**3.2 Etiology and pathogenesis of iatrogenic TMDs**

TMDs of iatrogenic etiology have a multicomponent pathogenetic structure. To determine the set of heterogeneous data in the clinical picture of TMDs, we used a system-structural analysis. This will make it possible to identify the paths of pathogenetic transformation of preclinical forms of TMDs into iatrogenic disease (**Figure 1**). Preclinical forms are predictors of TMDs of iatrogenic etiology, which we have classified as iatrogenic etiological risks.

Unidentified iatrogenic etiological risks (IERs) remain at the risk level until the treatment phase. Implementing incorrectly planned therapy brings the IER out of the "sleep state." The transition of preclinical forms of TMDs from the level of IER to the level of iatrogenic pathogenetic factors (IPFs) begins. IPF trigger the iatrogenic disease. Thus, TMDs of iatrogenic etiology result from the transformation of iatrogenic etiological risks into iatrogenic pathogenic factors and iatrogenic disease (**Table 2**).

Failure to identify iatrogenic etiological risks at the diagnostic stage leads to incorrect therapy planning for TMDs. IER predictors are biological, technological, and communicational (psychosocial) forms of risk (**Figure 1**). IERs do not run in isolation and mutually overlap each other.

Biological risks account for 85% of the total share of risks. They are formed in ontogeny and should do identified at the diagnostic stage. According to the level of violations, we single out iatrogenic biological risks of the macrosystem and intrasystem levels.

Biological iatrogenic risks at the macrosystem level:


**Figure 1.** *Structure of shares of iatrogenic risks.*

*Temporomandibular Disorders of Iatrogenic Etiology DOI: http://dx.doi.org/10.5772/intechopen.104479*

#### **Table 2.**

*Pathways of pathogenetic transformation of nosological forms—Precursors of TMDs.*


Biological iatrogenic risks of intrasystem level:


4. signs of undifferentiated forms of connective tissue dysplasia at the level of the articulation system: dysfunction of the TMJ; the high vault of the palate; dental anomalies; and short frenulum of the tongue.

Technological iatrogenic risks result from a violation of the protocol for examining a patient with TMDs at the diagnostic stage. For example, insufficient volume examination does not correctly collect the necessary diagnostic data, based on which the final diagnosis does formulate and treatment does plan. In such cases, the decision on the method of treating the disease and, in particular, the use of medical technologies to correct the contact of the dentition, the ratio of the jaws, and the function of the masticatory muscles is methodologically incorrect. Therefore, it leads to the development of iatrogenic disease.

Phenomenological dysfunctions constitute a significant component of communication iatrogenic risks. Communication iatrogenic risks are formed at the stage of diagnosis and manifest themselves in the form of a high level of treatment success expected by the patient, formed by the doctor. Unjustified expectations built into previous consultations form a communication gap between doctor and patient. TMD is a multifactorial disease based on reliably identified risk factors – phenomenological dysfunctions, complicated by psychosomatic disorders that prevail over peripheral nociceptive factors.

When formulating a diagnosis and choosing a medical technology, all unknown iatrogenic etiological risks transform into iatrogenic pathogenetic factors and, in association with other already identified clinical symptoms, form a new symptom complex – TMDs of iatrogenic etiology. Thus, at a new stage in the development of the disease, pathogenetic iatrogenic factors formed from iatrogenic pathogenetic risks are revealed. In the structure of the pathogenesis of iatrogenic TMDs, there is a change in the share of influence of pathogenetic iatrogenic factors – biological factors give way to technological factors (**Figure 2**). This is the result of the hidden influence of unknown iatrogenic risks on the pathogenesis of the disease and the implemented therapeutic and technological solutions. The implemented medical technology aggravates the disease and forms new TMDs of iatrogenic etiology.

### **4. Conclusions**

Thus, in order to avoid such complications as TMDs of iatrogenic etiology in one's practice, it is necessary at the diagnostic stage to identify preclinical forms of TMDs that can initiate the development of iatrogenic disease. Incorrect use of diagnostic methods and procedures is the leading cause of the occurrence and development of iatrogenic TMDs.

Biological risks not identified at the diagnostic stage at the treatment planning stage become the cause of iatrogenic pathogenetic factors and iatrogenic disease. If iatrogenic etiological risks are not identified and do not define as symptoms, they do not consider when formulating a diagnosis or choosing a medical technology. The diagnostic stage is the stage of missed opportunities, at which it is possible to avoid the occurrence of iatrogenic disease. Therefore, the diagnostic stage tests the professional competencies of the clinic. Thus, undiagnosed iatrogenic risks cause the formation of iatrogenic pathogenic factors, the failure to identify which leads to an incorrectly formulated or preliminary clinical diagnosis, treatment plan, negative outcome of therapy, and iatrogenic TMDs. Incorrect diagnosis > incorrect diagnosis > incorrect

#### **Figure 2.**

*Structure of shares of iatrogenic pathogenic factors.*

choice of medical technology > TMDs of iatrogenic etiology. Timely diagnosis of iatrogenic risks is the main preventive measure that prevents the development of iatrogenic TMDs.

## **5. Clinical example**

Patient K does treat in a previous clinic with a diagnosis of TMDs. She received occlusal therapy using a disengaging occlusal splint (**Figure 3**).

She does admit to our clinic with complaints of limited mouth opening, facial pain, and tooth contact problems. Using DC/TMD tools, we conducted a comprehensive examination of the functional and anatomical state of the articulation system and the psychosocial sphere. Examination of the CBCT of the TMJ with and without an occlusal splint revealed distal position and deformity of the TMJ head surfaces. MRI of the TMJ revealed an unreduced disk dislocation with ligament rupture (**Figures 4** and **5**).

Using an occlusal uncoupling splint in the mandible resulted in destabilization of the TMJ heads, displacement of the TMJ disk into an anterior-internal position, and a sizeable horizontal-to-vertical dentition ratio. Thus, the insufficient amount of applied methods for visualizing TMJ structures without considering data on soft tissue elements obtained by MRI is the cause of a diagnostic error, an incorrect diagnosis, and unreasonable treatment planning. Occlusal therapy uses an occlusal splint, which does indicate in preparation for the surgical solution of the problem, and not as the leading therapeutic solution (**Figure 3**).

Final clinical diagnosis: Deforming arthrosis of the TMJ; unreduced anterior dislocation of the TMJ disk on the right and subluxation on the left; the distal position of the heads of the lower jaw; instability of occlusion in the area of 4.4, 4.5, and 4.6 teeth with a decrease in bite height. Moderate anxiety. First-degree disability.

#### **Figure 3.**

*Photo of patient K. Phantom bite formed by an occlusal splint. A – An occlusal disconnecting tire is superimposed on the lower dentition; B – Occlusal slave splint removed from the oral cavity; C – The position of the dentition in the intertubercular position, a phantom bite is formed.*

#### **Figure 4.**

*MRI of the TMJ. A – Anterolateral location of the disk without reduction (↑↑↑) in the left TMJ. B – Anterolateral disk location without reduction with partial rupture of the posterior discotemporal ligament (↑↑↑) of the right TMJ.*

An unreasonable attempt to eliminate anatomical and functional disorders of the jaw ratio by separating the dentition led to the transformation of the IER in the direction of the IPF. For this reason, the phantom bite of iatrogenic etiology and TMDs of iatrogenic etiology have formed. We identified primary etiological factors (iatrogenic biological risks and anatomical pathogenetic factors, i.e. mismatch of the

**Figure 5.** *MRI of the TMJ. Rupture of the posterior ligaments of the TMJ disk.*

anatomical size, shape, and position of the bones of the facial part of the skull) and secondary etiological factors (crowded position and disruption of dynamic and static contacts of the teeth). The use of an occlusal disconnecting splint led to disk rupture and forced bite formation. In such clinical cases, it is impossible to compensate for anatomical (organ) risks by affecting only occlusal risks, changing the interocclusal height without considering the horizontal-vertical ratio of the dentition. Therefore, it does decide to prepare for reorganizing occlusal therapy with an occlusal stabilizing splint, provisional prosthetics, and pharmacotherapy in combination with CBPC. The use of an occlusal stabilizing splint makes it possible to stabilize the horizontal-vertical ratio of the jaws to model and carry out intraoral verification of occlusal guiding movements of the lower jaw in the protrusion and laterotrusion directions.

Failure to identify iatrogenic biological risks of the macrosystem and intrasystem levels in the patient led to an incorrect diagnosis formulation and incorrect therapy planning. The splint design does make on the lower jaw dentition without considering the vertical-horizontal ratio of the jaws, protrusion, and laterotrusion guides. Overlapping the frontal group of teeth with a splint led to the distalization of the lower jaw. After 2 years of wearing the splint, a phantom bite developed, characterized by lower jaw distalization, occlusion instability, pain syndrome, and TMJ dysfunction.

The use of dissociating occlusal devices, the manufacture of which did not consider the anatomical and functional conditions of occlusal guiding movements of the lower jaw in the protrusion and laterotrusion directions in conjunction with the horizontalvertical ratio of the jaws, is the cause of the formation of two types of iatrogenies:

1. Iatrogenia are formed by a dissociating occlusal splint and superimposed on the lower jaw with overlapping of the occlusal surface of the teeth of the frontal section. The frontal occlusal platform, when the dentition is closed, slides along

**Figure 6.**

*Photo of the dentition of the patient P. Disconnecting occlusal tire on the lower dentition with overlapping of the frontal group of teeth.*

the palatal surface of the incisors of the upper jaw and moves the lower jaw distally to a distance corresponding to the amount of desocclusion, i.e. the thickness of the overlap of the lower jaw incisors by the occlusal platform, which leads to a change in the excursions of the TMJ heads and the transfer of the load vector from vector to tangential. This causes pathological mobility, and frontal dislocation of the upper anterior group of teeth causes gum recession in the lower jaw (**Figure 6**).

When visualizing the TMJ by CT, the distal position of the heads is revealed with a critical approach to the neurovascular bundle in the petrotympanic fissure. The nature of the movements of the head of the lower jaw changes: it performs only rotational movements, the stage of sliding down and forward is replaced by a horizontal movement toward the slope of the tubercle. When visualizing soft tissue elements by MRI in all functional positions, anterior, at 8 or 10 o'clock, disk displacement is diagnosed, which leads to the formation of disk dislocation without self-reduction. The posterior ligaments of the disk experience pathological stresses, stretch, and lose their ability to regulate disk excursions.

#### **Figure 7.**

*Photo of patient E's teeth with an occlusal disconnecting splint made on the lower dentition without considering the occlusal guiding movements of the lower jaw in the frontal and laterotrusive planes. View at the initial visit after treatment for 2 years in another clinic.*

The vascular-nervous elements in the bilaminar zone experience compression of the TMJ head, which leads to fluid effusion in this area, the formation of a pain syndrome, a decrease in hearing acuity, and a symptom of a foreign body in the middle ear.

2. Iatrogenia are formed as a result of anatomically unreasonable use of an uncoupling occlusal device in the area of the chewing group of teeth. There is a loss of occlusal guides and the posterior contact position of the mandible (**Figure 7**). On CT, this is manifested by the displacement of the head of the mandible vertically downward and backward. MRI shows disk rupture, tear, and overstretching of the TMJ ligaments.
