, Periodontal Ligament (PDL) and the bone which is subjected to tooth movement by the means of orthodontics [6].

The forces to single-tooth system can also be modeled with the FEA with ease. The centre of resistance (CR) of the tooth lowers and creates an altered stress pattern which is seen in the root as there is an experience of alveolar bone loss. The same effect could be experienced when there is an alteration of root length. The biomechanical properties of PDL are not the same for adult and adolescents respectively [7].

#### **3. Road to finite element analysis**

The principal of FEM is based on the division of a complex structure into smaller sub sections called as elements, in which the physical properties such as modulus of elasticity are applied to indicate the object response against an external stimulus which could be even an orthodontic force. It is said to be finite element analysis since, the elements are finite in count and the nodal points are the blocks which builds the model, which in turn connects to attribute to the formation of element [8]. A meshwork is considered to be a degenerated material which is subjected to modeling. There is an absolute control in the degree of simplification with this method which is an advantage to the FEM [9]. FEA techniques are potential to replace the stereo lithographic models for the presurgical planning. Every finite element is based on an assumed-shape function which expresses an internal displacement as a function of nodal displacement. Which means a certain element may give accurate answer for a particular type and location of support and loading but can give inaccurate answers for another type and location [10].

#### **4. Steps in finite element analysis**


Basic Steps in Finite Element Method for any solution corresponds to the steps involved in finite element to analyze a structure.

#### **4.1 The geometrical model construction**

It is the first requirement for the analysis of the geometrical model. These can be created either in analysis software or the model can be created also in any CAD software and can be imported to the analysis software. The model has to be saved with extension \*.iges or \*.igs or \*.sat to achieve this. The usage of a computed tomography image (fig ct img) can be done to serve as a geometrical model.

#### **4.2 Discretization process**

Discretization is a process of dividing the domain or component into number of elements & nodes. For this purpose, an assumption is made that the elements are interconnected by nodes. The idea behind the process is to improve the accuracy of the results. The entire component is divided into number of elements, then the stress distribution in each element will be almost the actual results and the operator gets accurate plot of the stress distribution in a component.

#### **4.3 Applying material properties**

The mechanical properties such as young's modulus, Poisson's ratio etc., are defined to the component in this particular step. This is done to feed the values for calculation of the solution. These values mark the natural properties to the built up model so that it can behave and react in the same manner as that of a natural biologic body would, when subjected to external stimuli (stress). For the particular element, the property is to be defined. First of all the operator has to define the type of element. There are several types of elements available, which can be implemented to the domain component.

#### **4.4 Defining boundary conditions and nature of problem**

The boundary condition is chosen depending upon the mode of analysis such as structural, dynamic, thermal, fluid etc.

#### **4.5 Application of load**

After the application of boundary conditions, the discretized domain is applied to the known loads. The application of loads will depend upon the geometry of the component used. The nodes are applied with loads. Different types of loads will include Forces or Moments, pressure, gravity. - For structural problems- Gravity, radiation, convection and temperature for thermal problems.

#### **4.6 Solution or results**

The results can be obtained instantly as well as in the most accurate manner. It will consist of model images which represent levels of stress by various colors signifying different stress for different colors respectively, which can be directly read from a color chart (provided below the image). The results can be further tabulated and subjected to analysis.

#### **5. Computed tomography (CT) and extraction of morphological parameters from CT scans**

Computed Tomography or C.T is cross-sectional image of an object from either transmission or reflection data collected by illuminating (by any kind of penetrating radiation) the object from many different directions or angles. Frankly speaking, tomographic imaging deals with the reconstruction of an image from its projections. The technique constitutes of irradiating a section of a sample from a number of positional angles and then the intensity of the transmitted or reflected radiation is measured. For example, the projections symbolize the X-rays attenuation within a body, the bodies' radioactive nucleoids decay as in the case of emission tomography, or the variation seen in refractive index in an ultrasonic tomography (USG).

When the X-ray is considered, the projections consist of line integrals of the attenuation coefficient. This attenuation of photons (tiny particles that constitute an electromagnetic radiation) are due to either being absorbed by the atoms of the material, or being scattered away from their original paths of travel. Photoelectric absorption involves an X-ray photon imparting all its energy to a tightly bound inner electron in an atom. The images are 2D maps of the distribution of the attenuation coefficient of the X-rays. By stacking the obtained 2D images, we can reconstruct 3D images. The attenuation coefficient is measured in Hounsfield Units (HU) [11].

This macroscopic response of the trabecular bone is closely related to the underlying microstructure. It is beyond scope of this book to describe in details the geometry and spatial arrangement of the trabeculae and its advised to refer standard textbooks for the same, The volume fraction which is considered one among the major parameter in characterization of microstructure of cellular materials geometrically, gives no much clue about the orientation as well as the organization of the above said microstructures. The material microstructure is modeled using tensors of higher rank which mimics the architecture of the microstructure and is the most common method adapted for the same. Fabric tensors are needed as a quantitative measure of the microstructural architecture, to serve as positive definite. The principal axes of a tensor whose principal axes coincide with the principal microstructural direction and its eigenvalues are proportional to the microstructure distribution with respect to its principal direction. It is a must thing to include the parameters which can define those orientations. Hence it

**Figure 1.** *Conversion of CT scan into a finite element model.*

requires acquiring a 3D representation of the bone first using tomography. It is then a morphological analysis used to describe the microstructure (**Figure 1**) [12].

#### **6. Generation of finite element model**

Three primary considerations in the development of the three-dimensional finite element tooth model are to be considered; which includes the tooth and other periodontal geometry, properties of different materials and as well as the configuration of the load applied. In a given tooth geometry and structures of the periodontium and its associated geometry, one can say nodes simply as points that occupies the corners of the elements which meet each other; further the boundary conditions are well defined at all peripheral occupying nodes. A specific material property is assigned to individual elements. Location of the centre of resistance and centre of rotation of the modeled tooth will be deeply affected by the modeling of the root as a symmetric parabolic structure or as a real tooth, as well as root conicity, buccopalatal vs. mesiodistal bone levels and bone insertion [11].

The problem with three-dimensional models is that the geometrical input needs to be generated. The bone structure replicated with a CT scan is preferred as the geometrical input data which should be generated for the 3-D model, which is considered as one among the problems. It is suggested to convert the CT image voxel to eight node hexahedral; but the possibility of numerous element creations in model and the unwanted change in the model's external shape is the pay for this. In order to exempt the outer rough surfaces, it's better to model the external geometrical contours. After these steps, automatically a mesh is produced out as the result of the software. Material properties are assigned to each element of the model, once the generation of the mesh is done (**Figure 2**).

**Figure 2.** *FEA carried out on a modeled human skull.*

#### **7. Morphological analysis**

Morphological analysis provides the tools to extract morphological parameters of an object. The actual values of the parameters extracted depend on the object as

#### *Finite Element Analysis in Orthodontics DOI: http://dx.doi.org/10.5772/intechopen.100343*

well as the quality of the object representation. Better way to say is voxel size affects the 3D images and pixel size would affect the 2D images. Higher the resolution better is the analysis quality. TV, BV, Tb.Th, and MIL are the four respective parameters of morphology which are taken into account.

#### **7.1 Tissue (or total) volume TV**

TV does quantification of the volume in total at the region of interest (ROI). If bone is to be considered, the entire trabecular bone and the total volume of its pores along could be considered as the term 'tissue'. It is a simple task to calculate TV, just by taking the product of the total number of voxels at the region of interest and the volume of a single voxel. The usage of 2-D images could be an option to obtain the volume. The volume is computed by assuming the cut thickness to be same as the pixel's side length measurement.

#### **7.2 Bone volume BV**

By multiplying the number of voxels in the solid objects, one can find out this parameter and it's the representation of the 3-D object's volume in total. Bone volume (BV) will therefore be interpreted as the solid phase volume.

#### **7.3 Trabecular thickness (Tb. Th)**

It is the thickness of the rods of the cellular solid [13].

#### **7.4 BV/TV**

The important parameter is the ratio of the two previous parameters.

#### **8. Distribution of trabecular thickness (Tb.Th)**

It is the thickness of trabeculae and its associated distribution.

Locally when it comes to thickness specifically at a point within a state of body is said to be the biggest sphere which consoles the spot, the spot is not needed to be the centre of the body but within the surface of the object which is considered as a solid [14]. To calculate (Tb.Th), the idea of structuring the body of the object is carried out, where the trabecular midline is used [15].

#### **9. Fundementals in non linear computation method**

The mechanics which is an engineering branch is the soul element in the field of (**Figure 2**) biomechanics; one can never understand biomechanics without understanding the fundamentals of mechanics. Mechanics deals with forces and the response of the object or body, whereas bio means study of living organisms, so the application of the forces and its response to the forces in living bodies are dealt in biomechanics. The hierarchical arrangement in organisms starts from sub atoms ending in organized living body. With the help of quantum mechanics, we can study at the cell or atomic levels and Continuum mechanics could be used in the higher levels such as the organ levels [16].

#### **9.1 Finite strains associated with a body in its kinetics**

The Continuum Mechanics is the ideology where volume V(t) is the amount of matter contained by a body in the respective space at a given time T and the surface area of the body could be symbolized as S(t). Further when we look the reader must understand that the body undergoes change in dimension from its initial orientation for the respective boundary definition after a stress is being applied to the body. The fact is such that, the irrelevance of working with the same body with and without stress because of the obvious above said reason of reasonable transition in shape of the body from initial and final state of the body before and after applying stress. It is mandatory for the above said reasons a thorough understanding of the basis of kinematics is required [17].

#### **10. The FEM**

Coming to the FEM we must strictly adhere to the principles of kinematics. The chapter is never complete without discussing few important equations in FEM, where shape functions (N) and the displacement of the nodes (q), which we are not certain about could attribute the displacement fields shape and could be equated as follows;

$$\mathbf{U(x) = N(x)q} \tag{1}$$

In Eq. (1) the nodal values (q) are determined by the method of calculating the equation which is already in a state of equilibrium via formulation which is made incrementally [18].

$$\delta\mathbf{\dot{q}} \underbrace{\left[\mathbf{M}\ddot{\mathbf{q}} + \mathbf{F}\text{int} - \mathbf{F}\mathbf{ext}\right]}\_{\mathbf{F}^\*} = \mathbf{0} \quad \forall \,\delta\mathbf{q} \tag{2}$$

In Eq. (2) q represents the nodal accelerations, M the mass matrix and Fint and Fext the (nodal consistent) internal and external forces respectively

$$\begin{aligned} \mathbf{M} &= \int\_{V(t)} \rho \mathbf{N}^\top \mathbf{N} dV \\ F\_{\text{int}} &= \int\_{V(t)} \mathbf{B}^\top \alpha d\mathbf{V} \\ \mathbf{F}ert &= \int\_{V(t)} \rho \mathbf{N}^\top \mathbf{b} dV + \int\_{S(t)} \mathbf{N}^\top \mathbf{t} d\mathbf{S} \end{aligned} \tag{3}$$

In Eq. (3) B = ∇NT and t represents the traction on the surface.

$$\frac{\left\|\mathbf{F}^{\alpha}\right\|}{\mathbf{F}\_{\text{att}}} < \mathbf{pre}$$

*Finite Element Analysis in Orthodontics DOI: http://dx.doi.org/10.5772/intechopen.100343*

In Eq. (4) Foe denotes the residual or remaining forces and it's not equal to zero. Prec is a user defined precision. The equilibrium equations are iteratively solved using Newton–Raphson method. Starting from a trial nodal displacement is given as, q0 (several possibilities to evaluate such a trial [19].

Field exist but will not be treated in this work), the displacement field is iteratively updated in such a way that:

$$
\Delta q = -KT - \mathbf{1} \,\text{Foe}
$$

$$
\mathbf{qi} + \mathbf{1} = \mathbf{qi} + \Delta \mathbf{q} \,\tag{5}
$$

Eq. (5) denotes KT = d Foe/dq, which is considered to be called as the tangent stiffness matrix.

The tangent stiffness matrix will be resolved into its parts as well as the shape. The shape aspect of this depends on the shape functions used in FEM [20].

By use of linearization of the small stress values with its corresponding strain values this can be obtained. Intergration tool is used to discrete the matrix of material stiffness [21].

#### **11. Biomechanics of bone remodeling in orthodontics models in orthodontics**

Within the field of dentistry and to its related field, mathematical models are used for research and treatment planning. The tendencies in mathematical models (either numerical FE models or analytical models) for tooth movement and in particular the constitutive models used for dental tissues. Many contributions exist focusing on implant related problems, which are not our interest. The forces alone are only considered and it's not about the means of force delivery system which may also include the brackets are to be considered in here [22].

#### **11.1 The gingiva**

The mechanism which is responsible for the asymmetrical behavior of the tooth when rotated around its main axis is at times assumed to be in the gingival tissue which is a complex fibrous structure that envelops the entire dental arch and it provides an additional anchorage to the teeth, tends to contract. This creates force acting on the different proximal teeth, which in turn produce an internal momentum and asymmetries. The gingiva has a viscous nature due to its composition of collagen. We do not consider or value much the mechanical activity of the gingiva during tooth movement in Finite element studies [23].

#### **11.2 The dental components**

#### *11.2.1 Enamel*

It is the hard as well as a brittle substance probably seen in the human body, which is composed of mainly inorganic materials. Enamel could be categorized as an elastic material which is linear in nature [24].

#### *11.2.2 Cementum*

Very few studies focus on characterizing the cementum, either mechanically or histologically. The group of Darendelier provides a comprehensive body of work on the physical characteristics of cementum.

#### *11.2.3 The dentin*

The Dentin is reinforced by radial microscopic tubules. These tubules are filled with fluid and this gives the dentin a viscoelastic character. Since the mid-1970's, studies shows its viscoelastic property and this is a supporting evidence.

Dentin is also looked as a non-homogeneous and anisotropic material in various recent experimental model studies.

#### *11.2.4 Pulp*

When there literature is reviewed, barely any studies are done to characterize the properties of the neither dental pulp nor acknowledges its existence [25].

The crown of the tooth is modeled as one material with 19 GPA modulus of elasticity, without even considering the 2 components of the crown (enamel, dentin) independently shows young's modulus of 80 and 18 GPA respectively. The Poisson's ratio is, regardless of the proposed study, taken as 0.3 [26].

#### *11.2.5 The periodontal ligament (PDL)*

The periodontium is a structure which constitutes the cementum, the PDL fibers and the alveolar complex. The PDL constitutes the tissues which are loose connective type. It is innervated as well as vascularized. It holds the teeth to the bone and compensates the wearing of the crown structure of the tooth at points in contact or the incisal/occlusal portion of the tooth. The functions of the PDL include the regulation of mastication as well because of the associated sensory nerve fiber innervations. It works well as an attached cushion between tooth and the alveolar bone, as well as act as a shock absorber. The load applied to the teeth during the functions like chewing and clenching is transmitted to the respective jaw bones through the PDL fibers [27].

Many studies on PDL take bilinear elastic nature of it; one can also find many studies which speak or valuate the anisotropy of the fibers of the PDL. There are advantages when it's done so, as it provides more accurate and validity of the stress calculation for a better eccentricity of the movements of the teeth [28]. But studies talk about the PDL and its non- linear nature which is stated by the properties like Poisson's ratio and the modulus of elasticity (Young's) (**Figure 3**).

A Young's modulus around 0.1 MPa is most likely to represent best of the linear part of the PDL's mechanical behavior. Bilinear elastic models are also found and are defined with three values which are tangential modulus, Young's modulus and a limit value of about 7% strains in tension tests. Last but never the least, Cattaneo et al., Verna et al. introduced a multi-linear model, different in tension and in compression [29].

Many researchers consider the PDL as a hyper elastic material (Mooney-Rivlin material with, for Natali et al., reinforced fibers, expressed in an Ogden-type formulation) and estimated strain which corresponds well with the in vivo experimental data by Parfitt.

**Figure 3.**

*Mesh model after assigning the charecteristic material properties of each constituent of dento-alveolar complex independently.*

Models proposed by various other researchers, accounts for a time dependency through the use of viscoelastic models using up to four time-constants. These models are either generalized as Maxwell models [30].

There are instances where the periodontal ligament is believed to be composed of fibers which are arranged in linear nature [31]. The poroelastic model allows considering a time-dependent behavior through the fluid flow inside a porous matrix.

#### **12. Orthodontic tooth movement (OTM) models**

#### **12.1 Initial tooth movement**

The finite element (FE) method is used in orthopedic biomechanics since the early 1970's to evaluate and analyze and study the patterns of stress in the calcified tissues (bones). From then, this analytical tool of the modern era is being used in the field of Orthodontics as well. It very evident to find the use of FEM in the field of prosthodontics, implantology etc. as well to analyze the stress, the stress pattern and to optimize or go with the design of the appliances, to study the materialistic properties of the appliance as well as the reactions of the bone to it. We currently use for biomechanics in the field of orthodontics as well [32].

It is a wise decision to use the non-linear behavior of the periodontal ligament to study the wider aspects of tooth movements [33]. The initial design of models in Finite element methods FE models were 2 Dor axi symmetric models and now it's no more used since it's a 3-D era. The FEM can definitely analyze the stress and its patterns and can analyze the biomechanics and can determine the final position of the teeth from its initial positions [34]. Early models in the field of orthodontics were mainly directed to study the initial movement of the tooth in its socket (no bone remodeling included) following the implementation of a system of forces and moments by means of braces or fixed orthodontic appliances. Most current studies still follow the same principle, using geometry and a system of forces which is more complex. Within the initial tooth movement models, mainly fully linear elastic homogeneous isotropic models were used. How so ever, models with non uneven bone density is also used where modulus of elasticity is taken into account. Orthotropic behavior of the bone

and the anisotropic nature of PDL also exist [35]. Studies consider the periodontal ligament to be elastic. All these could be applied to the posterior teeth, multi rooted and of different forms of roots as well [36].

#### **12.2 Long-term tooth movement**

The tooth movement due to bone resorption and apposition which obeys the pressure tension theory is not obeyed by the teeth initially and the early tooth movement is just the effect of the PDL fibers which instigate the tooth movement initially. After an initial tooth movement under the applied pressure the tooth tries to stay in that position and tries to attain stability in the newly moved position [37]. FEA models at times usually involve an update of displacement (in addition to that due to external forces) or of forces based on an empirical bone remodeling law: The stimulus for remodeling is either the strain energy density, strain dependent or stress dependent remodeling algorithms obey the laws of mathematical tools such as the integration under the limit of time. The FEM analyses the forces and the associated tooth movement with it in the model and it all obeys the laws of equilibrium from its initial to final position under the stipulated time.

#### **13. Dento-facial orthopedics modeling**

Since the early 1980's, finite element models of maxillary and mandible were used. The model is built with elements which is comparable or represents the bone structure and symbolizing its properties. The magnitude of the force levels applied by appliance like brackets or others like head gears or the expansion appliance etc. is taken into consideration. As a part of modeling the movement of the jaw, a great effort is made to characterize the temporomandibular joint (TMJ). In most cases, the type of materials used for the bone is linear elastic in nature. It is considered that cortical bone is distinguishable from trabecular bone. However, the presence/absence of teeth in the cranio-facial models is variable in nature. As for the models of the TMJ, the cartilage and the disks are modeled either as linear elastic materials or as hyper elastic ones. It can be also found out that the models include muscle activation of the jaw, either performing an inverse dynamic analysis to compute the activity of the large amount of muscles in the face, or modeling a given number of muscles, often by applying a spring model to describe the muscular forces. Finally, one can also find models of the facial bones and skull by analyzing the response to external orthopedic systems [38].

#### **14. Bone remodeling models**

In addition to growth of the skeleton and resorption of fractures, which are of temporary in nature, the structure of bone is, stabilized by the action of osteoclast and osteoblast and its metabolism is a total different interest of subject which is to be discussed, which in turn is beyond the scope of this chapter. Through understanding of the remodeling process of the bone should be understood by an orthodontist to get an idea of how the teeth move in the maxilla or mandible during tooth movement. The Roux hypothesis claims the whole remodeling procedure is a self-organized procedure where the stiffness of the bone is achieved after a force is applied and stress

#### *Finite Element Analysis in Orthodontics DOI: http://dx.doi.org/10.5772/intechopen.100343*

is developed within the bone, the bone trabaculae obeys the Wolff's law and last but not the least the bone reacts upon itself for load application. It is equally important to understand the Frost model of the bone which is stated as the mechanostat theory where is notes that if the stress range exceeds the limit, there is a chance of formation of a new bone, but if the same stress is lesser to the optimal value there is a bone loss associated to it as well. Both these goes hand in hand which creates a balance. The theory sounds simple for the readers but it's simply an effective one and a tricky one when equations are derived from it mathematically and used for computing. Earlier the bone in a bone model was technically considered to be a poroelastic media which is pooled by a liquid. Later models have proposed the universal mechanical nature of a living substances, here the depth of biological activity is considered, where as there is also another model which does not propose the depth of remodeling within the bone (Phenomenological model) [39].

#### **15. FEM in orthodontic tooth movement**

Now coming to the soul of this reading, the reader must understand the real fact initially that the FEM is a theoretical study concept and does not stand alone debates of scientific evidence based ideology without the gold standard of clinical trials. FEM deals with material properties and parameters, further the geometrical aspects are even being considered. The complete system with its constituent initial force, dimension of the body, stress developed is drastically different with respect to its final state. It is logical to think that it's inevitable without mathematical formulations and definite numerical values one cannot calculate or predict the final position of the tooth from its initial one [40].

Before the application of the FEM, there were several other methods which were implemented to carry out the stress strain relations and its calculations over the PDL, but due to the complex nature of it the end results achieved or obtained stayed insignificant. When the sequence of reactive force developed after an implementation of load is checked, the root suffers the most, followed by the PDL and the alveolar bone the least (due to its higher density). These findings are due to the different mechanical properties of each structure: such as the tooth, periodontal ligament and alveolar bone. The stress applied on the bone is the active factor in the new configuration arrangement of the bone. There is a significant association of the PDL in the remodeling procedure of the bone due to its viscous nature and the storage of energy within it due to the same nature.

The stresses are of different types such as the longitudinal stress, compressive stress, or the shear stress depending on the type of the force and its line of action over the body, so it's mandatory to specify it. There is always a chance for a tooth or teeth to undergo a combination of the above said stresses in various directions as well. When comparison is done among the types of tooth movements against each other, the tipping, extrusion and intrusion result in the greatest stress at the root apex. For extrusion and intrusion, the stress concentration is mainly at the apex of the root. Stresses at the root apex after intrusive tooth movement is seen but the distribution is different when compared to other types of tooth movement. When a vertical force is applied on the buccal surface of the tooth, some torque may be expected due to the relationship between the point of application of force and the centre of resistance of the tooth. In such cases, labial and lingual portion of the apical region of the root experiences way higher reactive forces to the applied tension.

After analyzing different FEM studies in orthodontics, studies show the stress distribution patterns are more in the crest of the alveolar bone, when compared to the periodontal ligament nor the crown or the root of the tooth. When the tipping forces where studied, it showed more or less the same feature of the stress distribution over the crest of alveolar bone. The tooth and the bone suffer greatest stress at the cervical level and the PDL at the apex.

The forces in rotation create the only difference of all the situations, where the apical stress is comparatively lesser. The FEM depends on the model and the property of the material assigned and boundary conditions, any change or errors creeping in these aspects will affect the foreseeing of the results. The type of the force delivered by each system is never the same, so there is change in the results. To get these right results the proper implementation of the force system and its understanding is inevitable. After all this there are other instances to point out like, up to 50% or more of the applied force can dissipate as friction in an edgewise bracket system; which can significantly affect the stress produced at the PDL of the tooth [41].

#### **16. Limitations of finite element analysis**

As with any theoretical model of a biological system, there are some limitations which need to be considered. A thorough reading and interpretation of this chapter would give the insight of the limitation of the FEM and it's not much to emphasis on the same. But then as said before any errors in modeling or material property assignment or the boundary conditions application, even wrong forces applied to wrong formulation, will earn the wrong results. It's a sophisticated and computer dependent or programme dependent analysis, so at most care should be taken during the modeling stages and the prior stages before the final run for the results to feed the correct input data for the expected outcome or results. It is highly difficult or impossible to be frank to replicate the exact living substance into mechanical models till date due to its complex nature [42]. The major limitation which you would have never guessed all through this chapter is that the cost of the FEM study. It should be highlighted that the FEM does not come with a reasonable price currently in many countries and it's used more for the research purposes. It's not a question to ask if FEM is considered in building bridges or dams or aircrafts but definitely when comes to field of dentistry or orthodontics, to use FEM for every single patient is never feasible.

#### **17. Conclusion**

The main fundamental in orthodontics is the movement of teeth or tooth within bones, which in other words means the movement of solid (tooth) in another solid (jaw bones bone) which is the toughest movement of all mediums and it's a slow process which consumes time. If we are smart enough to estimate the final position of the teeth form its initial one, it's like predicting the end result without the trial and error methods or without any unwanted disturbances which even if occurs could be foreseen and a right component of force. This ideology actually saves time and the pain to both the clinician as well as for the patient. The mechanical and biological/ physiological reactions to orthodontic forces by the PDL and the alveolar bone are closely linked with each other. This coupling can be treated in biomechanical models, focusing on the mechanics and considering the phenomenological aspects of the

*Finite Element Analysis in Orthodontics DOI: http://dx.doi.org/10.5772/intechopen.100343*

biology. As a tool to describe the mechanics of orthodontic tooth movement due to remodeling, the Finite Element Method (FEM) can be definitely utilized. The FEM is an advanced engineering tool that has shown fruitful benefits in the field of dentistry, dental and biomedical research and as well as orthodontics. It is a highly precise technique which can expose various key research points in the research field.

It is a very big question to ask that have we discovered or implemented the complete aspect of the FEM and is it been used in our field. There are still researches going on. Clinically proved studies are rechecked with the software and after a series of studies, the FEM can be implemented in different cases to predict the results. Every person is unique, hence the bone density, the model etc. So definitely just one FEM study cannot predict all the results from that single result obtained from the unique model of a person. Running an FEM study for independently from person to person is also unique according to the author, which is not emphasized much in any of the literature ever before.

#### **Acknowledgements**

This humble chapter would be incomplete without words of gratitude to all those who have been a part of its existence. I would like to thank, Almighty and my parents and all my beloved ones, **Dr.Basil Joseph, MDS, Orthodontics, India** my beloved senior and friend**,** for his motivation and guidance till date.

#### **Conflict of interest**

The author declares no conflict of interest.

#### **Notes/thanks/other declarations**

I sincerely thank **Dr. Deena Dayalan**, professor, Dept. of Orthodontics and Dentofacial Orthopedics, SRMKDC, Chennai, Tamilnadu, India, for his keen support and motivation throughout my career.

Also, from the bottom of my heart I thank **Dr. Anil Kumar**, Reader, Dept. of Orthodontics and Dentofacial Orthopedics, AJIDS, Mangalore, Karnataka, India, for constantly guiding me in my postgraduate curriculum and for the support he offers me.

#### **Appendix and nomenclature**


*Current Trends in Orthodontics*

#### **Author details**

Nandakishore Rajgopal A.J. Institute of Dental Sciences, Mangalore, India

\*Address all correspondence to: nandaku007@yahoo.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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## Interdisciplinary Reverse Planning in Orthodontics

*Guilherme Nakagawa dos Santos, Charles Lenzi de Araujo and Romeu Cassiano Pucci da Silva Ramos*

#### **Abstract**

Most adult patient cases are multidisciplinary cases, so it's planning can become difficult when we need to connect many dentistry fields to achieve ideal results. The interdisciplinary reverse planning is a well-known topic for dental rehabilitation professionals, so this chapter will address the role of orthodontics in reverse digital planning, improving longevity, reducing biological impacts and helping to communicate with patients, other doctors and dental technicians. 3D CAD technology allows us to plan these complex cases before the patient starts treatment, this tool will be essential to orchestrate the exact moment to start orthodontic, prosthetic and/or surgical interventions, so the workflow becomes ordenate and the outcome will be aligned with aesthetics and functional aspects and in harmony with facial references.

**Keywords:** orthodontics, cad/cam, interdisciplinary, clear aligners, virtual setup

#### **1. Introduction**

Among some factors that significantly increase the demand for esthetic rehabilitative treatments in dental offices, we can observe the greater access of patients to information, as well as the constant development of new technologies and dental materials, which enable a treatment with greater quality and longevity, and a bigger media appeal in this digital age. Although the search for esthetics is a major complaint and the patient's desire should be pleased, it is imperative to think about the function and balance of stomatognathic structures. It is the professional's duty to establish clear goals that can be replicated with predictability and to outline goals to be achieved for the success of the treatment.

Unfortunately, it is common to come across more complex cases where the need for a planning of all the specialties involved is present, and aiming to address only the patient's complaint, some factors and primordial steps are ignored. Analogously, transcribing and visualizing the treatment plan becomes a little more difficult for professionals who, due to incompetence, imprudence or simply negligence, abstain from more detailed planning. In order to fulfill all requirements and have a holistic view of the case, the digital reverse planning is an indispensable tool.

#### **2. Interdisciplinary digital reverse planning**

When talking about different areas of dentistry, we must pay attention to this integration. A multidisciplinary case is one that requires more than one approach (periodontics, orthodontics, implantology, etc.). However, these areas must speak the same language, that is, the goal must be common and convergent. Therefore, we must have an interconnected approach, that is, an interdisciplinary one.

#### **2.1 Examples**

#### *2.1.1 Case 1*

A 29-year-old female patient came to the office complaining that she would like to improve her esthetics through dental veneers. Upon clinical examination and complementary imaging exams, it was observed that a central incisor would be condemned for presenting a fracture and dentoalveolar abscess, the adjacent lateral incisor was decayed, and there was a moderate tooth crowding, which would require greater compensatory prepping teeth for ceramic veneers, or even endodontic treatment if the prepping was greater (**Figure 1**). Thus, aiming at the best result with less esthetic and biological damage to the patient, the case would require tooth extraction 1.1, caries removal and restoration of tooth 1.2, orthodontic alignment, implant in the tooth extraction space 1.1, tooth whitening and veneers in the upper teeth, and prosthesis on implant 1.1. Given these fundamental steps, how to organize these steps? What procedure would be mandatory? How would the esthetic defect of the loss of the upper incisive be minimized? Extract before or after orthodontic treatment?

To answer these questions, the philosophy of digital reverse planning was used, through esthetic, functional concepts and facial references [1], referenced by the integration and overlapping of digital files from the imaging exams, so that the final result could be seen with the predictability and esthetics required by the patient. The traditional approach in orthodontics sometimes does not meet the patient's expectations

**Figure 1.** *First exam's intraoral picture.*

#### *Interdisciplinary Reverse Planning in Orthodontics DOI: http://dx.doi.org/10.5772/intechopen.100414*

regarding how long he will have compromised esthetics. The classic philosophy of planning in Orthodontics follows steps that make it difficult to immediately improve the patient's esthetics, always thinking about the diagnosis and long-term resolution. However, patients with esthetic problems suffer in relation to self-esteem and are in a hurry to remedy this type of problem. Therefore, solving the esthetic part, when possible without affecting the diagnosis of the case, should be shown to the patient.

Within a 3D planning software, the BDS Planning Center team performed a digital study [2] (**Figure 2**). As seen in the occlusal view (**Figure 3**), the need for greater prepping teeth 2.1 and 2.2 for the preparation of veneers is evident, and perhaps even the possibility of an endodontic treatment of the tooth 2.2. However, this study made it possible to visualize the needs of a multidisciplinary treatment, which facilitated decision-making by the patient and the professionals involved that the best conduct

**Figure 2.** *Facially driven reverse digital planning showing the veneers.*

**Figure 3.** *Wax-up and initial models overlapping.*

would be prior orthodontic treatment. After this orthodontic treatment plan was approved by the patient, she underwent tooth 11 extraction and a new intraoral scanning to proceed with the digital orthodontic setup, where this would be guided by the prior digital wax-up. (**Figures 4** and **5**).

We opted for a treatment with orthodontic aligners produced in-office to maintain an esthetic smile, with a pontic [3] on tooth 1.1, since this had a periradicular infection that prevented an immediate implant with a temporary one, thus as to be more predictable during orthodontic movements, enabling a centralization of the teeth for diagnostic waxing. As the biomodels exported by the Nemocast software (Nemotec) had a healing area of tooth 2.1, reliefs were created in the meshes in this area using the Meshmixer software (**Figure 6**), to allow tissue repair without compression of the alveolar ridge by the clear aligners. With the meshes already edited, the models were printed, and the orthodontic aligners were produced (**Figure 7**).

**Figure 4.** *Post extraction initial model and orthodontic setup.*

**Figure 5.** *Wax-up guided orthodontic setup.*

*Interdisciplinary Reverse Planning in Orthodontics DOI: http://dx.doi.org/10.5772/intechopen.100414*

**Figure 6.** *3D mesh relief in Meshmixer software.*

**Figure 7.** *Clear aligners with pontic on extraction space of tooth 1.1.*

The treatment was carried out with a protocol of biweekly changes, where 15 aligners were needed for the upper arch and 8 for the lower arch, in a total of 8 months of treatment, considering the staging for greater predictability of the programmed movements. At the end of the last stage, the patient underwent a new intraoral scan, where this was superimposed on the wax-up study that served as a guide. (**Figure 8**). As verified in the overlapping models [4], the dental position obtained orthodontically was consistent with the planned one, with no need for touch-ups and alterations to the waxing study. Finally, the patient went on to implant the central incisive and subsequently perform the dental veneers as already established by the digital reverse planning, which proved to be effective and reproducible, especially because orthodontic treatment was performed using transparent aligners.

**Figure 8.** *Wax-up and final treatment scanning's models overlapping.*

#### *2.1.2 Case 2*

Mesofacial patient, convex profile, good esthetic exposure of the smile with an inclined occlusal plane and angulation of the anterior teeth (**Figure 9**). Upper and lower tooth crowding, lower midline deviation of 2 mm to the right, caused by prolonged retention of tooth 75 with absence of its successor (tooth 35).

In view of the expectations of the results of the orthodontic treatment and the esthetic expectations of the patient, who did not accept having space for the extraction of the primary tooth, a reverse planning was carried out with an approach to installing the implant prior to orthodontic treatment. In this context, comfort and

**Figure 9.** *Initial aspect.*

#### *Interdisciplinary Reverse Planning in Orthodontics DOI: http://dx.doi.org/10.5772/intechopen.100414*

safety are provided for the patient with preservation of esthetics in the area to be rehabilitated. Furthermore, the option of replacing a provisional retained in the appliance or in teeth, which may suffer constant fractures, especially located in the premolars or molars, subject to constant masticatory forces, it was decided to perform this implant in advance.

In the Nemocast software, virtual orthodontic correction was performed, guided by the face and its references, with extraction of tooth 75 (**Figure 10**). With the prediction obtained by the virtual setup of the final position of the teeth, the waxing of the crown of the 35 with the respective implant was planned (**Figure 11**). For

**Figure 10.** *Facially driven orthodontic setup.*

**Figure 11.** *Implant positioned based by orthodontic digital setup.*

**Figure 12.** *CBCT and orthodontic setup model's overlapping to plan the ideal position of the implant.*

**Figure 13.** *Implant guide on the initial model. Tooth 75 was virtually extracted.*

#### *Interdisciplinary Reverse Planning in Orthodontics DOI: http://dx.doi.org/10.5772/intechopen.100414*

optimal placement of the implant, the STL model obtained from the orthodontic setup was overlaid with the CBCT DICOM file (**Figure 12**). About this project, there was the possibility of making a surgical guide for the installation of the implant, guided by the principles of ideal occlusion proposed by Angle in the 6 keys of occlusion (**Figure 13**) [5].

After planning (**Figure 14**) at the same surgical time, tooth 75 was extracted and tooth 35 was implanted guided, before the beginning of the orthodontic treatment.

In addition to the esthetic and functional gain with the anticipated surgery, the implant served as an absolute anchorage for the distalization of anterior teeth with midline correction and mesialization of the posterior teeth, guiding them to their positions predicted in the setup (**Figure 15**). With this mechanics, it is possible to establish the exact amount of movement of the adjacent teeth, having as the limit the dental contacts with this crown, minimizing the risk of loss of excessive anchorage or distalization less than necessary.

The remainder of the orthodontic sequence is not relevant to the purpose of the chapter, but rather the predictability and multiple functions of digital reverse

#### **Figure 14.**

*Ideal digital orthodontic setup planned with virtual extraction of tooth 75.*

**Figure 15.** *Implant and crown installed new intraoral scan.*

planning in orthodontics. It is noteworthy that performing the implant previously was essential to the success of the project for the acceptance of treatment and patient satisfaction.

#### **3. Conclusion**

As shown in the examples, digital reverse planning is a very important tool for the treatment of interdisciplinary cases, as it aims at better communication with the patient and among the professionals involved. The role of orthodontics in reverse planning is to orchestrate the progress of the clinical sequence, as dental rehabilitative planning often depends on the outcome of orthodontic treatment.

### **Acknowledgements**

Special thanks to the Beyond Digital Solutions team for mastering the interdisciplinary virtual planning of the cases presented.

### **Author details**

Guilherme Nakagawa dos Santos1 \*, Charles Lenzi de Araujo2 and Romeu Cassiano Pucci da Silva Ramos3

1 UNOPAR, Londrina, Brazil

2 Tuiuti University, Curitiba, Brazil

3 Pontifical University Catholic of Paraná, Curitiba, Brazil

\*Address all correspondence to: nksodontologia@hotmail.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Interdisciplinary Reverse Planning in Orthodontics DOI: http://dx.doi.org/10.5772/intechopen.100414*

#### **References**

[1] Margossian P, Laborde G, Koubi S, Tardivo D, Magne P. Determination of Facial References for Esthetic Restorative Treatment. Int J Periodontics Restorative Dent. 2021;Jan-Feb;41(1):113-119. DOI: 10.11607/prd.4642. PMID: 33528459.

[2] León R, Torre M, Rubio A, Javier O. Digital tools and 3D printing technologies integrated into the workflow of restorative treatment: A clinical report. The Journal of Prosthetic Dentistry. 2018; 121.10.1016/j.prosdent. 2018.02.020.

[3] Vaid N, Revankar A, Vandekar M. I-Pontics for CAD/CAM Aligners. The Journal of Indian Orthodontic Society. 2013; 47(3):169-170 DOI:10.5005/ jp-journals-10021-1152.

[4] Anacleto M, Souki B. Superimposition of 3D maxillary digital modelos using opensource software. 2019; Dental Press J. Orthod 24(02); Mar-Apr.

[5] Andrews LF. The Six keys to normal occlusion. J Orthod. 1992 Sept;62(3): 296-309.

#### **Chapter 7**

## Digital Workflow for Homemade Aligner

### *Dalal Elmoutawakkil and Nabil Hacib*

#### **Abstract**

Advanced digital technology is rapidly changing the world, as well as transforming the dental profession. The adoption of digital technologies in dental offices allied with efficient processes and accurate high-strength materials are replacing conventional aligners workflows to improve overall patients' experiences and outcomes. Various digital devices such as 3D printers, intraoral and face scanners, cone-beam computed tomography (CBCT), software for computer 3D ortho setup, and 3D printing provide new potential alternatives to replace the traditional outsourced workflow for aligners. With this new technology, the entire process for bringing clear aligner production in-office can significantly reduce laboratory bills and increase patient case acceptance to provide high-quality and customized aligner therapy.

**Keywords:** digital workflow, orthodontics, aligner, thermoforming, 3D Printing, facial scan, planning software, homemade aligners

#### **1. Introduction**

The increasing esthetic need of patients for orthodontic devices has lead to the development of clear aligner therapy [1, 2]. Traditionally, orthodontists contract with an outside service to provide clear aligner treatments. Outsourcing to a provider has drawbacks for both the patient and the orthodontist. It can take over a month to produce and deliver an aligner set, and the provider requires a substantial service fee, cutting into potential profits.

Advancements in 3D printing technology, Intra-oral scanners, and 3D setup software improve the production of clear aligners. Nowadays, these solutions are widely available in private dental practices, allowing orthodontists in-house aligner production.

In-house 3D printing accelerates aligner turnaround, increases profitability, and improves patient satisfaction while offering complete workflow control.

In this chapter, we will suggest to orthodontists to centralize the production of aligners in the dental office by detailing the different stages of the production flow. Form acquiring extra-oral and intra-oral patient data and exploring necessary hardware and software for this acquisition. Until the production of the aligners, where we will discuss the equipment and materials mandatory for this production. Going through the planning, this section will detail the different software that an orthodontist can use for the 3D setup and the particularities of each of these softwares.

#### **2. Materials and methods**

The conventional clear aligner treatment is based on a complete outsourcing workflow, in this flow, the orthodontist will be restrained to check the setup proposal and request changes if he judges it necessary. To refer a case the orthodontist uploads the patient's data such as photos, X-rays, and digital dental impressions; then, he submits a prescription setup to aligner labs/companies. After a few days, the practitioner receives a setup proposition for review; the orthodontist evaluates the setup made by a technician and asks for some changes if necessary. Generally, there are 2 to 3 revisions with most aligner's laboratories before achieving a good treatment setup. This interaction between the orthodontist and the technician wastes time. Once the treatment setup has been approved, the orthodontist has to wait for the aligners to be fabricated and shipped to the office. Usually, the whole process takes 2–6 weeks.

In homemade clear aligner workflow, there are three main axes: data acquisition totally made by dental staff, planning of aligner setup, and aligner fabrication; these last two steps can be internalized in the dental office or outsourced to a third party. The outsourcing choice will depend on the time the orthodontist can allocate to planning, the cost/benefit ratio of acquiring software, and hardware and dental staff's ability to expand functions and competencies **Figure 1**.

#### **2.1 Data acquisition**

#### *2.1.1 Digital model creation*

The maxillary and mandibular digital working models and recording of the patient occlusion can be done directly on the patient by an intraoral scanner or by digitizing the analog impressions and/or plaster models with a desktop scanner or by a cone-beam computed tomography (CBCT).

Extraoral 3D scanners can be used to capture 3D images of both impressions and physical casts to acquire digital models. An optical scanner (OS) is an extra-oral digitization method that uses a white light that is cast on the plaster dental model. Later, the projected pattern is captured using a high-resolution camera, and a 3D image of the model is created. Dental labs often prefer optical digitizers, involving less acquisition time for scan construction [3, 4].

Digital measurements of tooth size, arch width, and Bolton tooth size discrepancy on digital models obtained from plaster dental model scanning and dental impression scanning showed high accuracy and reliability. No statistically significant differences

**Figure 1.** *Different Workflows for in-office aligners.*

*Digital Workflow for Homemade Aligner DOI: http://dx.doi.org/10.5772/intechopen.100347*

were noticed between direct measurements on the plaster models with a caliper and digital measurements on digital models obtained from plaster dental model scanning and dental impression scanning methods. Digital models can be alternative to plaster models with clinically acceptable accuracy and reliability of tooth size, arch width measurements, and Bolton analysis [5].

Intraoral scanner (IOS) is an alternative to OS for the digitization procedures of plaster dental models [3]. Various intraoral scanners are available in the market, with many different technologies, each with its own limitations, advantages, and costs [6]. The 3D scanning technologies depend on different physical principles and are defined in the subsequent classes [5]:


Advancements in the CBCT systems have made the digitization of plaster dental models possible [8]. Several CBCT manufacturers have started integrating extra cast digitization tools into their machines to simplify the workflow for data acquisition and surface extraction [3]. CBCT scans are acquired using a volume scan method instead of a surface scan method using a laser or LED source; therefore, CBCT scans are not affected by the angle of irradiation or the shape of the subject around the undercut area proximal contact. CBCT can even be used in cases of crowding without managing raw scanned data [9].

Digital model fabrication using scans of patient impressions obtained with CBCT in a dental office is another alternative method to create a model without an intraoral scanner or a desktop scanner and without directly irradiating the patient. If necessary, digital models and plaster models can be fabricated using a single impression [10].

#### *2.1.2 3D Facial scan*

The assessment and analysis of facial soft tissues are essential for orthodontic and maxillofacial diagnosis and treatment planning. In aligner therapy, using a twodimensional (2D) digital photograph is a basic approach for facial structure assessment. However, this process has been progressively replaced by three-dimensional (3D) imaging. The 3D facial scan enables creating a virtual face that can be integrated with 3D models of the dentition obtained by intra-oral scanners and coupled with 3D radiographic images from CBCT for a 3D orthodontic set-up to achieve virtual patient [11].

There are two classifications of the scanning systems based on the type of equipment of the optical devices, namely stationary systems and portable/handled systems. In stationary systems, the optical devices are fixed on tripods or adjustable frames, while in handled/portable systems, the scanners are movable in real time around the target object [12].

#### *Current Trends in Orthodontics*

Stationary facial scanning systems based on stereophotogrammetry technology were first introduced in dentistry [13]. Digital stereophotogrammetry captures 3D facial surface data using at least two cameras configured as a stereo pair. This procedure may be: passive or active. In active stereophotogrammetry, structured-light techniques are incorporated for higher resolution [14]. Because of the encumbrance, high cost of this technology, and their operating methods that require frequent calibration, handheld scanning systems using laser or structured-light technology were developed [15].

Laser-based scanners function by projecting an eye-safe class 1 laser beam across a subject's face. The beam is scattered by the face and collected at a triangulation distance from the laser's origin. At the same time, Structured-light scanners (SLSs) generate 3D facial models by projecting a full structured light pattern (typically vertical stripes) onto a subject's face, recording deformations in this pattern produced by the face's morphology allow 3D face reconstruction [16].

Although most professional handheld scanners are considered acceptable in terms of their scan image quality, they are expensive and often require considerable training time to learn their complex scanning protocols [3, 9, 10]. Alternatively, 3D sensor cameras based on structured-light technology have been developed for smartphone and tablet devices [15]. Increasing interest is due to mobile devices' high portability, user-friendliness, cost-effectiveness, and popularity [17–19]. The advantages of smartphone face digitization include reducing time for scanning, image processing, technical learning [20, 21], and their high portability [22].

Motion artifacts were considered the primary source of error in the results of portable face-scanning systems [23–25], cautioning that the influence of involuntary facial movements has a more significant impact on mobile face-scan devices than stationary ones [11]. Prolonged scanning time and unstable movements of the scanners may magnify the motion artifacts caused by involuntary facial movements [25]. Therefore, using scanners that conduct a single and quick scan is recommended, mainly when the face scans are performed on children or people with special needs who struggle to stay immobile for a prolonged time [11, 25, 26].

#### *2.1.2.1 3D dentofacial integration*

The 3D dentofacial image integration is performed by matching the dental scans to the facial scans. Alignment of the two scans (facial scan and dental scan) can use teeth image only (TO), perioral area without marker (PN), or perioral area with markers (PM) [22].

For the 3D dentofacial integration using teeth images only, the teeth area visible on the facial scan images is used as a reference to match the facial scan with the intraoral scan **Figure 2** [27, 28].

The intraoral scan of the teeth area associated with the scan of perioral structures was proposed to enhance the accuracy of the dentofacial integration [29] **Figure 3**. This procedure aims to provide larger areas that can be used as a reference to coordinate the intraoral scan of the teeth with the 3D scan of the face. The effect of the perioral scan method on image matching depends on the use of artificial markers during the perioral scanning [22]. The absence of clear marks on the skin causes inaccuracy of the scan data obtained when capturing large areas of the perioral structures without the skin marker attachment by the intraoral scanner.

Artificial markers provide distinct references for similar adjacent areas so that they could help the image stitching process. Perioral scan with artificial skin markers significantly improved the accuracy of integration of dental model to the facial scan **Figure 4** [22].

#### **Figure 2.**

*Alignment of the two scans (facial scan and dental scan) using teeth image only (TO).*

#### **Figure 3.**

*Alignment of the two scans (facial scan and dental scan) using perioral area without marker (PN) The participant was scanned using Bellus 3D by rotating the head to the right and the left of the camera, following the manufacturer's instructions while maintaining the head at the camera's center. The scanning mode was set in highdefinition (HD mode) in the scanning software. The intraoral and perioral anatomical structures were acquired using an intraoral optical scanner mediti500. The perioral structures, including the upper lip, philtrum, and nose, were obtained with the participant's anterior teeth in a broad smile position. a: The first step is matching perioral scan to intraoral scan; fixed mesh is intraoral scan. b: The second step is matching the 3D facial scan with the perioral scan previously aligned on the intraoral scan; the fixed mesh in this step is the perioral scan.*

#### **Figure 4.**

*The two scans (facial scan and dental scan) are aligned using perioral area with markers (PM). A: The first step is matching perioral scan to intraoral scan; fixed mesh is intraoral scan. B: The second step is matching the 3D facial scan with the perioral scan previously aligned on the intraoral scan; fixed mesh in this step is perioral scan. Artificial skin markers provide distinct references for the image stitching process.*

#### *2.1.3 3D X-ray: Cone-beam CT*

Major planning solutions for aligners consider only the crown position, not the root shape. Complete tooth architecture information, including crown and root anatomies, would improve treatment planning and provide more predictable results [30].

#### *2.1.3.1 Procedure*

Dicom file is imported into 3D setup software; the orthodontist performs segmentation to have a 3D reconstruction of root morphology, then he stitches 3D segmented teeth to STL IOS model. Afterward, the orthodontist can adapt the position of the virtual tooth to segmented roots to have a correct pivot. Integrating 3D data from an optical scanner with volumetric data from CBCT imaging provides an optimal spatial reference for the most accurate hard and soft tissues models. **Figures 5** and **6**.

#### **2.2 Digital treatment planning**

Selecting software is the main concern for most clinicians to get started with homemade clear aligners. All 3D setup ortho planning software have typical workflow **Figure 7**. The software's options have comparable abilities at the core; however, some specific features add value and are determining when choosing a software. **Table 1** summarizes the different software available on the market with their respective options.

**Figure 5.** *Aligning 3D segmented Teeth (Roots & Crowns) to IOS Scanned teeth using teeth as references.*

**Figure 6.** *Aligning virtual teeth of 3D setup software according to segmented roots (CBCT).*

#### *Digital Workflow for Homemade Aligner DOI: http://dx.doi.org/10.5772/intechopen.100347*

#### **Figure 7.**

*Typical workflow for 3D ortho setup software.*


#### **Table 1.**

*Different software available on the market with their respective options.*

#### *2.2.1 Automatic segmentation*

Almost all programs offer an automatic segmentation feature. Artificial intelligence (AI) algorithm finds the gingival border of each tooth. Using AI, the software will automatically segment and identify the teeth. Next, they will label the teeth and then automatically create a long axis, center groove line. If necessary, the software can manually adjust borders with an intuitive brush-editing feature, edit tooth labels, correct grooves, and adapt the long axis if needed [31, 32].

#### *2.2.2 Realtime simulation*

3D ortho setup software authorizes real-time simulation with features as intuitive alignment, enabling easily drag teeth to where they need to be, occlusal contact collision calculation, and IPR options. Also, 3D ortho setup software allows aligning the teeth to a customizable arch shape by adjusting the arch shape using the control points placed around it [33].

However, not all programs allow skeletal movements, evaluation of multiple treatment strategies, and creating treatment simulations for surgical, restorative, and extraction cases [34]. Plus, features relative to model capabilities as Bolton analysis on every model, automated measurements of tooth width, arch width are not available in all software.

The SoftSmile, Blueskyplan orthodontic, Deltaface, and Orth'up aligner software [31–36] create a 3D model of the orthodontic treatment plan, including a representation of teeth roots and movement of the lower jaw during the treatment. It creates optimized teeth movement and suggests, along with the knowledge and skill from the orthodontist, the exact number of aligners needed for reaching better results.

#### *2.2.3 Advanced staging and sequencing*

3D setup softwares make a staging proposal; the user feels the difference in the possibility of customizing this staging. BSB ortho, uLab, et ArchForm enable the orthodontist to select the teeth to move first, achieving sequential distalization and establishing the order of teeth movements [32–35].

#### *2.2.4 Attachments*

Adding an attachment is a standard option in 3D setup software. Some softwares stand out by features such as automatic attachment placement depending on the tooth movement or customized attachment with adjustable attachment size and gingival tilt to control tooth movement [35–37].

#### *2.2.5 Ready to print models*

From finishing the treatment plan to starting a print, much valuable time is lost on preparing printable.STL. All softweares allow STL export, but some make the entire manufacturing process smooth, intuitive, and straightforward.

Blueskyplan ortho, Archform and ULab automatically prepare models for 3D printing: in few clicks, all models are made hollow, and a bar for vertical printing without support is attached to them [35–37]. Usually technicians spend 5–7 minutes *Digital Workflow for Homemade Aligner DOI: http://dx.doi.org/10.5772/intechopen.100347*

on the preparation of each model, but with BlueSkyPlan Ortho 2 minutes are spent on preparing the whole case's models. Features like hollowing models and vertical printing with optimized tilt make the virtual setup process smooth, quick and convenient, saving resin and printing time [35].

Labelling models is a standard feature that enables adding letters and numbers on models to identify patients and orthodontists. Nevertheless, special labelling such as auto labelling imprints onto the aligner is specific to only some software like BSB ortho, Archform, and Ulab [35–37].

#### *2.2.6 Automatic pontics for concealing gaps and missing teeth*

Developed especially for extractions cases, this functionality is not available in all software. On Archform, and ORTH'UP softweare [33, 37], teeth can be extracted at any stage during treatment planning. The two software allow clinicians to place a pontic that will change dimension as the space is closed. The pontic can have the same form as the extracted tooth, a mirror of the tooth on the other side, or a tooth selected from a library [37]. With SureSmile, either gaps are opened for an implant or closed after an extraction; once a space is bigger than 3 mm, a virtual tooth is added to fill the gap [34]. Efficient and fast, this functionality allows significant time-saving in the preparation of cases for the dental assistant.; avoiding manual waxing on printed models before thermoforming aligners [33].

#### *2.2.7 Variable trim line*

With BSB ortho, doctors can freely choose the trim line design; individualized positioning bases are added to the aligner to be trimmed in a high-precision automated laser cutting machine [35]. The Aligner Trim curve will be generated automatically based on the parameters "Curve Shape" and "Trim Margin" in Preferences. Both parameters can be adjusted as well and regenerate directly on the orthodontics panel. The export of the curve will be available in the last step for the automatic trimming of the aligners in the milling machines [35]. ORTH'UP software offers the possibility of calculating the aligner boundary at each step of the treatment plan and converts it into a 3D marking on the printed model. This visual reference makes cutting the aligners by the dental assistant faster and much more precise [33].

#### **2.3 3D Printing**

The dental sector has been undergoing radical change for many years, thanks to the digital dentistry movement. Additive manufacturing, in particular, has enabled the dental industry to expand its use of digital technologies. Indeed, the dental sector is a promising market for 3D printing technology because it responds to the issue of customized items.

3D printing is now easily approachable for orthodontists; 3d printing for orthodontics reduces production time and costs, and its potential is still growing [38].

#### *2.3.1 Fused deposition modeling (FDM) 3D printing*

Fused Deposition Modeling (FDM) 3D printing consists of creating several layers by injecting a molten plastic filament through a heated extruder. Any material that

can be injected through a heated nozzle at melting temperature is printable by this technology. It comes in a long filament with a 1.75 to 3 mm diameter wound in a 500 g or 1 kg coil. Polylactic acid (PLA), Acrylonitrile butadiene styrene (ABS), and GreenTech pro are the most suitable materials for orthodontic models. Their prices vary from 20 to 40 euros [39].

PLA is a fully biodegradable polymer by industrial composting. It is obtained from the fermentation of starch, beet, corn, or sugar cane. It has the advantage of not giving off toxic fumes during printing. However, its glass transition temperature is around 60°, which limits its use under thermal stress, which goes against the thermoforming of aligners [39, 40]. PLA is generally used in 3D printing due to its very affordable price also in dental 3D printing to make dental models. New reinforced forms are proposed to endure mechanical and thermal stresses. (Pla Ultra, PLA-X3,) [40, 41].

Acrylonitrile butadiene styrene (ABS) is a thermoplastic polymer with excellent mechanical and thermal resistance. It is very affordable and is easily recycled by steaming [42, 43].

GreenTech pro is a 100% biodegradable biopolymer (DIN EN ISO 14855), made from organic, CO2 neutral, and environmentally friendly materials. The FDA has approved it for food contact. It has a mechanical and thermal superior resistance to ABS and PLA, ideal for dental models subject to thermoforming constraints [44].

#### *2.3.2 Stereolithography 3D printing*

Stereolithography 3D Printing (SLA) is the most widely used technology in dentistry, both for its precision and well-finished surface. For the same layer thickness, the surface roughness is far well finished compared to FDM. Stereolithography (SLA) is an additive manufacturing process that refers to the Vat Photopolymerization family. In SLA, an object is formed by selectively curing a polymer resin layer-by-layer using an ultraviolet (UV) laser beam [45, 46].

UV light can be a simple micrometers laser beam that will sweep the entire layer, point by point, just like a colored pencil that colors a 2D drawing to follow the same way on the next layer [45]. UV light projection can also be a light projection of an entire layer by a DLP projector (Direct Light Processing), resulting in a single-shot polymerization of the entire layer. Compared to SLA, the DLP is definitely faster [45].

Among the leading manufacturers of 3D SLA printers, 3D Systems, is at the origin of this technology, but also more recent players like Asiga, which was the first to have launched the Direct Light Processing (DLP) 3D printers in 2011, and Formlabs, which initiated the introduction of in-office 3D printers to the dental practice through its FORM2 printer allowing 3D printing dental materials.

This technology uses 385 nm or 405 nm photopolymerizable resins depending on the wavelength of projected light. There are many resins dedicated to dental models which have the advantage over other resins of being very fast in printing and having a color that helps thermoforming control and good mechanical and thermal resistance.

#### *2.3.2.1 Dental model resin*

All resin manufacturers began to produce dedicated dental resins for both prosthodontic and orthodontic models. Compared to standard resins, those resins have faster print speed, are very precise, and have a significantly lower degree of shrinkage. Dental models resins have a beige color [47].

#### *2.3.2.2 Dental long term (LT) ® clear resin*

It is a class IIa long-term biocompatible resin for printing rigid splints, durable orthodontic appliances, and night guards. According to some preliminary studies, this resin may be suitable for clear aligner direct 3D printing because it has good geometric precision and comparable mechanical properties to the thermoformed aligners [48, 49].

#### *2.3.2.3 Tera Harz TC-85*

Graphy, a South Korean-based company of 3D printable photopolymer resins, has revealed a dental 3D printing material mark, Tera Harz, intending to overcome the constraints posed by other 3D printable resins used within the dental field.

Graphy's Tera Harz has obtained CE, FDA, and KFDA medical device certification and is available in clear (TC-85DAC) or white (TC-85DAW). The clear Tera Harz resin is fully transparent and has high durability agreed with orthodontic treatment device purposes. In comparison, the white Tera Harz material features esthetics alongside durability **Figure 8**.

#### *2.3.2.4 Post treatment*

Objects produced with 3D printing technologies usually need some degree of post-production treatment. This crucial step of the 3D printing workflow is known as post-processing. First, 3d printed models must be washed in isopropyl alcohol (IPA) or tripropylene glycol monomethyl ether (TPM). For optimal cleaning, users have to shake parts around in the solvent as well as soaked. Habitually, cleaning 3D Printed models requires two washes in IPA or TPM to be fully clean.

When an SLA part finishes printing, the polymerization reaction may not yet be completed. Wich means that parts have not reached their final material properties and may not function as expected, particularly tough parts under strain. Exposing the printed objects to light and heat, called post-curing, will help solidify its materials properties. A UV box post-treatment is usually required to achieve the light-curing process and maximize material strength.

Post-curing is not mandatory for standard resins. Other resin types require post-curing to achieve their optical-mechanical properties. Each material should be submitted to the curing process for a specific amount of time. Printed models should be cleaned and cured before removing supports [46].

#### **Figure 8.**

*Directly printed aligners with Tera Harz TC-85 resin (TC-85DAC) put, after post-treatment side by side with thermoformed aligner (Biolon 0,75 mm).*

#### **2.4 Thermoforming aligners**

The first aligners developed by Align Technology corresponded to a single-layer rigid polyurethane produced from methylene diphenyl diisocyanate and 1,6-hexanediol. To enhance its mechanical proprieties and transparency Smart Track (Align Technology, 2012) developed a new thermoplastic polyurethane [50, 51]. The expansion in demand for clear aligners has commanded the development of additional thermoplastic materials for clear aligners by other entreprises, such as e.g. Invisalign, Duran, Biolon, Zendura, Erkodur, ClearCorrect, Erkoflex 95, Erkoloc pro, etc. [52, 53] **Table 2** summarizes the different sheets currently on the market [54].

The manhood of current aligner companies uses transformed polyethylene terephthalate glycol (PETG), although polypropylene, polycarbonate, thermoplastic polyurethanes, copolyester, and many other materials are also used [50].

The mechanical characteristics of dental polymers exhibit a myriad of influence factors, such as intrinsic factors (molecular and crystal structures, etc.) and extrinsic factors (temperature, humidity, etc.) [55, 56]. The used polymers are either amorphous or semi-crystalline. Low crystallinity of polymers typically means high flexibility, high elasticity, and adaptability to the tooth shape, but on the other side, they present low tensile strength, low chemical resistance, and stability [56]. From a clinical perspective, polymers with high flexibility and elasticity are more convenient for patients to insert or remove the aligners. Furthermore, they adjust better to the complexity of the tooth anatomy, attach perfectly to any surface. Correlated to aligners of rigid materials, they also guarantee continuity of force expression during the orthodontic treatment [56].


#### **Table 2.**

*Different sheets currently on the market.*

#### *2.4.1 Thermoforming machines*

Thermoforming consists of hot shaping thermoplastic products made of polymers. There are two types of thermoforming machines:


Vacuum forming machines are not recommended for making aligners because they are not accurate enough. The aligner must have a tight fit on the models to transfer that fit over the teeth and have the proper amount of force. For this purpose, pressure-forming machines are more adapted. These machines are usually already present in the dental office for making retainers, night guards, etc.

The selection of a forming machine will be made according to the compatibility of the machine to different brands of trays, the space allocated to thermoforming in the dental office, the Drufosmart® for example, takes up a little less space than the others because of its vertical forming design, or according to features that will facilitate and automate the task of dental assistants, such as the barcode reader where the materials setting are just scanned, or the possibility of thermoforming several models at the same time for mass production.

#### **2.5 Tray trimming and polishing**

After thermoforming, the aligner is first cut on the 3D printed model with large chisels; then, it is delicately removed to avoid permanent deformation on the aligner. The cutout is finished with curved scissors. Polishing the edges is done with polishers to avoid having sharp edges. Solutions for automated trimming exist on the market

**Figure 9.** *Pressure forming machines for aligner's fabrication.*

like Inlase for dental practices with an expanded production volume of aligners [58]. There are solutions for automated trimming on the market like iNLASE®, which is a laser trimming machine that automatically cuts thermoformed aligners in less than 15 seconds, without the need for manual cutting or polishing **Figure 10** [58].

#### *2.5.1 Scalloped VS continuous curve*

According to Cowley et al. [59], there are three designs for aligners at the gingival margin:


The difference between the techniques was remarkable. The straight cut 2 mm from the margins was about twice as retentive as the scalloped cut for clear aligners without engagers. For clear aligners with attachments, the straight cut 2 mm from the margins was over four times as retentive as the scalloped cut.

Cutting the aligners differently had more of an impact than supplementing or excluding attachments. Aligners are more comfortable with this technique because the aligners impinging on the unattached marginal gingiva is less risk. The edge of the aligner is covered further under patients' lips during everyday use; this should also slightly increase the discreetness of the aligners.

#### **2.6 Packaging and delivery**

Packaging and labelling is a step that is often overlooked in aligner fabrication. Standards bags with a zip-lock function can be easily found on the market and

**Figure 10.** *In-office trimming of aligners.*

*Digital Workflow for Homemade Aligner DOI: http://dx.doi.org/10.5772/intechopen.100347*

handled for aligner packaging. Practitioners can easily utilize labels and print office logos and patient information. A bag or a box can be used to deliver the aligners to the patient; custom printed plastic bags are preferable to boxes. Besides being more costeffective, custom printed bags take up less space and are easier to stock and deliver to the patient, particularly when only a few stages are required. From a branding perspective, practices with in-house aligner production should package the aligners in a way that promotes their office **Figure 11**.

#### **2.7 Delegation**

Delegation is a fundamental concept in management. It allows the practitioner to "optimize his diploma" by performing only acts or tasks which fall solely and specifically within his competence. On the other hand, it helps develop team motivation. Delegating tasks relating to new technologies such as 3D printing or digital impression helps to motivate and, above all, enhance dental assistant work.

For homemade aligners, 90% of the tasks can be delegated to a dental assistant. 10% of the remaining tasks concern planning of 3D setup, some steps of which can also be delegated. When outsourcing 3D setup, the whole production chain is delegated. **Table 3** shows the distribution of tasks relating to the homemade aligner.

The dental assistant must do all patient records. Indeed intraoral scanning, taking 2D or 3D X-rays, and face scanning all these tasks can be delegated to a well-trained dental assistant.

The dental assistant will import /export various STL/OBJ files either to prepare the 3D setup or to print the various stages. The dental assistant will also process data such as tooth segmentation, labelling, and nesting models on 3D printer software. The interoperability and intuitiveness of the software will allow the dental assistant to switch from one software to another seamlessly.

All tasks relating to 3D printing are delegable: removing models from building platforms, washing, drying, curing models, and removing supports. When choosing a 3D printer, the practitioner should consider user-friendly and intuitive 3D printing software that exports the models with the bases set at the correct angle. Likewise, selecting a 3D printer with features like calculating the amount of resin or filament needed for 3D printing to not run out of materials is crucial for overnight 3D printing. Samely when purchasing post-treatment hardware, the practitioner must choose automated systems for washing, drying, and curing models to make the task as efficient as possible for the assistant.

**Figure 11.** *Homemade packaging for aligners.*


#### **Table 3.**

*The distribution of tasks relating to the homemade aligner.*

Aligner fabrication is a fully delegable task; the dental assistant must do the entire process, thermoforming, cutting, polishing, and packaging. Thus, the dental assistant performs the initial insertion of the appliance to check its fitting.

#### **3. Results**

Invisalign is the most common clear aligner option that is outsourced. The cost for Invisalign treatment is 575 \$ for five aligners, 1199\$ for 14 aligners cases, and 1779\$ for full cases. For ClearCorrect, the price for five aligners is 395 \$, 935\$ for 14 aligners cases, and 1495\$ for unlimited cases.


*\*5 \$ fabrication cost per aligner and 20 \$ software cost per case (2jaws) (10\$ one jaw). Cost per aligner include materials cost/ printing cost and assistant's time to fabricate the aligner.*

#### **Table 4.**

*Comparison cost fee for different aligners systems.*

When aligners are homemade, the cost for five aligners treatment turns around 70\$. This includes printing, materials, assistant time to fabricate the aligner, and software fee. The cost per printed model is for resin models 1,75 \$, and it depends on the brand of the resin and the use or not of supports while 3D printing. The cost per clear aligner sheet is 1,5\$ (biolon 0,75 mm), and it also depends on the brand of the aligners sheet. In the USA dental assistant's average wage per hour is \$ 25; for aligner fabrication, a dental assistant takes 5 minutes to make each clear aligner, so the cost per aligner for assistant time is roughly 2\$. The total fabrication cost per aligner for homemade aligners is 5,25\$. For an in-house clear aligner software, the fee per case is 20 \$ for two arches (Bluesky plan ORTHO) and 10\$ if only one arch is processed. If the orthodontist wants to outsource the planning, the cost for outsourcing planning is \$ 200 (LabPronto). **Table 4** recapitulates the different costs according to the treatment options and the number of aligners.

#### **4. Discussion**

Orthodontic practices that integrate in-house aligners solution into their operation gain full control over the workflow eliminate outside lab fees, and achieve faster production turnaround time. Internalizing aligners manufacturing in the dental office reduces by at least half of the cost compared to commercial aligners suppliers **Table 4**.

Being able to reduce aligner fees for patients will increase profit line and case acceptance. Nowadays, direct to consumers companies propose clear aligners with competitive cost compared to conventional aligner treatment. Thus the do-it-yourself (DIY) aligners companies are trying to eliminate the orthodontist from the equation. With the homemade aligners the orthodontist can be competitive even with such companies.

In-office aligner's production allows complete management for the entire alignermaking process. Compared to a custom commercial aligners laboratory, this flow enables complete control over the treatment plan because planning is done by the orthodontist and gives particular options like having additional aligners/refinement or producing several aligners for the same step in different thicknesses for specific case's need.

Orthodontists have also control of the 3D printing process: by controlling materials, resolution, printing direction, models Hollowing, etc.. and managing aligner

*<sup>\*\*200\$</sup> for outsourcing planning (Labpronto).*

sheets materials in terms of composition, thickness, toxicity (Bisphenol A (BPA) free) [60], and the trim line, also being able to customize this factors for each specific clinic case. All these aspects have a significant impact on the efficiency of clear aligner therapy.

In-house aligner production authorizes faster processes for patients; Aligner production can begin as soon as the patient is ready to undergo oral scans. Practices can provide same-day or next-day starts service depending on the patient queue. In a same-day appointment, an orthodontist can take oral scans, plan out treatment, and print and form the first aligner stages before the patient leaves the office or within a few hours of the appointment. The expedited service provides optimal customer service and an immediate customer lock-in advantage.

#### **4.1 Digital model creation**

Digital models offer more advantages such as instant accessibility of 3D information without the need for the retrieval of plaster models from a storage area, reduced need for large areas for plaster model storing, and less time-consuming analysis [61]. With 3D digital models, clinicians can evaluate dental models in three-dimensional aspects and perform dental analysis in more detail. Interrelation between maxillary and mandibular arches can be better observed in occlusion on different scenes in 3D software [62]. Digital models also provide virtual treatment and virtual setup [63]. 3D models can be processed to analyze specific teeth and to estimate the axis or position of individual teeth, which provides a three-dimensional prediction of tooth movement by superimposing dental changes on stable reference structures [5].

Desktop Optical Scanning is a simple, fast, and straightforward procedure; models do not require a second scan due to the scan's lack of data or non-completion. Likewise, the OS procedure is an entirely delegable task. However, despite all the advantages, it is very cost-intensive and therefore unaffordable for many dental offices and labs, and for impression scanning procedures, the record of the patient's occlusion cannot be obtained [3].

Intraoral scanners introduce innovations in orthodontics such as monitoring dental movement through digital model superimposition aligners [64, 65], further customization of orthodontic appliances such as removable retainers [65], and last but not least, more accurate diagnosis, treatment planning and even simulation of possible orthodontic movement on appropriate software [66, 67]. Furthermore, scanning requires more chairside time, but it was found less unpleasant than the standard procedure of impression taking [68]; evidence exists that patients when asked which type of impression satisfy them more, choose digital due to patient-centered outcomes [69].

A systematic review [70, 71] of the accuracy of intraoral scans reported that interand intra-arch measurements from intraoral scans were more reliable and accurate in comparison to those from conventional impressions. Another systematic review in prosthodontics [72] reported that dental restorations fabricated using digital impressions exhibited a similar marginal fit to those fabricated using conventional impressions [73].

Many factors affect the accuracy of the IOS, such as [74, 75]:

1.Scanner: capacity to register details and its accuracy.

2.OperatorUser: scanning fundamentals and path's scanning.


After a conventional alginate impression, a median of 22 minutes is required for plaster modeling, including pouring and trimming. In Park JY, study [9], the digital models were obtained within 5 minutes after a rubber impression, with 14 seconds for the CBCT scan of the impression, 1 minute for CBCT file export, and 2 minutes for generating an STL file for each arch. In terms of efficiency, digital modeling using CBCT seems to be clinically feasible and is correlated to reduced laboratory time. No significant differences were found in most measurements between the cast scan models and CBCT digital models. CBCT may be suitable for use in clinical practice because of its advantages, including a reduced working time for digital model rendering [9]. For a dental professional who previously has a CBCT or an IOS device, the acquisition of another digitization system might seem redundant [3].

However, the 3D ortho setup is done on maxillary and mandibular 3D models in occlusion. Using a CBCT to digitalize dental arches is undoubtedly possible. However, the registration of the occlusion, which is indexing one model in relation to the other with this method, is not as intuitive as with an OS or IOS and will require additional CBCT scans of the models in occlusion and the passage through a third-party software to align, relate and index the models before importing them into the 3D setup software.

For Emara A, OS is the best choice for dental models' digitization. The CBCT, however, proved to be a highly precise option. Even if the tested IOS showed the lowest results in terms of accuracy, it is still a valid affordable option for model digitization, with results falling within the "clinically acceptable" range [3].

#### **4.2 Facial scan**

Facial scanner using a mobile device 3D sensor camera has been captivating much interest in recent years because it is highly portable and cost-effective and because of the popularity of mobile devices [14]. Smartphone- and tablet-compatible 3D facial scanners have been described to be a valuable tool for clinical use in prosthodontic treatment [12, 15–18]. However, the digital facial impression accuracy obtained with mobile device–compatible face scanners has not been investigated [15].

No significant difference was found between stationary and portable face-scanning systems concerning the accuracy of the resultant digital face models. Within the comparison of scanning methods, stereophotogrammetry, laser, and structured-light systems showed similar levels of accuracy in generating a digital face model [11].

The accuracy of mobile device–compatible face scanners in the 3D facial acquisition was not comparable to that of professional optical scanning systems, but it was still within the clinically acceptable range of <1.5 mm in dimensional deviation [15].

Amornvit et al. [76] and Liu et al. [77] reported that mobile device–compatible face scanners are comparable to professional 3D facial scanners when scanning simple and flat areas of the face such as the forehead cheeks, and chin. However, scanning

accuracy was relatively low when mobile device–compatible face scanners were used to capture complex facial regions, such as the external ears, eyelids, nostrils, and teeth [76–79]. Higher inaccuracy was found in the facial areas with defects, depending on the depth of the defect [15, 20]. The teeth scan quality for the smartphone 3D face scan could be lower than that of the stereophotogrammetry because of the high sensibility to the depth of the smartphone facial scanner [16, 22].

The accuracy of the image integration using teeth images only principally relies on the spatial accuracy and the resolution of the captured anterior teeth image in the digital facial scan [28]. When only the teeth region was used for image matching between the facial scan and intraoral scan images, the alignement could be predisposed to error because of the image deformations of the 3D facial model at the mouth area due to the difficulties in scanning the complex structures of the teeth and the gingiva [22, 28].

The accuracy of virtual dentofacial combinations was mainly reliant on perioral scans and artificial skin markers. The most trivial midline deviation and frontal plan canting were found when the perioral image with artificial markers was used. In contrast, the highest divergences were found when the perioral image obtained without markers was employed for image alignment. Although stereophotogrammetry face scan generally showed higher accuracy of virtual dentofacial integration than the smartphone 3D depth camera face scan, the difference between the devices was not significant when the perioral scans were used as references for image matching.

#### **4.3 Setup planning**

Unique features make some software high valuable, when choosing software for homemade aligners, orthodontists should look for a program that includes the functionality of matching CBCT data to IOS data and the possibility of positioning the virtual roots of the 3D setup software according to 3D segmented teeth from CBCT. Accurate superimposition of the intraoral scan over the CBCT data would allow the orthodontist to clearly view a dimensionally true representation of a tooth and its root relative to the alveolar ridge [80, 81]. While the conventional virtual setup focuses on moving the crowns, the 3D digital model includes root positions, thus enabling a better outcome [82–84].

BSB ORTHO offers advanced options such as integration of CBCT and facial scan data, the superposition of these data with the 3D models is seamless with BSB ORTHO software, also import and export high definition models to have as little decimation as possible and achieve a good fitting of the aligner [35].

Archform, uLab, and 3Shape software create the same-day functionality without spending time creating a complete treatment set-up. This adds value for the clinician offering super-speed turnarounds and bringing instant orthodontics into their practices [84].

Carestream's Model+ software is a relative newcomer to the aligner software space; Carestream's Model+ software has a unique feature that only is within their software. Model+ allows the clinician to assess individual tooth movements and grade both case complexity and predictability of individual tooth movements [84].

ArchForm can be used across multiple computers and keep patient data in synchronization. For example, the orthodontist can start a design on the office computer and continue it on his laptop at home. Plus, the software keeps patients on track, turning around refinements in one day by instant adjusting treatments mid-course for faster treatment and more precise results [37].

*Digital Workflow for Homemade Aligner DOI: http://dx.doi.org/10.5772/intechopen.100347*

ArchForm and ULab's AI-assisted software includes one-touch bracket removal features that make finishing bracket cases in aligners or preparing finishing retainers in advance easier by allowing easy removal of the brackets post-scanning [85].

Direct 3D printing of aligners is more innovative and is gradually gaining market share, especially with the emergence of more suitable resins. It is a breakthrough. Deltaface & BSB Ortho are the only two software on the market that offer this functionality; the rigidity of the aligner is set on that software by locally adjusting the thickness of the aligners. This technic offers many advantages, notably: better precision, saving of time by eliminating the steps of thermoforming, cutting, and polishing; it also allows a saving of resin by removing the need to print the models, which has an ecological virtue [31, 35].

Many software options require monthly subscription fees, pay-per-case export fees, or pay-by-aligner pricing, and it is crucial to select cost-effective and functional software for the office.

#### **4.4 3D printing**

FDM printer extrudes a resin that has been heated just beyond its melting point, placing it layer by layer. The heated material hardens immediately after being extruded, thus minimizing inaccuracies. Of the available materials, the most common are polylactic acid and acrylonitrile butadiene styrene (ABS). These often come on spools that can easily be replaced as needed. FDM 3D printing has the advantage of printing at a low cost and not needing post-processing, but it is relatively slow and less well finished than stereolithography. However, it offers relatively sufficient precision for orthodontic models because it easily makes dental models print with 100 to 50 microns accuracy with semi-professional 3D printers like the Ultimaker S5 and Raise3D E2. It is possible to recycle old ortho models through filament extrusion machines (for example: 3DEVO) to achieve almost zero production cost and ecological production [86].

Nanometric particles are emitted during ABS 3D printing process and are harmful if inhaled. To avoid the harmful inhalation of these particles, practitioners who want to integrate this technology in their practice area should use a fully enclosed 3D printing room equipped with a fume extractor-ultrafine particle emissions from desktop 3D printers [87]. Adding adherent agents on the printing bed is strongly recommended to limit the warping (Detachment of the part from the plate during printing) of the ABS [86].

Generally, there is no post-processing for FDM 3D printed dental models as they are generally horizontally printed and do not need any supports or printing platform. Despite being slow, this technology requires the minimum intervention from the operator because after detaching the model from the printing bed, models are prompt for thermoforming process.

In the aligner-manufacturing context, biocompatibility resin is not mandatory except in direct 3D printing aligners that will emerge soon. However, according to other authors, the Dental LT could be subject to an overall thickness inaccuracy compared to the designed file, leading to undesired movements [88]. In addition, 3D printing orientation and post-processing conditions; (exposure time to UV light and heat) could impact mechanical properties and biocompatibility of Dental LT resin [53, 89]. Further studies both in vitro and in vivo are needed based on these claims to test this resin and other direct aligner printable resins [90].

With the evolution of materials, the direct printing of aligners will take over the thermoforming process, save a considerable amount of models resin, streamline production, and reduce costs [91].

#### **4.5 Thermoforming aligners**

#### *4.5.1 Influence of thermoforming*

Ruy et al. examined the impact of thermoforming on the physical and mechanical properties of various thermoplastic materials for clear aligners (Duran, Essix A+, Essix ACE, and eCligner). They observed that the optical transparency, the tensile force, and the elastic modulus of the aligner materials decline after the thermoforming process, while water absorption was increased [92].

Moreover, they recommended evaluating these materials' durability after thermoforming to characterize their properties for their clinical application [92]. From a clinical perspective, the authors also proposed choosing the polymers depending on the treatment required, as some of them show a significant decrease in flexural strength after thermoforming and exhibit permanent deformation during treatment. On the other side, the application of large forces to the teeth can lead to absorption of the apical root [92].

Kwon et al. [51] assessed the force delivery properties of thermoplastic orthodontic materials. They found that the forces delivered by thin materials were more significant than those delivered by thick materials of the same brand [92].

#### *4.5.2 Esthetic appearance*

Transparency is evaluated to investigate the esthetic aspect of the materials. The transparency of materials decreased with an increase in their thickness. In addition, with decreased thickness after thermoforming, the transparency also decreased, which can be explained by the structural deformation of thermoplastic materials resulting in decreased transparency. Nevertheless, this transparency change did not compromise the esthetic appearance of clear aligners [92].

Many studies evaluate the stability of the materials after their average use of two weeks through the colorimetric alterations of aligners [93]. Bernard et al. affirm that there are foods that stain more than others (above all black tea) and that the Invisalign aligners (TPU) were more prone to pigmentation than the ClearCorrect (PU) or the Minor Tooth Movement devices (PET-G) after exposure to coffee or red wine. Black tea caused important stains on the surface of the three tested brands [93, 94].

#### *4.5.3 Water absorption*

Water absorption can negatively influence the mechanical properties of polymers leading to irreversible deterioration because water absorption is often appended to swelling and, thus, a deterioration of the polymers [95, 96]. Besides the deterioration effect, the swelling also leads to dimensional variations of the mouth devices, which affects the orthodontic forces [96]. Therefore, an ideal thermoplastic material for a clear aligner should have a low water absorption [54].

Tamburino et al. investigated the properties of materials for the thermoforming production of aligners. The materials used in their study were: Duran® (PETG, Sheu dental GmbH), Biolon (PETG, Dreve Dentamid GmbH) and Zendura®

(PU, Zendura Dental). Artificial saliva was used as an aging agent at a temperature of 37°C for 7 days [97]. The liquid absorption of Duran material is only almost half of the Zendura one. In addition to higher water uptake, the authors observed a decline of the mechanical properties of the Zendura that can be related to the mechanism of intramolecular bond destruction by water molecules [97].

Ryokawa et al. [8] reported that water absorption by both PETG and copolyester increased to 0.8 wt% in their 2-week experiment. In addition, water absorption by PETG differed depending on the type of thermoplastic material [55]. Zhang et al. [93] reported that water absorption increased when polyurethane was added to PETG during the development of new thermoplastic material for thermoformed aligners [92].

#### *4.5.4 Mechanical properties*

Tamburino et al. investigated the mechanical properties of the aligner materials Duran, Biolon, and Zendura in the as-delivered state, after thermoforming, and after storage in artificial saliva [97]. The authors found that the tensile yield stress of the Duran and Biolon materials only slightly changed after thermoforming (9% increase for Duran, 6% decrease for Biolon), while it decreased by one-third for the Zendura [54]. After exposure to artificial saliva, the tensile yield stress of the Duran material decrease back to it as-supplied strength, while the tensile yield stress of Biolon and Zendura materials slightly increase (to −3% respectively to −28%). Based on their finding, these authors propose to select a material for orthodontic devices after characterizing its mechanical properties after the corresponding manufacturing process and storage test in an intraoral simulation environment [54].

#### *4.5.5 Elastic modulus*

A higher elastic modulus is beneficial for aligners as it increases the force delivery capacity of the aligner under constant strain [98, 99]. Plus, materials with a higher elastic modulus can produce the same forces from thinner thickness [99]. The elastic modulus is proportional to the material stiffness. In their study [97], Tamburino et al. also examined the elastic modulus of the aligner materials Duran, Biolon, and Zendura in the as-delivered state, after thermoforming and after storage in artificial saliva. The elastic modulus of the Duran and Zendura materials increased by 11% respectively 17% after thermoforming, while the one of the Biolon material falls by 7%. Looking at the elastic modulus after artificial saliva exposure of the materials shows different behavior [100]. The elastic modulus of Biolon and Zendura material is relatively stable, while a significant decrease was observed for Duran. This decrease can be explained by water uptake happening during the storage in artificial saliva fluid [54].

#### **5. Conclusions**

Practice owners need to invest in material resources, but they also need to invest in education to help their team implement homemade aligner workflow. While 3D printing aligners in-house require that practices invest time and money, eliminating lab fees and the ability to provide same-day high-quality, consistent services justifies the investment by increasing profit margins, decreasing treatment timelines, and

improving patient satisfaction. In-house production of aligners is the best option for practices that want more profitable and faster service. It just requires flexibility and an openness to learning new workflows that will carry the practice forward.

### **Conflict of interest**

The authors declare no conflict of interest.

### **Author details**

Dalal Elmoutawakkil\* and Nabil Hacib Independent Researchers

\*Address all correspondence to: dr.elmoutawakkil@gmail.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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[80] Macchi, A.; Carrafiello, G.; Cacciafesta, V.; and Norcini, A.: Threedimensional digital modeling and setup, Am. J. Orthod. 129:605-610, 2006.

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#### **Chapter 8**

## Surgical Digitally Guided Planning for the Mini-Screw Assisted Rapid Palatal Expansion (MARPE) and Suture Perforation: MARPE Guide

*Cristiane Barros André, Bruno de Paula Machado Pasqua, José Rino Neto and Fábio Dupart Nascimento*

#### **Abstract**

The surgical planning digitally guided for the mini-screw assisted rapid palatal expansion (MARPE) technique consists of a three-dimensional positioning of MARPE and its mini-implants by a nasomaxillary anatomic evaluation. This technique also includes the simulation of the perforation areas on the midpalatal and transpalatal sutures. This type of planning is performed by superimposing the patients' files (STL and DICOM). Correct positioning without colliding with the lateral tissues of the palate and the bicortical positioning of each mini-implant are important components of the case study. The MARPE device permits individualization of the height of the mini-implant rings in each region. To avoid incorrect insertion of the drill, the location of the midpalatal and transpalatal sutures was determined using digital planning. A positioning that avoids contact with important structures, such as the nasopalatine canal, while permitting bicortical drilling of the sutures is recommended. Then, a guide that reproduces MARPE positioning and another guide that reproduces the perforations are fabricated, providing exact reproducibility as performed virtually.

**Keywords:** orthodontic anchorage procedures, palatal expansion technique, skeletal anchorage, cone-beam computed tomography

#### **1. Introduction**

The mini-screw assisted rapid palatal expansion (MARPE) technique comprises rapid maxillary expansion (RME) in adult patients using a mini-implant-supported device, permitting orthopedic expansion with few side effects [1–3]. This procedure is well accepted by patients owing to its low cost and less invasiveness compared to surgically assisted RME [4].

To perform the MARPE technique, cone-beam computed tomography (CBCT) is essential as it allows a complete anatomical evaluation of the nasomaxillary complex region where the expander screw and mini-implants are placed [5]. Moreover, by assessing bone thickness from CBCT images, the amount of bicortical mini-implant thread insertion can be measured [6]. This is critical as the bicortical positioning of mini-implants permits wider distribution of expansion forces, avoiding the concentration of stress areas around the mini-implants, providing better skeletal effects [7, 8].

Therefore, an evaluation protocol using CBCT [9] was introduced to select the ideal region for the mini-implants. However, this technique does not consider all anatomical variations in each patient, and the lack of a guide that reproduces this planning in the patient's oral cavity is a matter of concern. Thus, André [6] described a technique that performs a careful evaluation of important anatomical structures, such as nasal septum deviation, maxillary sinus extension, the sinuosity of the sutures evaluated, and location of the incisive foramen and transpalatal suture. Although the planning is more comprehensive, there is still a lack of guidance for reproducibility in the oral cavity.

With the advent of digital flow technology, a new technique was introduced, not only for planning, but also to reproduce the virtual placement of the entire appliance, providing accuracy, reproducibility, and safety to the MARPE technique. This technique, called MARPE Guide, consists of a three-dimensional digital placement, which comprises the positioning of the mini-implants specific for MARPE, as well as the expander screw itself. To overcome the shortcomings of the previously described planning techniques, a guide is generated that reproduces this digital placement [5, 10–15].

By superimposing the intraoral digital scanning file (STL) and CBCT (DICOM), it is possible to choose the correct location accurately and safely for the placement of the mini-implants and expander screws. Additionally, the structures of the nasomaxillary complex in a three-dimensional form are individually evaluated (**Figure 1**). Thus, the

#### **Figure 1.**

*The image of this case shows a MARPE complex positioning between the incisive foramen and transpalatal suture, not extending to the soft palate area. The midpalatal suture is observed in green, transpalatal suture is represented in blue, nasoapalatine duct is visualized in red, and mini-implants are presented in orange.*

#### *Surgical Digitally Guided Planning for the Mini-Screw Assisted Rapid Palatal Expansion… DOI: http://dx.doi.org/10.5772/intechopen.100226*

chances of failure are reduced using the MARPE guide, as it is possible to select the size and amount of mini-implant thread insertion of each mini-implant. Moreover, it permits accurate prediction of the mini-implant trajectory. Even in the most complex cases of anatomical variations, injury to important anatomical structures is avoided. This increases the safety of the technique, as well as the chances of success. For patients with severe transverse maxillary deficiency, increased palatal depth, or severe asymmetry, the MARPE Guide is associated with a MAEPE model called MARPE EX, developed in 2017 by Peclab (Peclab®, Belo Horizonte, Brazil). This device has an individualized mini-implant ring height, which permits positioning of the MARPE complex without colliding with the lateral palatal soft tissues. Height adjustment is performed according to the anatomy of each patient's palate, even in severe cases of transverse deficiency and maxillary asymmetry [16]. Among the physical characteristics of MARPE EX, the increased distance between the anterior and posterior mini-implant rings is observed, in search of a larger support area for the mini-implants. Regarding the tension exerted by this device on the skull, less tension on the supporting teeth was observed, as well as a wider tension distribution over the entire lateral lamina of the pterygoid process [16].

However, in complex cases of varying thickness of the maxilla and cases of advanced maturation of the midpalatal suture, even with virtual planning, these cases are limited. The increased interdigitation of the midpalatal suture is a strong resistance during RME. Therefore, Suzuki et al. [17] proposed the performance of corticoperforations in the region of the midpalatal suture during RME, to reduce the resistance by weakening the midpalatal suture, relying on the phenomenon of regional acceleration (corticoperforations). Although it appears to be an effective method, it is not a precise procedure as drilling is performed based on the palatal raphe (soft tissue), which does not always coincide with the midpalatal suture itself. Therefore, the Corticoperfuration Guide (Cortex guide) provides the most effective weakening of this suture, enabling guided drilling, performed precisely following its path, that may be sinuous, rectilinear, or curved. Another important and unmentioned factor is perforation along the transpalatal suture. Perforation in the more posterior region is of utmost importance, as the maxillary posterior region demonstrates greater resistance during RME [16, 18].

By adding this new technique of digital planning with the advantages of MARPE EX, treatments are anticipated to become safer, more accurate; thus, expanding the possibility of treatment for patients with severe transverse deficiency, maxillary asymmetry, and variations in the maxillary thickness. Thus, this book chapter proposes the presentation of the virtual MARPE placement as well as the guided corticoperforation technique (Cortex Guide).

#### **2. Materials and methods**

#### **2.1 Anatomical evaluation and virtual placement**

The analysis of the maturation of facial sutures is performed through the file in DICOM format. For the midpalatal suture, the analysis follows the method proposed by Angelieri et al. [19], where the operator must be calibrated to perform this technique with reproducibility [20]. This technique is critical as an auxiliary diagnostic method, as it provides information regarding the challenge and resistance during the separation of the midpalatal suture according to its maturation stage. Next, another

suture, the zygomaticomaxillary suture, involved in RME is classified (established by Angelieri et al. [21]). This evaluation is performed by accessing the sagittal and coronal sections of the CT scan, and the suture is evaluated in a stage from A to E, where A is the earliest stage of maturation and E is the most advanced stage. The pterygopalatine suture was also evaluated, although there is no consolidated classification in the literature. When it is in an advanced stage of maturation, this suture is quite homogeneous compared to neighboring bone tissues, which is alarming to orthodontists as it suggests greater resistance to RME. Next, the location and shape of the transpalatal suture are analyzed. It is ideal to perform virtual placement of the mini-implants anteriorly to this suture (**Figure 1**); however, in many cases, owing to the positioning of the incisive foramen and reduced anteroposterior dimension of the maxilla, the most anterior virtual placement is not always feasible [5] (**Figure 2**).

In addition to the maturation stage, it is critical to verify the shape and aspect of these sutures as they can be straight, sinuous, or curvilinear. This can occur both horizontally and vertically (observed in coronal and axial sections). This verification is of total importance to perform the virtual placement without touching the sutures (**Figure 3**).

After suture analysis, the three-dimensional files (STL and DICOM, **Figure 4**) were superimposed [10–15]. As described in the literature [5], both files should be of good quality because they provide essential information, such as hard and soft tissue thickness, anatomical variations, and location and trajectory of the mini-implants. Failure to take this information into account may lead to complications and failure of the MARPE technique.

This procedure can be performed in any software that accepts the superimposition of the STL and CBCT files and also permits the importation of mini-implants and the MARPE expander screw-in STL format. This combination allows a three-dimensional

#### **Figure 2.**

*In this case, the posterior mini-implants could not be placed anterior to the transpalatal suture due to the reduced sagittal size of the maxilla, and the variation in shape and size of the incisive foramen. The midpalatal suture is observed in green, the transpalatal suture is observed in blue, the nasopalatine duct is visualized in red, and mini-implants are presented in red.*

*Surgical Digitally Guided Planning for the Mini-Screw Assisted Rapid Palatal Expansion… DOI: http://dx.doi.org/10.5772/intechopen.100226*

**Figure 3.** *Anterior mini-implants bordering a sinuous suture, without touching it.*

#### **Figure 4.**

*Superimposition of the CBCT file (DICOM) and the digital file reproducing the teeth and the soft tissue of the upper dental arch (STL).*

evaluation of the maxilla; therefore, the orthodontist can evaluate important aspects for the digital positioning of the MARPE device, as it permits simulation of the positioning in different regions.

The ideal region for the mini-implant insertion should contain sufficient bone to perform the expansion, advocating a bicortical positioning [7], as observed in **Figure 5A**. In cases of reduced bone thickness along the maxilla, it is currently feasible to add two more mini-implants to the device [22], as depicted in **Figure 5B**.

After the initial evaluation of the region with the most appropriate bone thickness, a complete anatomical evaluation is initiated, where the location of the midpalatal suture, transpalatal suture, and incisive foramen are first considered.

#### **Figure 5.**

*(A) Bicortical insertion of mini-implants in a patient with good bone thickness. (B) Reduced bone thickness along the entire maxilla, requiring the placement of two additional mini-implants.*

These three anatomical components plus adequate bone thickness are the key factors for positioning the EX expander screw and the four or six mini-implants. However, it is critical to observe the distance of this complex from the lateral mucosa to maintain soft tissue integrity during RME.

Anatomical variations are common and must be thoroughly observed when planning the MARPE digital placement such as deviated septum (**Figure 6**), maxillary sinus extension (**Figure 7**), impacted teeth (**Figure 8**), maxillary torus (**Figure 9**), palate depth, and maxillary reduced shape and size (**Figure 7**). For patients with V-shaped palate in the anterior region the digital planning requires a posterior displacement of the appliance for the mini-implant support rings to be well adapted, bicortical, and have an adequate amount of excess mini-implant thread.

Digital placement with MARPE EX permits not only to individualize the height of the mini-implant rings in each region (respecting the anatomy of each individual and a safe distance from the mucosa) but also to measure and place different mini-implant lengths, always preconizing a bicortical positioning [2, 14]. This positioning is verified in each section of the tomography (**Figure 10**) and in the three-dimensional reconstruction.

For more complex cases, such as bone volume variation, advanced age and advanced skeletal maturation, guided corticoperforation is performed. This is done following the anatomy of the midpalatal suture and the transpalatal suture. In some *Surgical Digitally Guided Planning for the Mini-Screw Assisted Rapid Palatal Expansion… DOI: http://dx.doi.org/10.5772/intechopen.100226*

**Figure 6.** *Nasal septum deviation to the left side of the patient.*

**Figure 7.** *Alveolar extension of the maxillary sinus and severe transverse deficiency of the maxilla.*

patients, the midpalatal suture is inclined and/or sinuous in the coronal direction. We do not use the soft tissue (palatine raphe) as a reference to locate the midpalatal suture, because sometimes they are not coincident (**Figure 11**).

For the simulation of the drilling, we used digital files with a cylindrical format that reproduces the thickness of the widest portion of the drill used. These cylinders are positioned in such a way that they reach bicortical positioning and maintain a uniform distance between them when possible. Each perforation is analyzed in the three-dimensional simulation and checked in each tomography section to ensure that the perforations are bicortical and if there is no collision with important structures such as the nasopalatine duct.

**Figure 8.** *Impacted tooth in the region near the anterior mini-implant installation placement site.*

#### **Figure 9.**

*(A) Sagittal section demonstrating the presence of the palatal torus. (B) Three-dimensional reconstruction of the maxilla illustrating the palatine torus.*

When installing drills, we always recommend an inclination that can be performed in the mouth. In this way, we inclined the drills between 10° and 30° with respect to the occlusal plane. The drills are performed precisely following the direction of the suture, either rectilinear or sinuous (**Figure 12**).

It is advisable to maintain a safe distance between the corticoperforation and the region of the MARPE mini-implants as when trying to weaken the suture, we should not weaken the region surrounding the mini-implants, as the tension exerted in this region is high [16] and close perforations can weaken this region, which requires a large bone supply (**Figure 12C**). For this reason, MARPE Guide and Cortex Guide planning should be performed together (**Figure 13**).

After this careful process, it is time to create the guides, which will reproduce both the digital positioning in the prototyped model (MARPE Guide), providing reproducibility to the appliance manufacturing, exactly as done virtually, and the *Surgical Digitally Guided Planning for the Mini-Screw Assisted Rapid Palatal Expansion… DOI: http://dx.doi.org/10.5772/intechopen.100226*

#### **Figure 10.**

*(A) Coronal section, illustrating the digital placement of MARPE, even in cases of severe atresia and asymmetry. (B) Sagittal section, showing the bicortical position of the mini-implants, respecting a discrete distance from the mucosa to avoid collision during expansion. (C) Placement of the mini-implants, respecting the midpalatal suture, as well as the transpalatal suture and the incisive foramen.*

#### **Figure 11.**

*Palatal raphe and midpalatal suture are not coincident. If the corticoperfortaion is not performed in a guided way. It can lead to an error during the procedure.*

corticoperforation guide (Cortex Guide), which reproduces the digital perforation of each point created, with angulation and insertion limits.

#### **2.2 Presentation of a complete planning**

Below, we present a complete MARPE Guide and Cortex Guide planning, following all the parameters discussed above (**Figures 14**–**19**).

Subsequently, the MARPE guide and cortex guide are made as detailed above.

#### **Figure 12.**

*(A) Perforations performed with bicortical positioning. (B) Note that the positioning respects the suture inclination in both coronal and axial directions. (C) The perforations are performed preserving bone tissue around the MARPE mini-implants.*

#### **Figure 13.**

*In the top image we see the simulations of the corticoperforations that would be ideal for this case. However, in the bottom image we note that the perforation in yellow is very close to the posterior mini-implants, which could compromise the technique.*

*Surgical Digitally Guided Planning for the Mini-Screw Assisted Rapid Palatal Expansion… DOI: http://dx.doi.org/10.5772/intechopen.100226*

#### **Figure 14.**

*(A) Virtual corticoperforation drills installed in the midpalatal suture and transpalatal suture. (B) Coronal view (transpalatal suture). (C) Lateral view in sagittal section (midpalatal suture).*

#### **Figure 15.**

*Sagittal section of the tomography – left side. MARPE installed respecting the bicortical positioning and with the distance of the mini-implant rings from the mucosa.*

#### **2.3 MARPE guide**

For the virtual placement of MARPE, a concern about injuries caused to the soft tissue due to the contact of the mini-implant rings is resolved with the digital placement (with the MARPE EX and MARPE guide). It has an internal stop that accommodates each mini-implant support ring (**Figure 20**), and its height is established according to the individual's anatomy. It is important to keep the expander screw body as horizontal as possible (**Figure 21**) in the coronal section of the tomography without touching the lateral mucosa.

**Figure 16.** *Sagittal section of the CT scan – left side.*

#### **Figure 17.**

*3D reconstruction of the CT scan illustrating a safe distance of the mini-implants from the transpalatal suture. Note the bicortical positioning of the four mini-implants.*

We should be aware of the occlusal plane and nasal floor inclination, which, when altered, can cause asymmetry in the patient. Thus, a stop that holds the expander screw body in position is necessary (**Figure 21**). This guide design is inserted into the patient's STL file, so they are printed at once, which reduces the chances of error by overlapping the guide to the patient's model, in addition to saving printed material.

#### **2.4 Corticoperforation guide**

The corticoperforation guide, requires a retentive design (that embraces the posterior teeth), as it will be adapted in the mouth, as a positioner and vertical limiter of each perforation (**Figure 22**) and must remain stable during the process.

*Surgical Digitally Guided Planning for the Mini-Screw Assisted Rapid Palatal Expansion… DOI: http://dx.doi.org/10.5772/intechopen.100226*

**Figure 18.** *Occlusal view of the virtually installed MARPE, preserving the lateral tissue and soft palate.*

#### **Figure 19.**

*MARPE guide and cortex guide in the same image to check if there is any collision between the digital plans, such as drilling too close to a mini-implant.*

#### **2.5 Laboratory phase – printing the MARPE guide and cortex guide**

**155** Finally, it is possible to fabricate MARPE with the reproducibility of each of the precautions taken during the virtual placement. The MARPE EX is made on the guide

#### **Figure 20.**

*In green we see the MARPE guide, which accommodates the adjustable mini-implant rings of the MARPE EX, to reproduce the positioning performed during the virtual placement.*

#### **Figure 21.**

*Digital horizontal support (gray) that are responsible for keeping the MARPE appliance at the planned height during the virtual placement, so that the expander screw does not touch the soft tissue and mainly, remains as horizontal as possible, preventing it from causing any asymmetry in the patient.*

template (**Figure 23**), where its mini-implant rings fit exactly inside each small guide, which eliminates transfer errors. It also determines the height and inclination of the expander screw, preventing asymmetries during expansion. Using laser welding, it is possible to weld the MARPE EX to the bands without damaging the prototype model or causing any swelling of the metal of the MARPE EX, owing to the heat of the formerly used silver-based welds.

After this phase, the appliance is polished, and it is ready to reproduce with accuracy the digital planning in the oral cavity. Note that the guide is not used in the oral cavity; it serves as a guide for fabricating the appliance. In the oral cavity the guide for cementation is the bands on the first permanent molars.

To reproduce the corticoperforations in the oral cavity, after designing the guide, it is critical to make an impression of the guide in biocompatible resin (**Figure 24**), and this protocol must be followed even if the guide remains in the oral cavity for some time.

*Surgical Digitally Guided Planning for the Mini-Screw Assisted Rapid Palatal Expansion… DOI: http://dx.doi.org/10.5772/intechopen.100226*

#### **Figure 22.**

*3D planning of the corticoperforation guide, which reproduces the angulation of each perforation, following the midpalatal suture and transpalatal suture. This guide will also be the limiter for the drill cutter, as soon as it touches the guide, the clinician will know that it has reached the nasal floor cortical.*

**Figure 23.** *MARPE device built over the printed MARPE guide template.*

**Figure 24.** *Cortex guide printed in biocompatible resin.*

#### **3. Discussion**

For a very short time, the MARPE technique was performed without CT scanning. This type of treatment required three-dimensional (3D) planning since the maxilla contains important structures that must be preserved, both for the patient's safety and success of the technique. The first safety protocols were based on bone and mucosa thickness measurements in the region of first premolars, second premolars, first molars, and second molars [6, 9]. Despite providing important information, these protocols did not show the exact trajectory of MARPE mini-implants. Moreover, the standardization of the patient's head position and evaluation of the tomography sections could not be faithfully reproduced in the oral cavity. This necessitated the creation of digital positioning guides [10–13]. In cases of severe transverse deficiency of the maxilla or asymmetry [23], devices such as the MARPE maxillary skeletal expansion (MARPE MSE) or MARPE SL cannot be indicated because the expander screw does not fit in the palate (**Figure 25**).

Thus, the present study proposes the development of a guide for planning the MARPE technique using MARPE EX [5, 16], to evaluate the capacity of this guide in performing an ideal positioning of the MARPE, prioritizing the adaptation of the mini-implant rings, and respecting the individual anatomy of the patient's palate. The distance between the mini-implants is higher in MARPE EX than that of the other models of MARPE, which, according to a previous study [16], was favorable for better results. Another advantage is that MARPE EX accepts this guide model, where we can place the mini-implant rings away from the palate at customized heights according to the patient's anatomy. This distance from the palate in its closest region is approximately 0.2 mm, both towards the palate (vertical) and towards the lateral mucosa (horizontal) [5]. Therefore, no ring juxtaposed should be left juxtaposed to the tissues.

The EX model was also chosen because it demonstrated less tension in the teeth and mini-implants during RME [16], and it presented more tension, with wide distribution, in the lateral lamina of the pterygoid process [16]. According to Brunetto et al. [18], the lateral lamina of the pterygoid process offers the greatest resistance during

#### **Figure 25.**

*Model of MARPE without adjustable mini-implant rings. This figure shows that without adjustable mini-implant rings the MARPE does not fit patients with severe transverse disability.*

#### *Surgical Digitally Guided Planning for the Mini-Screw Assisted Rapid Palatal Expansion… DOI: http://dx.doi.org/10.5772/intechopen.100226*

RME. Recent clinical studies have shown that bicortical directly influence treatment with MARPE [8, 24], particularly in patients with advanced maturation stage sutures as the bicortical positioning of mini-implants permits the separation of even the most posterior sutures, such as the lateral lamina from the medial lamina of the pterygoid process [8]. Thus, this demonstrates the importance of a guide that correctly reproduces this bicorticality in the patient, such as the MARPE Guide. It is also important to recognize the importance of the bands, which, in addition to distributing stress, are responsible for transferring the guide model to the oral cavity.

The three initial parameters for placing an MARPE must be discussed. First, it should not touch the midpalatal and transpalatal sutures; second, it should be distant from the incisive foramen; and third, preferably anterior to the transpalatal suture, avoiding collision/perforation of the mini-implants with sutures. We should not touch the incisive foramen to avoid contact with the nerve of the incisive canal, which can result in anterior maxillary paresthesia.

The location of the transpalatal suture does not always coincide with the soft palate; however, if it does, we avoid placing it posteriorly to the transpalatal suture, so that the mini-implants are not inserted in a region of free mucosa, with more chances of inflammation, great difficulty in cleaning, and loss of the mini-implants. However, in some cases of the reduced anteroposterior distance of the maxilla, this becomes unavoidable. The patient's anatomical variation should be considered as it influences the results, such as mini-implants placed in the nasal septum in a patient with palate asymmetry [25] and resulting in a unilateral opening [25]. This highlights the importance of using 3D planning, where insertion in the septum can be easily avoided and bilateral opening can be achieved, eliminating side effects.

While dealing with anatomical variations, it is common to find patients with variations in maxillary sinus extension (**Figure 7**). If the mini-implants are inserted into the sinus cavity, in addition to creating an oral-sinus communication that can generate pain, inflammation, and discomfort, this is a region without trabecular bone, that is, a region that lacks bone volume. Therefore, mini-implants cannot withstand the tension exerted during maxillary expansion [16].

Corticoperforation can be indicated when a torus palatine (**Figure 9**) is detected as it has the potential to decrease the chances of success. Guided corticoperforation, besides allowing perforation of the transpalatal suture, provides accuracy due to the angulation of the guide, which was determined in the virtual simulation, leaving the patient free of perforations outside the suture. Corticoperforations oriented by the palatine raphe may cause asymmetric fractures or even case failure because if performed too close to the mini-implant placement site, they reduce the bone volume required for the tension exerted in the mini-implant region [16]. Another risk of not virtually simulating the corticoperforations and creating a stop guide is to over drill the nasal cavity floor, causing pain to the patient and a bucco-nasal communication, which may lead to sinusitis; in case of inflammation, possibly worsening to bone necrosis or osteomyelitis.

#### **4. Conclusions**

The two-dimensional plans do not predict the mini-implant trajectory, and the choice of the mini-implant can be highly subjective and susceptible to errors. The use of the MARPE Guide has already presented interesting results in the literature. By combining the benefits of the MARPE Guide with the MARPE EX and the use of the

Cortex Guide, virtual placement may be performed in a patient with palate asymmetry, bone volume variation, and advanced stage of midpalatal suture classification. This results in tension in the lateral lamina considering the patient's anatomy. Clinical studies are needed to evaluate the results of this new technique in a considerable number of patients.

### **Conflict of interest**

The authors declare no conflict of interest.

#### **Author details**

Cristiane Barros André1 \*, Bruno de Paula Machado Pasqua2 , José Rino Neto2 and Fábio Dupart Nascimento1

1 Technology Research Center, University of Mogi das Cruzes, Mogi das Cruzes, Brazil

2 School of Orthodontics, University of São Paulo, São Paulo, Brazil

\*Address all correspondence to: kika@kikaortodontia.com.br

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Surgical Digitally Guided Planning for the Mini-Screw Assisted Rapid Palatal Expansion… DOI: http://dx.doi.org/10.5772/intechopen.100226*

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[1] Lee KJ, Park YC, Park JY, Hwang WS. Mini-implants-assisted nonsurgical palatal expansion before orthognathic surgery for a patient with severe mandibular prognathism. Am J Orthod Dentofacial Orthop 2010;(138): 830-839.

[2] Cantarella D, Dominguez-Mompell R, Moschik C, et al. Midfacial changes in the coronal plane induced by micro-implantsupported skeletal expander, studied with cone-beam computed tomography images. Am J Orthod Dentofac Orthop 2018;154(3):337-345.

[3] Celenk-Koca T, Erdinc AE, Hazar S, Harris L, English JD, Akyalcin S. Evaluation of mini-implants-supported rapid maxillary expansion in adolescents: A prospective randomized clinical trial. Angle Orthod 2018;(88):702-709.

[4] Stuart DA, Wiltshire WA. Rapid palatal expansion in the young adult: Time for a paradigm shift? J Can Dent Assoc 2003;(69):374-377.

[5] André CB. MARPE guide: from consolidation to technique evolution. Clin Orthod 2020;19(5):00-00.

[6] André CB. Análise tomográfica para técnica Marpe. Rev Clin Ortod Dental Press 2018;17(4):50-53.

[7] Lee RJ, Moon W, Hong C. Effects of monocortical and bicortical microimplant anchorage on bone-borne palatal expansion using finite element analysis. Am J Orthod Dentofac Orthop 2017;151(5):887-897.

[8] Li N, Sun W, Li Q, Dong W, Martin D, Guo J. Skeletal effects of monocortical and bicortical mini-implant anchorage on maxillary expansion using cone-beam computed tomography in young adults. Am J Orthod Dentofacial Orthop 2020;157(5):651-661.

[9] Nojima LI, Nojima M, Cunha ACD, Guss NO, Sant'Anna EF. Mini-implant selection protocol applied to MARPE. Dental Press J Orthod 2018;23(5):93-101.

[10] Maino BG, Paoletto E, Lombardo L, Siciliani G. A three-dimensional digital insertion guide for palatal micro-implant placement. J Clin Orthod 2016;50(1): 12-22.

[11] De Gabriele O, Dallatana G, Riva R, Vasudavan S, Wilmes B. The easy driver for placement of palatal micro-implants and a maxillary expander in a single appointment. J Clin Orthod 2017;51(11): 728-737.

[12] André CB. Instalação virtual dos aparelhos: para que serve? Rev Clin Ortod Dental Press 2019;18(5):52-58.

[13] Lombardo L, Occhiuto G, Paoletto E, Maino BG, SIiciliani G. Class II treatment by palatal mini-implants-system appliance: A case report. Angle Orthod 2019;90(2):305-313.

[14] Antonino Lo Giudice, Vincenzo Quinzi, Vincenzo Ronsivalle, Stefano Martina, Orazio Bennici, and Gaetano Isola. Description of a digital work-flow for CBCT-guided construction of microimplant supported maxillary skeletal expander. Materials 2020(13):1815.

[15] Cantarella D, Savio G, Grigolato L, Zanata P, Berveglieri C, Lo Giudice A, Isola G, Del Fabbro M, Moon W. A new methodology for the digital planning of micro-implant-supported maxillary skeletal expansion. Med. Devices Evid. Res. 2020;13:93-106.

[16] André CB, Rino-Neto J, Iared W, et al. Stress distribution and displacement of three different types of micro-implant assisted rapid maxillary expansion (MARME): A three-dimensional finite element study. Prog Orthod 2021; 22:20.

[17] Suzuki SS, Garcez AS, Reese PO, Suzuki H, Ribeiro MS, Moon W. Effects of corticopuncture (CP) and low-level laser therapy (LLLT) on the rate of tooth movement and root resorption in rats using micro-CT evaluation. Laser Med Sci 2018;33(4):811-821.

[18] Brunetto DP, Sant'Anna EF, Machado AW, Moon W. Non-surgical treatment of transverse deficiency in adults using microimplant-assisted rapid palatal expansion (MARPE). Dental Press J Orthod 2017;22(1):110-125.

[19] Angelieri F, Franchi L, Cevidanes LHS, Toyama-Hino C, Nguyen T, McNamara JA Jr. Zygomaticomaxillary suture maturation: A predictor of maxillary protraction? Part I: Classification method. Orthod Craniofac Res 2017;(20):85-94.

[20] Barbosa NMV, Castro AN, Conti F, Capelozza-Filho L, Almeida-Pedrin RR, Cardoso MA. Reliability and reproducibility of the method of assessment of midpalatal suture maturation: A tomographic study. Angle Orthod 2019;89(1):71-77.

[21] Angelieri F, Franchi L, Cevidanes LHS, Hino CT, Nguyen T, McNamara Jr JA. Zygomaticomaxillary suture maturation: A predictor of maxillary protraction? Part I – A classification method. Orthod Craniofac Res 2017;20(2):85-94.

[22] Cury SEN, Mondelli AL, André CB, Iared W, Guerra JGP, Rovira J, Berni L. Protocolo diferencial para a técnica MARPE em pacientes com

variação no volume ósseo do palato. Rev Clín Ortod Dental Press 2019;18(4): 116-129.

[23] Andrade T. MARPE: uma alternativa não cirúrgica para o manejo ortopédico da maxila – parte 2. Rev Clín Ortod Dental Press 2019;17(6):24-41.

[24] Moon HW, Kim, MJ, Ahn, HW, Kim, SJ, Kim, SH, Chung, KR, Nelson, G. Molar inclination and surrounding alveolar bone change relative to the design of bone-borne maxillary expanders: A CBCT study. Angle Orthod 2020;90(1):13-22.

[25] Santos AM, Miranda F, Rocha AD, Cruz AP, Naveda R, Garib D. Miniimplants-assisted rapid palatal expansion in adult patient with severe maxillary constriction: Case report. Clin Orthod 2021;19(6):101-112.

### Section 3

## Orthodontic Techniques and Trends

#### **Chapter 9**

## Understanding Orthodontic Bone Screws

*Agharsh Chandrasekaran, H.P. Naga Deepti and Harshavardhan Kidiyoor*

> *"Progress is impossible without change, and those who cannot change their minds cannot change anything."*

> > *—George Bernard Shaw*

#### **Abstract**

The field of orthodontia has been witnessing numerous reforms in terms of treatment modalities through the years, under which the concept of absolute anchorage employing mini-implants can be well subsumed. The usage of orthodontic bone screws has witnessed growing popularity and has been deemed to revitalize the management of complex malocclusions. Orthodontic bone screws are larger in diameter (2 mm) in comparison with the average mini-implant and are placed in areas of high bone mineral density like the infrazygomatic crest in the maxilla and the buccal shelf area in the mandible. Owing to a difference in size, they are placed away from the roots and hence, the term extra-radicular implants seem a befitting one. With an expansion of the envelope of discrepancy to skeletal anchorage, the employment of these bone screws in practice will have to be appraised further in terms of biological limits. Orthodontic bone screws have been successfully utilized as an absolute anchorage system in well-chosen cases, pushing the realm of treatment possibilities further ahead in the sands of time. This chapter aims to provide you with a narrative insight into the salient features of orthodontic bone screws starting right from its inception to its contemporary usage in practice.

**Keywords:** anchorage, orthodontic bone screws, extra-alveolar implants, infrazygomatic crest, buccal shelf

#### **1. Introduction**

A universally accepted scientific perspective, the best current explanation of a natural phenomenon, has been termed a paradigm. A paradigm can be thought of as the foundation upon which a scientific structure is erected, similar to laying brick upon brick of new findings and insights. As each newer paradigm replaces an older one, today's "truths" become tomorrow's myths. In orthodontics, at present, we are on the threshold of a paradigm shift that changes the fundamental conceptual underpinnings of orthodontics, and with it, the traditional emphasis on diagnosis and treatment planning.

The goal of any orthodontic treatment is to achieve desired tooth movement with the minimum number of undesirable side effects [1]. Strategies for anchorage control have been a major factor in achieving successful orthodontic treatment since the specialty began. With conventional orthodontics, it is almost impossible to achieve absolute intraoral anchorage. Recently, the use of skeletal anchorage has grown in popularity, especially in challenging situations [2].

The field of orthodontics has had a lot of landmarks in its evolution, but very few can match the clinical impact made by micro-implants and the recently introduced extra-radicular bone screws. Temporary anchorage devices have revolutionized the orthodontic field with their concept of absolute anchorage and have proved to be an adjunct in the hands of a clinician to gain control in handling complex malocclusions and clinical challenges.

It aids in the conversion of borderline surgical cases to cases that can be handled with bone screws in an equally effective way. The purpose of this review chapter is to offer to the reader, an insight into the depths of orthodontic bone screws from cradle to what has been explored till date, while touching upon integral aspects that might prove to be of use in both an academic and a clinical sense [3].

#### **2. History**

Creekmore and Eklund (1983) used a small-sized vitallium bone screw to depress the entire anterior maxillary dentition. The screw was inserted just below the anterior nasal spine. Ten days after placement, a light elastic thread was tied from the head of the screw to the archwire. The maxillary central incisors were intruded by about 6 mm. The bone screw did not move during treatment and was not mobile at the time of removal [4].

Shapiro and Kokich (1988) described the possibility of using dental implants for anchorage during orthodontic treatment. Melsen and co-workers (1998) introduced the use of zygomatic ligatures as anchorage in partially edentulous patients. Under local anesthesia, two holes were made in the superior portion of infrazygomatic crest. A double-twisted 0.012″ stainless steel wire was ligated between the two holes and inserted into the oral cavity. After surgery, nickel-titanium coil springs were attached from the zygomatic ligatures to the anterior fixed appliance for intrusion and retraction of maxillary incisors [5].

#### **3. Structure of an orthodontic bone screw**

Mindful of the fact that orthodontic bone screws have insertion points in areas with greater quantities of cortical bone, the regular mini-implant has been revamped with the following design features to form a bone screw (**Figure 1**) [2, 3]:


*Understanding Orthodontic Bone Screws DOI: http://dx.doi.org/10.5772/intechopen.100276*

#### **Figure 1.**

*Diagrammatic representation of orthodontic bone screw.*


#### **4. Material aspects of orthodontic bone screws**

Bone screws inserted in extra-alveolar areas are made up of either stainless steel or titanium alloys (Ti-6 AI-4 V). There has been a serious bone of contention over the material of choice. Pure surgical stainless steel has gained more popularity in being the preferred material of choice.

#### **4.1 Why stainless steel?**

The reason for stainless steel being the popular material of choice is attributed to the high placement torque that occurs when these screws are placed in areas of high bone density. This demands the requisite of a high fracture resistance, and stainless steel seems to be a befitting choice due to its high modulus of elasticity in comparison with titanium alloy. However, both materials seem to be acceptable materials with a comparable success rate [6].

A popular titanium alternative is the Peclab screw kit that was developed by Almeida [7] that has shown promising results and is inclusive in terms of the armamentarium that is required.

#### **5. Quantity and quality of bone at extra-alveolar sites**

The extra-alveolar sites of insertion correspond to D1 site as described by Misch [8], which comprises dense cortical bone of greater than 1250 HU.

According to Park [9], the cortical bone thickness and bone depth are as follows: Infrazygomatic crest region:


Buccal shelf region:


#### **5.1 Variability of bone thickness at different vertical facial heights**

The bone thickness also seemed to vary with different divergence patterns. Infrazygomatic crest region did not show any change with regard to the patient's vertical height. But the bone thickness at the buccal shelf region was found to be higher in short-faced individuals as compared to long-faced individuals [10]. Also, in comparison with the hyperdivergent counterparts, the buccal shelf has greater bone width and lesser bone height in hypodivergent individuals [11].

#### **5.2 Is an initial perforation required in self-drilling screws?**

In certain cases, an initial perforation with a clinical probe/spear tip is recommended even with a self-drilling bone screw to minimize the risk of fracture of the screw during placement, since it involves a considerable placement torque [9].

#### **6. Envelope of discrepancy**

The envelope of discrepancy is an expression of anteroposterior, vertical, and transverse in terms of the millimetric range of treatment possibilities. It gives us an estimate of tooth movement that can be deemed possible by purely orthodontics alone, orthodontic with dentofacial orthopedics, orthodontics with the employment of skeletal anchorage, and orthodontics with orthognathic surgery. Different colored zones connote the range of possibilities (**Figures 2**–**4**). The direction of movement in the diagrammatic illustration has been depicted by arrows. The different colors zones are as follows: 1) The pink zone denotes the envelope for orthodontics alone, 2) the yellow zone connotes orthodontics plus orthopedics, 3) the green zone shows skeletal anchorage, and 4) the blue zone any combination of the above with orthognathic surgery. The green zone has been depicted by a "fuzzy" area, as an indication of the paucity of reliable data available at this point to make any claims. The same drawback is why a figure depicting the mandibular transverse envelope does not exist at this juncture [12]. To sum up, the biological limits of the skeletal anchorage system in the management of severe malocclusions albeit proven useful in several case reports needs further research to arrive at a more definitive conclusion in the envelope.

*Understanding Orthodontic Bone Screws DOI: http://dx.doi.org/10.5772/intechopen.100276*

**Figure 2.** *Revised envelope of discrepency.*

**Figure 3.** *Revised envelope of discrepency.*

**Figure 4.** *Revised envelope of discrepency.*

### **7. Indications of orthodontic bone screws**

The indications of orthodontic bone screws [13]:


#### **8. Contraindications of orthodontic bone screws**

#### **8.1 Absolute contraindications**


#### **8.2 Relative contraindications**


#### **9. Concepts of placement of bone screws at different sites**

#### **9.1 Infrazygomatic crest (IZC) screws**

#### *9.1.1 Anatomy of the infrazygomatic crest (IZC)*

The infrazygomatic crest is a crest of bone emanating from the buccal plate of the alveolar process, lateral to the roots of the first and second maxillary molars. It extends superiorly up to 2 cm to the zygomaticomaxillary suture and inferiorly into the areas of first and second maxillary permanent molars. The sites of placement at first or second molar have been much discussed and have been proposed by authors Liou and Lin respectively. Comparisons of both sites have been summarized in **Table 1** [14].

Though both sites have been deemed fit, the IZC 7 site gains an upper hand in terms of having a greater bone thickness over the buccal surface of the second molar. Nevertheless, a CBCT evaluation of the area before placement is an important aspect of treatment planning with these screws.

#### *9.1.2 Insertion technique and angulations*

Liou [15] suggested orienting screws about 55–70° inferior to the horizontal plane to achieve maximal buccal bone engagement. During placement, the point of initial insertion is between the first and second molar, 2 mm above the mucogingival junction. The screw is directed first at the right angle to the occlusal plane and after a couple of turns when the initial notch has been made in the bone, the direction of the driver is altered by 55°–70° toward the tooth. This downward change aids in bypassing the roots of the teeth and helps direct the screw to the infra-zygomatic area of the maxilla (**Figure 5**). The bone screw is screwed until only the screw head is visible. The need for pre-drilling, flap raising, or a mucosal vertical slit has been deemed unnecessary.

#### *9.1.3 Magnitude of the employed force*

The recommended loading for orthodontic mechanics using miniscrews in the region of the IZC ranges from 220 to 340 g (8–12 oz). The force load can be employed by means of an elastomeric chain or closed coil springs [9].


#### **Table 1.**

*LIOU-LIN concept of IZC site: A comparison.*

#### *9.1.4 Anatomical considerations*

An important consideration that one cannot overlook during the placement of infrazygomatic crest screws is the soft tissue irritation and this is a frequent occurrence if there is contact or close intimacy between the inferior platform of the screw head and the mucosa.

As a general guideline, 1.5-mm clearance is considered a necessity between the mucosa and the inferior aspect of the screw platform. This is important irrespective of whether the screw is placed in a region of attached gingiva or movable mucosa though the selection of the size of the screw would vary accordingly.

It is vital to assess the anatomy of the IZC site to select an appropriate screw length. The average thickness of the attached gingiva in the maxillary first molar is about 1.0 mm, and the cortical bone thickness is about 1.1–1.3 mm The screw threads must engage cortical bone to insure primary stability. Generalizing the widths, for soft tissue clearance, attached gingiva and cortical bone at 1.5 mm each, reveals that 8–12-mm IZC screws penetrate the medullary bone or sinus from 3.5 to 7.5 mm. Under most clinical conditions, an 8-mm screw is adequate to engage the cortical plate and secure primary stability [14].

#### *9.1.5 Sinus considerations*

Cases with the maxillary sinus extending low between the teeth are not ideal candidates for infrazygomatic crest screws. The thickness of the sinus floor is preferred to be over 6 mm to ensure safe insertion. Small uncomplicated penetrations into the sinus heal spontaneously [16]. The penetration into the maxillary sinus with IZC screws was found to be rather high and double cortical engagement with sinus penetration within 1 mm was recommended for adequate primary stability. Penetrations above 3 mm led to thickening of the Scheniderian membrane and sinusitis eventually leading to failure [17].

#### *9.1.6 Guided infrazygomatic crest screws*

To ensure greater precision, a number of guides [14] have been made available for easy installation of IZC screws. They are as follows:


#### **9.2 Buccal shelf screws**

#### *9.2.1 Anatomy of the buccal shelf*

Mandibular buccal shelf area is located in the posterior part of the mandibular body, buccal to the roots of the mandibular, and anterior to the oblique line of the mandibular ramus. The area buccal to the distal root of the mandibular second molar, between 4 and 8 mm from the cementoenamel junction, has been claimed to be the best anatomical location for fixation. However, the region shows significant anatomic variations and also possibly ethnic variations wherein some patients present with a well-defined bony plateau and some with a straight bony profile. This could be better evaluated with a CBCT and clinical examination [9].

#### *9.2.2 Insertion technique and angulations*

While placing bone screws in the mandibular buccal shelf, the point of initial insertion is between the first and the second molar, 2 mm below the mucogingival junction. The screw is first directed at the right angle to the occlusal plane at this point and then, the driving direction is altered by 60°–75° toward the tooth. This upward change in direction helps to bypass the teeth roots and directs the screw to the buccal shelf area of the mandible. Pre-drilling or vertical slit in the mucosa may be necessary if the bone density is too thick. However, raising a flap is never required during placement.

#### *9.2.3 Magnitude of the employed force*

The recommended loading for orthodontic mechanics using miniscrews in the region of the buccal shelf area ranges from 340 to 450-g. The force load can be employed by means of an elastomeric chain or closed coil springs [9].

#### *9.2.4 Inflection point and limits of mandibular molar distalization*

The intersection of the line of occlusion and the internal oblique ridgeline is the inflection point (**Figure 6**). The second molar cannot move on the internal oblique line, and the amount of possible movement depends on the distance of the original position of the second molar to the inflection point. This varies from patient to patient. A comprehensive evaluation of the buccal shelf area and the alveolar housing with the help of a cone-beam computed tomogram seems pivotal to treatment planning [18].

**Figure 6.** *Limits of mandibular molar distalisation.*

**Figure 7.** *Ramus Screw insertion.*

#### **9.3 Ramus screws**

Ramus screws were developed to overcome the difficulties that buccal shelf screws posed during the dis-impaction of horizontally impacted lower molars. From the standpoint of biomechanics, these screws are installed in the anterior ramus of the mandible to offer a traction force that is more superior and posterior in direction.

This coupled with simple yet efficient mechanics to upright the lower molars in tandem with ramus screws has offered a brilliant treatment option in such cases.

#### *9.3.1 Anatomical location point*

The insertion site for a ramus screw (red arrows) is between external and internal oblique ridges, about 5–8 mm superior to the occlusal plane (**Figure 7**).

A relatively long (14 mm) ramus screw is selected because of the need to penetrate thick non keratinized mucosa, with an underlying layer of masticatory muscle. For hygiene access, the ramus screws were screwed in until the head of the TAD was ~5 mm above the level of the soft tissue. The average bone engagement for a ramus screw is ~3 mm [19].

#### **10. Biomechanics of orthodontic bone screws**

#### **10.1 Generations of biomechanical principles**

According to Robert et al. [20]


#### **10.2 Employed force magnitude**

The force magnitude employed is important in terms of anchorage stability. A force magnitude ranging from 220 to 340 g (8 to 12 oz) for mechanics with miniimplants in the IZC area, and from 340 to 450 g on the ones with mini-implants in the BS area, has been recommended. This is vital to achieve the en masse distalization that bone screws offer popularly in clinical settings. In cases that require partial retraction, force magnitude may be adjusted between 150 and 200 g.

#### **10.3 Biomechanics of buccal shelf screws**

Buccal shelf screws are employed for en masse retraction of the entire mandibular dentition since the screws are placed at extra-alveolar sites.

Three critical factors exist for this system to be deemed statically determinate when two screws are inserted into the buccal shelf areas for retraction:


Biomechanical effects of retraction with anchored buccal shelf screws:


#### **10.4 Biomechanics of infrazygomatic crest screws**

When two screws are installed in the IZC area for retraction, similar effects were found as in the buccal shelf region. With the retraction force from the coil spring to the screw, retraction occurs along with vertical side effects, that is, molar intrusion and incisor extrusion leading to rotation of the occlusal plane. The axis of rotation in the maxillary arch lies between the premolars and this change is beneficial in Class II cases with the open bite or where bite deepening is required.

#### **10.5 How can the force system be varied to suit the needs of a particular case?**

In order to overcome the side effects that are not suited for correction in all cases, the force system can be modified to obtain different kinds of dental movements:


#### **10.6 Height of hooks/power arm**

Depending on the force vector and direction required in each case, the height of the hook will help decide the type of tooth movement required along with torque and vertical control.

Short hook: Anterior teeth have a tendency to rotate clockwise when retraction/ distalization force is applied by means of a force that passes below the Center of resistance, which leads to torque loss and a vertical extrusion force on the incisors.

Medium hook: The force action line is passing over the anterior teeth's center of resistance, due to the middle positioning. When distalization force is applied to the entire maxilla, with force parallel to the occlusal plane, anterior teeth are likely to keep their initial inclination, minimizing vertical forces.

Long hook: The height of the hook is positioned mesial to the canine allows the force action line to pass above the incisors' center of resistance. The positioning simply produces a counterclockwise anterior moment during retraction and simultaneous extrusion of the incisors. In the clinical scenario, it might be pointed out that this may offer a possibility of injuring the oral mucosa of the patient.

*Understanding Orthodontic Bone Screws DOI: http://dx.doi.org/10.5772/intechopen.100276*


#### **Table 2.**

*Clinical applications of extra-alveolar bone screws [2, 3, 4, 9].*

#### **10.7 Simultaneous retraction and intrusion**

In cases with vertical maxillary excess, in order to facilitate gingival smile correction while also balancing the clockwise rotation effect of the maxillary occlusal plane, it was suggested that two mini-implants were to be installed between central and lateral incisors apart from the IZC screws. This would help counter-effect the anterior extrusion, resulting in the intrusion of the entire maxillary dentition and favoring gingival smile correction (**Table 2**).

#### **11. Conclusion**

To encapsulate, orthodontic bone screws have recast the approach to complex malocclusions in a significant way. These have been designed without losing sight of the fact that they are installed in extra-alveolar sites away from the roots and in areas of high amounts of cortical bone to affect tooth movement. While they gain an upper hand in terms of safety to roots and effective tooth movements, it is pivotal that the clinician must focus on the appropriate case selection for the same. One cannot deny their role of marching into the orthodontic field and that too with a roaring success. Considering that there is still a great deal of research that needs to be done about them, they are interesting areas of study to further the understanding and applications of these screws in orthodontic practice.

*Current Trends in Orthodontics*

#### **Author details**

Agharsh Chandrasekaran1 \*, H.P. Naga Deepti1 and Harshavardhan Kidiyoor2

1 Private Practitioner, Bengaluru, India

2 SDM College of Dental Sciences and Hospital, A Constituent Unit of Shri Dharmasthala Manjunatheshwara University, Dharwad, India

\*Address all correspondence to: agharshc@gmail.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Proffit WR. Contemporary Orthodontics. 6th ed. St. Louis: Mosby Yearbook; 1993. p. 307

[2] Jong Lin JL. Text Book of Creative Orthodontics: Blending the Damon System and TADs to Manage Difficult Malocclusions. Yong Chieh: Taipei, Taiwan; 2007

[3] Ghosh A. Infra-zygomatic crest and buccal shelf – Orthodontic bone screws: A leap ahead of micro-implants – Clinical perspectives. The Journal of Indian Orthodontic Society. 2018;**52**:S127-S141

[4] Jae-Hyun Sung. Microimplants in Orthodontics. Department of Orthodontics, School of Dentistry, Kyungpook National University, 2006.

[5] Shapiro PA, Kokich VG. Uses of implants in orthodontics. Dental Clinics of North America. 1988;**32**:539-550

[6] Chang CH, Lin JS, Roberts WE. Failure rates for stainless steel versus titanium alloy infrazygomatic crest bone screws: A single-center, randomized double-blind clinical trial. Angle Orthod. 2019 Jan;**89**(1):40-46.

[7] Almeida MR. Mini-implantes extraalveolares em Orrtodontia. 1st ed. Maringá: Dental Press; 2018

[8] Misch CE. Density of bone: Effect on treatment plans, surgical approach, and healing, and progressive loading. The International Journal of Oral Implantology. 1990;**6**:23-31

[9] Park JH. Temporary Anchorage Devices in Clinical Orthodontics. 1st ed. Wiley Blackwell; 2020. p. 111

[10] Vargas EOA, Lopes de Lima R, Nojima LI. Mandibular buccal shelf and infrazygomatic crest thicknesses in patients with different vertical facial heights. American Journal of Orthodontics and Dentofacial Orthopedics. 2020;**158**(3):349-356

[11] Gandhi V, Upadhyay M, Tadinada A, Yadav S. Variability associated with mandibular buccal shelf area width and height in subjects with different growth pattern, sex, and growth status. American Journal of Orthodontics and Dentofacial Orthopedics. 2021;**159**(1): 59-70

[12] Graber LW, Vanarsdall RL, Vig KWL, Huang GJ. Orthodontics: Current Principles and Techniques. 6th ed. Amsterdam, Netherlands: Elsevier; 2017

[13] Pablo Echarri, Tae-Weon Kim, Lorenzo Favero, Hee-Jin Kim. Orthodontics & Microimplants: Complete Technique, Step by Step.

[14] Lin J, Roberts WE. Guided Infrazygomatic screws: Reliable maxillary arch retraction. International Journal Orthodontics Implantology. 2017;**46**:4-16

[15] Liou EJ, Pai BC, Lin JC. Do miniscrews remain stationary under orthodontic forces? American Journal of Orthodontics and Dentofacial Orthopedics. 2004;**126**(1):42-47

[16] Baumgaertel S, Hans MG. Assessment of infrazygomaticbone depth for mini-screw insertion. Clinical Oral Implants Research. 2009;**20**:638-642

[17] Jia X, Chen X, Huang X. Influence of orthodontic mini-implant penetration of the maxillary sinus in the infrazygomatic crest region. American Journal of Orthodontics and Dentofacial Orthopedics. 2018;**153**(5):656-661

[18] Padmanabhan S, Kalia A. An interview with Dr. Junji Sugawara. Journal of Indian Orthodontic Society. 2018;**52**(4\_suppl1):62-67

[19] Chang CH, Lin JS, Roberts WE. Forty consecutive ramus bone screws used to correct horizontally impacted mandibular molars. Int J Orthod Implantol. 2016;**41**:60-72

[20] Almeida MR. Biomechanics of extra-alveolar mini-implants. Dental Press Journal of Orthodontics. 2019;**24**(4):93-109

#### **Chapter 10**

## Effectiveness and Stability of Treatment with Orthodontics Clear Aligners: What Evidence?

*Soukaina Sahim and Farid El Quars*

#### **Abstract**

Clear aligners, as a transparent and removable appliance, offer an alternative to conventional fixed appliance to patients with high demands for esthetics and comfort. Only a few investigations have focused on the efficacy of clear aligner therapy in controlling orthodontic tooth movement. Furthermore, the stability after treatment has not been thoroughly investigated. The purpose of this chapter was to update the knowledge of the available evidence about effectiveness and stability of clear aligners in non-growing subjects. Searches was made in different databases from January 2015 to January 2021. Relevant articles that met the inclusion criteria were selected. The level of evidence of the studies was moderate. The vertical movements of tooth were difficult to accomplish. Mesiodistal tipping showed the most predictability (82.5%) followed by vestibulolingual tipping. Molar distalization was also recorded as the highest accuracy. Derotation was difficult to accomplish with aligners especially of rounded teeth. The effectiveness of aligners in achieving the simulated transverse goals was 45%. The stability of clear aligner therapy was assessed by only two studies. Refinements are likely needed in almost all cases and to ensure treatment stability a retention period using a specific protocol is necessary.

**Keywords:** clear aligners, effectiveness, efficacy, stability, outcomes

#### **1. Introduction**

Orthodontic developments, especially during the last years, have been accompanied by a significant increase in the esthetic demands of the patients [1]. With the significant recent improvements in computer-aided design/computer-aid-ed manufacturing (CAD/CAM) and dental materials, there has been an increase in the demand for plastic systems [2]. Clear aligners provide an esthetic and comfortable treatment experience, facilitate oral hygiene, cause less pain as compared to fixed orthodontic appliances, and reduce the number and duration of appointments [3–5]. The aligner therapy also involves a lower incidence of demineralization, enamel abrasion, periodontal lesions, and mucosal irritations [6].

The concept of clear aligners was introduced by Kesling in 1946 with a tooth positioner fabricated by thermoplastic material molding technology and designed for minor tooth movements during the finishing stages of orthodontic treatment. In 1993, Sheridan and colleagues developed a technique of giving new clear retainers to the patient at each visit, incorporating interproximal reduction to provide the necessary space for tooth movement [3, 7]. With further advancement in orthodontic technology, Align Technology introduce the clear aligner treatment (CAT) rendering Kesling's concept a feasible orthodontic treatment option [8]. A series of removable polyurethane aligners were introduced as an esthetic alternative to fixed labial appliances. Scanned images are converted to physical models by using different stereolithography (STL) techniques to fabricate a series of aligners that sequentially reposition the teeth. Each aligner is programmed to move a tooth or a small group of teeth 0.25–0.33 mm every 14 days [9, 10]. Align Technology provides orthodontists with ClinCheck (Align Technology Inc., Santa Clara, Calif) models, which reflect the treatment outcomes. The aligners incrementally shift the teeth into place based on the outcome the orthodontist expects to achieve [11].

The primary focus of the clear aligner system was initially to solve cases of low and moderate crowding and to close small spaces [1]. However, it has continually evolved through the development of new aligner materials, attachments on teeth, as well as new auxiliaries, such as "Precision Cuts" and "Power Ridges" to address a wider range of malocclusions and to enable additional treatment biomechanics [2, 5, 12].

Despite the available body of literature pertaining to aligner technology, only a few investigations have focused on the efficacy of clear aligner therapy in controlling orthodontic tooth movement. Furthermore, the stability after treatment has not been thoroughly investigated.

The purpose of this chapter was to update the knowledge of the available evidence about effectiveness and stability of clear aligners and to answer the following clinical research question: "Are clear aligners effective in controlling the orthodontic movement in non-growing subjects and what about stability of this treatment modality?"

#### **2. Materials and methods**

#### **2.1 Search strategy**

A systematic search in the medical literature produced between January 2015 and January 2021 was performed to identify all peer-reviewed articles potentially relevant to the review's question.

The following databases have been used: CENTRAL, MEDLINE, MEDLINE in Process, Embase and Cochrane Library databases.

The search strategy comprised use of the following terms: (invisalign OR clear aligners OR aligners OR transparent aligners) AND (effectiveness OR efficacy) AND (dental changes OR treatment outcome) AND (stability).

Additionally, a manual search was conducted in orthodontic journals of interest, such as The Angle Orthodontist, the American Journal of Orthodontics and the European Journal of Orthodontics. Title and abstract screening was performed to select articles for full text retrieval.

*Effectiveness and Stability of Treatment with Orthodontics Clear Aligners: What Evidence? DOI: http://dx.doi.org/10.5772/intechopen.99998*

#### **2.2 Eligibility criteria**

The following inclusion and exclusion criteria were used:

#### *2.2.1 Inclusion criteria*

Study design: meta-analysis, systematic reviews, randomized and non-randomized clinical trials, prospective and retrospective studies were included.

Participants: non growing patients.

Intervention: articles that studied dental movement of cases treated with clear aligners.

Results: the efficacy of clear aligners in performing dental movements and the stability of treatment, superimposing virtual models or radiographs.

#### *2.2.2 Exclusion criteria*

We excluded for our study articles older than 6 years, samples with growing patients, articles written in a language other than English, in-vitro studies, author opinions, letters to the editor, isolated cases, series of cases, surgical cases, or reports of patients with syndromes.

#### **2.3 Level of evidence**

The grading system described by the Swedish Council on Technology Assessment in Health Care (SBU) [13] was used to assess the methodological quality and the level of evidence of the articles (**Tables 1** and **2**).


#### **Table 1.**

*Swedish Council on Technology Assessment in Health Care (SBU) criteria for grading assessed studies.*


**Table 2.** *Definitions of evidence level.*

#### **3. Results**

#### **3.1 Study selection**

The selection of articles included in this review is shown in the PRISMA flow chart (**Figure 1**). Study selection procedure was comprised of title-reading, abstractreading, and full-text-reading stages. After exclusion of not eligible studies, the full report of publications considered eligible for inclusion by the authors was assessed. Eleven studies were included in the qualitative synthesis.

#### **3.2 Study characteristics**

Of the eleven included articles, there were five retrospective studies [6, 14–17], two prospective studies [7, 11], two randomized controlled trials (RCT) [18, 19], two systematic reviews [2, 20] and one meta-analysis [20]. Most of the included studies evaluated mild to moderate malocclusions except for one [17] that involved first premolar extraction cases. The majority of studies used the Invisalign® system except two studies that used Nuvola® system [15] and F22 aligners [14].

Data collected from each of the included articles are described in **Tables 3** and **4**. Nine of the covered studies assessed predictability of tooth movements comparing

**Figure 1.** *Flow chart according to the PRISMA statement.*


*Effectiveness and Stability of Treatment with Orthodontics Clear Aligners: What Evidence? DOI: http://dx.doi.org/10.5772/intechopen.99998*


 **3.** *Design, participants, type of intervention, and results of studies included in the qualitative analysis.*

*Effectiveness and Stability of Treatment with Orthodontics Clear Aligners: What Evidence? DOI: http://dx.doi.org/10.5772/intechopen.99998*


#### **Table 4.**

*Studies assessing treatment stability of clear aligners.*


#### **Table 5.**

*Evidence grade according to Swedish Council on Technology Assessment in Health Care.*

post-treatment patient models to the predicted digital planned tooth movement models [2, 6, 7, 11, 14–18]. Two studies assessed the stability of the clear aligner therapy [19, 20].

#### **3.3 Level of evidence of studies**

According to the SBU tool (**Tables 1** and **2**), among the selected studies, the methodological quality was low for four studies [6, 11, 16, 17], moderate for four others [7, 14, 15, 19] and high for one study [18] (**Table 5**). Thus, conclusions with a moderate level of evidence could be drawn from the review process.

#### **4. Discussion**

In this review, we aimed to provide data on the effectiveness and stability of treatment with clear aligners. The level of evidence was moderate as we identified one study with level «A» and four studies with level «B».

The effectiveness of clear aligners was judged by the predictability of tooth movement which varies with the type of tooth and the type of movement. Lopez et al. [2] found that the expression of the programmed movement was not fully accomplished with Invisalign®.

Concerning **vertical movements**, the study by Lopez et al. [2] revealed that vertical movements are difficult to accomplish with aligners. Extrusion of a single tooth is moderately difficult using clear aligners when compared to fixed-appliance systems, however, some auxiliaries such as buttons, elastics and optimized extrusion attachments can be used to facilitate this movement [5, 21].

Many studies showed that intrusion was the most unpredictable movement especially for the maxillary central and lateral incisors [16, 21]. Invisalign has a bite-block effect, because 2 aligners of 0.38-mm width are interposed between posterior teeth throughout treatment. Unexpected intrusion of the molars would cause the incisors to appear extruded on the posttreatment models after superimposition [16]. In fact, according to Grunheid et al. [22], mandibular incisors tend to be positioned more occlusally than predicted. The bite-block effect may make open bites easier to treat with Invisalign [16].

Concerning **horizontal movements**, mesiodistal tipping showed the most predictability especially of upper molars and lower premolars (82.5%) followed by vestibulolingual tipping [14]. Lingual crown tip (53%) was significantly more accurate than labial crown tip (38%), particularly for maxillary incisors [23]. According to Rossini et al. [8], aligners can easily tip crowns but cannot tip roots because these appliances cause tooth movement by tilting motion rather than bodily movement. In the anterior region, the elasticity of the aligner at the gingival margin results in difficulty in controlling the applied forces [24]. With the use of Power Ridges (Align Technology, Amsterdam, The Netherlands), the aligner can accurately control root torque according to the crown position in the virtual setup [17]. Tepedino et al. [15] also concluded that with Nuvola® aligners, in patients with moderate crowding up to 6 mm, the torque movements for central and lateral incisors and canines of both arches predicted in the digital setup were, in general, clinically achieved. However, molar torque may not be fully achieved, with maxillary second molars often having a clinically relevant magnitude of more facial crown torque than predicted [22].

Molar distalization was recorded as the highest accuracy with no need for attachments. Simon et al. [25] also reported a high accuracy (88%) of the bodily movement of upper molars when a distalization movement of at least 1.5 mm was prescribed.

Several studies agreed that derotation of rounded teeth especially canines was difficult to achieve with aligners [16, 22, 26]. An amount of rotation greater than 15° has been identified as a risk factor for decreased accuracy for rotational prediction [25]. Interproximal contacts of rotated canines might also be considered a significant predictor for the diminished efficacy of tooth movement, especially in the absence of interproximal reduction of the enamel (IPR) [26]. The direction of derotation has been also documented to influence the accuracy of the maxillary canine, with distal movement demonstrating less accuracy than mesial [21]. This is possibly due to the actual contact area between canine and premolar and the potential challenges of providing enamel reduction in this area.

#### *Effectiveness and Stability of Treatment with Orthodontics Clear Aligners: What Evidence? DOI: http://dx.doi.org/10.5772/intechopen.99998*

It has been recommended to plan overcorrections, especially if rotations exceed 15°, to use attachments, and to reduce staging to less than 1.5° per aligner [8, 16, 25]. However, although various types or shapes of attachment grips or practices of interproximal enamel reduction have been reported as potential prognostic factors for better efficacy of rotational tooth movement, this does not necessarily translate into an identified substantial effect in practice [26].

Concerning **transverse movements**, the effectiveness of achieving the simulated transverse goals was 45% [6]. Aligners could increase the arch width, but expansion was achieved by tipping movement of posterior teeth rather than bodily expansion. In fact, Invisalign becomes less accurate going from the anterior to the posterior region being more effective in premolar area [27, 28]. Thus, according to the initial torque of the posterior teeth, an appropriate amount of negative torque in the crown could be preset in ClinCheck to improve bodily expansion efficiency. For patients who need a large amount of expansion, clinicians should consider reducing the amount of expansion for each aligner to ensure periodontal health [7].

According to Lopez and al. [2], Invisalign® was also able to alter intercanine, interpremolar, and intermolar width in the presence of crowding. Kravitz et al. [23] recommended to treat cases with severe lower crowding mostly by interproximal reduction (IPR) instead of dentoalveolar expansion. This recommendation comes from the finding that retraction is more accurate than dentoalveolar expansion of the lower anterior teeth. The expansion of the mandibular intercanine width also poses the greatest risk of relapse following treatment [29].

Concerning the effectiveness of the occlusal contacts with clear aligners, the study by Izhar et al. [10] found that the software models do not accurately reflect the patient's final occlusion immediately at the end of active treatment. Kassas et al. [30] also stated that clear aligners were not sufficient for providing ideal occlusal contacts. The deterioration in occlusal contacts was caused by the thickness of aligners, which interferes with the settling of the occlusal plane.

As far as the malocclusion type is concerned, the study by Graf et al. [19] showed that Invisalign® treatments are able to significantly reduce malocclusions in adult patients. The study found that all types of sagittal malocclusion (class I, class II, and class III) were 'greatly improved' with a rate of 77.44%. Graf and al. [19] also concluded that conventional attachments and the combination with optimized attachments equally led to treatment effectiveness regarding the total PAR score reduction with equally achieved effectiveness in mild, moderate, and rather severe cases. However, for Class II malocclusion, Patterson et al. [31] reported that there was no significant Class II correction or overjet reduction with elastics for an average of 7-month duration in the adult population. Additional refinements may be necessary to address problems created during treatment mainly posterior open bite.

One study of our review by Dai et al. [17] assessed the effectiveness of Invisalign in first premolar extraction treatment. According to this study, first molar anchorage control and central incisor retraction were not fully achieved as predicted. Only medium anchorage control was achieved as the first molars actually moved mesially. The G6-optimized attachment showed similar control in first molar angulation and mesiodistal translation as did 3- and 5-mm horizontal rectangular attachments. On the other hand, setting a distal tipping of 6.6 mm on the first molars might help clinically maintain the tooth angulation, leading to bodily tooth movement. According to the same study [17], the incisors inclined lingually under the retraction force.

Accordingly, the use of power ridges or attachments as well as overcorrection by setting greater buccal crown inclination during the virtual setup should be considered to achieve optimal incisor torque control.

Current evidence does not support the clinical use of aligners as a treatment modality that is equally effective to the gold standard of braces [32]. However, clear aligners have advantage in segmented movement of teeth and shortened treatment duration, but are not as effective as braces in producing adequate occlusal contacts, controlling teeth torque, and retention [5, 33].

Many variables influence the accuracy of dental movements, but very few studies have analyzed these parameters in treatments with clear aligners. According to Tepedino et al. [15], several factors determine successful tooth movement such as the attachment's shape and position, the aligner's material and thickness, the amount of activation present in each aligner, and the techniques used for the production of the aligners. Treatment outcomes depend also on the patient's characteristics, bone density and morphology, crown and root morphology of the teeth, as well as on factors related to the clinician. Orthodontists have to incorporate their expert knowledge in determining proper sequencing of tooth movements, tooth attachment design and placement, and prescribing overcorrection when needed for difficult tooth movements to increase efficiency and achieve better treatment outcomes [22, 34]. Patient compliance is also mandatory to achieve good results by wearing the aligners 22 hours a day or more [28].

One study from this review with a high level of evidence [18] evaluated the impact of wear protocol on the accuracy of clear aligners. It has concluded that fourteen-day changes were statistically significantly more accurate in some posterior movements mainly maxillary intrusion, distal-crown tip and buccal-crown torque, and in mandibular intrusion and extrusion.

As in all types of orthodontic treatment, stability is one of the most important issues to discuss regarding clear aligners. According to the systematic review by Zheng et al. [20], only one study compared the post-retention dental changes between patients treated with Invisalign and those treated with conventional fixed appliances. They found that the change in the total alignment score in the Invisalign group was significantly larger than that for the Braces group. There were significantly larger changes in maxillary anterior alignment in the Invisalign group than in the conventional bracket group. Tamer et al. [5] also reported that maxillary anterior leveling relapsed in the Invisalign group. On average, the posttreatment models lost twice as many points for alignment than the respective ClinCheck models. In other words, a full finishing phase of treatment may be needed to achieve the results indicated in the ClinCheck model [11].

The type and degree of tooth movement, the duration of active treatment and the retention protocol are among major influencing factors of posttreatment stability and relapse. The study by Graf et al. [19] is the first one to assess the stability of clear aligners outcome throughout a retention period of 10 months. The retention protocol involved a mandibular multistrand fixed retainer (0.0155 inch; stainless steel, 24 K gold plated) bonded on each lingual surface from canine to canine and a removable modified Hawley retainer for the upper arch (with mandatory Adams clasps on first molars). The study showed that the treatment outcome can be stable throughout this retention protocol. It has also concluded that treating patients with respect to their physiological boundaries and maintaining their original arch form would be key to treatment stability. Overexpansion of the dental arch, especially in the lower arch and in adult patients, is a potential risk for stable results.

*Effectiveness and Stability of Treatment with Orthodontics Clear Aligners: What Evidence? DOI: http://dx.doi.org/10.5772/intechopen.99998*

#### **5. Conclusion**

There is current evidence with a moderate level of certainty regarding the effectiveness of clear aligner therapy for certain tooth movements. Clear aligners can safely straighten dental arches in terms of leveling and derotating the teeth, except for canines and premolars. The crown tipping can be easily performed. However, important limitations include arch expansion through bodily tooth movements, extraction space closure, corrections of occlusal contacts, and larger antero-posterior and vertical discrepancies. The use of additional attachments might be more effective for various types of movement, such as bodily expansion of the maxillary posterior teeth, canine and premolar rotational movements, incisors torque control and extrusion of maxillary incisors. Overcorrections might also improve the effectiveness of orthodontic movement. However, overcorrections are not as simple for all movements and need to be made on a case-by-case basis depending on the goal of treatment.

Studies on effectiveness of clear aligners had methodological heterogeneity as they assessed predictability of different types of tooth movements for different teeth by using different materials like Invisalign, F22 aligner and Nuvola system. Retention and stability studies regarding aligners also remain limited in the literature. Therefore, further well-designed and reported researches are required on this subject.

#### **Acknowledgements**

Special thanks to the department of Orthodontics of the Faculty of the dentistry of the University Hassan II of Casablanca. We would also like to acknowledge the support of Professor Farid Bourzgui for the realization of this work and for sharing and discussing the initial idea of the project.

#### **Conflict of interest**

The authors declare no conflict of interest.

#### **Author details**

Soukaina Sahim\* and Farid El Quars Department of Orthodontics, Faculty of Dentistry, University Hassan II, Casablanca, Morocco

\*Address all correspondence to: souki-2s@hotmail.fr

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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#### **Chapter 11**

## The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol

*Suvetha Siva, Shreya Kishore, Suganya Dhanapal, Janani Ravi and Chandhini Suresh*

#### **Abstract**

In orthodontics there has been a change in the treatment plan of crowding cases from extraction protocol. This was mainly due to the introduction of self-ligating bracket and temperature activated wires. Even though there are certain exceptions, the self-ligating bracket have evolved in orthodontics because of its advantages such as low friction, shorter treatment duration and increased efficacy. Damon's selfligating system has been in existence since 1930 but it has been well developed in the past 30 years with the introduction of newer systems. Damon's self-ligating brackets have been designed to overcome the drawbacks of conventional bracket system and are often considered as the pinnacle of bracket technology. The main advantage of Damon's system was low friction and shorter treatment duration. But the efficiency of the appliance is influenced by several factors such as Biomechanics, frequency of dental visits and patient comfort. The chapter will highlight the efficiency of the appliance, the various possible outcomes and its influence on the ease of orthodontic therapy.

**Keywords:** self-ligating bracket, Damon's system, Damon brackets, passive self-ligating bracket, Damon philosophy

#### **1. Introduction**

Orthodontics and orthodontists have always worked towards delivering better care for patients. This has led to the invention of various bracket systems along with the changes in the protocol of management of extraction cases.

The Self Ligating Brackets (SLB) has come into orthodontic practice since 1930's with the invention of Boydband bracket. These bracket systems along with the thermally activated NiTi wires have reduced the treatment duration, chair-side time, and improved the treatment efficacy and patient co-operation. This led to the invention of Damon's system by Dr. Dwight Damon in the year 1996. It is called as "System" rather than "Brackets" because it utilizes the benefits of both the brackets and copper NiTi wires, thus delivering a "low force- low friction" mechanics for the management of dental malocclusion [1].

There has been lot of evidence in literature which states that "atraumatic" remodeling of periodontal tissues was rarely achieved using conventional orthodontic bracket system. This is mainly because the tooth was always moved in group. In Damon's system, the tooth is allowed to move individually, yet stay in the group. The bracket system allows for easy sliding of the tooth along the path of least or no resistance thus leading to faster leveling and alignment and reduced treatment duration [2]. The aim of this chapter is to describe the bracket prescription, efficiency of the appliance, the possible outcomes and its influence on orthodontic therapy.

### **2. Why choose Damon?**

Damon philosophy uses the concept of passive self-ligation technique which claims to have the lowest frictional resistance of any ligation system. Reduction in friction helps the force to transmit directly from the arch wires to the teeth and its supporting structures without any force dissipation by the ligature system [3].

Comparing the other prescriptions, Damon system has lots of benefits:


*The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol DOI: http://dx.doi.org/10.5772/intechopen.100536*


#### **3. Classification of Damon's system**

In orthodontics achieving ideal inclination of anterior using the edgewise system is challenging. In an attempt to overcome this drawback, Damon's system has different torque prescription. This includes:

#### **3.1 High torque brackets**

These brackets can be used in cases where the incisors or cuspids are severely retroclined or palatally placed. Examples are:


#### **3.2 Standard torque brackets**

These brackets can be used in cases where the inclination of anterior is satisfactory and when there will not be any obvious change in the inclination during the course of the treatment.

#### **3.3 Low torque brackets**


#### **4. Tip and torque**

The tip and torque values of Damon's system are as in **Tables 1** and **2**.


#### **Table 1.**

*Tip values in Damon's system.*


#### **Table 2.**

*Torque values in Damon's system.*

#### **5. Advantages and disadvantages**

#### **5.1 Advantages**


#### **5.2 Disadvantages**


#### **6. Arch wire sequencing**

The phases of tooth movement are generally.


There are two sequences which are generally followed in pre-adjusted edgewise prescription.

#### **6.1 Universal arch wire sequencing**

An older concept of a sequence which initially uses round steel wires from sizes.014, .016, .018 and .020 followed by rectangular steel wires from dimensions.018 × .025, .019 × .025 and.021 × .025 in.022 slots.

Multi-stranded wires of dimensions .015 and .0175 were used for initial aligning before .014 round Steel wire came into practice and finishing and detailing was done with.014 steel wires.

Later with the introduction of MBT prescription, arch wire sequencing started with initial .016 CuNiTi wire followed by .019 × .025 CuNiTi and then .019 × .025 Steel wire was used for major biomechanics and detailing was done with .014 round steel wire [12, 13].

A clinical research by Mandall, in which three wire sequences were randomly allocated to patients to compare are as follows:

Group A - 0.016 NiTi, 0.018 × 0.025nNiTi, and .019 × 0.025 Steel wires.

Group B- 0.016 Niti, 0.016 SS and finally 0.020-inch Steel wires.

Group C - 0.016 × 0.022 CuNiTi wire, followed by 0.019 × 0.025 CuNiTi, and ending with 0.019 × 0.025 Steel wire,

And found that all sequences were equally effective. However, the CuNiTi may be preferred by the clinicians as it reduces the number of appointments [14].

In another study by Ong, the three different archwire sequences were applied are as follows:


And found that there were no differences among the archwire sequences in terms of aligning or discomfort [15].

#### **6.2 Damon arch wire sequencing**

Phase 1: Light Round Wires

This phase of treatment uses 0.013, 0.014, or 0.016 CuNiTi arch wires. The aim of this first phase of treatment is to achieve tooth alignment including rotation correction except second molars, level the arches and initiate arch development with light forces to permit the soft tissues to desired arch shape. This phase of treatment normally extends from 10 to 20 weeks and the intervals between appointments are about 10 weeks.

Phase 2: High Rectangular Wires

Phase 2 uses two arch wires: 0.014 × 0.025 CuNiTi followed by 0.018 × 0.025 CuNiTi wires. In case of well aligned arches only 0.016 × 0.025 CuNiTi are used in this phase. If intrusion of anteriors is planned, 0.017× 0.025 or 0.019× 0.025 CuNiTi arch wires with preformed curves or reverse curves of Spee or additional torque can be applied anteriorly in this stage.

The main purposes of this phase are:


The duration of this phase ranges from 20 to 30 weeks. The first archwire is placed from 8 to 10 weeks and the second is from 4 to 6 weeks.

Phase 3: Major Mechanics

Preposted stainless steel arch wires of size 0.019 × .025 are used. Presence of cross bite at this stage when persisted can be corrected with the use of 0.016 × 0.025 preposted stainless steel arch wire with the use of cross elastics where buccal and lingual tipping can be achieved at this stage.

The main purposes of this phase are:


This phase of treatment extends from 8 to 10 weeks with an interval about 10-weeks between appointments.

Phase 4: Finishing and Detailing

The stainless steel arch wires continued in this phase with elastics for achieving proper interdigitation. But for individual teeth position 0.019× 0.025 ß-titanium arch wires may also be used [2, 3, 16].

In a study by Handem, used the arch sequence with initial round wires 0.014 or 0.016, followed by rectangular 0.016 × 0.025, 0.018 × 0.025, and 0.019 × 0.025 CuNiTi arch wires subsequently, rectangular 0.017 × 0.025 or 0.019 × 0.025 Steel arch wires [17].

*The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol DOI: http://dx.doi.org/10.5772/intechopen.100536*

#### **7. Bracket placement in Damon system**

Various clinicians have put forth bracket placement methodologies of the Damon bracket system to achieve the desired smile arc protection, functional occlusion and enhancing the facial esthetics.

Standard bracket placement by Dwight Damon [18]:

According to him, the arch wire slot should be at the distances mentioned below from the incisal edge.

Maxillary U-l 4.75 mm. U-2 4.50 mm. U-3 5.00 mm. U-4 4.50 mm. U-5 4.25 mm. Mandibular L-l 4.75 mm. L-2 4.50 mm. L-3 5.00 mm. L-4 4.50 mm. L-5 4.25 mm.

#### **7.1 Placement tips**


Dr. Dwight Damon advises placement of the bracket within the green zone (in between the green lines). The Damon prescription has variable torque prescriptions to foster the need for different clinical cases. A clinician can place the upper and lower mid-bracket slot within the green lines without dramatically impacting torque.

Dr. Thomas. R. Pitts Protocol [19]:

Dr. Thomas. R. Pitts worked with a philosophy of "beginning with the end in mind". He believed that developing acumen in precise bracket placement is the single most important protocol to achieve an esthetically pleasing smile and functional occlusion.

Basic principles of the Pitts placement protocol:

Detailed bonding plan before the day of bonding and to select brackets of appropriate torque based on the demand of the case.

Ensure tray setup entails all items for an efficient bonding.

Use two assistants to assist in bonding.

Recontour teeth for esthetics and bracket fit.

Follow an exacting placement protocol to achieve an ideal smile arc in the anteriors and leveling buccal cusps and marginal ridges in the posteriors.

Dr. Pitts bonds the maxillary anteriors to achieve a consonant smile arc at the end of the treatment, the mandibular anteriors for overjet and overbite and the remaining teeth for a good occlusion. He first bonds the mandibular teeth, from the second molar to canine on one side, and repeats the same on the opposite side, followed by lateral to lateral. This is followed to achieve symmetry on either side. The same sequence is repeated in the upper arch. He believed in keying off the maxillary canine to ensure that the canine-lateral and canine- premolar contacts are esthetic and functional.

In the posteriors, to achieve leveled marginal ridges and contact points, the teeth are bonded using the contact points as reference. This is done up to the canine and then the incisors are bonded based on the slot of the maxillary canine to give a sweep in the smile arc which gives a pleasing appearance **Figures 1** and **2**.

**Figure 1.** *Standard bracket placement of damon bracket.*

**Figure 2.** *Picture depicting the "green zone" for bracket placement in the Damon system.*

*The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol DOI: http://dx.doi.org/10.5772/intechopen.100536*

Dr. Pitt's occluso gingival positioning of brackets is slightly more gingival to the conventional placement on both arches. He believed positioning the brackets more incisally will prevent us from achieving the ideal smile arc and hinders torque control (**Figure 3**). Dr. Pitts along with Dr. Mike Steffan developed a method to making the bracket positioning easier by drawing lines on the stone models from contact points for the canine, premolars and molars to prevent mistakes in bracket positioning in the transition of contact points from posteriors to anteriors (**Figure 4**).

#### **7.2 Maxillary anteriors**

The position of the maxillary canine is given the prime importance for the sweep in the smile arc. Based on the positioning of this bracket, other anterior brackets were placed. In this method, the incisal edge of the canine bracket wing needs to be placed on a line drawn from mesial to distal contact at the height of contour interproximally. This line was called the mesiodistal (M-D) contact line. The level of the slot of this bracket was used as a reference for maxillary central and lateral incisor positioning. The maxillary lateral incisor bracket is placed 0.5 mm gingival to the canine bracket and central incisor bracket 0.25 mm gingival to this to achieve the ideal smile arc (**Figure 5**) Further to avoid the bracket positioning error, the author advises the use of a two inch large front surface mirror to avoid any error in bracket positioning (**Figure 6**).

**Figure 3.** *Gingival bracket placement for smile arc protection by Dr. Thomas Pitts.*

**Figure 4.** *Marking the contact points reference for establishing occlusogingival positioning of brackets.*

**Figure 5.** *Bracket positioning in the maxillary incisors and canines.*

**Figure 6.** *Use of a large front surface mirror to prevent errors in bracket positioning.*

#### **7.3 Maxillary premolars**

The maxillary premolars are positioned by aligning the scribe line with the crown long axis at the height of contour paralleling the central groove and the M-D buccal line angle. Following correct bracket placement, the bracket on the first premolar would seem too distal to the height of contour and the second premolar at times would appear mesial to the height of contour when viewed from the buccal aspect. The occlusal edge of the brackets should touch the M-D contact line (**Figure 7**).

#### **7.4 Maxillary molars**

The mesiodistal positioning of the buccal tube is done by centering the buccal tube pad over the buccal groove of the teeth and the occluso gingival positioning is done

**Figure 7.** *Bracket positioning in the maxillary premolars.*

*The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol DOI: http://dx.doi.org/10.5772/intechopen.100536*

by placing the occlusal edge of the pad on the M-D contact line of the first molar. The second molars follows the same rule for mesiodistal positioning but placed 1.5 mm more occlusally to the first molar tube (**Figure 8**).

#### **7.5 Mandibular incisors**

The mandibular incisors are placed such that the scribe line is aligned with the long axis of the tooth. The bracket position is viewed from the incisal aspect. For deep bite, the position of the top of the slot is 3.5 mm from the incisal edge to reverse the curve of spee and for open bite; the position of the top of the slot is 5 mm from the incisal edge to open the curve of spee (**Figure 9**).

#### **7.6 Mandibular canines**

The mesiodistal positioning is done by aligning the scribe line to the long axis of the crown at the height of contour. The position is verified by viewing from the incisal

**Figure 8.** *Bracket positioning in the maxillary molars.*

**Figure 9.** *Bracket positioning in the mandibular anteriors.*

aspect. The occluso gingival positioning is placing the incisal edge of the bracket wing at the M-D contact line (**Figure 10**).

#### **7.7 Mandibular premolars**

The mesiodistal positioning is done by aligning the scribe line to the crown long axis and viewed from the occlusal aspect. The occluso gingival positioning is based on positioning the occlusal edge of the bracket wing 0.5 mm gingival to the M-D contact line (**Figure 11**).

#### **7.8 Mandibular molars**

The mandibular molars are placed in the same way as the maxillary molars in terms of mesiodistal positioning by orienting the center of the buccal tip of the buccal tube with that of the buccal groove of the tooth. Unlike the maxillary molars, both the mandibular molars are placed at the same height, which is 0.5 mm gingival to the M-D contact line (**Figure 12**).

#### **Figure 10.** *Bracket positioning in the mandibular canine.*

**Figure 11.** *Bracket positioning in the mandibular premolars.*

**Figure 12.** *Bracket positioning in the mandibular molars.*

*The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol DOI: http://dx.doi.org/10.5772/intechopen.100536*

**Figure 13.** *Figure showing placement of brackets in the maxillary anteriors.*

Another technique that was proposed was the bracket placement in Beethoven's Orthodontic center. The bracket placement was similar to that given by Dr. Pitts except some modifications that were made in the maxillary canines. According to him, the maxillary canine bracket is placed by aligning it 1 mm mesially away from the long axis of the crown. The slot of the canine was used as a reference for placing the incisor brackets. The slots of the central and lateral incisor brackets are raised 0.5 mm consecutively (**Figure 13**).

#### **8. Ideal cases for Damon**

Dr. Damon has said that force applied to the bracket should be as light as possible to stimulate tooth movement. His philosophy was to employ the concept of biological adaptation and facially driven treatment plan that focuses on facial esthetics as a critical foundation for diagnosis.

The treatment objective in Damon cases is to


Damon system can be used in the following cases


Using the light forces from the Copper NiTi wires and friction less passive selfligating brackets along with Superelastic NiTi open coil springs wherever required we can achieve a desired treatment outcome with the Damon system.

In case of Class II patients with retrognathic mandibles we can go for Phase 1 therapy with functional appliances or fixed functional appliances.

#### **9. Recent advances**

The Damon self-ligating appliances have certain characteristics such as ease in ligation, wire engagement without undesirable force relaxation of elastomeric modules, which helps in maintaining a constant active status of engaged wires. This makes the Damon appliance more suitable than conventional appliances. This is in agreement with the findings by various other orthodontists, Berger [20], Harradine [9], Turnbull and Birnie [4].

Ormco, Damon Company keeps evolving over the years, coming out with different and more compatible bracket systems. Starting from Damon 3©, to Damon 3mx©, to Damon Q©, to Damon Q2© followed by the latest development, the Damon Ultima™© system. In clear ceramic braces from Damon clear© they have recently developed the Damon Clear 2© system.

#### **9.1 Damon Clear2 ©**

They are completely esthetic passive self-ligating brackets made of polycrystalline alumina (PCA) material, which is resistant to staining from coffee, mustard, red wine and other agents. It eliminates the need for the use of elastomers (modules) which generally stain and collect bacteria during the course of the treatment.

Damon Clear 2© brackets have a sturdy base with a fortified slide, window channel and tie wings for extra strength and durability. The four solid walls enable effective torque expression and rotation control for a good and meticulous finishing (**Figures 14** and **15**).

The base design of the Damon Clear 2© brackets is a patented laser etched pad that provides optimal bond strength for greater reliability (**Figure 16**). The contours *The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol DOI: http://dx.doi.org/10.5772/intechopen.100536*

**Figure 14.** *Damon clear 2© bracket.*

**Figure 15.** *Enhanced strength for effective torque expression.*

**Figure 16.** *Laser etched base for enhanced stability.*

of the brackets are smooth and rounded, which ensures patient comfort. The is an option to switch to brackets that have discrete contoured hooks for elastics and other auxiliaries (**Figure 17**).

Generally ceramic brackets are thought of as messy, while debonding as they tend to crack and splutter while using a debonding plier to remove the bracket. Whilst, for Damon Clear 2©, Ormco has a patented debonding instrument, the Damon Clear Debonding Instrument ©, which results in fast and comfortable debonding experience for patients (**Figure 18**). There is also no requirement for removing flash after the debonding procedure.

Removable positioning gauge with scaler notch is present in each of the clear brackets for easy and efficient placement of the bracket (**Figure 19**). There are colorcoded positioning gauges on brackets (13–23) present that denote torque values.

For a higher efficient and quality treatment, proper wire sequencing must be employed. The initial arch wires being the Damon Optimal-Force Copper Ni-Ti® to low-friction TMA and stainless-steel arch wires. Each wire must have sufficient time to express itself before progression to the next wire. For anterior torque expression,

**Figure 17.** *Discrete contoured hooks for auxiliaries.*

**Figure 18.** *Debonding of the bracket with Damon clear Debonding instrument ©.*

*The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol DOI: http://dx.doi.org/10.5772/intechopen.100536*

#### **Figure 19.** *Removable position gauge with scalar notch.*

either pre-torqued nickel titanium arch wires or TMA arch wires are to be used. For rotational bends, TMA arch wires or titanium niobium arch wires are to be used. However, care should be taken in employing finishing bends in stainless steel wires, since such bends may result in fractures.

#### **9.2 Damon Ultima ©**

Damon Ultima ™ © was designed and introduced for a faster and a more precise finishing. Traditional passive self-ligating brackets and wires have significant play which generally results in poor control, manual adjustments and extended treatment time. The Damon Ultima ™© system is the first system that is completely reengineered to virtually eliminate play, for a precise control of rotation, angulation and torque [3].

The enhanced features in Damon Ultima ™© are as follows:


**Figure 20.** *Reengineered tie wing in Damon Ultima ™©.*

#### **Figure 21.** *Smoother tie wings for patient comfort.*

The retrocline and procline bracket options were introduced for enhanced torque control. Brackets were designed from the centre point of the clot to the line-up with the FA point to express desired torque and provide easier and more precise placement (**Figure 26**).

*The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol DOI: http://dx.doi.org/10.5772/intechopen.100536*

**Figure 23.** *The enhanced bracket door design.*

**Figure 24.** *Rhomboid shaped pad in Damon Ultima ™©.*

**Figure 25.** *Vertical slot for placement of drop-in hooks.*

Additionally, extra arch wire options were included, for torque control when needed. Sizes available are: 0.019\*0.0275, 0.0020\*0.0275, and 0.021\*0.0275 in Copper NiTi, TMA and SS (**Figure 27**).

#### **Figure 26.**

*Adversity of procline and retrocline brackets in the Damon Ultima ™© system, that can be used to incorporate torque whenever needed.*

**Figure 27.** *Reengineered arch wire for better torque control.*

#### **10. Conclusion**

Passive self-ligation offers the most direct transmission of force from the arch wire to the tooth with very low friction, a very secure ligation along with excellent control of tooth position. Every contemporary modality of orthodontic treatment achieves tooth alignment; however passive self-ligation achieves the results effectively and efficiently. With the evolution of various systems like Damon Clear2 and Damon Ultima ©, the orthodontic tooth movement is achieved at its best.

#### **Conflict of interest**


Dr. Chandhini Suresh- No conflict of interest with the product (ORMCO).

*The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol DOI: http://dx.doi.org/10.5772/intechopen.100536*

#### **Author details**

Suvetha Siva1 \*, Shreya Kishore1 , Suganya Dhanapal<sup>2</sup> , Janani Ravi1 and Chandhini Suresh1

1 SRM Dental College, Ramapuram, Chennai, India

2 Sri Ramakrishna Dental College, Coimbatore, India

\*Address all correspondence to: suvetha150992@gmail.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

[1] Ramachandra. C. S. Damon system protocol for management of class I, class II & class III malocclusions [Modular based learning].

[2] Damon DH. The rationale, evolution and clinical application of the selfligating bracket. Clin Orthod Res. 1998 Aug;**1**(1):52-61

[3] Birnie D. The Damon Passive Self-Ligating Appliance System. Semin Orthod. 2008 Mar 1;**14**(1):19-35

[4] Turnbull NR, Birnie DJ. Treatment efficiency of conventional vs self-ligating brackets: effects of archwire size and material. Am J Orthod Dentofacial Orthop. 2007 Mar;**131**(3):395-399

[5] Gianoni-Capenakas S, Flores-Mir C, Vich ML, Pacheco-Pereira C. Oropharyngeal 3-dimensional changes after maxillary expansion with 2 different orthodontic approaches. Am J Orthod Dentofacial Orthop. 2021 Mar;**159**(3):352-359

[6] Lineberger MB, Franchi L, Cevidanes LHS, Huanca Ghislanzoni LT, McNamara JA Jr. Three-dimensional digital cast analysis of the effects produced by a passive self-ligating system. Eur J Orthod. 2016 Dec;**38**(6): 609-614

[7] Srinivas S. Comparison of canine retraction with self-ligated and conventional ligated brackets-a clinical study. India: Thesis in fulfillment of postgraduate degree, Tamilnadu Medical University, Chennai; 2003

[8] Eberting JJ, Straja SR, Tuncay OC. Treatment time, outcome, and patient satisfaction comparisons of Damon and conventional brackets. Clin Orthod Res. 2001 Nov;**4**(4):228-234

[9] Harradine NW. Self-ligating brackets and treatment efficiency. Clin Orthod Res. 2001 Nov;**4**(4):220-227

[10] Maijer R, Smith DC. Time savings with self-ligating brackets. J Clin Orthod. 1990 Jan;**24**(1):29-31

[11] Carels C, Willems G. The Future of Orthodontics. Leuven University Press; 1998. 281 p.

[12] McLaughlin RP, Bennett JC, Trevisi HJ. Systemized Orthodontic Treatment Mechanics. Mosby; 2001. 324 p.

[13] Fleming PS, DiBiase AT, Sarri G, Lee RT. Comparison of mandibular arch changes during alignment and leveling with 2 preadjusted edgewise appliances. Am J Orthod Dentofacial Orthop. 2009 Sep;**136**(3):340-347

[14] Mandall N, Lowe C, Worthington H, Sandler J, Derwent S, Abdi-Oskouei M, et al. Which orthodontic archwire sequence? A randomized clinical trial [Internet]. Vol. 28, The European Journal of Orthodontics. 2006. p. 561-6. Available from: http://dx.doi. org/10.1093/ejo/cjl030

[15] Ong E, Ho C, Miles P. Alignment efficiency and discomfort of three orthodontic archwire sequences: a randomized clinical trial. J Orthod. 2011 Mar;**38**(1):32-39

[16] Rahmani A, Oz U. The Effect of Copper Aided Nickel--Titanium Arch-Wire Sequences on Upper Jaw Expansion: A Comparison with Conventional

*The Value of Self-Ligating Brackets in Orthodontics: About the Damon Protocol DOI: http://dx.doi.org/10.5772/intechopen.100536*

Nickel--Titanium Wire Systems in Medical Decision Support Systems in Medical Internet of Things. Journal of Medical Imaging and Health Informatics. 2020;**10**(1):238-243

[17] Handem RH, Janson G, Matias M, de Freitas KMS, de Lima DV, Garib DG, et al. External root resorption with the self-ligating Damon system—a retrospective study. Prog Orthod. 2016 Jul 1;**17**(1):20

[18] de Freitas KMS, Vaz de Lima D. Comparison of changes in dental arch dimensions in cases treated with conventional appliances and self-ligating Damon system. Open Dent J [Internet]. 2018; Available from: https:// opendentistryjournal.com/VOLUME/12/ PAGE/1137/

[19] Pitts T. Begin with the end in mind: Bracket placement and early elastics protocols for smile arc protection. Clin Impressions. 2009;**17**(1):1-11

[20] Berger J. Self-ligation in the year 2000. J Clin Orthod. 2000;**34**(2):74-81

#### **Chapter 12**

## Pain Perception in Patients Treated with Ligating/Self-Ligating Brackets versus Patients Treated with Aligners

*Farid Bourzgui, Rania Fastani, Salwa Khairat, Samir Diouny, Mohamed El Had, Zineb Serhier and Mohamed Bennani Othmani*

#### **Abstract**

This study compared the perception of pain experienced by patients undergoing orthodontic treatment with conventional, self-ligating brackets and aligners, and investigated the impact that pain had on their daily lives. 346 consecutive patients were included in the study: 115 patients treated with conventional brackets, 112 Patients treated with self-ligating brackets, and 119 patients treated with aligners. The quantitative aspect of pain was assessed using the Visual Analogue Scale, while the qualitative aspect of pain was evaluated using the Moroccan Short Form of McGILL Pain questionnaire. In all three groups experienced pain after activation tended to decrease in the following week. This pain was greater in patients with conventional braces and less in patients with aligners. Using the M-SF-MPQ to describe the qualitative aspect of the pain revealed that the "cramping مزير," "aching تيألم "aspect was most accentuated in the 3 groups. Medication intake was correlated with the intensity of pain experienced in all 3 systems. As for the impact of pain on daily activities, patients in groups of conventional and self-ligating braces showed more pain than those in the aligners group. Overall, aligners were less painful than conventional and self-ligating appliances. Patients did not suffer from an alteration in their quality of life due to orthodontic treatment.

**Keywords:** orthodontics, corrective, clear aligner appliances, facial pain, pain measurement, Morocco

#### **1. Introduction**

Pain is defined as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage." (IASP) [1]; it: "is a mutually recognizable somatic experience that reflects a person's apprehension of threat to their bodily or existential integrity" [2].

Orthodontic tooth movement requires the application of force to the tooth, which usually results in a painful sensation [3]. It is important to note that there are individual differences in pain sensitivity related to the subjective aspect of pain perception [4].

Recently, orthodontic practices have evolved considerably. In addition to conventional or self-ligating appliances, aligners represent an esthetic and comfortable alternative option for orthodontic treatment. Even though these methods have revolutionized orthodontics practices, practitioners are still confronted with the painful aspect of the treatment. Some patients perceive orthodontic pain as discomfort or inconvenience; others continue to be in so much pain that it can cause them to discontinue treatment [5]. This feeling of discomfort could impact the quality of life of patients and their cooperation. Also, for some patients, factors such as comfort and pain during orthodontic treatment are as important as esthetic considerations. In most cases, the quality of information given to patients about the likely discomfort during orthodontic treatment is somewhat satisfactory, though many patients complain that they are not well informed before the onset of treatment [5].

Previous studies have investigated orthodontics pain and its components for each system there is a dearth of studies that have compared the character and type of pain experienced in qualitative and descriptive terms between the different options used in orthodontics, i.e., conventional appliances, self-ligating appliances, and aligners.

Against this background, the aim of this study was two-fold: First, to compare the perception of pain experienced by patients treated with conventional brackets, selfligating brackets, and those treated with aligners. Second, to investigate the impact that pain had on their daily lives.

#### **2. The perception of pain experienced by patients treated with conventional braces, self-ligating braces, and those treated with aligners**

#### **2.1 Patients and methods**

A cross-sectional stud was performed to compare the perception of pain between patients treated with self-ligating fixed appliances and those treated with aligners treated at both the Department of Orthodontics at Casablanca Ibn Rochd University Hospital, and at a private orthodontic office. The study lasted 4 months (November 2019–February 2020). All the patients underwent orthodontic treatment for a period exceeding 2 months, the chief complaint was purely aesthetic and all patients were in class I dento-maxillary disharmony. In relation to our inclusion criteria, we have chosen patients in the process of treatment, avoiding patients at the beginning of treatment where adaptation is not yet established, as well as patients at the end of treatment, as they may be accustomed to their orthodontic appliances.

Exclusion criteria included patients under 8 years of age, those at the beginning of treatment or less than 2 months or at the end of treatment, and those with no medical contraindications or the presence of systemic diseases that influence pain perception (including nervous system disorders).

The study group consisted of 346 consecutive patients: 115 treated with conventional brackets. 112 were treated with self-ligating brackets and 119 were treated with aligners.

The data collection tool was a self-made questionnaire consisting of the socioeconomic characteristics of patients, the type of appliance worn, and temporal

*Pain Perception in Patients Treated with Ligating/Self-Ligating Brackets versus Patients Treated… DOI: http://dx.doi.org/10.5772/intechopen.102796*

characteristics of pain during the week of activation, qualitative factors influencing pain after activation, actors influencing pain during the week of activation, the impact of pain on the patient's daily, professional and school life, the patient's attitude to pain, the most distressing element during the treatment stages. The patients were informed about the purpose of the study, and verbal consent was obtained.

The quantitative aspect of the pain was assessed using the Visual Analogue Scale (VAS). The scale used is a graduated ruler whose extremities represent the absence of pain 0 and the maximum imaginable pain 10. The VAS scale was presented to the patients by the operator after explaining the instructions for use, in two stages: After the activation appointment and during the week that followed.

To evaluate the qualitative aspect of pain, we used the M-SF-MPQ "the Moroccan Short Form of McGill Pain questionnaire" [6], previously translated from English and culturally adapted and validated in Moroccan Arabic.

Data were analyzed using SPSS statistical 16.0 software. The comparison of pain perception between the different types of systems was done using the Chi-square test, or Fischer's exact test when the theoretical numbers were low. The comparison of pain intensity according to the VAS score was carried out using the Kruskal Wallis test.

#### **2.2 Results**

**Table 1** contains the age distribution of our sample. The dominant age range for each type of appliance was: 16–25 years, 58 patients (50.4%) for conventional brackets, 8–15 years, 62 patients (55.4%) for self-ligating brackets, and more than 25 years 71 patients (59.7%) for Aligners. The statistical association between age group and type of appliance was significant (p<0.001). Of 346 patients, 137 (39.6%) were male and 209 were female (60.4%). We noted that the female gender was the most dominant in the three groups, respectively: 63 patients (54.8% with the conventional brace, 60 patients (53.6%) with self-ligating braces, and 86 patients (72.3%) with aligners: The statistical association between gender and the type of appliance was significant (p<0.001) (**Table 2**).

The socio-economic level in the sample was high in 63%, medium in 24.6%, and low in 12.4%. The association between socioeconomic level and the type of appliance used was statistically significant (p<0.001) (**Table 3**).

With respect to the duration of treatment, for 87 patients (25.1%) the beginning of treatment ranged between 2 and 8 months ago, and 259 patients (74.9%) started treatment more than 8 months ago. The comparison between the duration of treatment and the type of appliance used was statistically significant (p<0.001).


#### **Table 1.**

*Distribution of the sample by age group according to the type of appliance used.*


**Table 2.**

*Distribution of the sample by gender according to the type of appliance used.*


#### **Table 3.**

*Distribution of the sample by the socio-economic status according to the type of appliance used.*

The vulnerability to pain showed that 295 patients (85.3%) were able to tolerate pain, while 51 patients (14.7%) could not tolerate pain. The statistical correlation between pain vulnerability and the type of appliance used was significant, (p<0.001) (**Table 4**).

As for pain conditioning, 262 patients (75.7%) already knew someone who had undergone orthodontic treatment, 176 (66.18%) of which reported that this person had experienced pain. Only 84 patients 24.3%. did not know a person, who had received orthodontic treatment. The statistical correlation between the knowledge of a person who underwent orthodontic treatment and the type of appliance used was significant (p<0.001).

303 patients reported pain after orthodontic activation, representing 87.6% of the total sample. The statistical association between the presence of pain after activation and the type of appliance was significant (p<0.001) (**Table 5**). The intensity of this pain after activation had an average of 6 for conventional and self-ligating braces and 3 for aligners. Despite this intensity, 297 patients (85.8%) reported a reduction in pain the week following the activation. 106 patients (92.2%) with conventional braces, 101 patients (90.2%) with self-ligating braces, and 90 patients (75.6%) with aligners reported a decrease in pain the week following activation. The statistical association


**Table 4.**

*Distribution of the sample according to vulnerability to pain by type of appliance.*

*Pain Perception in Patients Treated with Ligating/Self-Ligating Brackets versus Patients Treated… DOI: http://dx.doi.org/10.5772/intechopen.102796*


**Table 5.**

*Distribution of the sample according to the presence of pain after activation.*

between pain reduction in the week following the activation appointment and the type of appliance was significant (p<0.001). During the second week, we found a median of 2, a minimum value of 0, and a maximum of 8 for conventional braces, a median of 0 and a maximum value of 8 for self-ligating, and a median of 0 and a maximum value of 7 for aligners.

The qualitative aspects of pain for the three types of orthodontic appliances are outlined in **Table 6**. The association of the different qualitative aspects of pain according to the type of appliance was statistically significant (p<0.001).

**Table 7** presents the distribution of the sample according to the most painful aspect during orthodontic treatment according to the type of appliance used. The statistical correlation between the most distressing aspect during orthodontic treatment and the type of appliance was significant (p<0.001). Patients' reactions to pain after activation, at 24 hours, after 3 days, and at one week are reported in **Table 8**.

#### **2.3 Discussion**

The aim of this study was to compare the pain perception of patients treated during orthodontic alignment with three different orthodontic appliance types. The results showed that the aligner system was less painful than the vestibular fixed appliances. There were minor differences in the reported pain intensity between conventional and self-ligating systems. Analgesics were mostly used by patients who reported severe pain. Despite the pain experienced by different patients, there was no impact on their quality of life, except for eating and chewing, where the aligners group showed promising results.

Several studies have analyzed the pain levels experienced with different types of brackets. In most of these studies, it was estimated that appliance-related pain was higher for the first 24 hours–3 days of appliance activation, then decreased to low levels within 5–6 days [4]. Scheurer et, al. [7] reported a trend of high pain within 2 days of appliance activation and a trend of pain relief after 5 days. This trend was confirmed in this study. The pain was higher after activation and significantly decreased within 3 days, then to zero within 7 days. Tecco et al. [3] suggested that regardless of the type of fixed appliance used (conventional or self-ligating), the highest intensity of pain was reported in the first two to three days after the initial activation of the appliance. Fleming et al. [8] confirmed that the subjective experience of pain at 4 hours, 24 hours, 3 days, and 7 days after placement of a fixed orthodontic appliance was independent of bracket type. Johal et al. [4] found a slight reduction in pain scores as the orthodontic therapy went on, although these differences were not statistically significant. Nevertheless, this suggests that orthodontic pain may decrease in intensity during treatment, or may reflect some degree of adaptation to discomfort.

#### *Current Trends in Orthodontics*


*Pain Perception in Patients Treated with Ligating/Self-Ligating Brackets versus Patients Treated… DOI: http://dx.doi.org/10.5772/intechopen.102796*


#### **Table 6.**

*Distribution of the sample according to the qualitative aspect of pain.*


#### **Table 7.**

*Distribution of the sample according to the most painful aspect during orthodontic treatment according to the type of appliance.*


#### **Table 8.**

*Patients' reaction to pain according to the type of appliance used.*

White et al. [9] showed that discomfort after the first and second monthly adjustments was also consistently lower for the aligner than for conventional treatment. For both groups, the levels of discomfort reported at subsequent adjustments reached lower levels than after the initial placement, or when the aligner was first worn.

Patients treated with self-ligating brackets reported significantly less pain than those treated with conventional brackets. These results were consistent with a study conducted by Pringle et al. [10] who reported that the self-ligating appliance (Damon *Pain Perception in Patients Treated with Ligating/Self-Ligating Brackets versus Patients Treated… DOI: http://dx.doi.org/10.5772/intechopen.102796*

3, Ormco) resulted in lower pain intensity, on average, compared to the conventional appliance (Tru Straight, Ormco Europe, Amersfoort, The Netherlands). However, Fleming et al. [8] found that significant discomfort was experienced during the insertion and removal of the archwire with the self-ligating device (SmartClip) compared to the conventional system (Victory). Other studies pointed out that there was no statistically significant difference in perceived discomfort levels between the two types of system, namely Damon3 and Synthesis [11] and SmartClipTM and Victory [12].

After activation, patients in the conventional brackets group reported more pain than those in the aligner group. This is in agreement with the results reported in White et al. [9] who maintained that conventional appliances produced significantly more discomfort than aligners. Fujiyama et al [13] noted that patients experienced less pain with Invisalign treatment than with conventional appliances during treatment. Shalish et al. [14] indicated that the results were opposite to those found previously. A greater proportion of patients treated with Invisalign aligners reported more severe pain than did vestibularly treated patients.

In this study, the pain experienced after wearing aligners was lower than that experienced by patients with self-ligating appliances. This finding was consistent with a study by Almasoud [15] who reported that during the first week of orthodontic treatment, patients treated with Invisalign experienced less pain than those treated with a passive self-ligating system. Similarly, in a systematic review, Cardoso et al.; [16] concluded that patients treated with Invisalign seemed to experience lower levels of pain than those treated with fixed appliances during the first days of treatment, and no difference was reported in the next 3 months. In fact, patients treated with aligners reported lower pain levels for a longer period of time, as the fixed appliance was activated once a month and the aligners were changed every 15 days.

The M-SF-MPQ is a very reliable tool for measuring pain in its two sensory and affective components [7]. The use of this criterion makes it possible to establish a comparative profile of the quality of the pain experienced by each group. It was noted that in all 3 systems, the sensory description "cramping مزير " was most reported by all patients in all 3 groups. Comparisons revealed that sensory and affective descriptors were used more in patients in the conventional group, than in the self-ligating or aligner group. Overall, patients in the conventional group identified 6 sensory descriptors, and those in the following descending order: 'cramping مزير',' aching In .'كضرب بحال اضو shooting 'and' تحرق بزاف burning hot ','ماضي sharp ','كيزدح throbbing ','تيألم contrast, patients in the self-ligating and aligner system identified 3 sensory descriptors: 'cramping مزير 'followed by 'aching تيألم 'and 'tender خفيف'. However, the proportion of subjects in each group who selected the descriptors was consistently lower in the aligner group than in the self-ligating group. For effective components, the self-ligating and aligner systems did not really raise this aspect of pain, while for the conventional system the most used description was "punishing-cruel بزاف تعدب". Tecco et al. [3] reported that the other two pain descriptors "shooting" and "dull" were used to a lesser extent. Whereas in Bergius et al.'s study [17], the terms "shooting" and "dull" were never used to describe the pain of their patients.

This study showed that tooth brushing could cause pain in patients with fixed appliances. Although the pain was generally minimal, it was experienced by a greater proportion of the sample in the conventional group than in the self-ligating group. However, patients in the aligner group reported almost no discomfort when brushing. The results of the Rakhshan et al. study [17] indicated that tooth brushing mainly induced mild pain. This result was consistent with other studies which suggested that orthodontic pain may have a negative effect on oral hygiene [18, 19].

Pain intensity scores and their impact on daily work/school activities had a minimal effect that peaked at a 24-hour period. In the following days, the number of patients reporting such an effect decreased. Scheurer et al. [7] found that the insertion of fixed appliances seemed to have only a minor effect on the patients' daily life. This is consistent with our results. Shalish et al. [14] noted that the levels of disturbance in oral symptoms and general activities with Invisalign were similar to those of patients with fixed appliances. In contrast, Miller et al. [20] found that the fixed appliance group reported more negative impact than the Invisalign group.

A correlation between pain intensity scores and analgesic use was also observed. In general, analgesics were mostly used by patients who reported more severe pain. In this study, a large proportion of patients did not use medication, as reported in Firestone [21] and Bergius's studies [22]. During orthodontic treatment, analgesic consumption differs according to the period of treatment. Wu et al [23] noted that analgesics were used more frequently during the initial phases of treatment, when pain intensity was highest, supporting the hypothesis that the pain experienced later in orthodontic treatment was relatively low. In our study, after activation, 27% of the patients treated with conventional appliances, 25% of the patients treated with a self-ligating system, and 5.9% treated with aligners used medication after activation. A small percentage of patients used analgesics at 24 hours and 3 days. These patients mainly took paracetamol and a few used non-steroidal anti-inflammatory drugs (ibuprofene) to relieve pain. Most patients used self-medication. Scheurer et al. [7] stated that perceived pain and analgesic consumption would decrease if the patient were effectively informed of the discomfort in advance.

At the end of this chapter, we are aware that our study was a descriptive study with significant selection bias with respect to the confounding factors of need for orthodontic treatment, stage of treatment, age, and undetectable susceptibility to pain and even to orthodontic treatment. A cohort study with three groups benefiting from the three therapeutic choices, taking into account age, gender, type of malocclusion, and facial typology, is the following step to move to observational studies for more epidemiological inference.

#### **3. Conclusion**

Orthodontic treatment creates pain at different stages, which seems to be particularly intense at the beginning of treatment and tends to diminish during the course of treatment. Its intensity and duration may be influenced by the type of appliance worn. The results of this study showed that the aligner system was less painful than fixed brackets. There were only minor differences in the reported pain intensity between the conventional and self-ligating appliances. This pain was characterized in all 3 systems by the descriptors "cramping مزير "and "Aaching تيألم".

The daily quality of life of patients treated with aligners was, therefore, better than that of patients treated with fixed appliances. The consumption of analgesics, correlated with the intensity of the pain experienced. Depending on the patient's pain threshold and psychological profile, clinicians should consider prescribing analgesics to alleviate patients' unpleasant experiences.

These observations can be used in clinical situations by informing patients in advance of a specific complaint associated with a particular type of device and will give practitioners and patients additional information that can be used when choosing the type of device. This can help reduce negative experiences of therapy and increase

*Pain Perception in Patients Treated with Ligating/Self-Ligating Brackets versus Patients Treated… DOI: http://dx.doi.org/10.5772/intechopen.102796*

patients' confidence in their orthodontist. Pain is not inevitable, it can be prevented and treated as well as possible.

#### **Conflict of interest**

Ethical clearance was obtained from the Ethics Committee of the Faculty of Dentistry, University of Hassan II University, and all participants and their respective teachers were informed about the aims of the study. Access to schools was granted by the Casablanca Regional Academy of Education and training. The parental consent and authorization of all students were also obtained. All authors stated that no conflict could influence their participation in this study.

#### **Acronyms and abbreviations**


#### **Author details**

Farid Bourzgui1 \*, Rania Fastani<sup>2</sup> , Salwa Khairat3 , Samir Diouny4 , Mohamed El Had<sup>5</sup> , Zineb Serhier<sup>6</sup> and Mohamed Bennani Othmani6

1 Department of Orthodontics, Dental School, University Hassan II, Casablanca, Morocco

2 Private Practice Rés. les collines, Casablanca, Morocco

3 Private Practice, Casablanca, Morocco

4 Neurolinguistics and Psychology of Language Hassan II University, Clinical Neuroscience and Mental Health Lab, Casablanca, Morocco

5 Orthodontist Private Practice, Casablanca, Morocco

6 Faculty of Medicine and Pharmacy, Laboratory of Medical Informatics, University Hassan II, Casablanca, Morocco

\*Address all correspondence to: farid.bourzgui@etu.univh2c.ma

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

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[2] Cohen M, Quintner J, van Rysewyk S. Reconsidering the international association for the study of pain definition of pain. Pain Reports. 2018;**3**(2):e634

[3] Tecco S, D'Attilio M, Tetè S, Festa F. Prevalence and type of pain during conventional and self-ligating orthodontic treatment. European Journal of Orthodontics. 2009;**31**(4):380-384

[4] Johal A, Fleming PS, Al Jawad FA. A prospective longitudinal controlled assessment of pain experience and oral health-related quality of life in adolescents undergoing fixed appliance treatment. Orthodontics & Craniofacial Research. 2014;**17**(3):178-186

[5] Ngan P, Kess B, Wilson S. Perception of discomfort by patients undergoing orthodontic treatment. American Journal of Orthodontics and Dentofacial Orthopedics. 1989;**96**(1):47-53

[6] Bourzgui F, Diouny S, Rguigue O, Aghutan H, Serhier Z, Othmani MB. Cross-cultural adaptation and validation of the Moroccan Short Form McGill Pain Questionnaire (SF-MPQ ). International Journal of Medical Reviews and Case Reports. 2020;**4**(11):81-86. DOI: 10.5455/ IJMRCR.McGill-Pain-Questionnaire

[7] Scheurer PA, Firestone AR, Bürgin WB. Perception of pain as a result of orthodontic treatment with fixed appliances. European Journal of Orthodontics. 1996;**18**(4):349-357

[8] Fleming PS, Dibiase AT, Sarri G, Lee RT. Pain experience during initial alignment with a self-ligating and a conventional fixed orthodontic appliance system. A randomized controlled clinical trial. The Angle Orthodontist. 2009;**79**(1):46-50

[9] White DW, Julien KC, Jacob H, Campbell PM, Buschang PH. Discomfort associated with Invisalign and traditional brackets: A randomized, prospective trial. The Angle Orthodontist. 2017;**87**(6):801-808

[10] Pringle AM, Petrie A, Cunningham SJ, McKnight M. Prospective randomized clinical trial to compare pain levels associated with 2 orthodontic fixed bracket systems. American Journal of Orthodontics and Dentofacial Orthopedics. 2009; **136**(2):160-167

[11] Scott P, Sherriff M, Dibiase AT, Cobourne MT. Perception of discomfort during initial orthodontic tooth alignment using a self-ligating or conventional bracket system: A randomized clinical trial. European Journal of Orthodontics. 2008;**30**(3): 227-232

[12] Rahman S, Spencer RJ, Littlewood SJ, O'Dywer L, Barber SK, Russell JS. A multicenter randomized controlled trial to compare a self-ligating bracket with a conventional bracket in a UK population: Part 2: Pain perception. The Angle Orthodontist. 2016;**86**(1):149-156

[13] Fujiyama K, Honjo T, Suzuki M, Matsuoka S, Deguchi T. Analysis of pain level in cases treated with Invisalign aligner: Comparison with fixed edgewise appliance therapy. Progress in Orthodontics. 2014;**15**(1):64

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[14] Shalish M, Cooper-Kazaz R, Ivgi I, Canetti L, Tsur B, Bachar E, et al. Adult patients' adjustability to orthodontic appliances. Part I: A comparison between Labial, Lingual, and Invisalign™. European Journal of Orthodontics. 2012;**34**(6):724-730

[15] Almasoud NN. Pain perception among patients treated with passive self-ligating fixed appliances and Invisalign® aligners during the first week of orthodontic treatment. Korean Journal of Orthodontics. 2018;**48**(5): 326-332. DOI: 10.4041/kjod.2018. 48.5.326

[16] Wiedel AP, Bondemark L. A randomized controlled trial of selfperceived pain, discomfort, and impairment of jaw function in children undergoing orthodontic treatment with fixed or removable appliances. The Angle Orthodontist. 2016;**86**(2):324-330

[17] Rakhshan H, Rakhshan V. Pain and discomfort perceived during the initial stage of active fixed orthodontic treatment. Saudi Dent Journal. 2015;**27**(2):81-87. DOI: 10.1016/j. sdentj.2014.11.002

[18] Krukemeyer AM, Arruda AO, Inglehart MR. Pain and orthodontic treatment. The Angle Orthodontist. 2009;**79**(6):1175-1181. DOI: 10.2319/ 121308-632R.1

[19] Sergl HG, Klages U, Zentner A. Pain and discomfort during orthodontic treatment: Causative factors and effects on compliance. American Journal of Orthodontics and Dentofacial Orthopedics. 1998;**114**(6):684-691. DOI: 10.1016/s0889-5406(98)70201-x

[20] Miller KB, McGorray SP, Womack R, Quintero JC, Perelmuter M, Gibson J, et al. A comparison of treatment impacts between invisalign aligner and fixed

appliance therapy during the first week of treatment. American Journal of Orthodontics and Dentofacial Orthopedics. 2007;**131**(3): 302.e1-302.e9. DOI: 10.1016/j.ajodo. 2006.05.031

[21] Firestone AR, Scheurer PA, Bürgin WB. Patients' anticipation of pain and pain-related side effects, and their perception of pain as a result of orthodontic treatment with fixed appliances. European Journal of Orthodontics. 1999;**21**(4):387-396

[22] Bergius M, Berggren U, Kiliaridis S. Experience of pain during an orthodontic procedure. European Journal of Oral Sciences. 2002;**110**(2):92-98. DOI: 10.1034/j.1600-0722.2002.11193. x

[23] Wu AK, McGrath C, Wong RW, Wiechmann D, Rabie AB. A comparison of pain experienced by patients treated with labial and lingual orthodontic appliances. European Journal of Orthodontics. 2010;**32**(4):403-407. DOI: 10.1093/ejo/cjp117

#### **Chapter 13**

## Effects of Various Dentofacial Orthopedic and Orthognathic Treatment Modalities on Pharyngeal Airway

*Tejashri Pradhan and Aarti Sethia*

#### **Abstract**

The function of respiration is highly relevant to orthodontic diagnosis and treatment planning. Significant relationships between pharyngeal, craniofacial as well as dentofacial structures have been reported in several studies. Many authors have emphasized that mouth breathing is concomitantly associated with constricted airway causing obstructive sleep apnoea. Associated symptoms can be cured with correction of either skeletal or dental problems or both. Therefore it would be very intriguing to understand and interpret the airway during diagnosis and treatment planning for a clear view of changes in the airway dimensions during the course of orthodontic treatment using various treatment modalities. Therefore a complete understanding of the concept of airway should be considered as an important one. This chapter gives us an insight to the intricate detailing on how the various orthodontic and dentofacial orthopedic treatment signifies the changes in the dimensions of pharyngeal airway.

**Keywords:** pharyngeal airway, skeletal changes, dental changes, functional appliances, Orthognatic surgeries, expansion

#### **1. Introduction**

Orthodontia being one of its kind specialty has always aimed at correcting the dento-facial esthetics which involves achievement of: ideal jaw relationship, normal oral function, proximal and occlusal contact of teeth. But the core aspect of function and performance has been taken up by the function of respiration or breathing which in fact is the top most important function for humans. The synchrony of ideal health and facial development is based on accurate posture of tongue and nasal breathing. Therefore the recent protocols be it Preventive, interceptive or corrective orthodontics, factoring the dire need of pharyngeal airway space improvement in addition to improvement in smile and facial appearance [1].

Today Orthodontists play a very crucial and integral role in the interdisciplinary team management of airway and sleep related disorders. Commencement of Sleep

Medicine as a speciality has brought about a very clear understanding of transformative or developmental biology, medicine; the jaw size and its spatial orientation has surfaced as the important factor of optimizing upper airway physiology. Airway passage, type of breathing and craniofacial formation are so interconnected during growth and development that form follows the function and function follows the form [2]. So the specialty of orthodontics,is well balanced to treat ideally form and function both in children and adults so that the function is optimized for life. The conventional treatment in orthodontics has always priortised primarily on teeth esthetics. This method, seldom addresses symptoms and as a result the airway is ignored. Therefore it is necessary to focus more at physiologic adaptations and its muscle to resolve sleep disordered breathing [3].

The nasal airway analysis requires adequate anatomical dimensions for the overall pharyngeal airway space [4]. Oral breathing in relation to nasal obstruction is a well known entity among orthodontic patients [5]. Obstruction of nasopharyngeal pathway is associated with various craniofacial features, such as backward and upward growth of condyle, backward and downward rotation of mandible, divergent gonial angle, anterior open bite and spacing w.r.t mandibular anteriors [6]. The eradication of respiratory obstruction and aquiring adequate functional nasal breathing with precise patterns of swallowing boosts the stability and functional balance of orthodontic treatment (**Figure 1**) [7, 8].

#### **2. Anatomy of airway**

The airway, or respiratory tract, describes its organs that allow airflow during ventilation. They pass through the nares and buccal opening till the blind end of the alveolar sacs. This respiratory tract is subdivided into different regions and various organs and tissues to perform specific functions. The airway passage is subdivided into the upper and lower airway, each of which has numerous compartments.

#### *Effects of Various Dentofacial Orthopedic and Orthognathic Treatment Modalities… DOI: http://dx.doi.org/10.5772/intechopen.101719*

The pharynx is the mucosal lined portion of the airway that is situated between the base of the skull and the esophagus. It is subdivided as follows:


Boundary between nasopharynx and oropharynx is known as soft palate, similarly the boundary between the oropharynx and laryngopharynx is the epiglottis. The soft palate is dangled at the posterior corner of the hard palate, and its top and bottom are comprises of the mucosal tissues. The centre portion of the soft palate includes muscles, aponeurosis, blood vessels, nerves, lymph and mucosal tissues. During the process of deglutition and injestion, the soft palate develops postero-superiorly and separates the nasopharynx and oropharynx. The mandible is interconnected to the hyoid bone, tongue, and soft palate by the strong musculature. Therefore, the location of the mandible can affect the size of the pharyngeal airway space.

#### **3. Pharyngeal airway space (PAS)**

Pharyngeal airway space is divided into three compartments: (**Figure 2**). *Upper pharyngeal width (UPW)*: Its is the smallest distance between the posterior border of the soft palate to the nearest point on the posterior pharyngeal wall.

**Figure 2.** *Various compartments of the pharyngeal airway space [9].*

*Middle pharyngeal width (MPW)*: It is the smallest distance between the posterior borders of the tongue to the nearest point on the posterior pharyngeal wall, through the tip of the soft palate.

*Lower pharyngeal width (LPW)*: It is the smallest distance from the intersection of posterior border of tongue and inferior border of the mandible to the closest point on the posterior pharyngeal wall.

Normal upper pharyngeal airway space is 15–20 mm while middle and lower pharyngeal airway (LPA) space is 11–14 mm [9].

Literature supports the hypothesis that mandibular deficiency is analogous to a narrower PAS. It is generally observed that a retrognathic mandible and reduced space between the cranial column and the corpus of the mandible often leads to a posteriorly placed tongue and soft palate, which inturn increases the chances of impaired respiratory function and possibly causing nocturnal breathing problems. Alterations in PAS have been described with various sleeping disorders such as obstructive sleep apnea. Advancement and setback surgeries are standard procedures for the correction of mandibular position whether its retrognathism and prognathism, respectively. Operation for the mandibular deformity changes hard and soft tissue components, including the PAS [10].

#### **4. Diagnosis**

Malocclusion can be perceived in several ways which more likely includes patients with enlarged adenoids, obstructive sleep apnoea (OSA), snoring and clefts. The relation between respiratory pattern and form of malocclusion is still disputed. Patients with craniofacial disorders including a short cranial base, reduction in the cranial base angle, bimaxillary retrusion, and retrognathic mandibles show common finding of narrow airways [11].

#### **5. Various methods for assessment**

The methods described to assess the airway include: nasal endoscopy, rhinomanometry, acoustic rhinomanometry, cephalometry, computed tomography (CT), magnetic resonance imaging (MRI) and cone-beam computed tomography (CBCT).

#### **6. Two dimensional versus three dimensional imaging**

Lateral cephalograms can provide us with useful, credible and replicable airway measurements while minimizing patient costs and radiation exposure. Studies have shown that while cephalometric measurements provide two-dimensional data, cephalometry is a reliable method for airway assessment and adenoid size estimation [12]. Another comparative study to assess the linear measurements with lateral cephalograms and CBCT was carried out and the conclusions drawn: that airway linear measurements are reliable, with both lateral cephalograms and CBCT reconstruction, as there is a positive correlation with the respective area measurements on axial slices [13].

*Effects of Various Dentofacial Orthopedic and Orthognathic Treatment Modalities… DOI: http://dx.doi.org/10.5772/intechopen.101719*

#### **7. Changes in pharyngeal airway space using functional appliance therapy**

In 1934, Pierre Robin proposed that use of an intraoral appliance helps in bringing the lower jaw forward in newborns with mandibular deficiency. This helps in preventing the posterior relocation of the tongue during sleep and the occurrence of oropharyngeal collapse [14]. This concept is now often used in adult obstructive sleep apnea (OSA) patients to avoid an upper airway collapse during sleep with the help of various myofunctional appliances [15]. Moreover, the idea to relocate the mandible anteriorly is applied in dentofacial orthopedics by the use of various myofunctional appliances which helps in stimulating mandibular growth in skeletal Class II growing patients with mandibular deficiency [16]. Several authors have hypothesized that the functional orthopedic treatment of growing patients with short mandibles may lead to increased oropharyngeal airway dimensions, and some have suggested a possible reduction in the risk of future respiratory problems (**Figures 3** and **4**) [17–20].

#### **Figure 3.**

*Two dimensional lateral cephalometric evaluation versus three dimensional CBCT evaluation.*

#### **Figure 4.** *Changes in the dimension of pharyngeal aiway width using functional appliance therpy [9].*

#### **8. Effect of various functional appliances on pharyngeal airway**

Twin block is considered to be one of the most patient compliant myofunctional appliance. Therefore prominent results can be drawn with this appliance [21]. According to Jena et al. [21] when twin block was compared with Mandibular protraction appliance MPA, the improvement of oropharynx dimension by twin-block appliance was significantly more. Another study showed significant increase in the dimensions of nasopharynx, oropharynx and hypopharynx following twinblock treatment [22]. Although the growth itself had very minor contribution in the improvement of oropharyngeal dimension, but the advancement of mandible through myofunctional orthopedic correction was evidentally beneficial. The anterior relocation of mandible by the functional appliances places the tongue more forward and thus increases the overall dimension of oropharynx [23]. The improvement in the dimension of oropharynx was more with removable functional appliance (twin block) compared to fixed functional appliance [21, 24]. An increase in oropharyngeal volume was found after functional appliance treatment in Class II patients, leading to an increase in final volume of the upper airway.

Forsus Fatigue Resistence Device (FFRD) brought about improvement in the oropharyngeal airway significantly when compared the untreated subjects. Post treatment, the mean values of Superior Pharyngeal Space and Middle Pharyngeal Space increased by 1.06 mm and 1.28 mm respectively in the FFRD group. Aksu et al. [25] measured the airway space equivalent to the depth of hypopharynx andconcluded that there was no significant improvement in the width of hypopharynx. Bavbek et al. [26] measured CV3 projection in FFRD group and control group and found that FFRD did not increase the hypopharyngeal width. Whereas the other three studies had not measured the hypopharyngeal airway dimension.

The following were the conclusions drawn from the systematic review [27]:

*Functional appliances help in improving the pharyngeal airway dimensions in Class II malocclusion subjects with retrognathic mandibles. But it is also evident that minimum effect on nasopharyngeal airway passage and the minor improvement is mainly due to growth. Improvement of oropharyngeal airway passage dimensions is a very prominent effects of functional appliance treatment. Removable functional appliance prove to be more efficient than fixed functional appliance in the improvement of positive airway pressure (PAP) dimension.*

#### **9. Hyoid bone and tongue position with changes in pharyngeal airway space**

The results obtained by treatment with functionalappliances are mainly dentoalveolar in nature, there ishowever a significant modification of the oropharyngeal airway dimension is observed in most of the studies. Hypothesiscould be presumed that, the dentoalveolar modifications occurringafter functional appliance treatment, guides the tongue to amore forward position, enlarging theposterior airway space (PAS). Therefore, it can be said that forward positioningof the tongue is part of a planned surgical strategywhen treatment of sleep disordered breathing is needed. Changes observed in the hyoid bone distance are moreprominent horizontally than that in the vertical direction [27].

The conclusions drawn with respect to hyoid bone position are as follows:

*Effects of Various Dentofacial Orthopedic and Orthognathic Treatment Modalities… DOI: http://dx.doi.org/10.5772/intechopen.101719*

Hyoid bone is found to be posteriorly and superiorly placed in patients with Class II skeletal malocclusion when compared to Class III and Class I skeletal cases. The hyoid bone position in males is foundto be more inferiorly and anteriorly when compared to females. Also the anterior cranial base is very strongly related to the nasal fossa length and a moderately related to positive correlation with the hyoid bone vertical position and lower airway width. The hyoid bone vertical position had a strong positive correlation with the length of the nasal fossa [4].

#### **10. Changes in pharyngeal airway space with various surgical procedures**

Orthognathic surgery is a common method to treat dentofacial deformities. It changes the position of facial skeletal structures and also affects the morphology of the pharynx drastically. Structures such as soft palate, tongue, hyoid bone and some surrounding tissues are attached directly or indirectly to the maxilla and mandible, therefore any desired movement of the jaws by orthognathic surgery affects these tissues, causing changes in the dimensions of the pharyngeal area [28].

#### **11. Mandibular set back surgery**

In a thesis by Jain et al. [29], statistically significant increase in the nasopoharyngeal airway dimension was observed. This finding has also been reported by Kitagawara et al. [30] and has been explained as a biological adaptation against postoperative swelling and edema, and for airway maintenance. It is a compensatory mechanism after the hypopharyngeal airway collapses. According to Susarla et al. [31], the upper airway length (UAL) contributes to resistance to airflow. Longer airways have more resistance to airflow than shorter airways [31].

#### **12. Bimaxillary surgeries**

Chen et al. [32] found that patients undergoing bimaxillary surgery had changes at the three levels, with increase at the nasopharynx and decreases at the oropharynx and hypopharynx. Bimaxillary operations mostly decrease the narrowing effect of the mandibular setback operations [33]. This indicates that Upper Airway Length increases along with narrowing of the airway, in patients who undergo bimaxillary surgery.

#### **13. Mandibular advancement**

Statistically significant increase in the oropharyngeal and hypopharyngel airway dimension was observed according to Jain et al. [29] and Turnbull et al. [34].

#### **14. Pharyngeal airway in cleft lip and palate patients**

Cleft patient presents more frequently with large adenoids than do the non-cleft population. This has been regarded as a compensatory phenomenon to decrease the pharyngeal depth and make velopharyngeal competence possible. After palatal operation, soft tissue is sometime short and scarred and frequently the uvula is missing, tissue deficit results in incompetence to velopharyngeal sphincter mechanism.

Gohilot et al. [35] in a study noted that adenoidal tissue size was larger in the juvenile and adolescent cleft group as compared to the adolescent cleft group and airway passage was decreased in juvenile subjects. The thickness of adenoidal tissues decreases with age in both subjects with and without CLP. Conversely, the upper airway dimensions increase in those with and without CLP.

#### **15. Effect of expansion on pharyngeal airway**

Iwasaki et al. [36] evaluated the effect of rapid maxillary expansion (RME) on nasal airway ventilation condition, tongue posture, and pharyngeal airway volume. They found that RME enlarges the pharyngeal airway bothways with and without improvement in nasal obstruction. Another study by Malkoç et al. [37] derived that expansion does not cause any significant change in the dimension of pharyngeal airway.

#### **16. Cervical spine posture**

Various researchers have been taking prime interest in finding the correlation between the cervical spine posture, head position and pharyngeal airway space, but significant evidence still needs to be procured through proper research.

#### **17. Effect of different growth patterns on pharyngeal airway**

A study by Kocakara et al. [38] showed that, the pharyngeal airway dimensions and hyoid bone position are similar in individuals in the sagittal direction. The vertical airway length is significantly shorter in Class III patients with hypodivergent patterns. Another study by Ucar et al. [39] concluded that the nasopharyngeal airway space and upper pharyngeal airway space in Class I subjects is larger in low angle cases than in high angle cases.

#### **18. Conclusions**

Impactful evaluation of orthodontic treatment on the pharyngeal airway dimensions is considered one of the prime aspects of orthodontic diagnosis and treatment planning. The protocol helps in emboldening the impersonation of what the nature had planned i.e. by fitting all the teeth early enough through various habit breaking appliances, expansion appliances, and functional jaw orthopedics. Although maxillomandibular advancement surgeries are very well known to improve the airway dimensions along with improvement in dento-facial esthetics. But the hypothetical percentage of cases undergoing this beneficial modality is far less due to its invasive nature. Although Orthodontia at the present juncture, recognizes the importance of evaluating and treating airway, sleep disorders, there are yet tremendous scope untouched.

*Effects of Various Dentofacial Orthopedic and Orthognathic Treatment Modalities… DOI: http://dx.doi.org/10.5772/intechopen.101719*

#### **Author details**

Tejashri Pradhan1 and Aarti Sethia<sup>2</sup> \*

1 Department of Orthodontics and Dentofacial Orthopedics, KLE VK Institute of Dental Sciences, KLE Academy of Higher Education and Research, Belagavi, Karnataka, India

2 Department of Orthodontics and Dentofacial Orthopedics, Dr. D.Y. Patil University School of Dentistry, Nerul, Navi Mumbai, Maharashtra, India

\*Address all correspondence to: aarti2701@gmail.com

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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#### **Chapter 14**

## Orthodontic Management of Adult Sleep Apnea: Clinical Case Reports

*Lahcen Ousehal, Soukaina Sahim, Hajar Bouzid, Hakima Aghoutan, Asmaa El Mabrak, Mohamed Mahtar and Mohamed El Fatmi Kadri Hassani*

#### **Abstract**

Obstructive sleep apnea (OSA) is a serious public health problem that has important impacts on the quality and life expectancy of affected individuals. It is characterized by repetitive upper airway collapse during sleep. OSA requires a multidisciplinary plan of treatment. There is increasing interest in the role of the orthodontist both in screening for adult obstructive sleep apnea and its management. Dental appliances and orthognathic surgery are two strategies that are currently used in the treatment of sleep apnea. This chapter focuses on the orthodontic management of sleep apnea in adults through three clinical cases with varying degrees of severity of sleep apnea. It provides a background on OSA treatment approaches and discusses the potential risks and benefits of each.

**Keywords:** adult sleep apnea, orthodontics, management, oral appliances, orthognathic surgery

#### **1. Introduction**

Obstructive sleep apnea (OSA) is a common sleep disorder resulting from repetitive narrowing and collapsing of the upper airway [1]. Its prevalence has increased worldwide and affects about one in four men and one in 10 women [2]. OSA is characterized by repeated episodes which lead to sleep fragmentation and oxygen desaturation. Clinically, OSA is defined by the occurrence of daytime sleepiness, loud snoring, witnessed breathing interruptions, or awakenings due to gasping or choking [3, 4]. Polysomnography (PSG) is the gold standard for OSA diagnosis and it allows to assess the apnea/hypopnea index (AHI) that is the expression of OSA severity [5]. The AHI is the mean number of sleep apneas and hypopneas per hour of sleep. The American Academy of Sleep Medicine (AASM) defines mild OSAH as an AHI of 5–15 events per hour; moderate OSAH as 15–30 events per hour; and severe OSAH as an AHI of greater than 30 events per hour [6].

The complexity of OSA is exemplified by its multifactorial etiology such as craniofacial structures and neuromuscular tone [7]. Many risk factors are associated with the occurrence of OSA: obesity (BMI > 35) with increased neck circumference,

sleeping in the supine position, smoking, alcohol, type 2 diabetes, nasal obstruction (septal deviation and rhinitis), endocrine abnormalities (hypothyroidism and acromegaly), genetics (family history of OSA), and menopause [8].

Untreated OSA is associated with a range of adverse health outcomes such as cardiovascular diseases, cerebrovascular events, diabetes, and cognitive impairment in addition to impaired quality of life [9, 10].

The treatments of OSA can range from weight loss to maxillomandibular advancement. The treatment of choice is influenced by the etiology of the problem, but also by its severity and the personal yearnings [2].

The orthodontist may play an important role in both screening for OSA and the multidisciplinary management of OSA in adults. The contribution of orthodontists to the study and treatment of respiratory disorders associated with sleep focus on three aspects: the diagnosis of the structural changes often present in these diseases, the treatment of mild to moderate forms using intraoral appliances, and presurgical orthodontic treatment of patients programmed for orthognathic surgery [11]. This chapter aimed to discuss, through three clinical cases, the role of the orthodontist in the management of adult sleep apnea according to the severity of the disorder.

#### **2. Case reports**

#### **2.1 Case 1**

A 63-year-old female was referred to the Department of Dento-Facial Orthopedics of the Dental Consultation and Treatment Center (CCTD) of the Ibn Rochd University Hospital in Casablanca, Morocco. She was diagnosed with moderate OSA based on polysomnography analysis that showed an apnea-hypopnea index (AHI) of 24. Her body mass index (BMI) was 32 kg/m2 . She exhibited severe snoring and excessive daytime sleepiness. She had no history of temporomandibular disorder.

Facial examination revealed a convex profile with protrusive upper lip, retruded chin, and short throat length (**Figure 1A**). Intraoral examination revealed a full set of teeth with maxillary anterior diastema, Class I molar and canine relationships, shallow overbite, and an important overjet (**Figure 1B**). Lateral cephalometric analysis showed skeletal Class II relationship with mandibular retrusion (SNB = 74°), hyperdivergent vertical pattern (GoGn/Sn = 45°), proclined lower incisors as well as low hyoid bone position, and narrow oropharyngeal airway space, particularly at the retroglossal airway (**Figure 1C**).

The primary objective was to relieve the symptoms of OSA by using a mandibular advancement device (MAD). The dental appliance chosen was the "KASPERSKY" appliance which corrects the retroposition of the mandible and, consequently, repositions the tongue (**Figure 2**). Initially, the mandibular position of the MAD was preset at 60% of maximal protrusion. Afterward, its position was advanced by 0.5–1 mm every 1–2 weeks until the patient was satisfied with the symptoms. The anterior interocclusal space was kept at 7 mm so that the oropharyngeal airway was opened during sleep, as a result of the anterior displacement of the tongue and hyoid bone, and in turn, the mouth was inhibited from opening wide. The device was worn overnight for 4 months. Regular follow-up visits were conducted to check for any dental problems or side effects (tissue and joint pain), device wear, and to make appropriate adjustments to optimize the desired clinical effect. The patient was seen once every 6 months the first year and once annually afterward. The patient was very positive

*Orthodontic Management of Adult Sleep Apnea: Clinical Case Reports DOI: http://dx.doi.org/10.5772/intechopen.101193*

**Figure 1.**

*(A) Pretreatment extraoral photographs: (a) frontal at rest and (b) profile. (B) Pretreatment intraoral photographs: (a) right lateral, (b) frontal, and (c) left lateral. (C) Pretreatment lateral cephalogram.*

#### **Figure 2.**

*(A) "KASPERSKY" appliance. (B) Intraoral photographs with the oral appliance: (a) right lateral, (b) frontal, and (c) left lateral.*

about the treatment effects. Subjective improvement was noticed with the reported absence of snoring, reduction of daytime sleepiness, and reduction of tiredness. A subsequent sleep test revealed no evidence of OSA with an AHI = 2.5.

#### **2.2 Case 2**

A 35-year-old male presented to the Department of Dento-Facial Orthopedics of the Dental Consultation and Treatment Center (CCTD) of the Ibn Rochd University Hospital in Casablanca complaining of chronic loud snoring, restless sleep, and daytime somnolence. His body mass index (BMI) was 27 kg/m2 . The diagnostic polysomnography (**Figure 3D**) revealed a severe OSA with AHI of 30 events/hour. The patient was otherwise healthy and did not smoke nor drink.

Extraoral examination revealed a long symmetrical face, a convex profile with the protrusive lower lip and retruded chin (**Figure 3A**). Intraoral examination showed a full set of teeth except for the first lower left permanent molar, Class II canine relationship in both sides, and right Class I molar relationship. A slight dental crowding in the upper arch was also noted (**Figure 3B**). Lateral cephalometric analysis showed skeletal Class II relationship with mandibular retrognathia (decreased Sella-Nasion-B point (SNB) angle of 70°), hyperdivergent vertical pattern (GoGn/Sn angle of 55°), and proclined lower incisors as well as narrow oropharyngeal airway space (**Figure 3C**).

#### **Figure 3.**

*(A) Pretreatment extraoral photographs: (a) frontal at rest, (b) profile, and (c) frontal smiling. (B) Pretreatment intraoral photographs: (a) right lateral, (b) frontal, and (c) left lateral. (C) Pretreatment lateral cephalogram. (D) Pretreatment polysomnography.*

#### *Orthodontic Management of Adult Sleep Apnea: Clinical Case Reports DOI: http://dx.doi.org/10.5772/intechopen.101193*

The primary objective was to relieve the symptoms of the severe OSA by mandibular and genioglossus advancement surgery. The presurgical orthodontic aimed to decompensate the teeth within arches and to correlate both arches. A treatment plan with the extraction of four premolars was set. After orthodontic preparation, a 9 mm mandibular advancement was performed by a bilateral sagittal split ramus osteotomy using rigid bone plate fixation associated with advancing genioplasty.

The main outcome measures were assessed by the functional, occlusal, radiographic, and esthetic changes achieved and also by a reduction in the AHI. A normal over-jet and over-bite were established, the inferior pharyngeal airway space was increased, and there was a profound esthetic profile enhancement (**Figure 4**). The patient snoring and overall AHI significantly improved; he was more rested with easy breathing.

#### **2.3 Case 3**

A 29-year-old male presented to the Department of Dento-Facial Orthopedics of the Dental Consultation and Treatment Center (CCTD) of the Ibn Rochd University Hospital in Casablanca for repetitive nocturnal apneas, gummy smile as well as unesthetic profile. His body mass index (BMI) was 22.3 kg/m2 . The diagnostic polysomnography (**Figure 5D**) revealed a severe OSA with AHI of 54.4 events/hour. The patient was otherwise healthy and neither smoke nor drink.

#### **Figure 4.**

*(A) Posttreatment extraoral photographs: (a) frontal at rest, (b) profile, and (c) frontal smiling. (B) Posttreatment intraoral photographs: (a) right lateral, (b) frontal, and (c) left lateral. (C) Posttreatment lateral cephalogram. (D) Posttreatment polysomnography (Surgery performed by Professor Kadiri).*

#### **Figure 5.**

*(A) Pretreatment extraoral photographs: (a) frontal at rest, (b) profile, and (c) lateral smiling. (B) Pretreatment intraoral photographs: (a) right lateral, (b) frontal, and (c) left lateral. (C) Pretreatment lateral cephalogram. (D) Pretreatment polysomnography.*

The patient reported a previous orthodontic treatment that relapsed. The clinical examination showed a long symmetrical face, a convex profile with lip incompetence, retruded chin, and a very poor chin-neck contour (**Figure 5A**). Intraoral examination revealed Class II canine and molar relationships in both sides, anterior open bite, important overjet, and maxillary interincisal diastema (**Figure 5B**).

Lateral cephalometric analysis showed skeletal Class II relationship with mandibular retrognathia (decreased Sella-Nasion-B point (SNB) angle of 68°), hyperdivergent vertical pattern (GoGn/Sn angle of 62°), proclined upper and lower incisors, as well as narrow oropharyngeal airway space (**Figure 5C**).

The patient received combined orthodontic and surgical treatment of his skeletal malocclusion to advance the mandible, manage the retroglossal obstruction and ensure an esthetically pleasing appearance. Presurgical orthodontic aimed to decompensate the teeth within arches and to correlate both arches, then maxillomandibular rotational advancement and advancing genioplasty were planned. The treatment led to good esthetics and well-settled occlusion (**Figure 6A** and **B**). The maxillomandibular advancement surgery (MMA) was very effective in nearly eliminating the obstructive events and in improving nocturnal breathing as evidenced by the postoperative polysomnography (**Figure 6D**). On lateral cephalometry, the posterior airway space was increased postoperatively (**Figure 6C**). The patient reported easier breathing, undisturbed sleep, and complete resolution of excessive daytime sleepiness.

*Orthodontic Management of Adult Sleep Apnea: Clinical Case Reports DOI: http://dx.doi.org/10.5772/intechopen.101193*

**Figure 6.**

*(A) Posttreatment extraoral photographs: (a) frontal at rest and (b) profile. (B) Posttreatment intraoral photographs: (a) right lateral, (b) frontal, and (c) left lateral. (C) Posttreatment lateral cephalogram. (D) Posttreatment polysomnography (Surgery performed by Professor Kadiri).*

#### **3. Discussion**

Obstructive sleep apnea (OSA) is a sleep disorder characterized by repeated interruption of breathing during sleep due to episodic collapse of the pharyngeal airway. The diagnostic strategy includes a sleep-oriented history, physical examination, and objective testing of the patient [12]. The gold standard for diagnosis of OSA is overnight polysomnography. The AHI, which is the mean number of sleep apneas and hypopneas per hour of sleep, is an objective and specific measure of the severity of OSA. The American Academy of Sleep Medicine (AASM) defines mild OSA as an AHI of 5–15 events per hour; moderate OSA as 15–30 events per hour; and severe OSA as an AHI of greater than 30 events per hour [6].

The orthodontist is well-positioned to perform an OSA screening assessment and refer at-risk patients for diagnostic evaluation [7]. Besides the clinical examination, some important anatomic features observed radiographically in patients with OSA include, narrow mandible arch; maxillary and mandibular retrognathism; increased lower facial height; the lower and more anterior position of the hyoid bone; reduced pharyngeal area; increased cranio-cervical angle; decreased distance between the base of the tongue and the posterior pharyngeal wall; hypertrophied tonsils and adenoids; over-erupted maxillary and mandibular dentition and enlarged tongue [4].

Besides lifestyle modification (weight loss, smoking cessation, reduction of alcohol intake, position management, and sleep hygiene), there are three major interventions for obstructive sleep apnea: positive airway pressure (CPAP) therapy, oral appliance therapy (OAT), or surgery [6, 13]. The treatment of choice is influenced by the etiology of the problem, its severity, and the patient's individual needs.

Although CPAP is widely used as a first-line treatment for OSA, OAT mainly mandibular advancement devices (MAD) are an alternative to CPAP in the treatment of mild to moderate OSA. Their lower cost, relative comfort, and ease of use lead to greater patient compliance [8]. Worn intraorally during sleep, the MAD can prevent upper airway collapse by holding the mandible and tongue forward [6].

The devices may vary in construction, material, coverage of the teeth, and the possibility of vertical and lateral movements of the mandible [14]. There are two main types of oral appliances namely: the monobloc and the bibloc appliance. A retrospective comparative study by Isacsson et al. [15] found that both the monobloc and bibloc appliances were equally effective and significantly reduced the AHI by a mean of about 12–14 events per hour.

Candidates for a MAD require adequate healthy teeth, no important TMJ disorder, adequate jaw range of motion, and adequate manual dexterity and motivation to insert and remove the OA [12]. A meta-analysis by Sharples et al. [6] found that the most important patient feature is the ability to protrude the mandible 6 mm or more. Oral appliances initially are delivered with the mandible advanced to a position approximating two-thirds of the maximum protrusion [7]. The amount of protrusion can be titrated or increased until optimum symptom relief is obtained as in the first clinical case.

Short-term side effects of MAD are common but most resolve within 2 months. They include dental and gingival tenderness, hypersalivation, dry mouth, TMJ discomfort or sounds, and myofascial pain, [16]. Skeletal changes occur soon after the onset of treatment (6 months). Small but statistically significant increases in face height are accompanied by a significant downward position of the mandible secondary to dental changes [17]. Occlusal changes start happening later on, and they will be significant at the 30-month follow-ups [4]. They include a decrease in overjet, proclination of mandibular incisors, retroclination of the maxillary incisors, decreased occlusal contacts, and mesial shift of the molar and cuspid occlusion [16]. Some effects can lead to beneficial orthodontic changes in Class II division one patients, as in the first clinical case, especially decreasing in overjet and the tendency toward a mesiocclusion [17]. The dental situation needs to be carefully checked during regular visits. In cases of unacceptable, progressive occlusal alterations, the indication for therapy with an OA has to be re-evaluated and might be changed to CPAP or even surgery [18].

If MADs are preferentially indicated for mild or moderate OSA, orthognathic surgery may be an effective and safe treatment in patients with severe sleep apnea as in cases 2 and 3 or in patients who do not desire or cannot tolerate long-term CPAP therapy. The principle of surgical treatment is to get a physical airway by a permanent skeletal change that leads to soft tissue adaptation [3]. Of the surgical procedures, mandibular advancement, maxillomandibular advancement (MMA), and genioplasty are the most frequently performed. In OSA patients with micrognathia or retrognathia the surgical mandibular advancement may be considered. In case two, mandibular and genioglossus advancement surgery illustrated objective improvement in the symptoms associated with severe OSA. With this type of surgical intervention, the entire body of the mandible is brought forward [19]. Presurgical orthodontics is mandatory, otherwise, the width of the maxilla is typically too narrow to accommodate the advanced mandible [20]. However, little evidence is present for isolated mandibular advancement. Currently, osteotomy of maxillo-mandibular advancement (MMA) is the first-choice treatment for severe OSA. Chang et al. [9] reported success rate of MMA ranges from 75 to 100%. Moving the jaw stretches the palatine tissue, which

#### *Orthodontic Management of Adult Sleep Apnea: Clinical Case Reports DOI: http://dx.doi.org/10.5772/intechopen.101193*

in turn exerts traction upon the palatoglossal muscle and increases lingual support, favoring pharyngeal patency [11]. MMA predictably leads to significant improvements in daytime sleepiness, QOL, sleep-disordered breathing, and neurocognitive performance, as well as a reduction in cardiovascular risk (blood pressure) [21]. The AHI score is improved over the long term and the results remain stable over time.

According to Calero et al. [11], two characteristics must be fulfilled to indicate MMA. First, there must be multiple sites of obstruction, or blockage must be diffuse and inaccessible. Second, the patient must present skeletal class II malocclusion, and MMA surgery must offer multiple benefits for the patient. Presurgical orthodontic therapy aims to obtain complementary maxillary and mandibular dental arches. Patients with a Class II malocclusion, as in the third clinical case, undergo surgical mandibular advancement to achieve a Class I dental and skeletal relationship. Advancement of the maxillomandibular complex by 8–12 mm is generally required to obtain the intended result [22]. According to Lee et al. [23], a non-extraction approach is preferred in patients with OSA to retain expanded pharyngeal volume after surgery. An additional procedure for completing MMA is genioglossal muscle advancement (GA). This technique expands the magnitude of genioglossal, geniohyoid, and digastric muscle replacement [11].

#### **4. Conclusion**

Adult sleep apnea is a complex sleep-related breathing disorder that decreases quality of life and increases morbidity and mortality in patients. It is a highly prevalent disease and requires long-term and multidisciplinary management.

Orthodontists should recognize the signs and symptoms of this disorder to identify patients at risk of developing the complications of sleep apnea and guide the selection of appropriate treatment. Various oral appliances can be applied with good results in mild to moderate cases. In severe OSA, a surgical orthodontic approach is indicated. Maxillomandibular advancement surgery is a safe, very effective, and highly skeletally stable procedure.

Long-term management of OSA and regular follow-up are required to monitor compliance to therapy, treatment efficacy, side effects, and development of medical complications related to OSA.

*Current Trends in Orthodontics*

#### **Author details**

Lahcen Ousehal1 \*, Soukaina Sahim1 , Hajar Bouzid1 , Hakima Aghoutan1 , Asmaa El Mabrak<sup>2</sup> , Mohamed Mahtar3 and Mohamed El Fatmi Kadri Hassani4

1 Faculty of Dentistry, Department of Dentofacial Orthopedics, University Hassan II, Casablanca, Morocco

2 Dental Consultation and Treatment Center, Ibn Rochd University Hospital, Casablanca, Morocco

3 Faculty of Medicine, Department of Otorhinolaryngology, University Hassan II, Casablanca, Morocco

4 Private Practice, Casablanca, Morocco

\*Address all correspondence to: lahcen2228@yahoo.fr

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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[2] Faber J, Faber C, Faber AP. Obstructive sleep apnea in adults. Dental Press Journal of Orthodontics. 2019;**24**(3):99-109. DOI: 10.1590/2177- 6709.24.3.099-109.sar

[3] Kim YK, Kim JW, Yoon IY, Rhee CS, Lee CH, Yun PY. Influencing factors on the effect of mandibular advancement device in obstructive sleep apnea patients: Analysis on cephalometric and polysomnographic parameters. Sleep & Breathing. 2014;**18**(2):305-311. DOI: 10.1007/s11325-013-0885-5

[4] de Oliveira Almeida MA, de Britto Teixeira AO, Vieira LS, Quintão CC. Treatment of obstructive sleep apnea and hipoapnea syndrome with oral appliances. Brazilian Journal of Otorhinolaryngology. 2006;**72**(5): 699-703. DOI: 10.1016/s1808- 8694(15)31028-4

[5] Bartolucci ML, Bortolotti F, Corazza G, Incerti Parenti S, Paganelli C, Alessandri Bonetti G. Effectiveness of different mandibular advancement device designs in obstructive sleep apnoea therapy: A systematic review of randomised controlled trials with meta-analysis. Journal of Oral Rehabilitation. 2021;**48**(4):469-486. DOI: 10.1111/joor.13077

[6] Sharples LD, Clutterbuck-James AL, Glover MJ, Bennett MS, Chadwick R, Pittman MA, et al. Meta-analysis of

randomised controlled trials of oral mandibular advancement devices and continuous positive airway pressure for obstructive sleep apnoea-hypopnoea. Sleep Medicine Reviews. 2016;**27**:108- 124. DOI: 10.1016/j.smrv.2015.05.003

[7] Behrents RG, Shelgikar AV, Conley RS, Flores-Mir C, Hans M, Levine M, et al. Obstructive sleep apnea and orthodontics: An American association of orthodontists white paper. American Journal of Orthodontics and Dentofacial Orthopedics. 2019;**156**(1): 13-28.e1. DOI: 10.1016/j.ajodo.2019. 04.009

[8] Șimon IM, Băciuț M. Orthodontic appliances in the management of obstructive sleep apnea syndrome— Types and therapeutic indications. Pneumologia. 2018;**67**(2):62-66

[9] Chang HP, Chen YF, Du JK. Obstructive sleep apnea treatment in adults. The Kaohsiung Journal of Medical Sciences. 2020;**36**(1):7-12. DOI: 10.1002/kjm2.12130

[10] Geoghegan F, Ahrens A, McGrath C, Hägg U. An evaluation of two different mandibular advancement devices on craniofacial characteristics and upper airway dimensions of Chinese adult obstructive sleep apnea patients. The Angle Orthodontist. 2015;**85**(6):962-968. DOI: 10.2319/040314-245.1

[11] Azagra-Calero E, Espinar-Escalona E, Barrera-Mora JM, Llamas-Carreras JM, Solano-Reina E. Obstructive sleep apnea syndrome (OSAS). Review of the literature. Medicina Oral, Patología Oral y Cirugía Bucal. 2012;**17**(6):e925-e929. DOI: 10.4317/medoral.17706

[12] Epstein LJ, Kristo D, Strollo PJ Jr, Friedman N, Malhotra A, Patil SP, et al. Adult obstructive sleep apnea task force of the american academy of sleep medicine. Clinical guideline for the evaluation, management and long-term care of obstructive sleep apnea in adults. Journal of Clinical Sleep Medicine. 2009;**5**(3):263-276

[13] Mintz SS, Kovacs R. The use of oral appliances in obstructive sleep apnea: A retrospective cohort study spanning 14 years of private practice experience. Sleep & Breathing. 2018;**22**(2):541-546. DOI: 10.1007/s11325-018-1643-5

[14] Wojda M, Jurkowski P, Lewandowska A, Mierzwińska-Nastalska E, Kostrzewa–Janicka J. Mandibular advancement devices in patients with symptoms of obstructive sleep apnea: A review. Medical Science and Research Advances in Experimental Medicine and Biology. 2019;**1153**:11-17. DOI: 10.1007/5584\_2019\_334

[15] Isacsson G, Fodor C, Sturebrand M. Obstructive sleep apnea treated with custom-made bibloc and monobloc oral appliances: A retrospective comparative study. Sleep & Breathing. 2017;**21**(1):93- 100. DOI: 10.1007/s11325-016-1377-1

[16] Jacobowitz O. Advances in oral appliances for obstructive sleep apnea. Advances in Oto-Rhino-Laryngology. 2017;**80**:57-65. DOI: 10.1159/000470865

[17] Martins OFM, Chaves Junior CM, Rossi RRP, Cunali PA, Dal-Fabbro C, Bittencourt L. Side effects of mandibular advancement splints for the treatment of snoring and obstructive sleep apnea: A systematic review. Dental Press Journal of Orthodontics. 2018;**23**(4):45-54. DOI: 10.1590/2177-6709.23.4.045-054.oar

[18] Rose EC, Staats R, Virchow C Jr, Jonas IE. Occlusal and skeletal effects of an oral appliance in the treatment of

obstructive sleep apnea. Chest. 2002;**122**(3):871-877. DOI: 10.1378/ chest.122.3.871

[19] Alami S, Aghoutan H, Diouny S, El Quars F, Bourzgui F. In: Motamedi MHK, editor. Orthodontic Considerations in Obstructive Sleep Apnea—State of the Art, A Textbook of Advanced Oral and Maxillofacial Surgery. Vol. 2. Mohammad Hosein Kalantar Motamedi. IntechOpen; 2015. IntechOpen, DOI: 10.5772/59086. Available from: https://www.intechopen. com/chapters/47489

[20] Conley RS. Evidence for dental and dental specialty treatment of obstructive sleep apnoea. Part 1: The adult OSA patient and Part 2: The paediatric and adolescent patient. Journal of Oral Rehabilitation. 2011;**38**(2):136-156. DOI: 10.1111/j.1365-2842.2010.02136.x

[21] Boyd SB, Chigurupati R, Cillo JE Jr, Eskes G, Goodday R, Meisami T, et al. Maxillomandibular advancement improves multiple health-related and functional outcomes in patients with obstructive sleep apnea: A multicenter study. Journal of Oral and Maxillofacial Surgery. 2019;**77**(2):352-370. DOI: 10.1016/j.joms.2018.06.173

[22] Cillo JE Jr, Dattilo DJ. Maxillomandibular advancement for severe obstructive sleep apnea is a highly skeletally stable long-term procedure. Journal of Oral and Maxillofacial Surgery. 2019;**77**(6):1231-1236. DOI: 10.1016/j.joms.2019.01.009

[23] Lee KH, Kim KA, Kwon YD, Kim SW, Kim SJ. Maxillomandibular advancement surgery after long-term use of a mandibular advancement device in a post-adolescent patient with obstructive sleep apnea. Korean Journal of Orthodontics. 2019;**49**(4):265-276. DOI: 10.4041/kjod.2019.49.4.265

#### **Chapter 15**

## Accidental Aspiration of Orthodontic Components or Appliances

*Siddharth Sonwane*

#### **Abstract**

**Background:** Contemporary orthodontic practice consists of innovative appliances for ease, safe, and quick results. However, the associated potential disadvantages are rarely published. **Objective** is to publish the literature on the accidental swallow of foreign objects such as orthodontic appliances or parts of fixed orthodontic appliances in patients. **Method:** An electronic search was performed on PubMed, Medline, Scopus, The Cochrane Library, and EMBASE until March 15th 2019. Methodological quality and synthesis of case series and case report tool (MQCC) was applied to determine the quality of these case reports and series. The outcome variable was to assess its effect on airway and gastrointestinal tract; methods of removal of these foreign bodies. Meta-analysis was not performed as the study included case reports and case series in which no control groups were present **Results:** Out of 113 case reports and series, twenty-nine articles were included in this systematic review. Only 31% of articles have satisfied the MQCC scale and maintained as high-quality case reports, 43% of articles were medium to high quality and 26% designated as low quality. **Conclusions:** An orthodontic appliance accidentally detaches from its position, and patient can engulf due to patient's negligence, lack of its maintenance education and awareness. Orthodontist should educate, instruct and provide a written format of management, precautions. Accidental ingested foreign body can be managed in two methods, first is noninvasive, check forth airway obstruction, encourage for fiber-rich diet and laxatives. Second method is the use of endoscopically and laparoscopy with use magill's forceps.

**Keywords:** accidental swallow, orthodontic appliances, arch wire, mini-screw

#### **1. Introduction**

Accidental ingestion of a foreign body is more often seen in children. Contemporary studies have reported that 1500 subjects die per year [1]. However, data published on a death rate depends upon the nature of the aspirated object, i.e. size, shape, and finishing [2]. Dhandapani et al. (2009) illustrate that 80% - 90% of the aspirated foreign bodies pass through the gastrointestinal tract routinely, approximately 10–20% need to be removed endoscopically, and 1% requires surgery [3].

Most researchers have described that high intake of fibrous diet; water and laxatives are the regular methods in the management of ingested blunt objects. But, accidental swallow of sharp objects always associates with a high rate of airway obstruction and gastrointestinal (GI) perforation corresponding to treatment dilemmas [1–4].

To date, various innovative appliances are being used in dentistry and orthodontics but very rare among these material limitations have been published. Through this chapter, I would like to present the associated drawbacks of such appliances to "GI" and airway systems, their clinical presentations, recommendations, and management. For a better understanding of readers, this chapter is divided into introduction, incidences; Types of appliances ingested or aspirated, Pathophysiology and associated symptoms of ingested "FBs", Management, Retrieval of accidental swallowed "FBs", Recommendations to prevent accidental swallow, Basic measures to prevent accidental swallow and Conclusion.

#### **2. Incidences of accidental ingestion of different orthodontic appliances reported in the literature**

In general, incidence of accidental aspiration of foreign body occurs in children (80%), elderly, mentally impaired, or alcoholic individuals and sometimes it may occur deliberately in prisoners or psychiatric patients. Coins, meat boli, and button batteries; sewing needles, tooth picks, straightened paper clips and razor blades are the most often ingested foreign bodies [5].

In dentistry, accidental aspiration of foreign bodies is recognized as a hurdle in all clinical specialties of dentistry. A wide range of complications succeeding from foreign bodies ("FBs") has been recognized in clinical practice as a broken denture, single-tooth crowns, inlays, edndo files, and broken orthodontic appliance's reason for the majority of "FBs" ingested by adults in the dental setting [1–6].

Kurkciyan et al. (1996), Pavlidis et al., (2008) and Dhandapani et al.,(2009) have reported that the overall incidence of dental "FBs" aspiration is higher in adult than in children, among which 10–20% required endoscopic removal and 1% alarm for surgical removal [1–7].

In orthodontics, Wasundhara A. Bhad (2011), Uday Kumar Wizziyiane Ahmad, and Priya Balakrishnan (2012), Appasaheb Naragond et al. (2013), have reported that the most frequently aspirated FBs are brackets, wire fragment, activation key, and fractured twin block, removable retention appliances, and lingual retainers. However, Tamura et al., reported that the incidence of accidental swallowing of orthodontic appliances ranges from 3.6% to 27.7% among them 2% -3.7% require emergency treatment as these foreign bodies obstruct in "GI" or respiratory tract, and the rest of the material pass "GI" without complications [7–11].

#### **3. Types of appliances or components of orthodontic appliance ingested or aspirated**

While the existing incidence of this complication in orthodontics is hypothetical, there is significant variation as to the types of appliances involved [8]. The reported "FBs" includes a lower spring retainer; fractured twin block appliance, expansion keys, fragment of a maxillary removable appliance, retainer, trans-palatal arch, and


*Accidental Aspiration of Orthodontic Components or Appliances DOI: http://dx.doi.org/10.5772/intechopen.100397*

> **Table 1.** *Summary of all case reports.*


**Table 2.** *Summary of all case reports.*

#### *Current Trends in Orthodontics*


#### *Accidental Aspiration of Orthodontic Components or Appliances DOI: http://dx.doi.org/10.5772/intechopen.100397*

**Table 3.** *Summary of all case reports.* pieces of the arch wire [9]. In orthodontics, Hinkle published the first case of accidental aspiration of removable retainer and its retrieval report in 1987 [8–12]. The detail of cases published on accidental ingestion of various components, and their management is illustrated in **Tables 1**–**3**.

#### **4. Pathophysiology and associated symptoms of ingested "FBs"**

The accidental ingestion of "FBs" and appearance of any symptoms or signs is highly inconstant and depends on the age of the subject (child or an adult), movement, or impaction of "FBs". According to Susini (2007), Yadav Yadav RK (2015), Thakral A,(2015) in 75% of children accidental aspirated "FBs" have impacted at the level of the upper esophageal sphincter, and in adults 70% of the ingested FBs lodge at the level of the lower esophageal sphincter. Thus, it's crystal clear that accidental ingested"FBs"travel across a long pathway from an oropharynx to a gastrointestinal system with providing the clinical features of each stage [5, 8, 10].

#### **4.1 "FBs" impacted at the oropharyngeal level**

60% of the foreign bodies become lodged at this level. Subject presents with clear sensation of impacted "FBs", discomfort, drooling of saliva, inability to swallow, airway compromise and also infection and perforation can also occur [5–13].

#### **4.2 "FBs" impacted at the esophageal level**

If the impacted "FBs" as expansion key, twin block, removable retainer, subject (child) represents with gagging, vomiting, recurrent aspiration pneumonia and due to tracheal impingement may develop stridor or respiratory embarrassment while in adults presents with, dysphagia, and salivary drooling/pooling [5, 7, 8, 11, 14]. Wasundhara bhad and Rohida reported that the use of a broken Twin-block appliance was accidentally ingested in sleep [11, 13, 15, 16]. The patient developed immediate symptoms as breathless with a severe cough. The patient's father tried Heimlich's Maneuver method to retrieve it but failed, immediately subject shifted to emergency medical service. Endoscopically removed and confirmed that broken part of twin block located in the esophageal region [15–20].

#### **4.3 "FBs" impacted at a sub-esophageal level**

At this level delayed, symptoms develop as recurrent vomiting, passing rectal blood, and melena. Ghori et al. published case report in which removable retainer was accidentally aspirated, passed uneventfully from the elementary canal and caused perforation of the sigmoid colon proving lethal to the patient [16, 18, 20–23].

#### **4.4 "FBs" impacted at gastrointestinal perforation**

Delayed symptoms presents as with acute mediastinitis with chest pain with signs of pleural effusion and acute/subacute peritonitis. Uday Kumar Umesan et al. 2012 reported a case of accidental aspiration of arch wire segment during adjustment and were located at the laryngeal region that necessitated endoscopic retrieval in the hospital [24–29].

#### **4.5 "FBs" impacted at body in airway**

Patient present with classic triad of wheezing, coughing, and dyspnea immediate after accidental swallow; It later may develop with signs of the respiratory arrest and stridor [5–39].

#### **5. Management**

The existing incidence of accidental ingestion of "FBs" complication in orthodontics is hypothetical; there is substantial dissimilarity as to the types of appliances involved [14, 17, 30]. The literature published on accidental swallowing of "FBs" includes a lower spring retainer; broken twin block appliance, expansion keys, quad helix, transpalatel arch, and pieces of arch wire (**Tables 1**–**3**). Although, there is scanty evidence to pinpoint appliance or procedure has been related with an augmented risk of aspiration; the minute size of orthodontic components and saliva, limited working access, apprehensive subject, chair position, operator knowledge are the contributing factors [2, 4, 5, 7–9, 13, 16–18].

#### **5.1 Case history**

If the incident occurs in resident (outside of the clinic), a positive history of accidental swallow could be elicited. Clinician should note that a high degree of disbelief should be maintained especially in children and impaired adult while recording case report with missing orthodontic appliance fragments or components. A wise clinician must have check for clinical signs and symptoms that could appears in subject, which helps for a clinician to advice further radiographic investigation or call medical emergency service [17–21, 31].

#### **5.2 Diagnosis**

Based on case history and appearance of clinical symptoms suspicious inspection of the complete oral cavity, pharynx, larynx, and esophagus should be the first step taken. As per the pathophysiology of "FBs", and clinical signs further investigations as abdominal and chest X-rays, endoscopy, and computed tomography scans of thorax should be advised to confirm the lodgment of "FBs" [2, 3, 6, 11, 13, 14, 16–18, 22, 23, 33].

#### **5.3 Radiographic assessment**

Generally, radiographic assessment designated for subject with a positive history of accidental swallow of "FBs" within a period of less than 24 hours and without appearance of any respiratory symptoms. A chest radiograph is mandatory, but the "FB" is acrylic (radiolucent object), becomes difficult in localization of its exact position. In such situation subjects are made to swallow to identify the precise site of impaction, and ask the patient for area of uneasiness [2–26, 30–36].

If both the attempt fail to locate "FBs", a small amount of barium sulfate suspension is mixed with cotton wool pallets given to subjects to form a radio-opaque bolus around the object; this method significantly allow to track "FBs" radiographically. Also, gastrografin (a contrast agent), "CT" and "CBCT" scans have proved to be highly useful in locating the radioluscent foreign bodies [26, 38, 39].

#### **6. Retrieval of accidental swallowed "FBs"**

If accidental swallowing of FB occurred in a dental office, there are two methods to retrieve FB, the first line of action is the use for the Heimlich maneuver technique, abdominal or chest thrusts; secondly, turn the patient head one side and ask to spite; if an object does not spill out check in the oral cavity and oropharynx, supra-tonsillar recess, epiglottic vallecula and the piriform recess under good illumination and if the object is visible, it should be retrieved with forceps or high-volume suction [1, 5, 9, 12].

If the incidence occurs outside the clinic or in resident, based on case history, symptoms, diagnosis, and location of aspirated FBs subjects can be managed as Noninvasive emergency measures, Invasive emergency measures, and Surgical intervention [1, 2, 4, 9, 12, 16, 20, 24].

#### **6.1 Non-invasive emergency measures**

Size of the ingested "FBs" (larger than 6 cm in children and longer than 10 cm in adults) cause cyanosis, loss of consciousness, and permanent brain damage occurs within 4 to 6 minutes alarming a medical emergency if the obstruction is not relieved [1, 3, 6, 8, 16, 20, 34]. Therefore, speed and updated cardiopulmonary resuscitation (CPR) skills are vital for the clinician. If the "FBs" is obstructive and the patient is in respiratory distress, dislodgement should initially be attempted with back blows and abdominal thrusts (Heimlich maneuver). If this cannot dislodge the object, positive airway pressure needs to be maintained by artificial respiration until emergency services arrive [4, 5, 7, 11, 14, 21, 32, 35].

#### **6.2 Invasive emergency measures**

In this stage, "FBs" has passed the vocal cords uneventfully, but the subject requires medical attention. Few authors have reported that in 1–2% of subjects ingested "FBs" spontaneously expel, still do not wait for this to happen. Consider the entire subject as in an extreme emergency and to be escorted to the hospital for radiographic investigation to locate the position of "FBs", because 6% mortality has been reported with such subjects [4, 11, 16, 25, 32]. In this phase of emergency if the "FB" lodged in esophageal and tracheal region endoscopy is the best method to retrieve "FBs". Flexible pan endoscopy under local anesthesia is preferred for "FBs" lodged in intrathoracic areas and is accessible in tertiary medical centers. However, in this situation rigid endoscopy is recommended to reduce complication rates. Most commonly available armamentarium is Foley's catheter, passed distal to ingested "FB" under fluoroscopic guidance, inflating the balloon object can be retrieved [14, 16, 17, 21, 31, 34, 36].

#### **6.3 Surgical intervention**

This method to be opted last measure to retrieve accidental ingested "FBs". Subject gives all the clinical signs and symptoms of vital organ damage. Few authors have reported that the mortality and morbidity rates are very high in this stage. However, surgery is relatively successful opted during gastrointestinal perforation or lodgment in the airway [23, 26, 33, 36, 38].

#### **7. Recommendations to prevent accidental swallow**

During orthodontic treatment, there is always a high risk of accidental swallow or aspiration of appliance components. So the aim of the orthodontist must be to prevent and secure loose orthodontic components during treatment procedures.

Measures to be taken to minimize accidental swallow of orthodontic components include the following recommendations.

#### **7.1 Case selection**

The clinician needs to be more alert during the first consult appointment with young children, at this age group subject cannot understand and follow the instructions given by the clinician. The principal responsibility of an orthodontist is to assess the amount of cooperation that can be achieved from the patients and their parents during treatment. So an orthodontist must check complete cooperation and persistent controlling of their children to confirm that professional instructions are respected [10, 16, 23, 24, 26, 27].

The medico-legal point of that an orthodontist must opt to delay treatment until a patient's parent should give consent about their awareness of risks involved during a course of orthodontic treatment to avoid fallouts later [1, 23, 24, 27, 38].

#### **8. Basic measures to prevent accidental swallow**

#### **8.1 Removable appliances**

Operate with textured latex gloves to have a firm grip on orthodontic components. Routine visits for appliance adjustment should ensure adequate retention and its integrity. The clinician must give patient instruction in both verbal and written forms, also warn or alert them not to self-adjust or repair broken fragments instead should visit the orthodontist to ensure the appliance uprightness [11, 13, 16, 30, 33].

Use of contrast color to gastrointestinal mucosal color, in case of accidental swallows, can be identified easily during its retrieval through endoscopy [16].

During the night, wares of appliance tie a silk thread knot to either clasp assembly or active components [1–27, 30–39].

In-office, on chairside adjustment of an appliance, 7'o'clock should be the operator's position and make the patient comfortable before doing any adjustment [37].

Tie a silk thread knot to the activation key, quad helix at the time of activation, if any accidental aspiration occurs, the appliance can be securely retrieved through tied silk thread [29].

#### **8.2 Fixed appliances**

During bonding brackets, the operator should be at 7'o'clock position; use of a high-intensity light cure unit is always recommended and a high-vacuum section should be used.

Molar bands should be preferred over bondable tubes; especially in the second molar figure of ligature (. 009) should be tied to the first molar and second pre-molar [21, 26, 31, 39].

During the cutting of excessive distal end of archwire segment, use the gauze pad as protection distal tissue, adjust the length of wire outside the mouth on study models, or cinch the excess wire.

During debonding should be carried along with its base wire attachments.

#### **9. Conclusion**

Accidental swallowing of orthodontic appliances or components of it can occur often. The orthodontist must be skillful, knowledgeable, and cautious during treatment procedures. To counteract such an emergency, someone must well equip the orthodontic office, well-trained nurse staff; the medical emergency number should be maintained.

At the first consultation, an orthodontist must well educate and must make aware of demerits and accidental situations, management protocol in such as condition. The clinician must follow a protocol of prevention is better than cure.

### **Abbreviations used**


### **Author details**

Siddharth Sonwane Department of Orthodontics, People's College of Dental Sciences and Hospital Bhopal, Madhya Pradesh, India

\*Address all correspondence to: siddharth5678@gmail.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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*Accidental Aspiration of Orthodontic Components or Appliances DOI: http://dx.doi.org/10.5772/intechopen.100397*

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