**7.1. Keystone 7.1. Keystone**

Table 2. Brishi

Keystone offers one of the most basic surgical guide systems, hence the coined term "Easy‐ Guide" for their planning software. EasyGuide can be utilized for planning implant placement in single tooth edentulous spaces, partially edentulous spaces, and completely edentulous arches. The Keystone surgical guide can only be used in single tooth edentulous spaces and partially edentulous spaces.

During the CBCT, the patient wears a laboratory fabricated radiographic guide with barium sulfate incorporated in the areas where the teeth will be replaced. This guide also has a built in radiographic "X Marker", which is subsequently used by Keystone to fabricate the surgical guide. The clinician then plans the implant placement in the EasyGuide computer program and virtually sends this information to Keystone to fabricate the surgical guide, if desired.

The surgical guide is fabricated from the digital planning. The clinician must send the radiographic guide with the incorporated "X Marker" to Keystone, which uses this to orient the guide to the patient's jaw. Keystone then will fabricate the surgical guide either as "directional" or "depth and directional", depending on the clinician's wishes. This means that the guide can be used to direct the implant at the correct angle and it can also be used to direct it to the correct depth in the bone.

#### **7.2. Biohorizons**

Biohorizons is another very simple and basic implant planning program that offers a userfriendly technique but limited options to the clinician. The surgical guide, called a Compu-Guide, can be fabricated for single implant placement, partially edentulous multiple implant placement, and fully edentulous multiple implant placement.

The patient wears a laboratory fabricated radiographic guide during the CBCT which is fabricated to the planning software, VIP, specifications. Then the clinician may digitally plan the implant placement using the VIP computer software. This software allows the placement of any type of implant system.

This information along with the radiographic guide is sent to Biohorizons which fabricates the Pilot Compu-Guide, a surgical guide that allows only the pilot drills to be sequenced through the guide. The clinician inserts the Compu-Guide and stabilizes it. The pilot osteomoties are drilled to length, then the guide is removed, and the twist drills are then used free-hand without the guide, according to the implant manufacturer's protocol. This method increases the possibility of error because the angulation may be altered when using the twist drills.

#### **7.3. NobelBiocare**

record to disclude the patient's posterior teeth by about 5 mm. Then a cast of the patient is scanned and a diagnostic wax‐up is scanned. The computer is then able to orient these images to each other and the practitioner can digitally plan the implant placement in reference to the patients alveolar bone and planned tooth positions. A surgical guide

All of these choices are viable options for fabricating a surgical guide. Each situation is unique and depending on the practitioners resources and relationship with their radiologist, the practitioner may choose any option he or she

The aim of this section is not to advertise any specific company, and we just want to share our experiences with these surgical guides. Surgical guides are fabricated by many manufactures, most notable the major implant companies. Each company has a unique planning software program as well as various choices for scanning protocol, guide materials, and design of the guide. Depending on the case, different manufacturers must be considered in certain situations. For example, if dual‐scan protocol was desired, only NobelBiocare and Anatomage offer this option.

‐ How well can you maneuver the software program? Or will your radiologist be manipulating most of the digital

‐ If you plan on doing the virtual placement yourself, make sure you are comfortable with the program. Each

‐ What kind of radiographic scanning protocol to you plan on using? Do you prefer the dual‐scan protocol in which a denture can be quickly converted into a radiographic guide? Or do you prefer to have your lab fabricate

‐ Do you plan on using bone, mucosa, or tooth supported guides? Or do you want to have the option of using all

These are all considerations that must be taken into account before investing in any imaging software because once

Another consideration is that different implant‐planning softwares allow different levels of resolution of the CBCT data. So even if the CBCT machine is capable of taking high resolution images, the planning software you choose may not be able to open the full resolution which was recorded. When placing implants, any fraction of a millimeter

> Keystone Universal ✔ ✔ \$\$ Biohorizon Universal ✔ ✔ ✔ \$\$ NobelBiocare NobelBiocare ✔ ✔ ✔ \$\$ Anatomage Universal ✔ ✔ ✔ ✔ \$ Materialise Universal ✔ ✔ ✔ ✔ \$\$\$

Keystone offers one of the most basic surgical guide systems, hence the coined term "Easy‐ Guide" for their planning software. EasyGuide can be utilized for planning implant placement in single tooth edentulous spaces, partially edentulous spaces, and completely edentulous arches. The Keystone surgical guide can only be used in single tooth edentulous spaces and

During the CBCT, the patient wears a laboratory fabricated radiographic guide with barium sulfate incorporated in the areas where the teeth will be replaced. This guide also has a built in radiographic "X Marker", which is subsequently used by Keystone to fabricate the surgical guide. The clinician then plans the implant placement in the EasyGuide computer program and virtually sends this information to Keystone to fabricate the surgical guide, if desired.

The surgical guide is fabricated from the digital planning. The clinician must send the radiographic guide with the incorporated "X Marker" to Keystone, which uses this to orient the guide to the patient's jaw. Keystone then will fabricate the surgical guide either as "directional" or "depth and directional", depending on the clinician's wishes. This means that the guide can be used to direct the implant at the correct angle and it can also be used to direct

Biohorizons is another very simple and basic implant planning program that offers a userfriendly technique but limited options to the clinician. The surgical guide, called a Compu-Guide, can be fabricated for single implant placement, partially edentulous multiple implant

The patient wears a laboratory fabricated radiographic guide during the CBCT which is fabricated to the planning software, VIP, specifications. Then the clinician may digitally plan the implant placement using the VIP computer software. This software allows the placement

This information along with the radiographic guide is sent to Biohorizons which fabricates the Pilot Compu-Guide, a surgical guide that allows only the pilot drills to be sequenced through the guide. The clinician inserts the Compu-Guide and stabilizes it. The pilot osteomoties are drilled to length, then the guide is removed, and the twist drills are then used free-hand

placement, and fully edentulous multiple implant placement.

**Support Type Material Cost Bone Mucosa Tooth Resin Stereolith**

company offers a different program and these are not all as user‐friendly as the next.

can then be fabricated from the digital design.

Dummy Text **Things to Consider When Choosing a System**

a separate radiographic guide for the scan?

**Company Implant**

158 Current Concepts in Dental Implantology

partially edentulous spaces.

it to the correct depth in the bone.

of any type of implant system.

**7.2. Biohorizons**

Table 2. Brishi

**7.1. Keystone 7.1. Keystone**

you do, you will be limited by that companies available options.

**Systems**

in the wrong direction may have a significant compromise on the outcome.

implant planning for you?

three, depending on the case?

prefers.

**7. Companies**

NobelBiocare offers a very sturdy stereolithographic surgical guide with multiple indications for use, but can only be used with NobelBiocare implants. This system can be used for single tooth edentulous sites, partially edentulous sites, and completely edentulous arches.

The CBCT prescription requests a dual-scan protocol. The dual-scan protocol requires two scans: one scan of the patient while wearing the radiographic guide and one scan of the radiographic guide by itself. The radiographic guide has built-in fiduciary markers, which allow the software to overlay the two separate scanned images. Fiduciary markers are gutta percha dots added into the radiographic guide. If the patient is already wearing a well-fitting denture, these markers can be added to the denture very easily. If the patient does not have a well-fitting denture, a new tooth-set up should be tried in and then duplicated or processed into a radiographic guide. The fiduciary markers can be added to the radiographic guide by drilling eight to ten round divots throughout and filling them with gutta percha. They should be 1mm x 1 mm in size, and spread throughout the guide in different horizontal and vertical levels.

The planning software, NobelClinician, will fuse the two files, using the fiduciary markers, so that the patient's anatomy can be visualized with and without the radiographic guide in place. In other words, the anatomical data and prosthetic data can be visualized separately. Nobel‐ Clinician allows various views and reslices of the scan. It also shows a yellow safety zone around implants, which is especially important when performing flapless surgery. This safety zone helps prevents implants from being placed too close to anatomical structures or to other implants. The program also shows technical restrictions in red. For example, the software prevents the clinician from placing implants close to each other due to the width requirement of the metal sleeve in the guide. This is a complication of the fabrication of the guide to be the strongest possible in the areas where the implant drill will be entering. If the acrylic between two sleeves is thin, the guide may break in that area. If a clinician desires to place implants fairly close together, another system may be better suited.

NobelBiocare offers tooth-borne and mucosal-borne guides, but not bone-based guides. So for the completely edentulous patient, a mucosal-borne guide must be chosen. The clinician will run into a problem if the edentulous patient has very thick gingival tissue. The mucosal-based surgical guide is fabricated so that the head of the implants are placed 3 mm from the intaglio surface of the surgical guide, assuming the average patient has 3 mm of gingival tissue thickness. So if the patients gingiva is more than 3 mm thick, and the implants were digitally planned to be at the crest of bone, then the intaglio surface of the surgical guide will impinge upon the patients tissue. The easiest way around this is to relieve the intaglio surface of the guide around the drill hole, before placing it in the patient's mouth.

The virtual planning will be completed on NobelClinician, which is one of the only programs that runs on Windows and Mac OS X. The NobelClinician software also allows planning of the abutments with digital visualization. This is particularly useful when placing angled implants which will need angled multi-unit abutments. The planned information from NobelClinician is sent electronically to NobelBiocare Production Center where the Nobel‐ Guide is produced centrally.

The following photos show how to make a Nobelguide and to restore a patient with an immediate implant-retained overdenture (Figures 1-20).

**Figure 1.** Complete denture with fiduciary markers is used as radiographic guide.

**Figure 2.** Patient wears complete denture with fiduciary markers during CBCT scan.

**Figure 3.** Occlusal view of maxillary surgical guide and maxilla on software.

the abutments with digital visualization. This is particularly useful when placing angled implants which will need angled multi-unit abutments. The planned information from NobelClinician is sent electronically to NobelBiocare Production Center where the Nobel‐

The following photos show how to make a Nobelguide and to restore a patient with an

Guide is produced centrally.

160 Current Concepts in Dental Implantology

immediate implant-retained overdenture (Figures 1-20).

**Figure 1.** Complete denture with fiduciary markers is used as radiographic guide.

**Figure 2.** Patient wears complete denture with fiduciary markers during CBCT scan.

**Figure 4.** Occlusal view of maxillary surgical guide on sofware after removing maxillary bone.

**Figure 5.** Frontal view of maxillary surgical guide and maxilla.

**Figure 6.** Occlusal view of actual surgical guide fabricated at NobelBiocare production center.

**Figure 7.** Surgical guide is inserted with bite-registration.

**Figure 8.** Anchor pins are placed to secure surgical guide.

**Figure 5.** Frontal view of maxillary surgical guide and maxilla.

162 Current Concepts in Dental Implantology

**Figure 6.** Occlusal view of actual surgical guide fabricated at NobelBiocare production center.

**Figure 9.** Drills are used to prepare implant sockets.

**Figure 10.** Implants are placed through metal sleeves.

**Figure 11.** All implants are placed.

**Figure 12.** Surgical guide is removed after all implants are placed.

**Figure 13.** Locater abutments are screwed on implants.

**Figure 10.** Implants are placed through metal sleeves.

164 Current Concepts in Dental Implantology

**Figure 11.** All implants are placed.

**Figure 12.** Surgical guide is removed after all implants are placed.

**Figure 14.** Metal housings are seated on locaters.

**Figure 15.** Enough room is needed for locaters and metal housings.

**Figure 16.** Enough room is created for locaters and metal housings.

**Figure 17.** Metal housing are attached to complete denture.

**Figure 18.** Complete denture is converted to immediate implant-retained overdenture.

**Figure 19.** Intra-oral view of patient.

**Figure 16.** Enough room is created for locaters and metal housings.

166 Current Concepts in Dental Implantology

**Figure 17.** Metal housing are attached to complete denture.

**Figure 18.** Complete denture is converted to immediate implant-retained overdenture.

**Figure 20.** Panoramic radiograph of patient.

#### **7.4. Anatomage**

Anatomage is a system which offers some of the most options when planning implant placement with a surgical guide. The biggest downside of this system is that the guides are fabricated out of a conventional acrylic resin, which easily flexes under high loads of stress during implant placement. One must be very careful when choosing to use this system in a patient with a large edentulous area because it can easily be torqued out of position. Due to the material used, one benefit of this system is that the guides are cheaper than any other system. The price is a fixed price no matter how many implants are being placed.

This system, similar to the NobelClinician, prescribes for a dual-scan protocol. The company boasts that their planning software does not require a scanning appliance (or radiographic guide). Instead, a stone model and/or wax-up is scanned in order to visualize the planned positions of the teeth on the image. The planning software, InVivo5, allows the planning of any type of implant as well as bone-based, mucosal-based, and tooth-based guides. InVivo5 offers high quality volume rendering with some of the best visualization options. The volume easily switches between transparent hard tissues, as well as detailed bone, airway, or skin profiles.

The surgical guide is fabricated centrally by Anatomage in order to preserve the fixed price. Along with the surgical guide, the clinician may choose to order specialized depth control drills to gain the most guidance.

#### **7.5. Materialise**

Materialise offers the most versatile implant planning program. They will provide bone-based, mucosal-based, and tooth-based guides. And all three types are fabricated by stereolithogra‐ phy so that they are the most rigid. A tooth-supported SurgiGuide is suitable for minimally invasive surgery. Since the guide was fabricated from virtual planning, it is not necessary to raise a flap for implant placement. A plaster cast of the pre-surgical teeth must be sent to Materialise with the SimPlant virtual plan. A mucosa-supported SurgiGuide is indicated when minimally invasive surgery is necessary for a fully edentulous case. A bone-supported SurgiGuide is appropriate for a partially or fully edentulous case when increased visibility or more surgical procedures are necessary.

The patient is scanned using the clinicians method of choice, either single-scan or dual-scan protocol. If choosing the dual-scan protocol, the clinician may purchase the dual scan markers from Materialise or add the fiduciary markers on their own. The digital planning is then performed using the software Simplant Planner. SimPlant Planner provides a library with more than 8000 different implants and abutments to provide easy surgical guide fabrication. Any implant system may be prescribed when using Materialise. The planned information is virtually sent to Materialise, and the surgical guide, Surgiguide, is fabricated.

If the clinician would like to convert the CBCT images into the 3D representation, the software SimPlant Pro is available for this. When using SimPlant Planner this conversion is performed by Materialise. SimPlant also offers a free software program, called SimPlant View, which allows anyone to view the files. So when planning a case between different team members, such as a surgeon, restorative dentist and lab technician, all team members may view the case on their personal computer.

There are three different options when choosing the surgical guide, SurgiGuide: Pilot, Universal, and SAFE. The Pilot SurgiGuide offers the guidance during the initial pilot drilling, and then the guide is removed and the drilling sequence is completed free-hand. This is best used in straightforward and simple cases. It is similar to Biohorizons Pilot Compu-Guide. The Universal SurgiGuide offers a fixed implant position and angulation, without depth control. The drill depth is provided in the prescription sent with the SurgiGuide so the clinician knows how deep to drill. The drills are guided through the SurgiGuide, and when the drilling sequence is completed, the guide is removed and the implants are placed in the osteotomies. Lastly, the SAFE SurgiGuide offers a fixed implant position, angulation, and depth. This guide provides the most controlled system.

Materialise also offers bone reduction guides. If the clinician is planning for a prosthesis which requires more restorative space than is available, a bone reduction guide can first be used to perform a precise amount of alveoloplasty. Afterwards, a bone-based implant surgical guide is placed, according to the amount of bone reduction, and the implants are predictable placed at that new bone level. When positioning the implants in the SimPlant Planner, place them at the desired subcrestal positions. The white dots around the implants in SimPlant show the bone height desired after placement. These can be moved up and down as desired. The SimPlant designers then have enough information to produce the drill guide as well as the bone reduction guide.

#### **7.6. Laboratory procedures**

offers high quality volume rendering with some of the best visualization options. The volume easily switches between transparent hard tissues, as well as detailed bone, airway, or skin

The surgical guide is fabricated centrally by Anatomage in order to preserve the fixed price. Along with the surgical guide, the clinician may choose to order specialized depth control

Materialise offers the most versatile implant planning program. They will provide bone-based, mucosal-based, and tooth-based guides. And all three types are fabricated by stereolithogra‐ phy so that they are the most rigid. A tooth-supported SurgiGuide is suitable for minimally invasive surgery. Since the guide was fabricated from virtual planning, it is not necessary to raise a flap for implant placement. A plaster cast of the pre-surgical teeth must be sent to Materialise with the SimPlant virtual plan. A mucosa-supported SurgiGuide is indicated when minimally invasive surgery is necessary for a fully edentulous case. A bone-supported SurgiGuide is appropriate for a partially or fully edentulous case when increased visibility or

The patient is scanned using the clinicians method of choice, either single-scan or dual-scan protocol. If choosing the dual-scan protocol, the clinician may purchase the dual scan markers from Materialise or add the fiduciary markers on their own. The digital planning is then performed using the software Simplant Planner. SimPlant Planner provides a library with more than 8000 different implants and abutments to provide easy surgical guide fabrication. Any implant system may be prescribed when using Materialise. The planned information is

If the clinician would like to convert the CBCT images into the 3D representation, the software SimPlant Pro is available for this. When using SimPlant Planner this conversion is performed by Materialise. SimPlant also offers a free software program, called SimPlant View, which allows anyone to view the files. So when planning a case between different team members, such as a surgeon, restorative dentist and lab technician, all team members may view the case

There are three different options when choosing the surgical guide, SurgiGuide: Pilot, Universal, and SAFE. The Pilot SurgiGuide offers the guidance during the initial pilot drilling, and then the guide is removed and the drilling sequence is completed free-hand. This is best used in straightforward and simple cases. It is similar to Biohorizons Pilot Compu-Guide. The Universal SurgiGuide offers a fixed implant position and angulation, without depth control. The drill depth is provided in the prescription sent with the SurgiGuide so the clinician knows how deep to drill. The drills are guided through the SurgiGuide, and when the drilling sequence is completed, the guide is removed and the implants are placed in the osteotomies. Lastly, the SAFE SurgiGuide offers a fixed implant position, angulation, and depth. This guide

virtually sent to Materialise, and the surgical guide, Surgiguide, is fabricated.

profiles.

**7.5. Materialise**

drills to gain the most guidance.

168 Current Concepts in Dental Implantology

more surgical procedures are necessary.

on their personal computer.

provides the most controlled system.

A virtually planned surgical guide for the placement of implants offers not only a predictable method for the surgical placement of the implants, but also a more convenient and time saving method for the fabricating provisional restorations. A clinician may use a surgical guide to its full advantage by preparing the provisionals before the day of surgery. Either the clinician or a lab technician can prefabricate the implant provisionals using the surgical template. First, a master cast is fabricated using the surgical guide. Implant analogs are attached to the guide, large undercuts are blocked out, a soft tissue matrix is fabricated, and stone is poured into the guide. This master cast can then be mounted against the opposing cast using the premade bite index which was utilized during the CBCT scan. Provisional restorations can be fabricated on this master cast, which will then be ready for chairside pick-up of the implants after surgery. This method provides an easy way to do immediate loading of implants on the day of surgery.

This is a popular method being advertised worldwide and is an advantageous strategy for attracting patients to your office. Patients are given an immediate result with predictable esthetics, phonetics, and function if the laboratory steps and chairside pick-up are followed correctly.

#### **8. Alternative benefits of virtual planning**

Another advantage of using virtual planning for dental implants is the ability to fabricate implant frameworks through scanning of the master cast. After implants have osseointegrated, a final implant-level impression is made, and a master cast is made and verified. Then a 3-D scanner will scan the implant positions and the framework can be designed virtually for the final prosthesis. From the virtual design, the framework is then milled from a block of metal [3]. Each scanning company has different milling materials to choose from. The framework can support a hybrid, bar-overdenture, or implant-supported fixed dental prostheses (such as screw-retained PFM crowns or FDPs). This framework can either be designed virtually or it can be designed in acrylic on the master cast and scanned (i.e., copy-milled). The latter of the two options is a better choice for complicated clinical situations with no room for error, such as implant-supported fixed dental prostheses. This prosthetic design requires very specific dimensions for the final porcelain layer, and thus should always be copy-milled. Hybrid cases which were planned well with enough restorative space can usually be designed virtually with retention elements added for the acrylic which will be surrounding the milled metal frame‐ work.

Milling provides a much more accurate framework than conventional casting because there is no shrinkage involved. When a multiple-implant framework is waxed and cast, it takes extra time because it must be sectioned and soldered after shrinkage. The milled frameworks, on the other hand, are milled to fit the implant positions exactly and involve no shrinkage or distortion of the metal. The major disadvantage of choosing a milled framework is that the companies offer only a limited number of material choices. Most companies do not offer a metal which porcelain can be added to predictably.

The following photos show how to make a milled titanium framework using NobelProcera software and scanner and to restore a patient with an implant-supported fixed dental pros‐ thesis (Figures 21-34).

**Figure 21.** Final impression for each arch is made.

**Figure 22.** Denture teeth are arranged in the laboratory.

**Figure 23.** Both trial dentures are verified clinically.

which were planned well with enough restorative space can usually be designed virtually with retention elements added for the acrylic which will be surrounding the milled metal frame‐

Milling provides a much more accurate framework than conventional casting because there is no shrinkage involved. When a multiple-implant framework is waxed and cast, it takes extra time because it must be sectioned and soldered after shrinkage. The milled frameworks, on the other hand, are milled to fit the implant positions exactly and involve no shrinkage or distortion of the metal. The major disadvantage of choosing a milled framework is that the companies offer only a limited number of material choices. Most companies do not offer a

The following photos show how to make a milled titanium framework using NobelProcera software and scanner and to restore a patient with an implant-supported fixed dental pros‐

metal which porcelain can be added to predictably.

work.

thesis (Figures 21-34).

170 Current Concepts in Dental Implantology

**Figure 21.** Final impression for each arch is made.

**Figure 22.** Denture teeth are arranged in the laboratory.

**Figure 24.** Mandibular definitive cast is sprayed with zinc-oxide powder before placing scanning abutments.

**Figure 25.** Scanning abutments are screwed on the implant replicas, and definitive cast mounted for scanning.

**Figure 26.** Occlusal view of mandibular cast with implant positions after scanning process.

**Figure 27.** Trial denture is sprayed with zinc-oxide powder after placing it on definitive cast.

**Figure 28.** Note red line generated by laser probe during trial denture scanning process.

**Figure 29.** Occlusal view of trial denture overlapping mandibular cast including implants after scanning process.

**Figure 30.** Frontal view of final design of mandibular framework.

**Figure 26.** Occlusal view of mandibular cast with implant positions after scanning process.

172 Current Concepts in Dental Implantology

**Figure 27.** Trial denture is sprayed with zinc-oxide powder after placing it on definitive cast.

**Figure 28.** Note red line generated by laser probe during trial denture scanning process.

**Figure 31.** Occlusal view of final design of mandibular framework.

**Figure 32.** Clinical fit of mandibular framework verified.

**Figure 33.** Intraoral view after both restorations are inserted.

**Figure 34.** Panoramic radiograph after maxillary complete denture and mandibular FDP are inserted.

#### **9. Conclusion**

This chapter aimed to explain virtual treatment planning by using softwares, scanners and CAD/CAM technology. Each person involved in this process should possess the knowledge to use these softwares and hardwares, which require advanced training and experience. Otherwise, failures would be inevitable and costly. Although each step was explained and illustrated in great detail, the readers need to make to sure that they have proper knowledge, armemantarium, and experience before attempting to these types of treatment.

#### **Author details**

**Figure 32.** Clinical fit of mandibular framework verified.

174 Current Concepts in Dental Implantology

**Figure 33.** Intraoral view after both restorations are inserted.

**Figure 34.** Panoramic radiograph after maxillary complete denture and mandibular FDP are inserted.

Ilser Turkyilmaz1\*, Caroline Corrigan Eskow1 and Gokce Soganci2

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

1 Department of Comprehensive Dentistry, University of Texas Health Science Center at San Antonio, Texas, United States of America

2 Department of Prosthodontics, Oral and Dental Health Center, Ankara, Turkey

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## **Role of Implants in Maxillofacial Prosthodontic Rehabilitation**

Derek D'Souza

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Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/59578

#### **1. Introduction**

Maxillofacial prostheses play a vital role in comprehensive rehabilitation by restoring physical and psychological well-being in patients with missing or disfigured anatomical structures due to congenital abnormalities, trauma, or disease [1]. It is possible to restore esthetics, function and re-establish the self confidence of the patient by providing a well designed prosthesis such as a prosthetic ear, eye, nose, cranial plate or a combination of these.

The last few decades have witnessed a significant increase in extensive malignancies of the head and neck region [2]. This has resulted in increasing number of patients with exten‐ sive post-surgical defects. Many of them need to be suitably rehabilitated to minimize longterm physical, functional and psychological consequences and ensure early return to normal life. In addition, these patients could be more willing to accept large surgical resections, if counseled about prosthetic reconstruction, prior to definitive surgery. It is crucial that all such patients receive a pre-operative referral to a maxillofacial prosthodontist prior to surgery [3].

When these patients report to the maxillofacial prosthetic clinic they report with complex defects and their general health status is also compromised. Achieving adequate retention of the prosthesis, especially when the defect is extensive, is a big challenge and requires a multi-disciplinary approach. With the advent of predictable osseointegration, a new era dawned in the field of prosthodontic rehabilitation of the head and neck region. Cases that were earlier condemned as "hopeless" were suddenly given a new range of options and the chance to be comprehensively restored to form and function. This chapter discusses the role of implants in comprehensive maxillofacial rehabilitation.

© 2015 The Author(s). Licensee InTech. 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 eproduction in any medium, provided the original work is properly cited.

#### **2. Retention of maxillofacial prostheses**

Historically the means of achieving retention of facial prostheses has been primarily by use of medical adhesives or by means of anatomical or mechanical retention using various devices such as spectacles, springs, studs, clips or magnets [3]. An ideal adhesive should be one that provides firm functional retention under flexure or extension during speech, facial expres‐ sions, and moisture or perspiration contact, however such an adhesive is not yet available. Facial prostheses may additionally be retained by judicious use of anatomic tissue undercuts, thereby minimizing the displacement potential caused by other external forces. There is a potential for tissue irritation with use of this technique and due care and regular follow up is a must. Special care is warranted where tissues have been previously irradiated.

#### **2.1. Cellular level changes of osseointegration**

It is necessary to have a clear concept about the science of implantation and the healing of bone following a successful implant placement. Osseous healing along an implant follows a similar process to fracture healing but is subjective to the nature of the surface of the implant [4]. As soon as blood comes into contact with the surface of the implant, proteins adsorb to it, platelets get activated and bind to the adsorbed protein which results in the formation of a clot. This coagulum at the implant surface supports the deposition of proteins, releases inflammatory mediators and initiates new tissue formation. The release of numerous signaling molecules influence the migration of monocytes, neutrophils (both involved in inflammation), and mesenchymal cells (cells that can differentiate into osteoblasts) towards the implant surface [4]. Following the aggregation of neutrophils and macrophages from nearby capillary beds to the implant site there is further release of inflammatory mediators which are necessary for the initiation of osteogenesis. Components of tissue growth factor β (TGF-β) super-family are also expressed within 24 hours of implantation, including bone morphogenetic proteins (BMPs) and growth & differentiation factors (GDFs). These signaling molecules result in the collection, migration, and differentiation of mesenchymal cells, which take part in the formation of woven bone. Woven bone subsequently undergoes a sequence of remodeling, resulting in the formation of mature bone which is the desired end result [5].

#### **2.2. Implant surface modifications**

Various surface modifications are being commercially marketed since the days of the first Brånemark implants [6]. Grit-blasting and acid etching still remain the most commonly employed surface modification techniques in use today. Sand blasting increases the surface area of the implant as compared to machined surfaces. The resultant increase in surface area has been shown to improve cell attachment and proliferation which results in increased implant stability [7 – 10]. Electrochemical anodization is another chemical surface modification method that has been employed. This process increases surface micro-texture and also modifies the chemistry of the implant coating resulting in a titanium oxide layer that is several orders of magnitude thicker than a passivated surface [11, 12]. The addition of a ceramic coating to the roughened surface is another method of improving osseoconductivity. Here a plasma collection, migration, and differentiation of mesenchymal cells, which take part in the formation of woven bone. Woven bone subsequently undergoes a sequence of remodeling, resulting in the formation of mature bone which is the desired

blasting and acid etching still remain the most commonly employed surface modification techniques in use today. Sand

sprayed hydroxyapatite (HA) coating is used to create an irregular surface for osseointegra‐ tion. The process involves blasting the implant surface with HA particles at a high temperature. The result is a coating that develops cracks as it rapidly cools. These coatings show enhanced bone-to-implant contact initially, in vivo, however the mechanical properties of the bonecoating interface has exhibited non-uniform degradation in the long term [13-16]. blasting increases the surface area of the implant as compared to machined surfaces. The resultant increase in surface area has been shown to improve cell attachment and proliferation which results in increased implant stability [7 – 10]. Electrochemical anodization is another chemical surface modification method that has been employed. This process increases surface micro‐texture and also modifies the chemistry of the implant coating resulting in a titanium oxide layer that is several orders of magnitude thicker than a passivated surface [11, 12]. The addition of a ceramic coating to the roughened surface is another method of improving osseoconductivity. Here a plasma sprayed hydroxyapatite (HA)

In other alternatives, crystalline deposition of nano-sized calcium phosphate and addition of a fluoride treatment to roughened titanium surfaces have also been tried with varying success [17-19]. While several advances in surface modification have been made in order to improve implant osseointegration, no treatment addresses the issue of reducing infection. While some manufacturers claim to be bacteria-proof due to their tight interlocking, the implant itself does not prevent bacterial attachment which can lead to formation of biofilms and subsequent implant failure [20, 21]. coating is used to create an irregular surface for osseointegration. The process involves blasting the implant surface with HA particles at a high temperature. The result is a coating that develops cracks as it rapidly cools. These coatings show enhanced bone‐to‐implant contact initially, in vivo, however the mechanical properties of the bone‐coating interface has exhibited non‐uniform degradation in the long term [13 ‐ 16]. In other alternatives, crystalline deposition of nano‐sized calcium phosphate and addition of a fluoride treatment to roughened titanium surfaces have also been tried with varying success [17 ‐ 19]. While several advances in surface modification have been made in order to improve implant osseointegration, no treatment addresses the issue of reducing

#### **2.3. Craniofacial implants** infection. While some manufacturers claim to be bacteria‐proof due to their tight interlocking, the implant itself does not prevent bacterial attachment which can lead to formation of biofilms and subsequent implant failure [20, 21].

end result [5].

**4. Implant surface modifications**

**2. Retention of maxillofacial prostheses**

180 Current Concepts in Dental Implantology

**2.1. Cellular level changes of osseointegration**

formation of mature bone which is the desired end result [5].

**2.2. Implant surface modifications**

Historically the means of achieving retention of facial prostheses has been primarily by use of medical adhesives or by means of anatomical or mechanical retention using various devices such as spectacles, springs, studs, clips or magnets [3]. An ideal adhesive should be one that provides firm functional retention under flexure or extension during speech, facial expres‐ sions, and moisture or perspiration contact, however such an adhesive is not yet available. Facial prostheses may additionally be retained by judicious use of anatomic tissue undercuts, thereby minimizing the displacement potential caused by other external forces. There is a potential for tissue irritation with use of this technique and due care and regular follow up is

It is necessary to have a clear concept about the science of implantation and the healing of bone following a successful implant placement. Osseous healing along an implant follows a similar process to fracture healing but is subjective to the nature of the surface of the implant [4]. As soon as blood comes into contact with the surface of the implant, proteins adsorb to it, platelets get activated and bind to the adsorbed protein which results in the formation of a clot. This coagulum at the implant surface supports the deposition of proteins, releases inflammatory mediators and initiates new tissue formation. The release of numerous signaling molecules influence the migration of monocytes, neutrophils (both involved in inflammation), and mesenchymal cells (cells that can differentiate into osteoblasts) towards the implant surface [4]. Following the aggregation of neutrophils and macrophages from nearby capillary beds to the implant site there is further release of inflammatory mediators which are necessary for the initiation of osteogenesis. Components of tissue growth factor β (TGF-β) super-family are also expressed within 24 hours of implantation, including bone morphogenetic proteins (BMPs) and growth & differentiation factors (GDFs). These signaling molecules result in the collection, migration, and differentiation of mesenchymal cells, which take part in the formation of woven bone. Woven bone subsequently undergoes a sequence of remodeling, resulting in the

Various surface modifications are being commercially marketed since the days of the first Brånemark implants [6]. Grit-blasting and acid etching still remain the most commonly employed surface modification techniques in use today. Sand blasting increases the surface area of the implant as compared to machined surfaces. The resultant increase in surface area has been shown to improve cell attachment and proliferation which results in increased implant stability [7 – 10]. Electrochemical anodization is another chemical surface modification method that has been employed. This process increases surface micro-texture and also modifies the chemistry of the implant coating resulting in a titanium oxide layer that is several orders of magnitude thicker than a passivated surface [11, 12]. The addition of a ceramic coating to the roughened surface is another method of improving osseoconductivity. Here a plasma

a must. Special care is warranted where tissues have been previously irradiated.

In order to obtain predictable craniofacial osseointegration, different protocols had to be developed. It was necessary to have certain modifications as compared to the oral implants. These implants were made from titanium alloys and were generally shorter i.e. 3 – 5 mm long, threaded and with the same machined surface as the oral implants. It was further found important to attach a flange in the coronal part of the fixture [Figure 1]. The reason for this was the idea that even if the implant was subjected to a longitudinally directed trauma, the flange would prevent it to from being pushed into the deeper structures. This has also proved to be a safe and secure measure, as several trauma cases have occurred, but only a minority have caused fractures of the skull bone, and none have caused severe damage [22]. **5. Craniofacial implants** In order to obtain predictable craniofacial osseointegration different protocols had to be developed. It was necessary to have certain modifications as compared to the oral implants. These implants were made from titanium alloys and were generally shorter i.e. 3 – 5 mm long, threaded and with the same machined surface as the oral implants. It was further found important to attach a flange in the coronal part of the fixture [Figure1]. The reason for this was the idea that even if the implant was subjected to a longitudinally directed trauma, the flange would prevent it to from being pushed into the deeper structures. This has also proved to be a safe and secure measure, as several trauma cases have occurred, but only a minority have caused fractures of the skull bone, and none have caused severe damage [22].

**Figure 1.** Design of craniofacial implants

different types were developed. These include abutments for the bone‐anchored hearing aid (BAHA) and abutments for bone‐anchored epistheses (BAE). The length of the fixtures to be used is determined by the thickness of the cranial bones. In a normal adult the temporal bone has a thickness of approximately 4 mm. This is also the length of the most commonly available implants. It may be possible to install longer fixtures in the frontal bone, zygoma and maxilla. The The first abutment that was originally used was also of an intraoral type, but with time, extraoral abutments of different types were developed. These include abutments for the boneanchored hearing aid (BAHA) and abutments for bone-anchored epistheses (BAE). The length of the fixtures to be used is determined by the thickness of the cranial bones. In a normal adult

Fig 1 Design of craniofacial implants The first abutment that was originally used was also of an intraoral type, but with time, extra‐oral abutments of

skin over the abutments has to be reduced to a minimum. This is to prevent constant discomfort or trauma experienced

the temporal bone has a thickness of approximately 4 mm. This is also the length of the most commonly available implants. It may be possible to install longer fixtures in the frontal bone, zygoma and maxilla. The skin over the abutments has to be reduced to a minimum. This is to prevent constant discomfort or trauma experienced by the patient when the prosthesis will move. Patients who have split skin grafts around the implant abutment show the least skin penetration problems [22, 23].

In pediatric cases the skull bone is much thinner, sometimes barely 1–3 mm thick. In these cases a different approach is necessitated. A simple technique is by the utilization of a semipermeable membrane at the first stage surgery [24]. By utilizing this technique, 1–2 mm bone can be gained during a 6-month healing period, thus making it possible to install a 4-mm long fixture also in children. The semi-permeable membrane is then removed at the second stage surgery.

Osseointegration in irradiated bone was early believed to be contraindicated. Patients who are recovering from various forms of cancer need comprehensive rehabilitation and can benefit a lot from the use of osseointegrated implants. Clinically though there were higher failure rates along with certain other problems such as dehiscence of the soft tissue as well as osteoradio‐ necrosis [25]. Taking into consideration that the irradiated bone will take longer to heal it is advisable to first delay the placement of the implant and also to allow 4 to 8 months for osseointegration. Another approach is to expose the patients to adjunctive hyperbaric oxygen therapy (HBO). HBO has been shown to accelerate healing and also prevent osteoradionecrosis [26, 27]. In 2013, de Oliveira, Abrahão and Dib [28] however found that there is no difference in implant success between irradiated and normal bone. Keeping all things constant and knowing the risk factors involved it seems to be better to ensure all precautions are maintained in case selection, implant placement and also to ensure that the patient receives HBO therapy to reduce failures in patients who have received some form of radiotherapy and/or chemo‐ therapy.

#### **2.4. Factors of importance for predictable osseointegration**

There are six factors of importance that must be carefully monitored to ensure predictable osseointegration [29-31].

*Material of the fixture*-Titanium alloys are the most commonly used as these are known to integrate in the bone without causing adverse effects. It can remain incorporated into the bone for many decades, and be used as anchorage for different prostheses.

*Macrostructure of the implant*-A screw-shaped implant ensures better primary stability as compared to a conical shaped implant. This may be due to micro-movements of the conical shape and reduced osseointegration.

*Microstructure of the implant*-Original Brånemark implants had a smooth surface as they were manufactured by machining. Clinically however it has been observed that very smooth surfaces have lesser degree of osseointegration, along with minor amount of resorption. On the other hand a highly roughened surface shows rapid integration; but later secondary inflammation and secondary resorption is noticed that can endanger the long-term survival of the implant.

*Osseous bed into which the implant is placed*-Geriatric patients with bone that is osteoporotic will show lesser degree of osseointegration. Similar is the case of patients who have had radio‐ therapy or who have sustained severe burns that alter the osseous quality and reduce its capacity for osseointegration.

*Surgical technique* – The surgical intervention should be carefully monitored with slow speed, high torque and copious irrigation with cold water. The temperature should never be allowed to rise as the osteoblasts are extremely heat labile and get damaged easily. The implant itself should never be touched by gloves or gauze. It is vital that the surgical bed be free from fibers, powder and any other foreign matter that might hinder osseointegration.

*Loading the implant* – The implant should be loaded along its long axis as far as feasible. Lateral, torsional or cantilever forces are least tolerated and should be minimized by efficient planning and design.

#### **2.5. Retention of maxillofacial prostheses and craniofacial implants**

the temporal bone has a thickness of approximately 4 mm. This is also the length of the most commonly available implants. It may be possible to install longer fixtures in the frontal bone, zygoma and maxilla. The skin over the abutments has to be reduced to a minimum. This is to prevent constant discomfort or trauma experienced by the patient when the prosthesis will move. Patients who have split skin grafts around the implant abutment show the least skin

In pediatric cases the skull bone is much thinner, sometimes barely 1–3 mm thick. In these cases a different approach is necessitated. A simple technique is by the utilization of a semipermeable membrane at the first stage surgery [24]. By utilizing this technique, 1–2 mm bone can be gained during a 6-month healing period, thus making it possible to install a 4-mm long fixture also in children. The semi-permeable membrane is then removed at the second stage

Osseointegration in irradiated bone was early believed to be contraindicated. Patients who are recovering from various forms of cancer need comprehensive rehabilitation and can benefit a lot from the use of osseointegrated implants. Clinically though there were higher failure rates along with certain other problems such as dehiscence of the soft tissue as well as osteoradio‐ necrosis [25]. Taking into consideration that the irradiated bone will take longer to heal it is advisable to first delay the placement of the implant and also to allow 4 to 8 months for osseointegration. Another approach is to expose the patients to adjunctive hyperbaric oxygen therapy (HBO). HBO has been shown to accelerate healing and also prevent osteoradionecrosis [26, 27]. In 2013, de Oliveira, Abrahão and Dib [28] however found that there is no difference in implant success between irradiated and normal bone. Keeping all things constant and knowing the risk factors involved it seems to be better to ensure all precautions are maintained in case selection, implant placement and also to ensure that the patient receives HBO therapy to reduce failures in patients who have received some form of radiotherapy and/or chemo‐

There are six factors of importance that must be carefully monitored to ensure predictable

*Material of the fixture*-Titanium alloys are the most commonly used as these are known to integrate in the bone without causing adverse effects. It can remain incorporated into the bone

*Macrostructure of the implant*-A screw-shaped implant ensures better primary stability as compared to a conical shaped implant. This may be due to micro-movements of the conical

*Microstructure of the implant*-Original Brånemark implants had a smooth surface as they were manufactured by machining. Clinically however it has been observed that very smooth surfaces have lesser degree of osseointegration, along with minor amount of resorption. On the other hand a highly roughened surface shows rapid integration; but later secondary

**2.4. Factors of importance for predictable osseointegration**

for many decades, and be used as anchorage for different prostheses.

penetration problems [22, 23].

182 Current Concepts in Dental Implantology

surgery.

therapy.

osseointegration [29-31].

shape and reduced osseointegration.

With the increased use of osseointegrated implants, dependence on adhesive and anatomic methods of retention has diminished. Magnets or clips can be used to effectively retain the prostheses [Figure 2] and will also minimize force transfer to the implant and supporting bone. The resultant decrease in dependence on chemical (adhesives) and anatomic (tissue undercuts) retention is beneficial to both the patient and the prosthodontist [31 – 35].

situations or with acquired defects from accidents. Other designs may also be provided if the distance between the two implants is too close or too far apart. Other crucial factors in rehabilitating this type of defect are marginal fit, good retention, and acceptable esthetics. Various studies have shown that retention using craniofacial implants has improved the satisfaction of patients with craniofacial prostheses. However, the actual level of satisfaction depends, to a large

In order to address the area of rehabilitation of the orbit it is vital to understand the different types of surgical techniques used in ophthalmic surgeries. Evisceration, enucleation, and exenteration are the three main surgical techniques by which all or parts of the orbital contents are removed [39]. Evisceration is the removal of the contents of the globe while leaving the sclera and extra‐ocular muscles intact. Enucleation is the removal of the eye from the orbit while preserving all other orbital structures. Exenteration is the most radical of the three procedures and involves

Evisceration is usually indicated in cases of endophthalmitis unresponsive to antibiotics and for improvement of esthetics in an eye that is damaged and has lost its vision. Enucleation is indicated for the above two conditions as well as for painful eyes with no useful vision, malignant intraocular tumors, in ocular trauma to avoid sympathetic ophthalmia in the second eye, in phthisis with degeneration, and in congenital anophthalmia or severe microphthalmia to enhance development of the bony orbit. Exenteration is indicated mainly for large orbital tumors or orbital extension

The first two namely evisceration and enucleation can be easily rehabilitated with excellent cosmetic results using custom made ocular prostheses [1, 3]. These are fabricated after custom made impressions using silicone impression materials and can be retained fairly well if the eyelids and ocular muscles are intact [Figure 3 – 5]. If required

Figure 2 Different retention options for attachment of craniofacial prostheses Craniofacial implants require adequate osseous thickness of the bone on the temporal and mastoid regions, for example in the rehabilitation of a case of congenital microtia. Thus, implant placement may not be as ideal in normal **Figure 2.** Different retention options for attachment of craniofacial prostheses

removal of the eye, adnexa, and part of the bony orbit.

**Orbital prosthesis**

of intraocular tumors [39].

extent, on the location or type of defect, sex, and age of the patient [36 – 38].

Craniofacial implants require adequate osseous thickness of the bone on the temporal and mastoid regions, for example in the rehabilitation of a case of congenital microtia. Thus, implant placement may not be as ideal in normal situations or with acquired defects from accidents. Other designs may also be provided if the distance between the two implants is too close or too far apart. Other crucial factors in rehabilitating this type of defect are marginal fit, good retention, and acceptable esthetics. Various studies have shown that retention using craniofacial implants has improved the satisfaction of patients with craniofacial prostheses. However, the actual level of satisfaction depends, to a large extent, on the location or type of defect, sex, and age of the patient [36 – 38].

### **3. Orbital prosthesis**

In order to address the area of rehabilitation of the orbit it is vital to understand the different types of surgical techniques used in ophthalmic surgeries. Evisceration, enucleation, and exenteration are the three main surgical techniques by which all or parts of the orbital contents are removed [39]. Evisceration is the removal of the contents of the globe while leaving the sclera and extra-ocular muscles intact. Enucleation is the removal of the eye from the orbit while preserving all other orbital structures. Exenteration is the most radical of the three procedures and involves removal of the eye, adnexa, and part of the bony orbit.

Evisceration is usually indicated in cases of endophthalmitis unresponsive to antibiotics and for improvement of esthetics in an eye that is damaged and has lost its vision. Enucleation is indicated for the above two conditions as well as for painful eyes with no useful vision, malignant intraocular tumors, in ocular trauma to avoid sympathetic ophthalmia in the second eye, in phthisis with degeneration, and in congenital anophthalmia or severe microphthalmia to enhance development of the bony orbit. Exenteration is indicated mainly for large orbital tumors or orbital extension of intraocular tumors [39].

The first two namely evisceration and enucleation can be easily rehabilitated with excellent cosmetic results using custom made ocular prostheses [1, 3]. These are fabricated after custom made impressions using silicone impression materials and can be retained fairly well if the eyelids and ocular muscles are intact [Figure 3 – 5]. If required then additional soft tissue components may be fabricated using silicone elastomers which can be shaded and colour matched to the skin of the subject. They may be retained with suitable eye-frames or by use of local undercuts and adhesives [1, 3].

Exenteration surgical procedures are far more extensive and need expert and multi-specialty approach for rehabilitation. Post operatively when the patient reports for rehabilitation it may be necessary to advise the patient to undergo an additional surgical procedure to deepen the existing socket or for thinning of the skin flaps used for the initial wound closure. This will ensure better cosmetic outcome as there will be adequate space to accommodate the retentive framework, ocular component as well as the bulk of silicone elastomer. These large prostheses do not function well with adhesives or eye glasses alone [Figure 6 – 8]. Application of implants in these large orbital defects reduces the need for adhesives and enables easy insertion and

**Figure 3.** Ocular Defect Left eye

Craniofacial implants require adequate osseous thickness of the bone on the temporal and mastoid regions, for example in the rehabilitation of a case of congenital microtia. Thus, implant placement may not be as ideal in normal situations or with acquired defects from accidents. Other designs may also be provided if the distance between the two implants is too close or too far apart. Other crucial factors in rehabilitating this type of defect are marginal fit, good retention, and acceptable esthetics. Various studies have shown that retention using craniofacial implants has improved the satisfaction of patients with craniofacial prostheses. However, the actual level of satisfaction depends, to a large extent, on the location or type of

In order to address the area of rehabilitation of the orbit it is vital to understand the different types of surgical techniques used in ophthalmic surgeries. Evisceration, enucleation, and exenteration are the three main surgical techniques by which all or parts of the orbital contents are removed [39]. Evisceration is the removal of the contents of the globe while leaving the sclera and extra-ocular muscles intact. Enucleation is the removal of the eye from the orbit while preserving all other orbital structures. Exenteration is the most radical of the three

Evisceration is usually indicated in cases of endophthalmitis unresponsive to antibiotics and for improvement of esthetics in an eye that is damaged and has lost its vision. Enucleation is indicated for the above two conditions as well as for painful eyes with no useful vision, malignant intraocular tumors, in ocular trauma to avoid sympathetic ophthalmia in the second eye, in phthisis with degeneration, and in congenital anophthalmia or severe microphthalmia to enhance development of the bony orbit. Exenteration is indicated mainly for large orbital

The first two namely evisceration and enucleation can be easily rehabilitated with excellent cosmetic results using custom made ocular prostheses [1, 3]. These are fabricated after custom made impressions using silicone impression materials and can be retained fairly well if the eyelids and ocular muscles are intact [Figure 3 – 5]. If required then additional soft tissue components may be fabricated using silicone elastomers which can be shaded and colour matched to the skin of the subject. They may be retained with suitable eye-frames or by use of

Exenteration surgical procedures are far more extensive and need expert and multi-specialty approach for rehabilitation. Post operatively when the patient reports for rehabilitation it may be necessary to advise the patient to undergo an additional surgical procedure to deepen the existing socket or for thinning of the skin flaps used for the initial wound closure. This will ensure better cosmetic outcome as there will be adequate space to accommodate the retentive framework, ocular component as well as the bulk of silicone elastomer. These large prostheses do not function well with adhesives or eye glasses alone [Figure 6 – 8]. Application of implants in these large orbital defects reduces the need for adhesives and enables easy insertion and

procedures and involves removal of the eye, adnexa, and part of the bony orbit.

defect, sex, and age of the patient [36 – 38].

tumors or orbital extension of intraocular tumors [39].

local undercuts and adhesives [1, 3].

**3. Orbital prosthesis**

184 Current Concepts in Dental Implantology

**Figure 4.** Custom-made ocular prosthesis

**Figure 5.** Customised orbital prosthesis *in situ*

removal of the prosthesis. Patients can easily remove the prosthesis when not in use and also replace it quickly and effortlessly [39 – 41].

The ideal locations where craniofacial implants may be placed are the supero-lateral rim and the infero-lateral rim. The implants are placed in such a manner that they project into the defect space. The advantage of this is that the boundaries of the prosthesis can conceal the retentive mechanism effectively. It is advisable to place at least three implants both in the upper and the lower orbital rims. This ensures adequate retention even if one or more implants fail. In case the patient has received irradiation as part of the onco-therapeutic process they need to be advised hyperbaric oxygen therapy as described earlier [25 – 27]. The bony architecture in this region is mostly cortical and therefore shorter implants may be are used. It is advisable to wait for 6-8 months for complete osseointegration before the implants are uncovered. The eye prostheses gain maximum retention by use of Neodymium magnets housed in a carrier superstructure within the orbit. Due to the natural shape of the orbit being oval, the abutments, once placed on the implants, will converge toward the center of the orbit. It is therefore important to allow for adequate space of at least 1cm apart between the implants during the surgical phase so that the abutments do not contact thereby interfering with the superstructure.

**Figure 6.** Post-exenteration orbital defect

**Figure 7.** Custom-made orbital prosthesis

**Figure 8.** Orbital prosthesis retained with spectacles

After the abutments are attached the fabrication of the prosthesis may be carried out by the maxillofacial prosthodontic team. The margins of the prosthesis may be thinned to ensure better esthetic outcome. Simple frames may also be used so that the borders are concealed [Figure 8]. Patients need to be kept on regular follow-up protocol for any changes in the implants, skin or colour changes in the prosthesis itself [39, 41].

#### **4. Nasal prosthesis**

The ideal locations where craniofacial implants may be placed are the supero-lateral rim and the infero-lateral rim. The implants are placed in such a manner that they project into the defect space. The advantage of this is that the boundaries of the prosthesis can conceal the retentive mechanism effectively. It is advisable to place at least three implants both in the upper and the lower orbital rims. This ensures adequate retention even if one or more implants fail. In case the patient has received irradiation as part of the onco-therapeutic process they need to be advised hyperbaric oxygen therapy as described earlier [25 – 27]. The bony architecture in this region is mostly cortical and therefore shorter implants may be are used. It is advisable to wait for 6-8 months for complete osseointegration before the implants are uncovered. The eye prostheses gain maximum retention by use of Neodymium magnets housed in a carrier superstructure within the orbit. Due to the natural shape of the orbit being oval, the abutments, once placed on the implants, will converge toward the center of the orbit. It is therefore important to allow for adequate space of at least 1cm apart between the implants during the surgical phase so that the abutments do not contact thereby interfering with the superstructure.

**Figure 6.** Post-exenteration orbital defect

186 Current Concepts in Dental Implantology

**Figure 7.** Custom-made orbital prosthesis

The nose and its adjacent structures play a vital role in facial esthetics. Unlike other facial structures it cannot be easily hidden or camouflaged and hence any person with a congenital or acquired defect looks for early rehabilitation. Small defects are best reconstructed by the plastic surgeon but when both bone and soft tissue have been lost as a result of malignancy related surgeries or due to severe mid-face trauma, then other alternatives are required [1, 42]. Retention using less invasive methods such as the use of tissue or bony undercuts or mechanical with spectacles has been tried with limited success. Even though it may be a challenge, the use of osseointegrated fixtures will ensure excellent retention and esthetic outcome. Ideally three implants need to be placed for adequate retention. It is recommended that a triangular placement around the residual nasal aperture be used. Two implants should be placed at the area of alar base in a vertical line drawn downward from the medial canthus of each eye. One additional implant is placed at the nasal bridge in the midline inferior to the frontal sinus to complete an isosceles triangle [Figure 9]. The implants at the alar base should project out at 90° to surface. The implant at the midline of the nasal bridge should project downward 30° or at the same angle as the nasal bones project from frontal bone [43].

Figure 9. Nasal defect with bar attachment on three implants **Figure 9.** Nasal defect with bar attachment on three implants

#### these prostheses has been their retention. Traditionally tissue undercuts, mechanical retention with springs, clips, **Figure 10.** Nasal prosthesis in situ

strong and can be dislodged by daily activities of life [47 – 50]. Figure 12 Bilateral auricular defect following severe burns distribution over all the three fixtures. In certain cases where there is complete or partial loss of the maxilla and associated midfacial structures, the nasal component may be magnetically connected to the intraoral obturator [Figure 11] thus providing mutual retention to each other [44 – 46]. The use of spectacles once again distracts the observer's vision from the borders between the skin and the prosthesis and ensures better esthetic outcome [1, 3]. The prosthetic superstructure is fabricated in silicone and retained with the help of clips or magnets [Figure 10] within the prosthesis that engage a metal bar connecting the implants [1, 3]. The connector framework ensures even force distribution over all the three fixtures. In certain cases where there is complete or partial loss of the maxilla and associated midfacial

strong and can be dislodged by daily activities of life [47 – 50].

**Auricular defects**

challenging and technically demanding. In contrast an esthetically pleasing and excellent shade matched auricular prosthesis may be fabricated from acrylic polymers or from silicone elastomers [Figure 12 – 15]. The main problem with

Figure 10 Nasal prosthesis in situ

The prosthetic superstructure is fabricated in silicone and retained with the help of clips or magnets [Figure 10]

hairpieces and adhesives have been used to hold them in place [3]. These have serious limitations as retention is not very

within the prosthesis that engage a metal bar connecting the implants [1, 3]. The connector framework ensures even force

Figure 13 Wax patterns of ear prosthesis

Figure 11 Nasal and maxillary obturator prosthesis connected with magnets

Figure 14 Finished and polished silicone ear prostheses

road traffic accidents, burns, acid attacks, or animal or human bites. Surgically they may be removed due to local malignancies. Plastic surgeons may attempt an autogenous reconstruction of the external ear but it is extremely challenging and technically demanding. In contrast an esthetically pleasing and excellent shade matched auricular prosthesis may be fabricated from acrylic polymers or from silicone elastomers [Figure 12 – 15]. The main problem with these prostheses has been their retention. Traditionally tissue undercuts, mechanical retention with springs, clips, hairpieces and adhesives have been used to hold them in place [3]. These have serious limitations as retention is not very

Figure 15 Bilateral auricular prosthesis (mechanically retained)

cases two or three implants placed external to the external auditory meatus in the temporo‐mastoid region are sufficient

Figure 12 Bilateral auricular defect following severe burns

Figure 13 Wax patterns of ear prosthesis

Figure 14 Finished and polished silicone ear prostheses

Figure 15 Bilateral auricular prosthesis (mechanically retained)

cases two or three implants placed external to the external auditory meatus in the temporo‐mastoid region are sufficient [Figure 16]. Implants placed to retain a prosthetic ear are limited in length by the thickness of the mastoid and temporal bones as well as the mastoid air cells. Positioning of implants in the temporal bone is critical to the overall esthetic result and so the use of a surgical guide is mandatory. In cases of microtia or where there are a malformed tissue tags it may be

beneficial to have them surgically removed prior to the start of the rehabilitation process [48, 51].

Once again osseointegrated implants have proven to be a boon and are presently the method of choice. In these

Once again osseointegrated implants have proven to be a boon and are presently the method of choice. In these

The auricle may be congenitally malformed as in microtia or may be disfigured as a result of trauma following

structures, the nasal component may be magnetically connected to the intraoral obturator [Figure 11] thus providing mutual retention to each other [44 – 46]. The use of spectacles once again distracts the observer's vision from the borders between the skin and the prosthesis and ensures better esthetic outcome [1, 3].

**Figure 11.** Nasal and maxillary obturator prosthesis connected with magnets

#### within the prosthesis that engage a metal bar connecting the implants [1, 3]. The connector framework ensures even force distribution over all the three fixtures. In certain cases where there is complete or partial loss of the maxilla and **5. Auricular defects**

frontal sinus to complete an isosceles triangle [Figure 9]. The implants at the alar base should project out at 90° to surface. The implant at the midline of the nasal bridge should project

Figure 9. Nasal defect with bar attachment on three implants

strong and can be dislodged by daily activities of life [47 – 50].

The prosthetic superstructure is fabricated in silicone and retained with the help of clips or magnets [Figure 10] within the prosthesis that engage a metal bar connecting the implants [1, 3]. The connector framework ensures even force distribution over all the three fixtures. In certain cases where there is complete or partial loss of the maxilla and associated midfacial

strong and can be dislodged by daily activities of life [47 – 50].

**Auricular defects**

**Auricular defects**

**Figure 9.** Nasal defect with bar attachment on three implants

188 Current Concepts in Dental Implantology

**Figure 10.** Nasal prosthesis in situ

Figure 10 Nasal prosthesis in situ The prosthetic superstructure is fabricated in silicone and retained with the help of clips or magnets [Figure 10]

associated midfacial structures, the nasal component may be magnetically connected to the intraoral obturator [Figure

Figure 11 Nasal and maxillary obturator prosthesis connected with magnets

Figure 10 Nasal prosthesis in situ

Figure 12 Bilateral auricular defect following severe burns

vision from the borders between the skin and the prosthesis and ensures better esthetic outcome [1, 3].

Figure 13 Wax patterns of ear prosthesis

Figure 11 Nasal and maxillary obturator prosthesis connected with magnets

Figure 14 Finished and polished silicone ear prostheses

road traffic accidents, burns, acid attacks, or animal or human bites. Surgically they may be removed due to local malignancies. Plastic surgeons may attempt an autogenous reconstruction of the external ear but it is extremely challenging and technically demanding. In contrast an esthetically pleasing and excellent shade matched auricular prosthesis may be fabricated from acrylic polymers or from silicone elastomers [Figure 12 – 15]. The main problem with these prostheses has been their retention. Traditionally tissue undercuts, mechanical retention with springs, clips, hairpieces and adhesives have been used to hold them in place [3]. These have serious limitations as retention is not very

Figure 15 Bilateral auricular prosthesis (mechanically retained)

cases two or three implants placed external to the external auditory meatus in the temporo‐mastoid region are sufficient

Figure 12 Bilateral auricular defect following severe burns

Figure 13 Wax patterns of ear prosthesis

Figure 14 Finished and polished silicone ear prostheses

Figure 15 Bilateral auricular prosthesis (mechanically retained)

cases two or three implants placed external to the external auditory meatus in the temporo‐mastoid region are sufficient [Figure 16]. Implants placed to retain a prosthetic ear are limited in length by the thickness of the mastoid and temporal bones as well as the mastoid air cells. Positioning of implants in the temporal bone is critical to the overall esthetic result and so the use of a surgical guide is mandatory. In cases of microtia or where there are a malformed tissue tags it may be

beneficial to have them surgically removed prior to the start of the rehabilitation process [48, 51].

Once again osseointegrated implants have proven to be a boon and are presently the method of choice. In these

Once again osseointegrated implants have proven to be a boon and are presently the method of choice. In these

The auricle may be congenitally malformed as in microtia or may be disfigured as a result of trauma following

vision from the borders between the skin and the prosthesis and ensures better esthetic outcome [1, 3].

downward 30° or at the same angle as the nasal bones project from frontal bone [43].

11] thus providing mutual retention to each other [44 – 46]. The use of spectacles once again distracts the observer's The auricle may be congenitally malformed as in microtia or may be disfigured as a result of trauma following road traffic accidents, burns, acid attacks, or animal or human bites. Surgically they may be removed due to local malignancies. Plastic surgeons may attempt an autogenous reconstruction of the external ear but it is extremely challenging and technically demanding. In contrast an esthetically pleasing and excellent shade matched auricular prosthesis may be fabricated from acrylic polymers or from silicone elastomers [Figure 12 – 15]. The main problem with The auricle may be congenitally malformed as in microtia or may be disfigured as a result of trauma following road traffic accidents, burns, acid attacks, or animal or human bites. Surgically they may be removed due to local malignancies. Plastic surgeons may attempt an autogenous reconstruction of the external ear but it is extremely challenging and technically demanding. In contrast an esthetically pleasing and excellent shade matched auricular prosthesis may be fabricated from acrylic polymers or from silicone elastomers [Figure 12 – 15]. The main problem with these prostheses has been their retention. Traditionally tissue undercuts, mechanical retention with springs, clips, hairpieces and adhesives have been used to hold them in place [3]. These have serious limitations as retention is not very strong and can be dislodged by daily activities of life [47 – 50].

these prostheses has been their retention. Traditionally tissue undercuts, mechanical retention with springs, clips, hairpieces and adhesives have been used to hold them in place [3]. These have serious limitations as retention is not very The prosthetic superstructure is fabricated in silicone and retained with the help of clips or magnets [Figure 10] within the prosthesis that engage a metal bar connecting the implants [1, 3]. The connector framework ensures even force distribution over all the three fixtures. In certain cases where there is complete or partial loss of the maxilla and associated midfacial structures, the nasal component may be magnetically connected to the intraoral obturator [Figure 11] thus providing mutual retention to each other [44 – 46]. The use of spectacles once again distracts the observer's Once again osseointegrated implants have proven to be a boon and are presently the method of choice. In these cases two or three implants placed external to the external auditory meatus in the temporo-mastoid region are sufficient [Figure 16]. Implants placed to retain a prosthetic ear are limited in length by the thickness of the mastoid and temporal bones as well as the mastoid air cells. Positioning of implants in the temporal bone is critical to the overall esthetic result and so the use of a surgical guide is mandatory. In cases of microtia or where there are

**Figure 12.** Bilateral auricular defect following severe burns

a malformed tissue tags it may be beneficial to have them surgically removed prior to the start of the rehabilitation process [48, 51]. Figure 13 Wax patterns of ear prosthesis

Figure 12 Bilateral auricular defect following severe burns

Figure 14 Finished and polished silicone ear prostheses

The maxillofacial prosthodontist should fabricate a diagnostic wax-up of the proposed prosthesis replicating the anatomic features of contra-lateral ear and properly positioned to provide facial symmetry [51]. Using the wax pattern a surgical guide is then replicated with acrylic resin or vinyl acetate. The guide should indicate the most optimal location for implant placement. The implants are usually related to the anti helix of the external ear. In this position maintenance is a must and should be ensured at follow‐up [51 – 54].

prostheses. The advantage of having long hair to hide the margins is and added advantage. Cleanliness and proper

Figure 14 Finished and polished silicone ear prostheses **Figure 14.** Finished and polished silicone ear prostheses

Figure 14. Finished and polished silicone ear prostheses

Figure 13. Wax patterns of ear prosthesis

a malformed tissue tags it may be beneficial to have them surgically removed prior to the start

beneficial to have them surgically removed prior to the start of the rehabilitation process [48, 51].

Figure 12 Bilateral auricular defect following severe burns

Figure 13 Wax patterns of ear prosthesis

Figure 14 Finished and polished silicone ear prostheses

Figure 15 Bilateral auricular prosthesis (mechanically retained) Once again osseointegrated implants have proven to be a boon and are presently the method of choice. In these cases two or three implants placed external to the external auditory meatus in the temporo‐mastoid region are sufficient [Figure 16]. Implants placed to retain a prosthetic ear are limited in length by the thickness of the mastoid and temporal bones as well as the mastoid air cells. Positioning of implants in the temporal bone is critical to the overall esthetic result and so the use of a surgical guide is mandatory. In cases of microtia or where there are a malformed tissue tags it may be

Figure 16 Craniofacial implants placed for ear prosthesis

Figure 17 Bar retainer connected to the abutments

Figure 18 Implant retained ear prosthesis in situ The maxillofacial prosthodontist should fabricate a diagnostic wax‐up of the proposed prosthesis replicating the anatomic features of contra‐lateral ear and properly positioned to provide facial symmetry [51]. Using the wax pattern a surgical guide is then replicated with acrylic resin or vinyl acetate. The guide should indicate the most optimal location for implant placement. The implants are usually related to the anti helix of the external ear. In this position the exposed implants and the retention system have the best opportunity to be hidden from view. Two retention systems using either metal bars of 2 mm diameter soldered to metallic cylinders or retention clips may be used separately or in combination [Figure 17, 18]. The fabrication steps of the silicone prosthesis follow the routine steps as for other external prostheses. The advantage of having long hair to hide the margins is and added advantage. Cleanliness and proper

The maxillofacial prosthodontist should fabricate a diagnostic wax-up of the proposed prosthesis replicating the anatomic features of contra-lateral ear and properly positioned to provide facial symmetry [51]. Using the wax pattern a surgical guide is then replicated with acrylic resin or vinyl acetate. The guide should indicate the most optimal location for implant placement. The implants are usually related to the anti helix of the external ear. In this position

maintenance is a must and should be ensured at follow‐up [51 – 54].

of the rehabilitation process [48, 51].

190 Current Concepts in Dental Implantology

**Figure 12.** Bilateral auricular defect following severe burns

**Figure 13.** Wax patterns of ear prosthesis

Figure 15 Bilateral auricular prosthesis (mechanically retained) Once again osseointegrated implants have proven to be a boon and are presently the method of choice. In these **Figure 15.** Bilateral auricular prosthesis (mechanically retained)

the exposed implants and the retention system have the best opportunity to be hidden from view. Two retention systems using either metal bars of 2 mm diameter soldered to metallic cylinders or retention clips may be used separately or in combination [Figure 17, 18]. The fabrication steps of the silicone prosthesis follow the routine steps as for other external prostheses. The advantage of having long hair to hide the margins is an added advantage. Cleanliness and proper maintenance is a must and should be ensured at follow-up [51 – 54]. [Figure 16]. Implants placed to retain a prosthetic ear are limited in length by the thickness of the mastoid and temporal bones as well as the mastoid air cells. Positioning of implants in the temporal bone is critical to the overall esthetic result and so the use of a surgical guide is mandatory. In cases of microtia or where there are a malformed tissue tags it may be beneficial to have them surgically removed prior to the start of the rehabilitation process [48, 51].

cases two or three implants placed external to the external auditory meatus in the temporo‐mastoid region are sufficient

**Figure 16.** Craniofacial implants placed for ear prosthesis

**Figure 17.** Bar retainer connected to the abutments

**Figure 18.** Implant retained ear prosthesis in situ

#### **6. Management of the dentate maxillectomy patient**

The dental health status of the patient is the first consideration when planning for prosthetic implantation. Preservation of all possible teeth and vigorous dental hygiene are important in the preoperative period to reduce problems in the postoperative period, when cleaning will be difficult if not impossible. The decision to remove maxillary teeth may come into question if the patient may receive pre and post-operative radiation. It is felt by most prosthodontists that the potential risk of osteoradionecrosis resulting from dental treatment in the maxilla is minimal. Each tooth that can be saved has tremendous potential value as an abutment for the obturator prosthesis. Therefore, all teeth should be retained except those that are grossly carious and cannot be restored by any means [55]. In addition to assessment and preservation of teeth, it important to obtain maxillary and mandibular casts in the pre-operative period. Two maxillary casts should be obtained; one to be used as a permanent record, and the other for reproduction of the anticipated surgical defect to be used as a guide for fabrication of the prosthesis. One copy of the pre-operative cast should be kept at all times and further dupli‐ cation done if so required.

Various designs of intra-oral prostheses are possible keeping in mind the principles as applicable for removable cast framework partial dentures. Where required other forms of additional retention are possible using the myriad commercially available intra-coronal or extra-coronal precision attachments. These should suffice to provide a prosthesis that is functionally stable and acceptable to the patient [55 – 58].

#### **6.1. Obturators**

**Figure 16.** Craniofacial implants placed for ear prosthesis

192 Current Concepts in Dental Implantology

**Figure 17.** Bar retainer connected to the abutments

**Figure 18.** Implant retained ear prosthesis in situ

Various types and designs of obturators may be planned. Based on the time of placement they can be classified as: surgical, interim and definitive. Surgical obturators are those that are placed immediately after surgery. Although there has been some disagreement about the value of surgical obturators, they do offer distinct advantages for the surgeon and the patient.

Design of the surgical obturator is a challenge, and involves communication between the surgeon and the prosthodontist. The preoperative plan should be discussed, and actual anticipated defects should be clearly marked on the preoperative cast. Areas that will definitively be resected should be outlined, as well as areas that may be involved. The type of retention method that the surgeon prefers should be communicated prior to surgery [56, 59]. Retention holes in the acrylic plate should be created on the defect side so that the edges can be sutured immediately after surgery to the cheek to support the surgical pack *in situ* [Figure 19, 20].

Interim obturators are those prostheses which are placed immediately after removal of the surgical packing and should be used until tissue contracture is minimal [Figure 21 – 24]. Time between removal of the pack and obturator placement should be minimal, as tissue contraction and edema will quickly alter the shape of the defect, making it difficult to insert an obturator. For this reason, it is important to have a post-surgical obturator made prior to removal of packing. It is also important that the prosthodontist be present with the surgeon when packing is removed so the prosthesis can be inserted immediately after inspection of the surgical site by the surgeon [59].

The definitive obturator is designed when the surgical defect has stabilized, approximately 3 to 12 months after definitive surgery [Figure 25]. The bulb portion that extends into the defect area must be kept hollow in order to lessen the weight of the prosthesis [Figure 26]. The design of the prosthesis should allow maximal distribution of forces to all available teeth, remaining hard palate, walls of the defect, and areas of remaining alveolus. In addition, occlusion must be restored to the best extent possible so that the prosthesis can be functional and not just cosmetic. Regular follow-up is mandatory and modifications should be carried out as required. The prosthodontist must be careful to note signs that the obturator is no longer functioning, such as fluid reflux into the nasal cavity, change in voice quality or TMJ problems [56, 59].

**Figure 19.** Surgical obturator with retentive holes on surgical side (left)

**Figure 20.** Surgical obturator fixed in situ immediately following surgery

**Figure 21.** Healed maxillary defect (mirror image)

is removed so the prosthesis can be inserted immediately after inspection of the surgical site

The definitive obturator is designed when the surgical defect has stabilized, approximately 3 to 12 months after definitive surgery [Figure 25]. The bulb portion that extends into the defect area must be kept hollow in order to lessen the weight of the prosthesis [Figure 26]. The design of the prosthesis should allow maximal distribution of forces to all available teeth, remaining hard palate, walls of the defect, and areas of remaining alveolus. In addition, occlusion must be restored to the best extent possible so that the prosthesis can be functional and not just cosmetic. Regular follow-up is mandatory and modifications should be carried out as required. The prosthodontist must be careful to note signs that the obturator is no longer functioning, such as fluid reflux into the nasal cavity, change in voice quality or TMJ problems [56, 59].

by the surgeon [59].

194 Current Concepts in Dental Implantology

**Figure 19.** Surgical obturator with retentive holes on surgical side (left)

**Figure 20.** Surgical obturator fixed in situ immediately following surgery

**Figure 22.** Impression made in irreversible hydrocolloid

**Figure 23.** Try-in of maxillary obturator prosthesis

**Figure 24.** Interim obturator prosthesis in situ

Figure 25 Definitive obturator prosthesis in situ **Figure 25.** Definitive obturator prosthesis in situ

resist the wear and tear applied by the obturator as compared to the friable oral tissues.

*Skin graft the cheek flap* The edentulous patient requires maximal distribution of forces, and the mucosa on the cheek will be an area of contact with the obturator. The thick squamous epithelium of a split‐thickness skin graft will

*Remove the inferior turbinate*. By removing the inferior turbinate, the prosthesis can be contoured to fit into the nasal cavity. This vertical height will resist the rotational forces applied during mastication. In addition, by adding an extension into the nasal cavity, a larger surface of bone may be utilized to balance the stresses generated during

*Skin graft the maxillary sinus walls* This is necessary as the movements of the obturator bulb will transmit greater force to the sinus walls in the edentulous patient. These walls can be prepared during surgery to allow the bony undercuts to serve for retention or for vertical support to keep the prosthesis from rotating into the defect during mastication. The sinus walls are covered with respiratory mucosa, which must be denuded and covered with a split‐ thickness skin graft. Grafting the sinus walls stops formation of polypoid tissue and mucus generation within the sinus

Figure 28 Skin graft on lateral wall of maxillary post‐surgical defect With the increased use of osseointegrated implants, dependence on mechanical and anatomic methods of retention has diminished. Osseointegrated implants provide excellent retention to the definitive obturator. Retentive magnets and various designs of clips are available to minimize force transfer to the implant and supporting bone [3, 63,

Figure 27 Maximum retention of hard palate (mirror image) **Figure 26.** Definitive obturator prosthesis showing hollow bulb

and allows the walls to become load‐bearing areas [Figure 28].

mastication.

64].

#### **6.2. Management of the edentulous maxillectomy patient**

Edentulous maxillectomy patients are always a challenge for the maxillofacial team due to the complexity of postoperative rehabilitation. Retention of the obturator is a problem since there is a lack of support of adjacent teeth for stabilization. In addition, the reduced volume of residual ridge of the edentulous patient demands that stress be distributed to all available portions of the palate.

Some of the important guidelines to be informed to the maxillofacial surgeon or oncosurgeon at the time of resection are as follows:-[59-62].

*Maintain as much hard palate as possible*. Since the edentulous patient must rely on remnants of the hard palate for primary retention, support and stability, the prosthodontist should advise the surgeon to resect only that portion of the hard palate that is mandatory to allow for clean margins [Figure 27]. It is vital to ensure that the ipsilateral palate is preserved which will allow a tripoding effect. If the anterior alveolus can be maintained, the patient will have better facial esthetics and less contracture postoperatively.

**Figure 27.** Maximum retention of hard palate (mirror image)

**Figure 24.** Interim obturator prosthesis in situ

196 Current Concepts in Dental Implantology

**Figure 25.** Definitive obturator prosthesis in situ

**Management of the Edentulous Maxillectomy patient**

distributed to all available portions of the palate.

facial esthetics and less contracture postoperatively.

**Figure 26.** Definitive obturator prosthesis showing hollow bulb

and allows the walls to become load‐bearing areas [Figure 28].

as follows: ‐ [59 ‐ 62].

mastication.

64].

Figure 25 Definitive obturator prosthesis in situ

Figure 26 Definitive obturator prosthesis showing hollow bulb

Edentulous maxillectomy patients are always a challenge for the maxillofacial team due to the complexity of postoperative rehabilitation. Retention of the obturator is a problem since there is a lack of support of adjacent teeth for stabilization. In addition, the reduced volume of residual ridge of the edentulous patient demands that stress be

Some of the important guidelines to be informed to the maxillofacial or oncosurgeon at the time of resection are

*Maintain as much hard palate as possible*. Since the edentulous patient must rely on remnants of the hard palate for primary retention, support, and stability, the prosthodontist should advise the surgeon to resect only that portion of the hard palate that is mandatory to allow for clean margins [Figure 27]. It is vital to ensure that the ipsilateral palate is preserved which will allow a tripoding effect. If the anterior alveolus can be maintained, the patient will have better

*Remove the inferior turbinate*. By removing the inferior turbinate, the prosthesis can be contoured to fit into the nasal cavity. This vertical height will resist the rotational forces applied during mastication. In addition, by adding an extension into the nasal cavity, a larger surface of bone may be utilized to balance the stresses generated during

*Skin graft the maxillary sinus walls* This is necessary as the movements of the obturator bulb will transmit greater force to the sinus walls in the edentulous patient. These walls can be prepared during surgery to allow the bony undercuts to serve for retention or for vertical support to keep the prosthesis from rotating into the defect during mastication. The sinus walls are covered with respiratory mucosa, which must be denuded and covered with a split‐ thickness skin graft. Grafting the sinus walls stops formation of polypoid tissue and mucus generation within the sinus

Figure 28 Skin graft on lateral wall of maxillary post‐surgical defect With the increased use of osseointegrated implants, dependence on mechanical and anatomic methods of retention has diminished. Osseointegrated implants provide excellent retention to the definitive obturator. Retentive magnets and various designs of clips are available to minimize force transfer to the implant and supporting bone [3, 63,

Figure 27 Maximum retention of hard palate (mirror image) *Skin graft the cheek flap* The edentulous patient requires maximal distribution of forces, and the mucosa on the cheek will be an area of contact with the obturator. The thick squamous epithelium of a split‐thickness skin graft will

resist the wear and tear applied by the obturator as compared to the friable oral tissues.

*Skin graft the cheek flap* The edentulous patient requires maximal distribution of forces, and the mucosa on the cheek will be an area of contact with the obturator. The thick squamous epithelium of a split-thickness skin graft will resist the wear and tear applied by the obturator as compared to the friable oral tissues.

*Remove the inferior turbinate*. By removing the inferior turbinate, the prosthesis can be contoured to fit into the nasal cavity. This vertical height will resist the rotational forces applied during mastication. In addition, by adding an extension into the nasal cavity, a larger surface of bone may be utilized to balance the stresses generated during mastication.

*Skin graft the maxillary sinus walls* This is necessary as the movements of the obturator bulb will transmit greater force to the sinus walls in the edentulous patient. These walls can be prepared during surgery to allow the bony undercuts to serve for retention or for vertical support to

**Figure 28.** Skin graft on lateral wall of maxillary post-surgical defect

keep the prosthesis from rotating into the defect during mastication. The sinus walls are covered with respiratory mucosa, which must be denuded and covered with a split-thickness skin graft. Grafting the sinus walls stops formation of polypoid tissue and mucus generation within the sinus and allows the walls to become load-bearing areas [Figure 28].

With the increased use of osseointegrated implants, dependence on mechanical and anatomic methods of retention has diminished. Osseointegrated implants provide excellent retention to the definitive obturator. Retentive magnets and various designs of clips are available to minimize force transfer to the implant and supporting bone [3, 63, 64].

For a long time it was considered taboo to place implants in irradiated bone. However numerous studies have shown that use of hyperbaric oxygen chambers can be of immense value in such patients and allow for successful osseointegration as discussed earlier [25 – 27].

#### **6.3. Zygomatic implants**

Remote bone anchorage using zygoma implants for extensive maxillofacial defects is another option. Effective axial loading of the zygoma implant is accomplished by cross-arch stabiliza‐ tion with a rigid splint framework using at least 4 implants with adequate anterior – posterior spread [Figure 29]. When patients present with maxillary defects that do not have ideal residual anatomy, it is may be possible to place zygoma implants in areas that will enhance the desired splinting effect of the bar assembly. The most significant and immediate benefit of this approach is the ability to extend the prosthesis anchorage points into defect areas, thus minimizing the cantilever forces on teeth and implants in residual ridge tissue. Maxillectomy and severely resorbed maxilla are challenging to restore with provision of removable pros‐ theses. Dental implants are essential to restore aesthetics and function and subsequently quality of life in such group of patients. Zygomatic implants reduce the complications associated with bone grafting procedures and simplify the rehabilitation of atrophic maxilla and maxillectomy [65, 66].

**Figure 29.** Diagrammatic representation of zygomatic implants

keep the prosthesis from rotating into the defect during mastication. The sinus walls are covered with respiratory mucosa, which must be denuded and covered with a split-thickness skin graft. Grafting the sinus walls stops formation of polypoid tissue and mucus generation

With the increased use of osseointegrated implants, dependence on mechanical and anatomic methods of retention has diminished. Osseointegrated implants provide excellent retention to the definitive obturator. Retentive magnets and various designs of clips are available to

For a long time it was considered taboo to place implants in irradiated bone. However numerous studies have shown that use of hyperbaric oxygen chambers can be of immense value in such patients and allow for successful osseointegration as discussed earlier [25 – 27].

Remote bone anchorage using zygoma implants for extensive maxillofacial defects is another option. Effective axial loading of the zygoma implant is accomplished by cross-arch stabiliza‐ tion with a rigid splint framework using at least 4 implants with adequate anterior – posterior spread [Figure 29]. When patients present with maxillary defects that do not have ideal residual anatomy, it is may be possible to place zygoma implants in areas that will enhance the desired splinting effect of the bar assembly. The most significant and immediate benefit of this approach is the ability to extend the prosthesis anchorage points into defect areas, thus minimizing the cantilever forces on teeth and implants in residual ridge tissue. Maxillectomy and severely resorbed maxilla are challenging to restore with provision of removable pros‐ theses. Dental implants are essential to restore aesthetics and function and subsequently quality of life in such group of patients. Zygomatic implants reduce the complications associated with bone grafting procedures and simplify the rehabilitation of atrophic maxilla

within the sinus and allows the walls to become load-bearing areas [Figure 28].

minimize force transfer to the implant and supporting bone [3, 63, 64].

**Figure 28.** Skin graft on lateral wall of maxillary post-surgical defect

**6.3. Zygomatic implants**

198 Current Concepts in Dental Implantology

and maxillectomy [65, 66].

Studies using three-dimensional finite element analysis were carried out to study the impact of different levels of zygomatic bone support (10, 15, and 20 mm) on the biomechanics of zygomatic implants. Results indicated maximum stresses within the fixture were increased by three times, when bone support decreased from 20 to 10 mm, and concentrated at fixture/bone interface. However, stresses within the abutment screw and abutment itself were not signifi‐ cantly different regardless of the bone support level. Supporting bone of 10 mm showed double the stress as compared to levels of 15 and 20 mm. The deflection of the fixtures was decreased by two to three times as the level of bone support increased to 15 mm and 20 mm respectively. Therefore, it important that the zygomatic bone support should not be kept at less than 15 mm. This will reduce the amount of deflection of the fixture and ensure long-term success of the implants [67, 68].

Placement of zygomatic implants lateral to the maxillary sinus, according to the extra-sinus protocol, is one of the treatment options in the rehabilitation of severely atrophic maxilla or following maxillectomy surgery in the head and neck cancer patients. Studies on a full-arch fixed-prosthesis supported by four zygomatic implants in the atrophic maxilla under occlusal loading have shown that maximum von Mises stresses were significantly higher under lateral loading compared with vertical loading within the prosthesis and its supporting implants. Peak stresses was found to be concentrated at the interface between the prosthesis and the fixtures when subjected to vertical load and also at the internal line angles of the prosthesis when subjected to lateral load. The zygomatic bone exhibited much lower stress levels as compared to the alveolar bone especially under lateral load. The zygomatic bone overall showed less values of stress than the alveolar bone and the prosthesis-implant complex under both types of loading [67]. Further research and long-term studies needs to be carried out on these types of implants so that the rehabilitation of the atrophied or missing maxilla can be successfully carried out.

#### **7. Microimplants and maxillofacial rehabilitation**

Patients with craniofacial birth defects present with extreme skeletal deformities and often require a multi-pronged approach for achieving acceptable esthetic results. Vachiramon et. al. [69], have described a series of cases in which orthodontic microimplants were used to better the surgical outcome of such patients. Use of these microimplants for support helped in distraction osteogenesis procedures involving the mandible, maxilla, or midface. The micro‐ implants were additionally used to stabilize the dentition for orthodontic tooth movement or for resisting change from long-term use of inter-arch elastics. They concluded that microim‐ plants appear to have good potential in the approach to treat patients with craniofacial anomalies. They can also be useful to present an alternative treatment plan in patients who refuse orthognathic surgery. Microimplants may be of great utility for the rehabilitation of craniofacial patients with congenitally missing permanent teeth; malformed teeth or patients with ectodermal dysplasia with reduced dentition that makes reciprocal orthodontic anchor‐ age difficult [69].

#### **8. Future trends in maxillofacial rehabilitation**

The use of Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) in conjunc‐ tion with Rapid Prototyping (RP) have revolutionized the methods of old-fashioned impres‐ sions using various types of dental materials and sculpting of the prosthesis by hand in wax or clay [Figure 30, 31]. Recently advances in 3D optical imaging using 3D whole field profil‐ ometer based on the projection of incoherent light and 3D laser eye-safe scanners have been utilized [70, 71]. The advantages of such a system are that they are non-invasive, have a higher speed of data acquisition, and the scanners are more rugged and portable than the CT or MRI scanners [70].

Once the data has been acquired the virtual 3D models are obtained and the final prosthesis can be designed virtually. Two models one with the defect and another with the built up prosthesis are generated using epoxy photo-polymerising resins in a 3D printer [Figure 32, 33]. The final prosthesis is then fabricated from silicone rubber using these moulds [70 – 72].

In order to minimize the harmful effects of the metallic implants and their by-products, several newer materials are being tried. New alloys like tantalum, niobium, zirconium, and magne‐ sium are receiving attention given their satisfying mechanical and biological properties. Nonoxide ceramics like silicon nitride and silicon carbide are being currently developed as a promising implant material possessing a combination of properties such as good wear and corrosion resistance, increased ductility, good fracture and creep resistance, and relatively high hardness in comparison to alumina. Polymer/magnesium composites are being developed to improve mechanical properties as well as retain polymer's property of degradation [73].

Nanotechnology and tissue engineering along with the concepts of stem cell technology are poised to dramatically define the next quantum leap in the field of maxillofacial reconstruction.

**Figure 30.** 3D virtual reconstruction and planning

**7. Microimplants and maxillofacial rehabilitation**

**8. Future trends in maxillofacial rehabilitation**

age difficult [69].

200 Current Concepts in Dental Implantology

scanners [70].

Patients with craniofacial birth defects present with extreme skeletal deformities and often require a multi-pronged approach for achieving acceptable esthetic results. Vachiramon et. al. [69], have described a series of cases in which orthodontic microimplants were used to better the surgical outcome of such patients. Use of these microimplants for support helped in distraction osteogenesis procedures involving the mandible, maxilla, or midface. The micro‐ implants were additionally used to stabilize the dentition for orthodontic tooth movement or for resisting change from long-term use of inter-arch elastics. They concluded that microim‐ plants appear to have good potential in the approach to treat patients with craniofacial anomalies. They can also be useful to present an alternative treatment plan in patients who refuse orthognathic surgery. Microimplants may be of great utility for the rehabilitation of craniofacial patients with congenitally missing permanent teeth; malformed teeth or patients with ectodermal dysplasia with reduced dentition that makes reciprocal orthodontic anchor‐

The use of Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) in conjunc‐ tion with Rapid Prototyping (RP) have revolutionized the methods of old-fashioned impres‐ sions using various types of dental materials and sculpting of the prosthesis by hand in wax or clay [Figure 30, 31]. Recently advances in 3D optical imaging using 3D whole field profil‐ ometer based on the projection of incoherent light and 3D laser eye-safe scanners have been utilized [70, 71]. The advantages of such a system are that they are non-invasive, have a higher speed of data acquisition, and the scanners are more rugged and portable than the CT or MRI

Once the data has been acquired the virtual 3D models are obtained and the final prosthesis can be designed virtually. Two models one with the defect and another with the built up prosthesis are generated using epoxy photo-polymerising resins in a 3D printer [Figure 32, 33]. The final prosthesis is then fabricated from silicone rubber using these moulds [70 – 72].

In order to minimize the harmful effects of the metallic implants and their by-products, several newer materials are being tried. New alloys like tantalum, niobium, zirconium, and magne‐ sium are receiving attention given their satisfying mechanical and biological properties. Nonoxide ceramics like silicon nitride and silicon carbide are being currently developed as a promising implant material possessing a combination of properties such as good wear and corrosion resistance, increased ductility, good fracture and creep resistance, and relatively high hardness in comparison to alumina. Polymer/magnesium composites are being developed to improve mechanical properties as well as retain polymer's property of degradation [73].

Nanotechnology and tissue engineering along with the concepts of stem cell technology are poised to dramatically define the next quantum leap in the field of maxillofacial reconstruction.

**Figure 31.** Rapid prototype modelling of maxillofacial prosthesis

Whether it is regeneration of new osseous tissue *in vivo* for placement of implants or even the regeneration of a complete ear or nose literally 'grown' from the stem cells of the person or a suitable donor-the possibilities are endless [74, 75]. It seems to be just a matter of time before the dream of autologous reconstruction of defective or missing anatomical structures soon becomes a reality.

**Figure 32.** 3D printer

**Figure 33.** 3D printed model of mandibular defect

#### **9. Conclusion**

The discovery of osseointegration has been arguably one of the most beneficial medical breakthroughs especially in the head and neck region. The number of successful implants being placed is increasing rapidly as better implants, more efficient investigative techniques and superior armamentarium is readily available. These implants have also revolutionized the scope and the efficacy of rehabilitation of the entire craniofacial region [76].

Despite the rise in cancers of the head and neck region there is also a deeper understanding of the changes at cellular level and better treatment options and targeted medication. It is hoped that with each passing day there will be continued dedicated research to fight and eradicate all these killer diseases. Until then the science of craniofacial implantology will ensure that the patients receive the most comprehensive rehabilitation that can be offered and ensure that their early return to form and function.

In future it is hoped that technological advances in allied fields such as radio-diagnosis and imaging, CAD-CAM manufacturing, tissue engineering, laser scanning, 3D-printing, devel‐ opment of newer nano-based materials and robotic placement of implants will work in tandem to ensure that larger numbers of patients can be treated early, economically and effectively [77-79]. Then alone will the dream of health for all be truly a reality.

#### **Acknowledgements**

I gratefully acknowledge all my respected teachers, enthusiastic students and tolerant patients who have taught me that I know so little and shown me that there is so much more learn.

#### **Author details**

Derek D'Souza\*

Address all correspondence to: dsjdsouza@gmail.com

Consultant Prosthodontist, Pune, India

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**9. Conclusion**

**Figure 33.** 3D printed model of mandibular defect

**Figure 32.** 3D printer

202 Current Concepts in Dental Implantology

The discovery of osseointegration has been arguably one of the most beneficial medical breakthroughs especially in the head and neck region. The number of successful implants being placed is increasing rapidly as better implants, more efficient investigative techniques and superior armamentarium is readily available. These implants have also revolutionized the

Despite the rise in cancers of the head and neck region there is also a deeper understanding of the changes at cellular level and better treatment options and targeted medication. It is hoped that with each passing day there will be continued dedicated research to fight and eradicate all these killer diseases. Until then the science of craniofacial implantology will ensure that the

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### **Miniscrew Applications in Orthodontics**

Fatma Deniz Uzuner and Belma Işık Aslan

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/59879

#### **1. Introduction**

Anchorage control during tooth movement is one of the main factors for ensuring successful orthodontic treatment. Anchorage can be defined as the resistance that a tooth or a group of teeth offer when they are subjected to a force [1]. The aim of orthodontic treatment is to maintain sufficient anchorage control to create appropriate force systems that provide the desired treatment effects.

Recently, implants have been used as skeletal anchorage devices for orthodontic purposes [2-5]. Temporary anchorage devices (TADs) [1,9,10], including miniplates, implants and miniscrews, have been used for skeletal anchorage [6-8]. TADs are inserted into the bone and aim to enhance orthodontic anchorage either by supporting the anchoring teeth or by being an independent anchorage unit eliminating the need for supporting teeth; they are removed once their function has been completed. They can be fixed into the bone either biomechanically (osseointegration) [11] or mechanically (cortical stabilization) [8]. Clinicians can better control anchorage by using TADs in orthodontic treatment, thereby achieving more satisfactory treatment results than could be achieved with conventional mechanics [6,12].

Currently, clinicians mostly prefer to use miniscrews for combined orthodontic treatment [13]. Despite the high success rate of miniplates, their invasive placement procedures require an oral surgeon and the associated high costs of such a procedure overshadow their use in terms of anchorage [1]. The use of osseointegrated mini-implants has also been limited because of the long waiting period for osseointegration, their large size and high cost [14,15]. Miniscrews, however, are available in favorable sizes, have relatively lower costs and are simple to insert and remove; therefore, they can be easily placed by an orthodontist with minimal tissue invasion [13]. Miniscrews obtain their stability mainly from mechanical retention in the bone [1,9], so they can be loaded immediately after placement [16]. In the literature, there is no general agreement about the terminology used [17,18]; this varies between 'miniscrews',

© 2015 The Author(s). Licensee InTech. 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 eproduction in any medium, provided the original work is properly cited.

'microscrews', 'miniscrew implants'. and 'mini-implants' [13,19-21]. In this chapter, we refer to them as miniscrews. Miniscrews are now accepted as a simple and effective tool in daily orthodontic practice and orthodontists commonly use them in a variety of clinical situations [20-25].

This chapter focuses on the principles of application for miniscrews including screw sizes, application sites and fundamental placement methods. Management of complications, the use of miniscrews in specific orthodontic situations and appliance design are also discussed.

### **2. General considerations**

#### **2.1. Location and dimensions of the miniscrew**

The stability of miniscrews immediately following their placement (primary stability) and during orthodontic treatment is important for clinicians in terms of achieving their desired treatment results. The primary factors for stability are the quality and quantity of the bone [26-28], as well as the thickness, type and health of the soft tissue [29].

Cortical bone with a thickness of less than 0.5 mm is not suitable for miniscrew placement. Higher success rates have been reported with cortical bone at least 1.0 mm thick [27].

To maximize stability, it is better to place miniscrews in the attached gingiva (keratinized gingiva), which is more resistant to inflammation and less likely to develop soft-tissue hypertrophy [26, 29]. However, if the miniscrew has to be placed in non-keratinized mucosa, a 3-mm vertical stab incision should be used to prevent the soft tissue from surrounding the miniscrew, as this small incision requires no sutures [1].

Placement site is another important factor in the success of miniscrews [30]. Miniscrews can be placed in the inter-radicular space between tooth roots, either buccally or lingually; in the hard palate (midpalatal/parapalatal region); below the anterior nasal spine; and in the infrazygomatic crest, maxillary tuberosity, edentulous areas, chin and retromolar areas [8,30].

Conflicting reports exist regarding success rates for miniscrews in the mandible and maxilla. Park et al. [31], found that the maxilla had a higher success rate than the mandible, while others [16, 30] reported that placement of the miniscrews in the maxilla or mandible was not associ‐ ated with the success rate. Moon et al. [30] found that the area between the first and second premolars in the maxilla and mandible of both young and adult patients had the highest success rate.

In the maxilla, the buccal and palatal aspects of the posterior region have been defined as safe areas for miniscrew placement, while the maxillary tuberosity is not suitable because of the minimal bone thickness in the area [32]. Ishii et al. [33], and Poggio [32] reported that the safest region for placement is the inter-alveolar septum between the maxillary first molar and second premolar, 6–8 mm apical to the alveolar crest on the palatal side. The inter-radicular distance is greater on the palatal side; however, the thickness of the palatal mucosa renders this region less favorable. This problem could be alleviated by using a miniscrew with a longer head. However, the midpalatal suture region is the most favorable placement site for miniscrews in terms of both bone and soft-tissue characteristics. This region, with its high density of cortical bone and thin keratinized soft tissue ensures the biomechanical stability of the miniscrews [23,34] and has been shown to have a higher success rate (90%) than the parapalatal suture region (84%) [35]. However, the parapalatal area is the most suitable region for miniscrew placement in adolescents for preventing developmental disturbances of the midpalatal suture, as the transverse growth of the midpalatal suture continues up until the late teens [36].

'microscrews', 'miniscrew implants'. and 'mini-implants' [13,19-21]. In this chapter, we refer to them as miniscrews. Miniscrews are now accepted as a simple and effective tool in daily orthodontic practice and orthodontists commonly use them in a variety of clinical situations

This chapter focuses on the principles of application for miniscrews including screw sizes, application sites and fundamental placement methods. Management of complications, the use of miniscrews in specific orthodontic situations and appliance design are also discussed.

The stability of miniscrews immediately following their placement (primary stability) and during orthodontic treatment is important for clinicians in terms of achieving their desired treatment results. The primary factors for stability are the quality and quantity of the bone

Cortical bone with a thickness of less than 0.5 mm is not suitable for miniscrew placement.

To maximize stability, it is better to place miniscrews in the attached gingiva (keratinized gingiva), which is more resistant to inflammation and less likely to develop soft-tissue hypertrophy [26, 29]. However, if the miniscrew has to be placed in non-keratinized mucosa, a 3-mm vertical stab incision should be used to prevent the soft tissue from surrounding the

Placement site is another important factor in the success of miniscrews [30]. Miniscrews can be placed in the inter-radicular space between tooth roots, either buccally or lingually; in the hard palate (midpalatal/parapalatal region); below the anterior nasal spine; and in the infrazygomatic crest, maxillary tuberosity, edentulous areas, chin and retromolar areas [8,30]. Conflicting reports exist regarding success rates for miniscrews in the mandible and maxilla. Park et al. [31], found that the maxilla had a higher success rate than the mandible, while others [16, 30] reported that placement of the miniscrews in the maxilla or mandible was not associ‐ ated with the success rate. Moon et al. [30] found that the area between the first and second premolars in the maxilla and mandible of both young and adult patients had the highest

In the maxilla, the buccal and palatal aspects of the posterior region have been defined as safe areas for miniscrew placement, while the maxillary tuberosity is not suitable because of the minimal bone thickness in the area [32]. Ishii et al. [33], and Poggio [32] reported that the safest region for placement is the inter-alveolar septum between the maxillary first molar and second premolar, 6–8 mm apical to the alveolar crest on the palatal side. The inter-radicular distance is greater on the palatal side; however, the thickness of the palatal mucosa renders this region less favorable. This problem could be alleviated by using a miniscrew with a longer head.

Higher success rates have been reported with cortical bone at least 1.0 mm thick [27].

[26-28], as well as the thickness, type and health of the soft tissue [29].

[20-25].

success rate.

**2. General considerations**

212 Current Concepts in Dental Implantology

**2.1. Location and dimensions of the miniscrew**

miniscrew, as this small incision requires no sutures [1].

In the mandible, the safest region is either between the second premolar and first molar, or between the first and second molars, owing to the adequate bone thickness [22,32]. The thinnest bone was found between the first premolar and the canine. If a miniscrew has to be implanted into this region, it should be placed 11 mm below the alveolar crest [32]. Although the area between the second premolar and the first molar has thicker cortical bone than the area between the first and second premolars in the mandible, the success rate in this area is significantly lower [30]. These results suggest that other factors beyond bone quality, such as soft-tissue thickness [37], oral hygiene [38] and root proximity [39,40] might also affect the success rate of miniscrews.

Miniscrews are available in a variety of materials, shapes, head designs, length and diameter, being 5–12 mm long and having a diameter from 1.2 to 2.3 mm [6,11,20,41-43]. In general, l.2– l.6 mm miniscrews are used. Because of its low success rate, the 1.0-mm diameter miniscrew is not suitable for clinical use [16]. However, the 1.2-, 1.3-and 1.5-mm diameter miniscrews have had similar or higher success rates than the 1.6-mm miniscrew [16,38]. The design of the miniscrew also affects primary stability, with a conical thread design achieving superior primary stability when compared with a cylindrical design [42].

Selection of the correct diameter and length depends on the region in which the miniscrew will be placed. If it is placed in the inter-radicular region, a miniscrew with a smaller diameter will be preferred, as it will decrease the risk of root damage [30]. The recommended diameter is l.3 mm in the maxilla, 1.4 mm in the mandible and l.5 or l.6 mm in the midpalatal area [12].

Determining the length of the miniscrew primarily depends on the quality of the bone, the screw angulation, the soft-tissue thickness and the adjacent anatomic structures [8,38,44]. In regions with adequate cortical density, small miniscrews are preferred, while longer minis‐ crews are preferred if stability is required in trabecular bone.

The screw should be embedded into the bone at least 5–6 mm [45,46], yet deeper placements have been recommended when bone quality is low [47,48]. Minimal depth of placement is at least 6 mm for the maxilla and 4 mm for the mandible [12]. In maxillary buccal alveolar bone, 7–8 mm miniscrews are recommended, while 5–6 mm long miniscrews are suitable in the mandibular buccal bone [12]. Short screws can become dislodged when they are placed in the palatal region owing to the thick palatal soft tissue [44,49]. Long miniscrews (10–12 mm) are preferred in the palatal region to compensate for the thick palatal soft tissue and to keep 6-mm miniscrews embedded in the bone [48,49]. Because the midpalatal region has dense cortical bone, a long miniscrew may not be needed for stability.

#### **2.2. Placement of the miniscrew**

Before placing the miniscrews, clinicians should radiographically assess their position relative to the roots. Panaromic or periapical radiographs, however, may not provide adequate information for optimizing the placement of a miniscrew. Computed tomography (CT) or cone-beam CT can allow clinicians to make an accurate and reliable evaluation of bone thickness and the adjacent anatomic structures, and therefore improves the success rate and ensures safe placement of the screws [33,50,51].

The patient is instructed to rinse with a chlorhexidine solution; then, infiltrative anesthesia is applied. Light local anesthesia is preferred so that the nerve fibers in the periodontal ligament remain sensitive [12], and the patient is aware if the miniscrew touches the root of the tooth, allowing the clinician to change the insertion direction.

There are two different placement methods: self-tapping and self-drilling.

*Self-tapping method*: Before placing the miniscrew, a hole is drilled in the cortical bone and a miniscrew is screwed through this hole with a hand driver. The diameter of the pilot drill should be slightly smaller (0.2–0.3 mm) than the inner (or core) diameter of the miniscrew [46]. Care must be taken to keep the axis of the drill stable so as not to enlarge the hole. To reduce heat generation while drilling, clinicians should not apply too much pressure and should irrigate the bone with coolants [52,53].

*Self-drilling method:* Self-drilling is a simpler method for placing the miniscrew than selftapping. The miniscrew is inserted into the bone without drilling and screwed in with the hand driver [12] or motor driver [54]. Using a motor driver is helpful for gaining a higher placement success rate [54]. Self-drilling screws are reported to have better stability, with more bone to metal contact than self-tapping screws [55,56].

An incision may be made in the soft tissue before drilling [54,57]. Miyawaki et al. [16], reported that the flapless (non-incision) group had a higher success rate than the flap surgery (incision) group. By contrast, Moon et al. [30], found no difference between non-incision and incision groups in their study.

Generally, miniscrews are inserted in the buccal or lingual cortical plates; this is defined as monocortical placement. Occasionally, the miniscrew can be placed across the entire width of the alveolus (bicortical placement). Although bicortical placement provides superior force resistance and stability compared with monocortical placement, more care has to be taken during placement. Bicortical placement may be preferred when increased orthodontic loading is needed or in cases where there is insufficient cortical bone thickness [58-60].

It is usually recommended that miniscrews are placed perpendicular (at an angle of 90°) to the bone surface [45]. However, this might not always be clinically achievable, and an angular approach might be needed. If the buccal alveolar bone volume is sufficient relative to the long axis of the teeth, the miniscrew can be placed at an angle of 30–40° for the upper jaw and 20– 60° for the lower jaw [12]. This angular placement minimizes root contact, as there is relatively more space [50] and the surface area of cortical bone in contact with the miniscrew is increased, allowing placement of longer miniscrews and improved stability [12]. When placing a miniscrew at an angle into dense cortical bone using the self-drilling method, clinicians can damage the cortical bone; in such cases, the self-tapping method would be a better option [12].

Clinicians should apply slow and gentle force during insertion to avoid fracture of the miniscrew. The recommended insertion torque value is 5–10 N cm [61]. Insertion torque values are associated with the success of the procedure. The success rate of the miniscrew also depends on the clinician's experience and the type of the placement: whether self-tapping or self-drilling. If the self-tapping method is used, the following factors also affect the success rate: flap or flapless surgery, sterilization, pilot hole preparation depth and diameter, cooling technique, drill speed and pressure, direction of placement and placement procedure (steady or wiggling) [6,8,16,18,27,30,43,47].

The stability of the miniscrew should be checked after placement. If any mobility is detected, the implant needs to be removed. If primary stability is not achieved upon insertion, the miniscrew implant may loosen during orthodontic treatment [26].

Patients should be informed that they might have pain for 1–2 days and that they can take antiinflammatory agents if required. Most patients do not have noticeable discomfort or inflam‐ mation. Patients need to be instructed in oral hygiene techniques [35] and should be advised that they can brush their teeth as usual. A compressed water spray such as Waterpik [12] and daily use of mouth rinses will be useful. Caution should be taken not to apply excessive force to the miniscrew while brushing and during mastication.

#### **2.3. Timing of loading, force magnitude and direction**

**2.2. Placement of the miniscrew**

214 Current Concepts in Dental Implantology

ensures safe placement of the screws [33,50,51].

irrigate the bone with coolants [52,53].

groups in their study.

metal contact than self-tapping screws [55,56].

allowing the clinician to change the insertion direction.

There are two different placement methods: self-tapping and self-drilling.

Before placing the miniscrews, clinicians should radiographically assess their position relative to the roots. Panaromic or periapical radiographs, however, may not provide adequate information for optimizing the placement of a miniscrew. Computed tomography (CT) or cone-beam CT can allow clinicians to make an accurate and reliable evaluation of bone thickness and the adjacent anatomic structures, and therefore improves the success rate and

The patient is instructed to rinse with a chlorhexidine solution; then, infiltrative anesthesia is applied. Light local anesthesia is preferred so that the nerve fibers in the periodontal ligament remain sensitive [12], and the patient is aware if the miniscrew touches the root of the tooth,

*Self-tapping method*: Before placing the miniscrew, a hole is drilled in the cortical bone and a miniscrew is screwed through this hole with a hand driver. The diameter of the pilot drill should be slightly smaller (0.2–0.3 mm) than the inner (or core) diameter of the miniscrew [46]. Care must be taken to keep the axis of the drill stable so as not to enlarge the hole. To reduce heat generation while drilling, clinicians should not apply too much pressure and should

*Self-drilling method:* Self-drilling is a simpler method for placing the miniscrew than selftapping. The miniscrew is inserted into the bone without drilling and screwed in with the hand driver [12] or motor driver [54]. Using a motor driver is helpful for gaining a higher placement success rate [54]. Self-drilling screws are reported to have better stability, with more bone to

An incision may be made in the soft tissue before drilling [54,57]. Miyawaki et al. [16], reported that the flapless (non-incision) group had a higher success rate than the flap surgery (incision) group. By contrast, Moon et al. [30], found no difference between non-incision and incision

Generally, miniscrews are inserted in the buccal or lingual cortical plates; this is defined as monocortical placement. Occasionally, the miniscrew can be placed across the entire width of the alveolus (bicortical placement). Although bicortical placement provides superior force resistance and stability compared with monocortical placement, more care has to be taken during placement. Bicortical placement may be preferred when increased orthodontic loading

It is usually recommended that miniscrews are placed perpendicular (at an angle of 90°) to the bone surface [45]. However, this might not always be clinically achievable, and an angular approach might be needed. If the buccal alveolar bone volume is sufficient relative to the long axis of the teeth, the miniscrew can be placed at an angle of 30–40° for the upper jaw and 20– 60° for the lower jaw [12]. This angular placement minimizes root contact, as there is relatively more space [50] and the surface area of cortical bone in contact with the miniscrew is increased, allowing placement of longer miniscrews and improved stability [12]. When placing a

is needed or in cases where there is insufficient cortical bone thickness [58-60].

The timing of loading depends largely on the miniscrew type [62-65]. For osseointegrated miniscrews, loading can commence 2–3 months after placement. Miyawaki et al. [16], observed no significant difference between loading at 1–2 months and at 3 months after placement. However, miniscrews that do not require osseointegration are often used, and they can be loaded immediately [61].

The maximum force-load that a miniscrew can withstand remains controversial [66]. Dalstra et al. [67], recommended 50 g of immediate loaded force for miniscrews placed into thin cortical bone and fine trabeculae. Many studies have reported miniscrew stability with loading forces of 300 g or less [68,69]. In their study, Buchter et a1. [69], evaluated the transverse loading of miniscrews placed in dense mandibular bone and reported that immediate loads of up to 900 centinewtons per millimetre [cN/mm] remained clinically stable. Kim et al. [70], investigated whether the specific directions of the force vectors were associated with the stability of miniscrews. The results indicated that miniscrews were fixed evenly in three dimensions and were not more resistant to any particular direction of load. Park [12] recommends loading immediately after placement and keeping the force minimal (< 70 g) until 2 months after placement, and then increasing the force up to 150–200 g.

Cortical thickness, miniscrew characteristics, force magnitude, direction and loading period are reported to be factors related to miniscrew stability [16,64-66,71]. However, one study found that the duration of loading did not influence the success rate of the miniscrews [70]. To prevent the miniscrew from loosening, the moments created during force application that may tend to unscrew the miniscrew have to be taken into consideration. To control these moments, clinicians have to carefully evaluate the force system applied to the miniscrew. If the application of such undesirable moments to the screw cannot be avoided, indirect anchor‐ age is recommended [1,8].

Although the miniscrews may initially be stable, they may not remain stationary when subjected to orthodontic forces [72,73]. Liou et al. [72], placed miniscrews in the zygomatic buttress for direct anchorage and reported that when the screw was subjected to orthodontic force, extrusion and 0.4-mm tipping were observed at the level of the head of the screw. Liu et al. [73], evaluated the displacement of miniscrews placed in inter-radicular areas of the maxilla as anchorage for the en masse retraction of anterior teeth using three-dimensional CT registration evaluations. The researchers observed that both the molars and the miniscrews were displaced in the direction of force application and drifted mesially, but not by the same amount. The molars drifted mesially 0.91 mm and the miniscrews moved 0.23 mm on average. This result implied that the miniscrews might have come into contact with the roots following treatment. The different mesial-drift ratios of the molars and the miniscrews may be a critical factor in the loosening of miniscrews [74]. As a precaution, the researchers [73] advised placing the miniscrews mesially for long-term stability.

The conventional periodontal pressure–tension theory cannot explain the miniscrew displace‐ ment process. The Frost mechanostat theory instead identifies complex bone biomechanics [75,76]. The bone remodelling process at the bone–screw interface and the mechanism of screw displacement are correlated to the stress–strain field in the surrounding bone as a result of dynamic loading [77,78].

### **3. Complications**

Complications may be related to factors such as the clinician, the patient and the miniscrews themselves [79].

*Clinician-related complications:* Clinicians' skills and experience are critical to the success rate of the procedure [70]. Once clinicians become accustomed to using miniscrews, their success rates increase [12]. Operators need to develop their skills to avoid damaging adjacent anatomical structures and the root of the tooth while placing the miniscrew.

*Patient-related complications:* These result from factors such as systemic diseases, periodon‐ tal disease, osteoporosis, drugs, pharmacologic prescriptions such as bisphosphonates, poor oral hygiene, smoking and cortical thickness of the bone [31,63,80-82], all of which can affect the stability of the miniscrew. It may be better not to use miniscrews for patients with adverse risk factors; however, if miniscrews have to be used, longer healing periods should be allowed and specific loading protocols should be applied [81,82]. It is notable that in their animal study, Park et al. [83], found that the presence of diabetes and variation in the placement system (self-drilling or self-tapping) did not affect the initial stability of orthodontic mini-implants.

*Miniscrew-related complications:* Anticipated complications with miniscrews include [6,72,79]:


may tend to unscrew the miniscrew have to be taken into consideration. To control these moments, clinicians have to carefully evaluate the force system applied to the miniscrew. If the application of such undesirable moments to the screw cannot be avoided, indirect anchor‐

Although the miniscrews may initially be stable, they may not remain stationary when subjected to orthodontic forces [72,73]. Liou et al. [72], placed miniscrews in the zygomatic buttress for direct anchorage and reported that when the screw was subjected to orthodontic force, extrusion and 0.4-mm tipping were observed at the level of the head of the screw. Liu et al. [73], evaluated the displacement of miniscrews placed in inter-radicular areas of the maxilla as anchorage for the en masse retraction of anterior teeth using three-dimensional CT registration evaluations. The researchers observed that both the molars and the miniscrews were displaced in the direction of force application and drifted mesially, but not by the same amount. The molars drifted mesially 0.91 mm and the miniscrews moved 0.23 mm on average. This result implied that the miniscrews might have come into contact with the roots following treatment. The different mesial-drift ratios of the molars and the miniscrews may be a critical factor in the loosening of miniscrews [74]. As a precaution, the researchers [73] advised placing

The conventional periodontal pressure–tension theory cannot explain the miniscrew displace‐ ment process. The Frost mechanostat theory instead identifies complex bone biomechanics [75,76]. The bone remodelling process at the bone–screw interface and the mechanism of screw displacement are correlated to the stress–strain field in the surrounding bone as a result of

Complications may be related to factors such as the clinician, the patient and the miniscrews

*Clinician-related complications:* Clinicians' skills and experience are critical to the success rate of the procedure [70]. Once clinicians become accustomed to using miniscrews, their success rates increase [12]. Operators need to develop their skills to avoid damaging adjacent anatomical

*Patient-related complications:* These result from factors such as systemic diseases, periodon‐ tal disease, osteoporosis, drugs, pharmacologic prescriptions such as bisphosphonates, poor oral hygiene, smoking and cortical thickness of the bone [31,63,80-82], all of which can affect the stability of the miniscrew. It may be better not to use miniscrews for patients with adverse risk factors; however, if miniscrews have to be used, longer healing periods should be allowed and specific loading protocols should be applied [81,82]. It is notable that in their animal study, Park et al. [83], found that the presence of diabetes and variation in the placement system (self-drilling or self-tapping) did not affect the initial stability of

structures and the root of the tooth while placing the miniscrew.

age is recommended [1,8].

216 Current Concepts in Dental Implantology

dynamic loading [77,78].

**3. Complications**

orthodontic mini-implants.

themselves [79].

the miniscrews mesially for long-term stability.


Generally, patients do not experience pain and discomfort following miniscrew placement [6,16,58,35]. If pain is present, it may last 1–2 days [58,47]. Kuroda et al. [38], analyzed patients' pain duration and intensity during the first 2 weeks after placement. One hour after placement, 95% of patients reported pain in the group in which miniscrews were placed after raising a mucoperiosteal flap, whereas in the group who had undergone a flapless approach, only 50% of patients reported pain. After 2 weeks, the values were 10% and 0% for the respective techniques.

Cheek irritation was generally not observed when miniscrews were placed in the buccal alveolar bone; however, when placed in the palatal area, tongue irritation primarily occurred. Bonding resin or a periodontal wound dressing can be applied to the head of the miniscrew to smooth its surface and to minimize soft-tissue irritation [1,84].

**2.** Inflammation around miniscrews

Peri-implantitis is the most commonly observed complication, and is considered to be the major factor in implant failure [43]. The localization of the miniscrew, its relationship with the soft tissue and the hygiene habits of the patient are the main factors that affect inflammation [30]. Takaki et al. [35], reported that inflammation frequency depended on the degree of mucosal penetration and stated that chronic inflammation mostly occurred when miniscrews were placed in the anterior alveolar region of the maxilla. When the miniscrew was placed in the attached gingiva or in the palatal mucosa, less inflammation was observed [12]. By contrast, when miniscrews were placed in the oral mucosa, deep in the vestibule or near a frenulum, persistent inflammation occurred [29,31]. If miniscrews are placed 1 mm below the mucogingival junction, they do not produce serious inflamma‐ tion. To prevent inflammation, the screws need to be thoroughly cleaned. Mild infections can be controlled by using antiseptic mouthwash and by brushing [35]. Taking a differ‐ ent view, Kim et al. [70], emphasized that unlike inflammation from poor oral hygiene, inflammation caused by mobile miniscrews was not controlled with improved oral hygiene. Therefore, inflammation or swelling around a miniscrew might be the result of it loosen‐ ing, rather than the cause. When taking this view, primary stability becomes increasingly important.

#### **3.** Soft-tissue impingement

In conditions where the miniscrew is placed deep in the vestibule, into the free gingiva or the retromolar area, the head of the miniscrews may become embedded in the overgrowth of surrounding soft tissue [85]. Placing miniscrews into attached gingiva can avoid soft-tissue impingement over the head of the screw. Additionally, the elastic chain, arch wire or coils may impinge on the gingiva and may cause inflammation, as well as gingival recession. Clinicians should be careful, as bending of the arch wire can eliminate impingement. Thin soft-tissue impingement overlying the miniscrew can be exposed with light finger pressure without having to apply a local anesthetic [85]. Soft-tissue impingement may be minimized by placing a wax pellet or an elastic separator over the miniscrew. Additionally, patients may be instruct‐ ed to use chlorhexidine mouthwash. Rather than acting as an antibacterial agent and mini‐ mizing tissue inflammation, chlorhexidine reduces probable soft-tissue overgrowth by slowing down epithelialization [85,86].

#### **4.** Damage to surrounding anatomical structures

While placing the miniscrew, the clinician needs to be careful not to cause damage to adjacent structures, nerves, arteries and the roots of the teeth. In the mandible, as the inferior alveolar nerve runs lingual and inferior to the molar roots and moves buccally at the premolar area, the miniscrews will be placed far above the inferior alveolar nerve and will not cause any damage. When placing the miniscrew in the palatal alveolar bone, angular placement near the apex of the roots of the maxillary molars will reduce the risk of making contact with the greater palatine nerve and artery, which are situated higher in the palate [12].

#### **5.** Root injury

Iatrogenic root injury may occur while placing the miniscrew in a narrow inter-radicular space [87]. Clinicians need to evaluate the distance between the roots using periapical or panoramic radiographs to avoid root contact during placement. A safety clearance of 2 mm is recom‐ mended in interdental areas [64]. When this space is insufficient, the interdental space should be widened before placement during the alignment of the teeth.

Caution must be taken while placing the miniscrew. A small amount of local anesthesia is preferred to keep the nerve fibers in the periodontal ligament sensitive [12], so that the patients can feel it if the miniscrew touches the root. Clinicians can also sense contact with the root. During insertion of the miniscrew, cortical bone resistance may at the outset be quite strong; however, after penetrating the cortical bone, resistance remains minimal until the miniscrew is fully placed. If any strong resistance is felt, it should be used as an indicator of possible root contact [88]. Should this occur, the clinician should remove the miniscrew and change the insertion angulation. Angular placement of the miniscrew may minimize root contact. Placing the miniscrew slightly mesial to the contact point of teeth is also recommended. It has been shown that the distance from the outer bone surface to the buccal surface of the root is larger at the second premolars than that at the first molars [50].

Potential complications of root damage include root resorption, devitalization, dentoalveolar ankylosis and osteosclerosis [79, 89]. Researchers have determined that close proximity or contact between a miniscrew and a root can be a major risk factor for failure of the procedure [39, 40, 90]. This view is supported by Lee et al. [91], who reported that the incidence of root resorption increased when the distance between the miniscrew and the root was less than 0.6 mm, and that the incidence of bone resorption and ankylosis was increased when the minis‐ crew came close to the root surface, even without root contact.

Asscherickx et al. [89], reported that if damage occurs, recovery time is relatively quick. If trauma to the root does not involve the pulp and is limited to the cementum or the dentin of the tooth, the prognosis will not be heavily influenced and healing will take place [85,88]. After removal of the miniscrew, the damaged root will be repaired in 12–18 weeks [85]. In their animal studies, Kim and Kim [92] observed that when a miniscrew was left touching the root, the normal healing response did not occur; the root surface was mostly resorbed and partial repair began at 8 weeks.

During orthodontic treatment, contact between the root and the miniscrew may occur as the tooth moves. The tooth will then stop moving and the miniscrew may become mobile. If further tooth movement is required, the miniscrew must be removed and placed elsewhere.

**6.** Miniscrew mobility or failure

**3.** Soft-tissue impingement

218 Current Concepts in Dental Implantology

slowing down epithelialization [85,86].

**5.** Root injury

**4.** Damage to surrounding anatomical structures

palatine nerve and artery, which are situated higher in the palate [12].

be widened before placement during the alignment of the teeth.

at the second premolars than that at the first molars [50].

In conditions where the miniscrew is placed deep in the vestibule, into the free gingiva or the retromolar area, the head of the miniscrews may become embedded in the overgrowth of surrounding soft tissue [85]. Placing miniscrews into attached gingiva can avoid soft-tissue impingement over the head of the screw. Additionally, the elastic chain, arch wire or coils may impinge on the gingiva and may cause inflammation, as well as gingival recession. Clinicians should be careful, as bending of the arch wire can eliminate impingement. Thin soft-tissue impingement overlying the miniscrew can be exposed with light finger pressure without having to apply a local anesthetic [85]. Soft-tissue impingement may be minimized by placing a wax pellet or an elastic separator over the miniscrew. Additionally, patients may be instruct‐ ed to use chlorhexidine mouthwash. Rather than acting as an antibacterial agent and mini‐ mizing tissue inflammation, chlorhexidine reduces probable soft-tissue overgrowth by

While placing the miniscrew, the clinician needs to be careful not to cause damage to adjacent structures, nerves, arteries and the roots of the teeth. In the mandible, as the inferior alveolar nerve runs lingual and inferior to the molar roots and moves buccally at the premolar area, the miniscrews will be placed far above the inferior alveolar nerve and will not cause any damage. When placing the miniscrew in the palatal alveolar bone, angular placement near the apex of the roots of the maxillary molars will reduce the risk of making contact with the greater

Iatrogenic root injury may occur while placing the miniscrew in a narrow inter-radicular space [87]. Clinicians need to evaluate the distance between the roots using periapical or panoramic radiographs to avoid root contact during placement. A safety clearance of 2 mm is recom‐ mended in interdental areas [64]. When this space is insufficient, the interdental space should

Caution must be taken while placing the miniscrew. A small amount of local anesthesia is preferred to keep the nerve fibers in the periodontal ligament sensitive [12], so that the patients can feel it if the miniscrew touches the root. Clinicians can also sense contact with the root. During insertion of the miniscrew, cortical bone resistance may at the outset be quite strong; however, after penetrating the cortical bone, resistance remains minimal until the miniscrew is fully placed. If any strong resistance is felt, it should be used as an indicator of possible root contact [88]. Should this occur, the clinician should remove the miniscrew and change the insertion angulation. Angular placement of the miniscrew may minimize root contact. Placing the miniscrew slightly mesial to the contact point of teeth is also recommended. It has been shown that the distance from the outer bone surface to the buccal surface of the root is larger

Potential complications of root damage include root resorption, devitalization, dentoalveolar ankylosis and osteosclerosis [79, 89]. Researchers have determined that close proximity or

Miniscrew dislodgement and mobility mostly occur in the first 1–2 months and more than 90% of the failures occur within the first 4 months [30]. When a miniscrew has resisted more than a 4-month period of force application, it can be considered successful and stable [30].

When mobility occurs, the clinician can tighten the miniscrew and leave it for 1–2 months with no loading, or light loading if necessary [1]. Supporting this recommendation, researchers reported that non-infected dental implants may reintegrate after tightening [93]; even when accidentally avulsed, an implant can become stable after reimplantation and immediate loading [94]. If stability cannot be regained, the miniscrew needs to be removed and replaced.

Miniscrew mobility and failure is mostly the result of low bone density owing to inadequate cortical thickness [85]. The health, thickness and type of soft tissue are other important factors in this context.

According to Moon et al. [30], sex, age, jaw (maxilla/mandible), soft-tissue management (incision/no incision) and placement side (left/right) are not related to the success rate of the miniscrew. By contrast, others have stated that miniscrews placed in the maxilla show a higher success rate than those placed in the mandible [10,31,35,43,54]. Occlusal stress and food impaction force may be factors causing mobility and failure of miniscrews in the mandible [35], while failure of miniscrews placed in the midpalatal area may be the result of tongue pressure [85].

There are conflicting reports about the relationship between success rate and the patient's age. Success rate tends to be lower in younger patients (< 20 years old) compared with older patients (> 20 years old) [54]. This may be because of the thinner cortical bone and poorer bone quality in younger patients. However, in another study, Park [95] reported that against expectations, the success rate was higher for the below 20 years age group compared with the over 20 years age group, which might be explained by the higher rate of metabolism in the young adult group. Contrarily, Miyawaki et al. [16], stated that there was no significant difference in the success rates of the below 20 years age group, the 20–30 years age group and the over 30 years age group.

Excessive stress at the screw–bone interface may cause miniscrew failure. Miniscrew geometry and the placement method (self-drilling/self-tapping) can have an effect on the stress distri‐ bution of the peri-screw bone. Self-drilling miniscrews have been reported to have greater screw–bone contact (mechanical grip) and holding strength compared with self-tapping screws [96,97], although the technique causes greater stress to the peri-screw bone. Placing a pilot hole before self-drilling may reduce this stress.

**7.** Fracture of miniscrews

Miniscrew fracture is a more serious clinical complication than root contact [87]. Fractures most commonly occur during the last turn of miniscrew insertion and the first turn of the removal phase [1,98]. Lima et al. [98], stated that excessive force and the inability of the implant to resist rotational forces during insertion were the main causes of fractures. Clinicians should apply slow and gentle force to avoid fracture of the miniscrew. If the insertion resistance reaches the fracture strength of the implant, it would be better to wait 1–2 min to relieve the internal stress accumulated in the miniscrew and the surrounding bone [1].

In their in vitro study, Choa et al. [87], evaluated the effects of insertion angle and implant thread type on the fracture properties of orthodontic miniscrews during insertion. They reported that maximum insertion torque increased with an increase in insertion angle. When a miniscrew contacts the artificial root at a critical contact angle, deformation or fracture of the miniscrew can occur at a lower insertion torque value than that of penetration.

The fracture of a miniscrew may also occur during the removal phase. Miniscrews can be easily removed by turning them in the opposite direction of placement. To eliminate the possibility of fracture, clinicians should apply gentle untightening pressure or use an ultrasonic scaler on the screw's head until the interface between the miniscrew and the bone breaks. If the removal torque approaches the fracture torque range, the clinician should wait 1–2 weeks before again attempting to remove it [1]. The greater the duration of the miniscrew in the bone and the older the patient, the greater the removal torque of the miniscrew [3]. Stress concentrates in the cervical part of the miniscrew during removal.

Fracture of miniscrews primarily depends on the screw size. Miniscrews with a smaller diameter are easier to place between the roots; however, a small decrease in this dimension results in a meaningful increase in the torsional strength and, therefore, in the risk of fracture [6,8,10]. Screws with a larger diameter demonstrate minimal fracturing. The core (inner) diameter affects fracturing more than the outer diameter. Clinicians may prefer to use a miniscrew with a larger diameter to reduce the risk of fracture; however, doing so will increase the fracture torque [22,99].

The material that the miniscrews are made of is also a factor that affects the likelihood of fracture. Pure titanium implants are preferred as they are more biocompatible than titanium alloy implants [1]; however, titanium alloys are stronger and provide more resistance to fracture [6].

### **4. Clinical applications**

group. Contrarily, Miyawaki et al. [16], stated that there was no significant difference in the success rates of the below 20 years age group, the 20–30 years age group and the over 30 years

Excessive stress at the screw–bone interface may cause miniscrew failure. Miniscrew geometry and the placement method (self-drilling/self-tapping) can have an effect on the stress distri‐ bution of the peri-screw bone. Self-drilling miniscrews have been reported to have greater screw–bone contact (mechanical grip) and holding strength compared with self-tapping screws [96,97], although the technique causes greater stress to the peri-screw bone. Placing a

Miniscrew fracture is a more serious clinical complication than root contact [87]. Fractures most commonly occur during the last turn of miniscrew insertion and the first turn of the removal phase [1,98]. Lima et al. [98], stated that excessive force and the inability of the implant to resist rotational forces during insertion were the main causes of fractures. Clinicians should apply slow and gentle force to avoid fracture of the miniscrew. If the insertion resistance reaches the fracture strength of the implant, it would be better to wait 1–2 min to relieve the internal stress

In their in vitro study, Choa et al. [87], evaluated the effects of insertion angle and implant thread type on the fracture properties of orthodontic miniscrews during insertion. They reported that maximum insertion torque increased with an increase in insertion angle. When a miniscrew contacts the artificial root at a critical contact angle, deformation or fracture of the

The fracture of a miniscrew may also occur during the removal phase. Miniscrews can be easily removed by turning them in the opposite direction of placement. To eliminate the possibility of fracture, clinicians should apply gentle untightening pressure or use an ultrasonic scaler on the screw's head until the interface between the miniscrew and the bone breaks. If the removal torque approaches the fracture torque range, the clinician should wait 1–2 weeks before again attempting to remove it [1]. The greater the duration of the miniscrew in the bone and the older the patient, the greater the removal torque of the miniscrew [3]. Stress concentrates in the

Fracture of miniscrews primarily depends on the screw size. Miniscrews with a smaller diameter are easier to place between the roots; however, a small decrease in this dimension results in a meaningful increase in the torsional strength and, therefore, in the risk of fracture [6,8,10]. Screws with a larger diameter demonstrate minimal fracturing. The core (inner) diameter affects fracturing more than the outer diameter. Clinicians may prefer to use a miniscrew with a larger diameter to reduce the risk of fracture; however, doing so will increase

The material that the miniscrews are made of is also a factor that affects the likelihood of fracture. Pure titanium implants are preferred as they are more biocompatible than titanium

miniscrew can occur at a lower insertion torque value than that of penetration.

pilot hole before self-drilling may reduce this stress.

accumulated in the miniscrew and the surrounding bone [1].

cervical part of the miniscrew during removal.

the fracture torque [22,99].

**7.** Fracture of miniscrews

220 Current Concepts in Dental Implantology

age group.

Planning of orthodontic treatment should consider the desired force system to act on the teeth that need to be moved, as well as any undesired effects on the anchorage unit of teeth. This will guide ideal placement of the miniscrew for the proper appliance design.

Clinicians also should be aware of any anatomical limitations for the placement of miniscrews. The location of the miniscrew will affect the appliance design and the force system. Therefore, clinicians should plan the placement area of the miniscrews in the buccal alveolar region and/ or in the palatal alveolar region or midpalatal area according to the required tooth movement. In conditions where miniscrews cannot be placed in the ideal position, the force direction should be adjusted depending on the changes in tooth movement during the treatment time.

Selection of the appropriate miniscrew design is crucial. Clinicians mostly prefer miniscrews with slotted heads, which are convenient for the attachment of different types of orthodontic wires (round, square or rectangular) and complex wire activations.

Many reports describe the application of miniscrew-supported orthodontic treatment for achieving a variety of orthodontic tooth movements, including intrusion [25,49,100], extrusion, space closure (distalization, mesialization) [24, 101], uprighting, eruption of impacted teeth [102] and the correction of canted occlusal planes [103]. In addition, miniscrews can be used in the application of dentofacial orthopedics such as rapid palatal expansion and Class II and III correction (Figure 1) [12,45,104,105]. This chapter does not cover the use of miniscrews for dentoskeletal orthopedics.

**Figure 1.** Miniscrews used in the application of dentofacial orthopedics with the placement of four miniscrews be‐ tween the inter-radicular areas of the maxilla. Stainless steel arch wire (0.021 × 0.025 inch) was passively connected to the miniscrews, and two hook shapes were connected to the arch wire in the lateral root region for facemask elastics.

Miniscrews aim to strengthen orthodontic anchorage either by connecting to a tooth or a group of teeth to reinforce their anchorage (indirect anchorage) (Figure 2 and 3a) [105], or by acting as anchorage units themselves, eliminating the need for supporting teeth (direct anchorage) (Figures 3b and 4) [106].

**Figure 2.** Miniscrew used as indirect anchorage to avoid buccal flaring of the anterior teeth with a forsus appliance.

Miniscrews are most often used for direct anchorage. Generally, direct forces are applied between the miniscrew and the target tooth by using elastic chain, elastic thread or a coil spring to move the tooth toward the miniscrew. If a miniscrew is used as a direct anchor, it is advantageous to place the miniscrew along the line of the desired tooth movement. If force applied between the tooth and the miniscrew causes undesirable moments, then the miniscrew should be used as indirect anchorage to support the anchorage teeth, rather than acting as a direct anchor [8].

**Figure 3.** Canine distalization combined with miniscrew use as (a) indirect anchorage and (b) direct anchorage.

**Figure 4.** a and b: Use of a miniscrew for direct anchorage inserted between the second premolar and first molar where the molar could not be included in the arch wire because of incomplete eruption.

#### **4.1. Intrusion**

Miniscrews aim to strengthen orthodontic anchorage either by connecting to a tooth or a group of teeth to reinforce their anchorage (indirect anchorage) (Figure 2 and 3a) [105], or by acting as anchorage units themselves, eliminating the need for supporting teeth (direct anchorage)

(a) (b)

**Figure 2.** Miniscrew used as indirect anchorage to avoid buccal flaring of the anterior teeth with a forsus appliance.

Miniscrews are most often used for direct anchorage. Generally, direct forces are applied between the miniscrew and the target tooth by using elastic chain, elastic thread or a coil spring to move the tooth toward the miniscrew. If a miniscrew is used as a direct anchor, it is advantageous to place the miniscrew along the line of the desired tooth movement. If force applied between the tooth and the miniscrew causes undesirable moments, then the miniscrew should be used as indirect anchorage to support the anchorage teeth, rather than acting as a

(a) (b)

**Figure 3.** Canine distalization combined with miniscrew use as (a) indirect anchorage and (b) direct anchorage.

(Figures 3b and 4) [106].

222 Current Concepts in Dental Implantology

direct anchor [8].

#### *4.1.1. Intrusion of posterior teeth*

Anterior open bites can be closed successfully through the intrusion of posterior teeth using various mechanical methods incorporating miniscrews (Figure 5).

**Figure 5.** Miniscrew placed in the buccal vestibule apical to the maxillary molars, to be used for the intrusion of the posterior teeth to correct an anterior open bite.

Intrusion of posterior teeth is considered one of the most difficult types of tooth movement to achieve using conventional mechanics. A miniscrew-combined treatment may solve this problem. However, side effects such as buccal tipping have to be taken into consideration. As the intrusive force passes from the buccal to the centre of resistance, it will cause buccal tipping of the molars. When bilateral intrusion of posterior teeth is the goal, transpalatal arches can be used to avoid buccal tipping [20,21]. In unilateral intrusion, an additional miniscrew can be placed on the palatal side to apply a palatal intrusive force for achieving intrusion of the overerupted molar without tipping (Figure 6a and b).

**Figure 6.** a and b: Miniscrew in the palate to achieve intrusion of over-erupted posterior teeth.

#### *4.1.2. Intrusion of anterior teeth*

Miniscrews may be used to stabilize the molars during the incisor intrusion process, or can be placed anteriorly and used for direct application of the intrusive force to the incisors. The miniscrews should be placed as close to the midline of the anterior arch as possible. Alternately two miniscrews may be inserted into the lateral and canine interradicular area on both left and right sides.

#### **4.2. Extrusion**

While correcting an anterior open bite, activation of an extrusion arch results in mesial tipping and an intrusive force at the molars [107]. In such cases, miniscrews can be used to avoid these side effects.

In their case report, Roth et al. [108], treated an occlusal cant with miniscrew-supported mechanics by extruding the central incisors and the canine teeth. To avoid involving the other anterior teeth, a miniscrew was placed into the alveolus of the missing upper lateral incisor and an open coil was applied perpendicularly to an orthodontic wire connecting the central incisor and the canine.

#### **4.3. Space closure**

Generally, miniscrews are best suited to use as indirect anchorage during retraction of the anterior teeth or protraction of the posterior teeth [20]. In this way, the miniscrew is used to avoid undesirable movement of anchorage teeth, while conventional mechanics are used to close the space created (Figures 3a and 7).

placed on the palatal side to apply a palatal intrusive force for achieving intrusion of the over-

(a) (b)

Miniscrews may be used to stabilize the molars during the incisor intrusion process, or can be placed anteriorly and used for direct application of the intrusive force to the incisors. The miniscrews should be placed as close to the midline of the anterior arch as possible. Alternately two miniscrews may be inserted into the lateral and canine interradicular area on both left and

While correcting an anterior open bite, activation of an extrusion arch results in mesial tipping and an intrusive force at the molars [107]. In such cases, miniscrews can be used to avoid these

In their case report, Roth et al. [108], treated an occlusal cant with miniscrew-supported mechanics by extruding the central incisors and the canine teeth. To avoid involving the other anterior teeth, a miniscrew was placed into the alveolus of the missing upper lateral incisor and an open coil was applied perpendicularly to an orthodontic wire connecting the central

Generally, miniscrews are best suited to use as indirect anchorage during retraction of the anterior teeth or protraction of the posterior teeth [20]. In this way, the miniscrew is used to avoid undesirable movement of anchorage teeth, while conventional mechanics are used to

**Figure 6.** a and b: Miniscrew in the palate to achieve intrusion of over-erupted posterior teeth.

erupted molar without tipping (Figure 6a and b).

224 Current Concepts in Dental Implantology

*4.1.2. Intrusion of anterior teeth*

right sides.

**4.2. Extrusion**

side effects.

incisor and the canine.

close the space created (Figures 3a and 7).

**4.3. Space closure**

**Figure 7.** The use of a miniscrew as indirect anchorage during the distalization of the premolars and canine.

When direct anchorage is preferred for space closure, the direction and point of force appli‐ cation becomes crucial. Segmented arches may be preferred for canine distalization to provide a more appropriate force application point (Figure 8a and b). When the miniscrews are placed apically, a more favourable line of force direction passing closer to the centre of the resistance of the teeth can be achieved.

**Figure 8.** Miniscrews used as direct anchorage in canine distalization. Canine distalization with (a) a segmental arch and (b) a hybrid retraction arch.

Miniscrews can be used as direct anchorage when retracting the anterior teeth. Open coils/ elastic chains are applied directly between the miniscrew placed between the second premolar, the first molar and the hooks on the arch wire (Figure 9). Therefore, the point of force appli‐ cation is close to the centre of resistance of the anterior teeth, so that the anterior segment may slide bodily with minimal tipping; 150 g of force is used for retraction [109]. In some cases, miniscrews can be placed in the palatal region. Anchorage may be indirectly reinforced by connecting a transpalatal bar to a miniscrew in the palate [110].

**Figure 9.** En mass retraction of the anterior teeth with miniscrew anchorage. Open coils/elastic chains can be applied directly between the miniscrew and the hooks on the arch wire.

#### **4.4. Molar distalization**

During molar distalization with conventional intraoral appliances, tipping and extrusion can occur in conjunction with the distal movement. In addition, reactive forces on the anterior anchoring teeth occur in the form of mesialization of upper anteriors/premolars and increased overjet. Many types and designs of appliances such as the pendulum [111,116], the Keles slide appliance [112], the distal-jet [113] and the compressed coil spring [116] can be combined with a miniscrew anchorage system (Figure 10).

**Figure 10.** Miniscrew-supported pendulum application.

Miniscrew-supported molar distalization can only prevent undesired side effects on the anterior anchoring teeth; however, the side effects on the molars such as tipping, extrusion and rotation still remain. To avoid these undesired movements, miniscrew-supported mechanics can be designed (Figures 11 and 12). For bilateral molar distalization, rotation, tipping and extrusion can be controlled by placing the miniscrews in both the buccal and palatal region, and by using transpalatal arches [117].

**Figure 11.** Design of the retraction unit may differ because of anatomic limitations, although the miniscrew is placed in the same region; (a) the distalizing force passes through the center of resistance of the first molar, which may provide parallel distalization[118] rather than the system used in (b).

#### **4.5. Uprighting**

**Figure 9.** En mass retraction of the anterior teeth with miniscrew anchorage. Open coils/elastic chains can be applied

During molar distalization with conventional intraoral appliances, tipping and extrusion can occur in conjunction with the distal movement. In addition, reactive forces on the anterior anchoring teeth occur in the form of mesialization of upper anteriors/premolars and increased overjet. Many types and designs of appliances such as the pendulum [111,116], the Keles slide appliance [112], the distal-jet [113] and the compressed coil spring [116] can be combined with

(a) (b)

Miniscrew-supported molar distalization can only prevent undesired side effects on the anterior anchoring teeth; however, the side effects on the molars such as tipping, extrusion and rotation still remain. To avoid these undesired movements, miniscrew-supported mechanics can be designed (Figures 11 and 12). For bilateral molar distalization, rotation, tipping and extrusion can be controlled by placing the miniscrews in both the buccal and

directly between the miniscrew and the hooks on the arch wire.

a miniscrew anchorage system (Figure 10).

**Figure 10.** Miniscrew-supported pendulum application.

palatal region, and by using transpalatal arches [117].

**4.4. Molar distalization**

226 Current Concepts in Dental Implantology

Uprighting is generally needed when second molars are impacted and the first molar tips mesially because of early premolar extraction. Uprighting vectors with intrusion are very hard to accomplish; therefore, absolute anchorage is required. Miniscrews can be used as direct anchorage to prevent reactive forces on adjacent teeth that may result in negative side effects.

For second molar uprighting, a miniscrew can be placed in the buccal inter-radicular area of the second premolar and first molar. This area is the most reliable mandibular buccal cortical site.

For first molar uprighting, the miniscrew can be placed mesially in the area between the second and first premolars; 6-to 8-mm miniscrews are preferable and 0.17 × 0.25 inch TMA wires are preferred for preparing sectional arches with tip-back bending. Once the wire has been engaged by the miniscrew's head, intrusion and distalization forces are applied to the molar.

#### **5. Conclusion**

In dentistry today, it is becoming more difficult to cooperate with and satisfy patients. They have higher expectations for esthetics and comfort, yet they are impatient with longer treatment periods. Clinicians will continue to research alternative approaches to provide patients with their desired treatment outcomes over the shortest time possible. Because miniscrews provide an alternative to conventional mechanics for anchorage control, clinicians are showing increasing interest in this field. Desired treatment outcomes that are not possible with conventional mechanics may be achieved with miniscrew-supported orthodontic treatment. Miniscrews have recently become commonly accepted as a simple and effective tool in daily orthodontic practice.

With further studies and the development of new designs, appliances using miniscrews are expected to become more commonly used not only in orthodontic tooth movement, but also in the application of dentofacial orthopedics.

#### **Acknowledgements**

We thank Dr. Eren Korunmuş and Dr. Myumyun S. Myumyun for their valuable contributions in preparing this chapter.

#### **Author details**

Fatma Deniz Uzuner\* and Belma Işık Aslan

\*Address all correspondence to: fduzuner@yahoo.com.tr

Department of Orthodontics, Faculty of Dentistry, Gazi University, Emek Ankara, Turkey

#### **References**

[1] Lindauer SJ, Shroff B. Temporary anchorage devices: Biomechanical opportunities and challenges. In: R. Nanda and S. Kapila (ed.) Current therapy in orthodontics Mosby Inc. 2010; p278-290.

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preferred for preparing sectional arches with tip-back bending. Once the wire has been engaged by the miniscrew's head, intrusion and distalization forces are applied to the molar.

In dentistry today, it is becoming more difficult to cooperate with and satisfy patients. They have higher expectations for esthetics and comfort, yet they are impatient with longer treatment periods. Clinicians will continue to research alternative approaches to provide patients with their desired treatment outcomes over the shortest time possible. Because miniscrews provide an alternative to conventional mechanics for anchorage control, clinicians are showing increasing interest in this field. Desired treatment outcomes that are not possible with conventional mechanics may be achieved with miniscrew-supported orthodontic treatment. Miniscrews have recently become commonly accepted as a simple and effective tool

With further studies and the development of new designs, appliances using miniscrews are expected to become more commonly used not only in orthodontic tooth movement, but also

We thank Dr. Eren Korunmuş and Dr. Myumyun S. Myumyun for their valuable contributions

Department of Orthodontics, Faculty of Dentistry, Gazi University, Emek Ankara, Turkey

[1] Lindauer SJ, Shroff B. Temporary anchorage devices: Biomechanical opportunities and challenges. In: R. Nanda and S. Kapila (ed.) Current therapy in orthodontics

**5. Conclusion**

228 Current Concepts in Dental Implantology

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**Acknowledgements**

in preparing this chapter.

**Author details**

**References**

Fatma Deniz Uzuner\*

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and Belma Işık Aslan

\*Address all correspondence to: fduzuner@yahoo.com.tr

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### **Drug Delivery Systems in Bone Regeneration and Implant Dentistry**

Sukumaran Anil, Asala F. Al-Sulaimani, Ansar E. Beeran, Elna P. Chalisserry, Harikrishna P.R. Varma and Mohammad D. Al Amri

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/60003

#### **1. Introduction**

Bone regeneration is a complex, well-orchestrated physiological process involving a number of cell types and intracellular and extracellular molecular signaling pathways [1]. Bone grafts provide a structural framework for clot development, maturation and remodeling that supports bone formation in osseous defects. These materials must possess biocompatibility and osteoconductivity, as well as the properties that support osteogenesis. The ideal charac‐ teristics of a bone graft are that it must be nontoxic, non-antigenic, resistant to infection, easily adaptable, readily and sufficiently available to stimulate new attachment and able to trigger osteogenesis [2].

Osseous defects in the oral cavity have been successfully managed with a variety of biological and synthetic materials, including autografts, allografts, xenografts and alloplastic materials. Although autografts are unequivocally accepted as the gold standard, donor site morbidity and limitations on the quantity of bone that can be harvested demand that clinicians seek alternatives [3]. In light of the immunological and disease transfer risks from allogeneic bone, research has focused extensively on developing alloplastic bone substitutes that are predom‐ inantly based on ceramics, such as calcium phosphates (CaP), calcium sulfates, and bioactive glasses [4]. In general, these ceramic materials are renowned for their osteoconductive and bioactive properties [5]. The most commonly used ceramics are the CaP-based ceramics hydroxyapatite (HA) and beta tricalcium phosphate [6].

Considering engineered grafts, the most important factor is to prepare a three-dimensional structure consisting of biodegradable material, generally called a scaffold [7]. The nature and

© 2015 The Author(s). Licensee InTech. 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 eproduction in any medium, provided the original work is properly cited.

structure of the scaffold should support cell proliferation and differentiation, accelerating the process of tissue regeneration. Furthermore, the growth factor providing a scaffold to an injury site should enhance progenitors, causing inflammatory cells to migrate and activate the healing process [8, 9]. However, among the basic challenges for scaffold implantation is to control infection due to bacterial load, which can create immune problems and finally result in implant rejection. To overcome implant-related infection and bacterial load on the scaffold, antibiotic drug incorporation and its controlled release have been suggested as a promising strategy [10]. Bone is among the few tissues of the human body that has high endogenous healing capacity. Various concepts for local drug delivery to bone have been developed in recent decades to overcome such healing deficits.

Several methods are used for drug loading and release from scaffolds. However, the basic aim for drug release is to reduce infections and bacterial load to the site of implant, but if the drug is released too quickly, there could be a chance of infection because the entire drug has drained from the scaffold in the initial time itself. Similarly, if there is too much delay to drug release, infection can set in further, making it more difficult to manage the healing of wounds. Hence, better options for drug release would incorporate higher antibiotic release at the initial time and sustained release at an effective rate to inhibit the risk of infection from bacteria in the scaffold at an effective level [11]. Different techniques have been used for drug loading to the scaffold, and controlled release has been studied. One of the simplest strategies is the appli‐ cation of biodegradable polymer coatings loaded with specific drugs onto the scaffold structure. The other methods reported for coating the drug-loaded polymer have included solvent casting, thermally induced phase separation, evaporation, freeze drying and foam coating. Among these methods, an interesting approach for drug loading and release consists of combining drug-loaded microspheres with a macroporous scaffold `matrix' [12-15].

In a recent study, a biodegradable nanoporous bioceramic system was used as a highly bioresorbable matrix for drug delivery. This study emphasized the efficacy of hydroxyapatitebased material having interconnected nanoporosity as a vehicle for a therapeutic agent. An in vitro experiment was conducted with the goal of assessing this material and comparing it with commercially available gentamicin-loaded PMMA cement. It was found that the nanoporous bioceramic granules could act as antibiotic carriers, exhibiting a high initial burst effect followed by sustained low-level release for 3 weeks. It was very effective, confirming that the concentration of drug eluted was greater than that needed to maintain bactericidal levels [16].

In addition to the above-mentioned technique, magnetic nanoparticle-incorporated materials have also been used as a bone regeneration scaffold, and they are schematically represented in figure 3 [17]. To obtain homogenous dispersion of magnetic particle loading and surfactant, a porous structure generated by ceramic crystals, the in-situ method was followed. Further, it was made to a specific shape, and the specific drug was loaded via dip loading or other methods. The drug-loaded scaffold was placed at the defective site in the presence of a magnetic field (MF), which facilitated easy drug release from the scaffold, helping to protect it from bacterial colonization, and the MF stimulated the scaffold for cell proliferation. Recently released in vitro results support MF-induced bone regeneration [18-20].

Engineered biomaterials combined with growth factors, such as bone morphogenetic protein-2 (BMP-2), have been demonstrated to constitute an effective approach in bone tissue engineer‐ ing because they can act both as a scaffold and as a drug delivery system to promote bone repair and regeneration. Despite the substantial progress made in developing porous materials as bone substitutes, the realization of synthetic structure able to harness fully bone's capability of regenerating and remodeling itself and to mimic the complicated physiochemical attributes of bone continues to present challenges.

In the following sections of this chapter, the materials and drug delivery techniques used to enhance bone regeneration and to control infection are discussed. The methods to enhance the surface of titanium implants to promote osseointegration are also detailed.

#### **2. Bone regeneration materials**

#### **2.1. Calcium phosphate ceramics**

structure of the scaffold should support cell proliferation and differentiation, accelerating the process of tissue regeneration. Furthermore, the growth factor providing a scaffold to an injury site should enhance progenitors, causing inflammatory cells to migrate and activate the healing process [8, 9]. However, among the basic challenges for scaffold implantation is to control infection due to bacterial load, which can create immune problems and finally result in implant rejection. To overcome implant-related infection and bacterial load on the scaffold, antibiotic drug incorporation and its controlled release have been suggested as a promising strategy [10]. Bone is among the few tissues of the human body that has high endogenous healing capacity. Various concepts for local drug delivery to bone have been developed in recent decades to

Several methods are used for drug loading and release from scaffolds. However, the basic aim for drug release is to reduce infections and bacterial load to the site of implant, but if the drug is released too quickly, there could be a chance of infection because the entire drug has drained from the scaffold in the initial time itself. Similarly, if there is too much delay to drug release, infection can set in further, making it more difficult to manage the healing of wounds. Hence, better options for drug release would incorporate higher antibiotic release at the initial time and sustained release at an effective rate to inhibit the risk of infection from bacteria in the scaffold at an effective level [11]. Different techniques have been used for drug loading to the scaffold, and controlled release has been studied. One of the simplest strategies is the appli‐ cation of biodegradable polymer coatings loaded with specific drugs onto the scaffold structure. The other methods reported for coating the drug-loaded polymer have included solvent casting, thermally induced phase separation, evaporation, freeze drying and foam coating. Among these methods, an interesting approach for drug loading and release consists of combining drug-loaded microspheres with a macroporous scaffold `matrix' [12-15].

In a recent study, a biodegradable nanoporous bioceramic system was used as a highly bioresorbable matrix for drug delivery. This study emphasized the efficacy of hydroxyapatitebased material having interconnected nanoporosity as a vehicle for a therapeutic agent. An in vitro experiment was conducted with the goal of assessing this material and comparing it with commercially available gentamicin-loaded PMMA cement. It was found that the nanoporous bioceramic granules could act as antibiotic carriers, exhibiting a high initial burst effect followed by sustained low-level release for 3 weeks. It was very effective, confirming that the concentration of drug eluted was greater than that needed to maintain bactericidal levels [16].

In addition to the above-mentioned technique, magnetic nanoparticle-incorporated materials have also been used as a bone regeneration scaffold, and they are schematically represented in figure 3 [17]. To obtain homogenous dispersion of magnetic particle loading and surfactant, a porous structure generated by ceramic crystals, the in-situ method was followed. Further, it was made to a specific shape, and the specific drug was loaded via dip loading or other methods. The drug-loaded scaffold was placed at the defective site in the presence of a magnetic field (MF), which facilitated easy drug release from the scaffold, helping to protect it from bacterial colonization, and the MF stimulated the scaffold for cell proliferation. Recently

released in vitro results support MF-induced bone regeneration [18-20].

overcome such healing deficits.

240 Current Concepts in Dental Implantology

The calcium phosphates have been widely studied due to their biocompatibility, tailorable bioabsorbability and bioactivity. Calcium phosphates have been used as novel delivery carriers for antibiotics, anti-inflammatory agents, analgesics, anticancer drugs, growth factors, proteins and genes [21, 22]. Furthermore, they can be synthesized using simple methods, and these drugs can easily be incorporated via different routes, such as wet chemical processes, solid state reactions, hydrothermal and micelle-mediated processes, etc. [23, 24]. Most of the polymeric systems show an acidic nature, and their degradation by-products can alter drug activity. The major advantages of CaPs, compared with other biodegradable polymeric systems, is that the degradation ions are Ca2+ and PO4 3- ions, which already exist in the body in higher concentrations [25].

Nanotechnology-derived calcium phosphates have also successfully maintained a sustained and steady drug release over time. Calcium phosphate scaffolds not only provide initial structural integrity for bone cells but also direct their proliferation and differentiation and assist in the ultimate assembly of new tissue. Therefore, ceramic nanoscaffolds are usually 3- D and porous, although in some cases they consist of 2-D coatings or films. They mimic the in vivo environment of cells more completely than nanoparticles.

Therefore, most drug-eluted ceramic nanoscaffolds serve multiple functions, such as drug delivery, directing cell growth or tissue generation, and mechanical support. Indeed, the mechanical support provided by ceramic scaffolds far exceeds that provided by polymeric scaffolds. Studies have shown that drug-release kinetics could be further controlled by tailoring calcium phosphate nanoparticle grain size, surface area and calcium-to-phosphorus ratios [26]. Hollow silica nanospheres have been fabricated into well-controlled shapes and sizes using self-templating molecules [20]. For example, studies have shown that hollow silica nanospheres were capable of entrapping an eight-fold greater quantity of drug species than solid silica nanospheres. Time-delayed multiple-stage release profiles were also possible with these hollow silica nanospheres [27].

**Figure 1.** The micromorphology (SEM) of calcium sulfate-phosphate injectable cement. **a)** The set cement surface of unmodified low-dimensional medical grade calcium sulfate (crystal sizes less than 5 microns). **b)** The phosphate-con‐ taining material, which inhabits very small crystal formations grown into folding sheets. Energy dispersive (EDS) data, corresponding to the samples, are shown below each. The phosphorous content in the second sample is evident, whereas no separate phosphate phase appeared in XRD. The phosphate content resides as a substitution in the calcium sulfate crystals.

#### **2.2. Porous spherical hydroxyapatite granules for drug delivery**

Calcium phosphate-based bioceramics, such as hydroxyapatite (HA), are known for their excellent biocompatibility due to their similarity in composition to the apatite found in natural bone [28]. Various forms of HA bone grafts, such as dense and porous blocks, dense and porous granules, and powder forms, are available as bone substitutes [29]. The porous matrices enable cell migration and provide favorable conditions for nutrient transport, tissue infiltration, and vascularization [30, 31]. The spherically shaped particles are suitable for implantation as injectable bone cements, and the inter-granular space promotes cell migration and the growth of extracellular matrix [32, 33].

Porous HA is produced using methods such as ceramic slip foaming [34], positive replication of reticulated foam scaffolds [35], burnout of sacrificial porogens, such as polymer beads [3], and techniques that exploit naturally occurring porous calcium-based structures, such as the hydrothermal conversion of either coral or bone [36, 37]. Porous spherical HA granules can be used for drug delivery systems. The various pore and channel structures of spherical granules were obtained by adjusting the ratio of water to HA powder and the amount of sodium chloride (NaCl). Earlier studies focused on the use of anti-inflammatory or anti-bacterial drug release from HA, to control inflammation and infection at the site of implantation [38]. Currently, several drugs have been found to enhance bone formation, and the loading of HA with these drugs and agents could be a very effective method for enhancing bone formation at the site of implantation [39, 40]. Research is under way to control the drug release rate using the complex micro-channel structures of HA granules [41].

**Figure 2.** Scanning electron microscopic images of: a) polycaprolactone polymer microspheres; and b) magnetic hy‐ droxyapatite-loaded polycaproctone polymer microspheres.

#### **2.3. Demineralized bone matrix**

**Figure 1.** The micromorphology (SEM) of calcium sulfate-phosphate injectable cement. **a)** The set cement surface of unmodified low-dimensional medical grade calcium sulfate (crystal sizes less than 5 microns). **b)** The phosphate-con‐ taining material, which inhabits very small crystal formations grown into folding sheets. Energy dispersive (EDS) data, corresponding to the samples, are shown below each. The phosphorous content in the second sample is evident, whereas no separate phosphate phase appeared in XRD. The phosphate content resides as a substitution in the calcium

Calcium phosphate-based bioceramics, such as hydroxyapatite (HA), are known for their excellent biocompatibility due to their similarity in composition to the apatite found in natural bone [28]. Various forms of HA bone grafts, such as dense and porous blocks, dense and porous granules, and powder forms, are available as bone substitutes [29]. The porous matrices enable cell migration and provide favorable conditions for nutrient transport, tissue infiltration, and vascularization [30, 31]. The spherically shaped particles are suitable for implantation as injectable bone cements, and the inter-granular space promotes cell migration and the growth

Porous HA is produced using methods such as ceramic slip foaming [34], positive replication of reticulated foam scaffolds [35], burnout of sacrificial porogens, such as polymer beads [3], and techniques that exploit naturally occurring porous calcium-based structures, such as the hydrothermal conversion of either coral or bone [36, 37]. Porous spherical HA granules can be

**2.2. Porous spherical hydroxyapatite granules for drug delivery**

sulfate crystals.

242 Current Concepts in Dental Implantology

of extracellular matrix [32, 33].

Bone void fillers, such as demineralized bone matrix (DBM), offer a broad range of materials, structures and delivery systems to use in bone grafting procedures. Allogenic DBM possesses osteoinductive properties and could serve as an ideal drug delivery device for prophylactic treatment in a variety of different anatomical locations [42, 43]. The use of DBM would allow for the release of the entire quantity of antibiotic as the material is being remodeled.

#### **2.4. Carriers and delivery systems for growth factors**

Growth factors (GFs), such as bone morphogenetic protein, transforming growth factor-beta, fibroblast growth factor, platelet-derived growth factor, and insulin-like growth factor, are proteins secreted by cells that act on the appropriate target cell or cells to perform specific actions. A variety of so-called bone-graft substitutes, including demineralized bone matrix, calcium phosphate-containing preparations and Bioglass (BG), are also potential carriers for recombinant proteins [44]. Bioglass and calcium phosphate-based materials, such as hydrox‐ yapatite, coralline hydroxyapatite, and tricalcium phosphate, have been shown to be biocom‐ patible and to provide osteoconductive scaffolds that could potentially be combined with GFs to enhance bone repair [45].

Demineralized bone matrix preparations are particularly attractive as potential carriers for growth factors because they are osteoconductive and can have some osteoinductive potential as well. The disadvantages of these materials include poor handling characteristics and concerns about their overall bio-resorbability, as well as limited potential for remodeling and an unclear understanding of their effects on bone strength [46]. Recombinant bone morpho‐ genetic protein (BMP) has been used to enhance the bone regeneration in graft and implant osseointegration in dentistry [47]. Recombinant human BMP-2 (rhBMP-2) has been shown to be effective in bone regeneration [48].

Among surface modification techniques, coating the implant surface with bone stimulating agents, such as GFs, is very promising. The most commonly used GFs include bone morpho‐ genetic proteins (BMP-2), TGF-β1, platelet-derived growth factor, insulin-like growth factor and combinations [47, 49]. The actual mechanisms of GF combinations are not fully under‐ stood. From early reported studies, after implantation, both GFs (TGF-β and BMP) could directly increase the local pool of osteoprogenitor cells by stimulating their migration [50]. The circulation of pathways acts as a source of osteoprogenitor cells throughout ectopic BMPinduced bone regeneration. Similarly, the presence of both TGF-β1 and BMP-7 cooperatively interact to increase angiogenesis and vascular invasion after their co-administration increased vessel constitution [51]. The results demonstrated that the presence of GF associated with implant surfaces improved bone regeneration, vascular invasion and angiogenesis. Research is under way to optimize the carrier properties and the characteristics of the GF and its dose to maximize the regeneration potential.

#### **2.5. Nanoscaffolds**

The application of nanotechnology for drug delivery and the use of nanometer scale materials has helped to develop innovative approaches in this field. At this scale, materials display different physicochemical properties due to their small size, surface structure and high surface area. The nanoparticles based ceramic scaffolds have also demonstrated great potential for controlled drug delivery and is currently a fast growing research area. The ceramic nanoscaf‐ folds have several advantages such as high porosity, high volume-to-area ratios, high surface area, high structural stability and long degradation times. These properties make them potent systems for controlled release of drugs. At the implantation sites drugs/chemical agents are applied for decreasing infection, reducing inflammation, and increasing bone growth on titanium surfaces. The nanotubular titania and calcium phosphate-based nanoscaffolds have showed good potential for drug and growth factor delivery.

#### **2.6. Magnetic nanoparticles (FE-hydroxyapatite)**

Superparamagnetic nanoparticles (MNPs) have been progressively explored for their potential in biomedical applications and in particular as contrast agents for diagnostic imaging, for magnetic drug delivery and, more recently, for tissue engineering applications [52-54]. MNPs have been used for biomedical applications, such as in hyperthermia [55], as a contrast agent for diagnostic imaging [56], for magnetic drug delivery [57, 58] [13], and for cell mechanosen‐ sitive receptor manipulation to induce cell differentiation [59].

**Figure 3.** Schematic presentation of engineered magnetic scaffold preparation and implantation.

The most popular MNPs used in medicine and biotechnology are iron oxide-based phases, but their potential as a tissue engineering scaffold has not yet been fully assessed [60]. Although Fe is a vital element in the human body, its concentration within hard tissue is low, and its presence into the body scarcely affects bone remodeling [61]. In contrast, the biocompatibility and bioactivity of HA are already well established [62-64], and, in fact, more than 60% of the currently available bone graft substitutes involve calcium phosphate-based materials [65]. Hence, a Fe-HA phase endowed with superparamagnetic ability could be used as an active scaffold for bone and osteochondral regeneration or as a nontoxic, biodegradable, magnetic nanocarrier [17, 66, 67].

#### **2.7. Chitosan hydroxy apatite**

Demineralized bone matrix preparations are particularly attractive as potential carriers for growth factors because they are osteoconductive and can have some osteoinductive potential as well. The disadvantages of these materials include poor handling characteristics and concerns about their overall bio-resorbability, as well as limited potential for remodeling and an unclear understanding of their effects on bone strength [46]. Recombinant bone morpho‐ genetic protein (BMP) has been used to enhance the bone regeneration in graft and implant osseointegration in dentistry [47]. Recombinant human BMP-2 (rhBMP-2) has been shown to

Among surface modification techniques, coating the implant surface with bone stimulating agents, such as GFs, is very promising. The most commonly used GFs include bone morpho‐ genetic proteins (BMP-2), TGF-β1, platelet-derived growth factor, insulin-like growth factor and combinations [47, 49]. The actual mechanisms of GF combinations are not fully under‐ stood. From early reported studies, after implantation, both GFs (TGF-β and BMP) could directly increase the local pool of osteoprogenitor cells by stimulating their migration [50]. The circulation of pathways acts as a source of osteoprogenitor cells throughout ectopic BMPinduced bone regeneration. Similarly, the presence of both TGF-β1 and BMP-7 cooperatively interact to increase angiogenesis and vascular invasion after their co-administration increased vessel constitution [51]. The results demonstrated that the presence of GF associated with implant surfaces improved bone regeneration, vascular invasion and angiogenesis. Research is under way to optimize the carrier properties and the characteristics of the GF and its dose

The application of nanotechnology for drug delivery and the use of nanometer scale materials has helped to develop innovative approaches in this field. At this scale, materials display different physicochemical properties due to their small size, surface structure and high surface area. The nanoparticles based ceramic scaffolds have also demonstrated great potential for controlled drug delivery and is currently a fast growing research area. The ceramic nanoscaf‐ folds have several advantages such as high porosity, high volume-to-area ratios, high surface area, high structural stability and long degradation times. These properties make them potent systems for controlled release of drugs. At the implantation sites drugs/chemical agents are applied for decreasing infection, reducing inflammation, and increasing bone growth on titanium surfaces. The nanotubular titania and calcium phosphate-based nanoscaffolds have

Superparamagnetic nanoparticles (MNPs) have been progressively explored for their potential in biomedical applications and in particular as contrast agents for diagnostic imaging, for magnetic drug delivery and, more recently, for tissue engineering applications [52-54]. MNPs have been used for biomedical applications, such as in hyperthermia [55], as a contrast agent for diagnostic imaging [56], for magnetic drug delivery [57, 58] [13], and for cell mechanosen‐

be effective in bone regeneration [48].

244 Current Concepts in Dental Implantology

to maximize the regeneration potential.

showed good potential for drug and growth factor delivery.

sitive receptor manipulation to induce cell differentiation [59].

**2.6. Magnetic nanoparticles (FE-hydroxyapatite)**

**2.5. Nanoscaffolds**

Chitosan is considered an appropriate functional material for biomedical applications because of its high biocompatibility, biodegradability, non-antigenicity and adsorption properties [68, 69]. The mechanical and biological properties of chitosan scaffolds could be improved by the incorporation of bioceramics, such as HA, β-tricalcium phosphate and calcium phosphate biomaterials, such as gelatin alginate, or inorganic material, such as wollastonite [70, 71]. Chitosan scaffolds are osteoconductive and can enhance bone formation both in vitro and in vivo [72]. Currently, the development of chitosan-nanohydroxyapatite (nHA) composites through in situ hybridization by ionic diffusion processes, freezing and lyophilization, stepwise co-precipitation, and mineralization via double diffusion are being undertaken successfully [73-75].

#### **3. Surface functionalization of titanium implants**

The long-term success of dental implants also depends on the complex **biointegration** of these alloplastic materials, determined by the responses of the different surrounding host tissues. The osteoinductivity of calcium phosphate coatings has attracted significant interest, using various coating techniques, including plasma spraying, magnetron sputtering, electrophoretic deposition, hot isostatic pressing, sol-gel deposition, pulsed laser deposition, ion beam dynamic mixing deposition, electrospray deposition, biomimetic deposition, and electrolytic deposition [76]. Non-ceramic implant coating is also used, allowing for drug incorporation during the coating process. The currently available techniques can be broadly divided into three categories, including hydrogel coatings, layer-by-layer coatings, and immobilization. Techniques such as 'dip-coating' methods and 'layer-by-layer' (LbL) coating techniques are used for the incorporation of BMP-2 and TGF-β1 to the implant surface [77].

**Figure 4.** a) Scanning electron microscopic pictures of HAP microspheres; b) high-resolution SEM picture showing in‐ terconnected nanopores.

#### **3.1. Nanotubular titanium surface**

Nanotubular titania structures can be readily fabricated via direct anodization of titanium implants into an electrochemical cell that uses the titanium as an anode and platinum as a cathode in the presence of fluorine-based electrolytes [78, 79]. Penicillin-based antibiotics could be loaded to the nanotubular titania as a drug delivery platform by co-precipitating the drug and calcium phosphate crystals onto the nanostructures [80, 81].

Anodic oxidation has many advantages for surface modification, such as its ability to fabricate porous TiO2 films through dielectric breakdown, the changeability of the crystalline structure and the chemical composition of the oxide film depending on the fabrication conditions, and it has been suggested to provide storage room for the delivery of GFs, such as rhBMP-2, to enhance osseointegration [82, 83]. In vitro studies have suggested that a dose response could be produced with appropriate period of delivery of the GF to the cells [84].

**Figure 5.** Scanning electron microscopic image of an anodized titanium implant surface showing uniform nano-tubules of titanium oxide throughout the surface.

#### **3.2. Hydroxyapatite**

biomaterials, such as gelatin alginate, or inorganic material, such as wollastonite [70, 71]. Chitosan scaffolds are osteoconductive and can enhance bone formation both in vitro and in vivo [72]. Currently, the development of chitosan-nanohydroxyapatite (nHA) composites through in situ hybridization by ionic diffusion processes, freezing and lyophilization, stepwise co-precipitation, and mineralization via double diffusion are being undertaken

The long-term success of dental implants also depends on the complex **biointegration** of these alloplastic materials, determined by the responses of the different surrounding host tissues. The osteoinductivity of calcium phosphate coatings has attracted significant interest, using various coating techniques, including plasma spraying, magnetron sputtering, electrophoretic deposition, hot isostatic pressing, sol-gel deposition, pulsed laser deposition, ion beam dynamic mixing deposition, electrospray deposition, biomimetic deposition, and electrolytic deposition [76]. Non-ceramic implant coating is also used, allowing for drug incorporation during the coating process. The currently available techniques can be broadly divided into three categories, including hydrogel coatings, layer-by-layer coatings, and immobilization. Techniques such as 'dip-coating' methods and 'layer-by-layer' (LbL) coating techniques are

**Figure 4.** a) Scanning electron microscopic pictures of HAP microspheres; b) high-resolution SEM picture showing in‐

Nanotubular titania structures can be readily fabricated via direct anodization of titanium implants into an electrochemical cell that uses the titanium as an anode and platinum as a cathode in the presence of fluorine-based electrolytes [78, 79]. Penicillin-based antibiotics could

used for the incorporation of BMP-2 and TGF-β1 to the implant surface [77].

**3. Surface functionalization of titanium implants**

successfully [73-75].

246 Current Concepts in Dental Implantology

terconnected nanopores.

**3.1. Nanotubular titanium surface**

Coating of titanium implant surfaces with HA has shown better integration with bone. HA can be coated to the surface by plasma spraying, sputtering, pulse laser deposition and electrostatic multilayer assemblies, fabricated using the layer-by-layer technique [85]. HA coatings enhance new bone formation on implant surfaces with a line-to-line fit, in areas with

**Figure 6.** a) An anodized titanium implant; b) An anodized titanium implant coated with hydroxyapatite.

gaps of 1-2 mm between the coated implant and the surrounding bone. The coating also helps to prevent the formation of fibrous tissue that would normally result due to the micromovements of an uncoated titanium implant [86].

HA coatings have been used as a method for the delivery of GFs, bioactive molecules, and DNA [85, 87, 88]. HA coatings augmented with bone morphogenetic protein-7 (BMP-7), placed on segmental femoral diaphyseal replacement prostheses, improved bone ingrowth in a canine extra-cortical bone-bridging model. Titanium alloy plasma-sprayed porous HA coatings, infiltrated with collagen, recombinant human bone morphogenetic protein (rhBMP-2) and RGD peptide, improved mesenchymal stem cell (MSC) adhesion, proliferation and differen‐ tiation in vitro and increased bone formation in ectopic muscle and intra-osseous locations in vivo [85].

Another group used hydroxyapatite nanoparticles complexed with chitosan into nanoscale non-degradable electrostatic multilayers, which were capped with a degradable poly(b-amino ester)-based film incorporating physiological amounts of rhBMP-2 [89]. Plasmid DNA, bound to calcium phosphate coatings deposited on poly-lactide-co-glycolide (PLG), was shown to be released in vitro according to the properties of the mineral and solution environment [87]. These methods of delivery of bioactive molecules extended the function of HA as a coating to enhance new bone formation around implants.

#### **3.3. Antibiotics: Surface tethering of antibiotics**

The initial adhesion and colonization of bacteria to an implant surface are considered to play key roles in the pathogenesis of infections related to biomaterials [90]. Two recent strategies are: (1) coating implants with antibiotics; and (2) covalently attaching antimicrobial molecules onto the implant surface. The objective of these bioactive surfaces is to disrupt the colonization

**Figure 7.** Hydroxyapatite-coated titanium implant.

gaps of 1-2 mm between the coated implant and the surrounding bone. The coating also helps to prevent the formation of fibrous tissue that would normally result due to the micro-

**Figure 6.** a) An anodized titanium implant; b) An anodized titanium implant coated with hydroxyapatite.

HA coatings have been used as a method for the delivery of GFs, bioactive molecules, and DNA [85, 87, 88]. HA coatings augmented with bone morphogenetic protein-7 (BMP-7), placed on segmental femoral diaphyseal replacement prostheses, improved bone ingrowth in a canine extra-cortical bone-bridging model. Titanium alloy plasma-sprayed porous HA coatings, infiltrated with collagen, recombinant human bone morphogenetic protein (rhBMP-2) and RGD peptide, improved mesenchymal stem cell (MSC) adhesion, proliferation and differen‐ tiation in vitro and increased bone formation in ectopic muscle and intra-osseous locations in

Another group used hydroxyapatite nanoparticles complexed with chitosan into nanoscale non-degradable electrostatic multilayers, which were capped with a degradable poly(b-amino ester)-based film incorporating physiological amounts of rhBMP-2 [89]. Plasmid DNA, bound to calcium phosphate coatings deposited on poly-lactide-co-glycolide (PLG), was shown to be released in vitro according to the properties of the mineral and solution environment [87]. These methods of delivery of bioactive molecules extended the function of HA as a coating to

The initial adhesion and colonization of bacteria to an implant surface are considered to play key roles in the pathogenesis of infections related to biomaterials [90]. Two recent strategies are: (1) coating implants with antibiotics; and (2) covalently attaching antimicrobial molecules onto the implant surface. The objective of these bioactive surfaces is to disrupt the colonization

movements of an uncoated titanium implant [86].

248 Current Concepts in Dental Implantology

enhance new bone formation around implants.

**3.3. Antibiotics: Surface tethering of antibiotics**

vivo [85].

of the microbes or to prevent bacterial adhesion to the implant and subsequent development of biofilm [91]. Hydrophilic surfaces have been shown to be less prone to become infected with microorganisms than hydrophobic surfaces [92]. The topical application of antibiotics on the implant surface might be more efficient because bacteria are killed locally directly upon binding, before the formation of biofilm. Local delivery of antibiotics has long been applied in bone cements used to repair orthopedic and dental implants [93].

Antibiotics such as gentamicin are incorporated into the cement, which slowly releases the drugs after setting *in situ*. Local delivery can prevent adhesion and growth of significant numbers of bacteria. HA coatings are frequently applied to dental implants to stimulate osseointegration and to accelerate bone formation. Antibiotics can be co-precipitated on titanium surfaces to obtain drug-releasing surface coatings. Studies have shown that antibi‐ otics with optimal calcium-chelating properties had long lasting antimicrobial properties [94, 95]. Alt et al [96] demonstrated that both gentamicin-hydroxyapatite and gentamicin-RGD (arginine-glycineaspartate)-HA coatings could release antibiotics for up to twenty-four hours without inhibiting new bone formation. Erythromycin-impregnated strontium-doped calcium polyphosphate (SCPP) was found to inhibit bacterial growth completely for up to 14 days [97] Nanoporous implants are suitable for the incorporation of antibiotics to obtain controlled release of drugs [98]. Nanostructured surfaces play a major role in advanced biomedical implant design because these surfaces have been studied for their enhanced bioactive prop‐ erties, as well as their antagonistic behavior toward bacterial colonization. To maintain sustained drug elution properties and better bone bonding ability, significant efforts have been undertaken to develop bioactive hollow nanostructures on implant surfaces [99]. In this context, one of the implant titania nanotubular surfaces created via anodization showed enhanced bioactivity, conjugated with the capacity to store diverse compounds and control their elution. The anodization technique could create porous structures with controlled sizes of three-dimensional networks on metallic surfaces [100].

Anodization followed by HA coating was adopted as a surface modification technique to make drug-loadable Ti implants for dental applications. Self-organized titania nano-tubes were grown on titanium substrate as drug-carrying vehicles by coating HA ceramic using laser deposition. Nanostructured surfaces were achieved on titanium via anodization in a glycerol-NH4F electrolyte system, followed by annealing. The nano-tubules were then capped with HA deposited with pulsed laser ablation. HA-coated polished titanium, nano-structured titanium and hydroxyapatite coated nano-structured titanium were analyzed for their drug-carrying capacity using gentamicin sulfate. The ceramic-coated anodized substrates were found to be most efficient among the aforementioned three compounds in controlled delivery for longer than 160 h, with drug content of 0.5 µg/cm2 , compared to the anodized substrate, which delivered the whole drug within 140 h. It was thus evident that laser deposition facilitated the controlled release of drug, compared to the anodized and bare substrates. This study proposed the application of laser deposition of bioceramics, such as HA, over nano-structured titanium for drug-eluting metallic implants [101].

#### **3.4. Tan-Ag coatings**

Due to the risk of the development of antibiotic resistance associated with antibiotic-loaded coatings, non-antibiotic agents in the coating have been used as alternatives. Among the various dopants, silver nanoparticles are among the most popular agents used due to their inhibition of bacterial adhesion, broad anti-bacterial spectrum, long lasting anti-bacterial effects, and propensity for being less prone to the development of resistance. Ag and Cu are known to be efficient antibacterial agents because of their specific antimicrobial activity and the nontoxicity of active Ag and Cu ions to human cells [102, 103]. Sputter coating of Ag, along with HA, resulted in an antibacterial-bioactive coating, which inhibited bacterial attachment without cytotoxic effects [104]. TaN-Ag nano-composite coating of titanium dental implants also showed significant antibacterial properties without any cytotoxic effects. Hence, it could be concluded that coating of titanium implants with materials having antimicrobial properties might be useful in preventing infection [105].

#### **3.5. Bisphosphonate**

Bisphosphonates (BPs) constitute a group of drugs that inhibit osteoclast action and the resorption of bone, and they are used to treat metabolic diseases such as osteoporosis, Paget's disease, hypercalcemia of malignancy and multiple myeloma [106]. The nitrogen-containing BPs are more potent, and they accumulate in maximum concentrations in the matrix and osteoclasts [107]. BPs have a high affinity for bone minerals and bind strongly to HA, resulting in selective uptake to the target organ and high local concentrations in bone, particularly at sites of active bone remodeling. The BPs have similar chemical structures to pyrophosphate, but their chemical stability is greater. In pyrophosphates, the phosphate group is bonded through phosphoanhydride bond (P-O-P), whereas in BP, P is bonded through a germinal carbon atom (P-C-P); hence, these bonds are resistant to hydrolysis under acidic conditions [108]. The affinity of BP to Ca2+ ions helps to target specific bony sites, and BP can be coupled with a gamma-emitting radioisotope, such as technetium, for simultaneous bone scanning [109]. BPs inhibit osteoclast differentiation, reduce their activity, and induce their apoptosis [110]. The nitrogen-containing BPs bind to and inhibit farnesyl pyrophosphate synthase (FPPS), a key enzyme of the mevalonate pathway, thereby preventing the prenylation and activation of small GTPases, which are essential for the bone-resorption activity and survival of osteoclasts [111].

Systemic and local delivery of BPs improved the osseointegration of dental implants in osteoporotic animal models [112-116]. Improved osseointegration and the mechanical stability of titanium implants were reported in ovariectomized rats supplemented with alendronate [112]. Kurth et al [113] showed enhanced integration of HA-coated titanium implants via the administration of ibandronate to osteoporotic rats. Similar observations of enhanced osseoin‐ tegration have been reported in other studies via the local release of BPs (pamidronate and zoledronic acid) from the surface coatings of implants [115, 116]. An experimental study in an ovariectomized rabbit model showed that systemic zoledronic acid (ZA) administration improved the osseointegration of titanium implants [117].

#### **3.6. Simvastatin**

Nanoporous implants are suitable for the incorporation of antibiotics to obtain controlled release of drugs [98]. Nanostructured surfaces play a major role in advanced biomedical implant design because these surfaces have been studied for their enhanced bioactive prop‐ erties, as well as their antagonistic behavior toward bacterial colonization. To maintain sustained drug elution properties and better bone bonding ability, significant efforts have been undertaken to develop bioactive hollow nanostructures on implant surfaces [99]. In this context, one of the implant titania nanotubular surfaces created via anodization showed enhanced bioactivity, conjugated with the capacity to store diverse compounds and control their elution. The anodization technique could create porous structures with controlled sizes

Anodization followed by HA coating was adopted as a surface modification technique to make drug-loadable Ti implants for dental applications. Self-organized titania nano-tubes were grown on titanium substrate as drug-carrying vehicles by coating HA ceramic using laser deposition. Nanostructured surfaces were achieved on titanium via anodization in a glycerol-NH4F electrolyte system, followed by annealing. The nano-tubules were then capped with HA deposited with pulsed laser ablation. HA-coated polished titanium, nano-structured titanium and hydroxyapatite coated nano-structured titanium were analyzed for their drug-carrying capacity using gentamicin sulfate. The ceramic-coated anodized substrates were found to be most efficient among the aforementioned three compounds in controlled delivery for longer

delivered the whole drug within 140 h. It was thus evident that laser deposition facilitated the controlled release of drug, compared to the anodized and bare substrates. This study proposed the application of laser deposition of bioceramics, such as HA, over nano-structured titanium

Due to the risk of the development of antibiotic resistance associated with antibiotic-loaded coatings, non-antibiotic agents in the coating have been used as alternatives. Among the various dopants, silver nanoparticles are among the most popular agents used due to their inhibition of bacterial adhesion, broad anti-bacterial spectrum, long lasting anti-bacterial effects, and propensity for being less prone to the development of resistance. Ag and Cu are known to be efficient antibacterial agents because of their specific antimicrobial activity and the nontoxicity of active Ag and Cu ions to human cells [102, 103]. Sputter coating of Ag, along with HA, resulted in an antibacterial-bioactive coating, which inhibited bacterial attachment without cytotoxic effects [104]. TaN-Ag nano-composite coating of titanium dental implants also showed significant antibacterial properties without any cytotoxic effects. Hence, it could be concluded that coating of titanium implants with materials having antimicrobial properties

Bisphosphonates (BPs) constitute a group of drugs that inhibit osteoclast action and the resorption of bone, and they are used to treat metabolic diseases such as osteoporosis, Paget's

, compared to the anodized substrate, which

of three-dimensional networks on metallic surfaces [100].

than 160 h, with drug content of 0.5 µg/cm2

for drug-eluting metallic implants [101].

might be useful in preventing infection [105].

**3.4. Tan-Ag coatings**

250 Current Concepts in Dental Implantology

**3.5. Bisphosphonate**

Statins are prescribed to decrease cholesterol biosynthesis by the liver, thereby reducing serum cholesterol concentrations and lowering the risk of heart attack. A liposoluble statin, simvas‐ tatin, could induce the expression of bone morphogenetic protein (BMP) 2 mRNA and, as a result, promote bone formation on the calvaria of mice following daily subcutaneous injections [118, 119]. Another study showed that the topical application of statins to alveolar bone increased bone formation and concurrently suppressed osteoclast activity at the bone healing sites [120]. Yang et al [119] demonstrated that simvastatin-loaded porous titanium surface potently increased ALP activity and the extracellular accumulation of proteins, such as osteocalcin and type I collagen, in mouse preosteoblast MC3T3-E1 cells. Du et al [121] dem‐ onstrated that administration of simvastatin resulted in significant improvement in the osseointegration of titanium implants in osteoporotic rats. This finding could be attributed to the increased expression of bone morphogenic protein 2, which stimulates osteoblast differ‐ entiation [118]. Statins are known to enhance the expression of VEGF (vascular endothelial growth factor), a bone anabolic factor, in osteoblasts and to regulate osteoblast function by increasing the expression of bone sialoprotein (BSP), osteocalcin (OCN), and type I collagen (COL-I), as well as suppressing the gene expression of collagenases, such as matrix metallo‐ proteinase (MMP)-1 and MMP-13 [122, 123]. Thus the competitive inhibition of simvastatin interferes with the malevonate pathway, leading to decreased protein prenylation, which is necessary for normal osteoclast function [118].

**Figure 8.** A trabecular implant that could be used to load drugs.

#### **3.7. Calcitonin**

Calcitonin (CT), produced by the C-cells of thyroid tissue, has been reported to stimulate hard tissue formation [124]. It acts on bone tissue via the suppression of osteolysis and the induction of Ca2+ release. It was reported that CT inhibited osteoclastic bone resorption by binding to specific cell surface receptors [125]. This hormone favors bone formation, inhibits osteoclastic activity and prevents osteopenia [126-128]. In vitro and in vivo studies have shown that this hormone stimulates the growth of bone tissue [40, 129, 130]. Calcitonin also showed increases in the amount and rate of bone formation, as observed in rat calvaria and extraction sockets in dogs [131].

#### **3.8. Pantaprazole**

A class of substituted benzimidazoles known as proton pump inhibitors (PPIs) have been shown to promote bone regeneration and peri-implant healing. Examples of these drugs include omeprazole and pantoprazole, which are employed clinically in the treatment of gastroesophageal reflux disorder (GERD). PPI-loaded calcium phosphate cements demon‐ strated not only inherent biocompatibility and osteoconductivity but also the ability to retard bone resorption through a drug delivery mechanism [132, 133]. Pantoprazole-loaded calcium phosphate cements inhibited osteoclastic resorption without interfering with the peri-implant bone resorption rate in a study performed rat femoral condyles [134]. Another advantage of the addition of omeprazole is that it inhibits osteoclastic acidification, which help to inhibit bone resorption and increases the lifespan of osteoclasts [135]. The drugs were dissolved in dimethyl sulfoxide to the desired concentration and were added to the liquid phase of the calcium phosphate.

#### **4. Conclusions**

proteinase (MMP)-1 and MMP-13 [122, 123]. Thus the competitive inhibition of simvastatin interferes with the malevonate pathway, leading to decreased protein prenylation, which is

Calcitonin (CT), produced by the C-cells of thyroid tissue, has been reported to stimulate hard tissue formation [124]. It acts on bone tissue via the suppression of osteolysis and the induction of Ca2+ release. It was reported that CT inhibited osteoclastic bone resorption by binding to specific cell surface receptors [125]. This hormone favors bone formation, inhibits osteoclastic activity and prevents osteopenia [126-128]. In vitro and in vivo studies have shown that this hormone stimulates the growth of bone tissue [40, 129, 130]. Calcitonin also showed increases in the amount and rate of bone formation, as observed in rat calvaria and extraction sockets

A class of substituted benzimidazoles known as proton pump inhibitors (PPIs) have been shown to promote bone regeneration and peri-implant healing. Examples of these drugs include omeprazole and pantoprazole, which are employed clinically in the treatment of gastroesophageal reflux disorder (GERD). PPI-loaded calcium phosphate cements demon‐

necessary for normal osteoclast function [118].

252 Current Concepts in Dental Implantology

**Figure 8.** A trabecular implant that could be used to load drugs.

**3.7. Calcitonin**

in dogs [131].

**3.8. Pantaprazole**

Drug delivery systems (DDS) targeting specific organs and tissues and their bioavailability at specific sites have become critical issue in modern medicine. Local drug delivery systems in bone could be used to promote regeneration, prevent infection, or treat post-surgical pain. The quest for new bone scaffold materials to overcome the shortcomings of existing materials, such as ceramics and polymers, is undertaken to overcome the limited mechanical properties required for temporary bone substitutes. Mixing of polymers, natural or synthetic, and inorganic components, such as HA, TCP and BG, might help to develop better composite scaffolds that combine the advantages of both biodegradable polymers and bioactive ceramics [136].

If DDS are used in combination with implants, the coating strategies should allow for the choice of a drug or combination of drugs and their doses, localization and release due to intraoperative considerations. HA coatings on titanium implants themselves provide an osteocon‐ ductive and an osteoinductive approach for the enhancement of bone formation. These biological properties could be augmented further by adding growth factors and other mole‐ cules to produce a truly osteoinductive platform.

Proteins or glycosaminoglycans, such as collagen and chondroitin sulfate, provide a biomi‐ metic coating on the surface of an implant, which can improve osseointegration [137]. Biomo‐ lecules such as GFs are also widely used for implant coatings, to modulate cellular functions, such as decreasing inflammation, enhancing stem cell differentiation, inducing blood vessel formation, or acting as chemoattractants for circulating osteoprogenitors [138, 139]. Although the implant materials available for the reconstruction of craniofacial bone defects have shown favorable results in most craniofacial and dental applications, the presence of complications related to infection and poor osseointegration still represent challenges in the biomedical field.

The current trend in the field of bone repair indicates that the tissue engineering field is moving toward the development of biomaterials with improved surfaces that will stimulate bone formation and avoid infections through the incorporation of surface modification techniques and antibacterial coatings and agents, as well as the incorporation of GFs, stem cells and other pharmacological drugs.

### **Author details**

Sukumaran Anil1\*, Asala F. Al-Sulaimani2 , Ansar E. Beeran3 , Elna P. Chalisserry4 , Harikrishna P.R. Varma3 and Mohammad D. Al Amri5

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

1 Department of Periodontics and Community Dentistry, College of Dentistry, King Saud University, Riyadh, Saudi Arabia

2 King Saud University, Riyadh, Saudi Arabia

3 Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences & Technology, Poojappura, India

4 College of Dentistry, King Saud University, Riyadh, Saudi Arabia

5 Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University, Riyadh, Saudi Arabia

#### **References**


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**Author details**

Harikrishna P.R. Varma3

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2 King Saud University, Riyadh, Saudi Arabia

, Ansar E. Beeran3

1 Department of Periodontics and Community Dentistry, College of Dentistry, King Saud

and Mohammad D. Al Amri5

3 Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences &

5 Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University,

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### *Edited by Ilser Turkyilmaz*

Implant dentistry has changed and enhanced significantly since the introduction of osseointegration concept with dental implants. Because the benefits of therapy became apparent, implant treatment earned a widespread acceptance. Therefore, the need for dental implants has caused a rapid expansion of the market worldwide.

Dental implantology continues to excel with the developments of new surgical and prosthodontic techniques, and armamentarium. The purpose of this book named Current Concepts in Dental Implantology is to present a novel resource for dentists who want to replace missing teeth with dental implants. It is a carefully organized book, which blends basic science, clinical experience, and current and future concepts. This book includes ten chapters and our aim is to provide a valuable source for dental students, post-graduate residents and clinicians who want to know more about dental implants.

Current Concepts in Dental Implantology

Current Concepts in

Dental Implantology

*Edited by Ilser Turkyilmaz*

Photo by edwardolive / iStock