Temporomandibular Disorders: Effects of Occlusion, Orthodontic Treatment, and Orthognathic Surgery

Published on 13/06/2015 by admin

Filed under Surgery

Last modified 22/04/2025

Print this page

This article have been viewed 2326 times

Temporomandibular Disorders

Effects of Occlusion, Orthodontic Treatment, and Orthognathic Surgery

Jeffrey C. Posnick, DMD, MD

Incidence of Temporomandibular Disorders in the General Population and the Basic Treatment Approach

The prevalence of temporomandibular disorders (TMDs) in the general population as reported in the literature varies widely. It is estimated that an average of 32% of the population reports at least one symptom of TMD, whereas an average of 55% demonstrates at least one clinical sign.* Schiffman and colleagues completed a cross-sectional epidemiologic study that indicated that, at any given time, between 40% and 75% of individuals who were not currently seeking treatment had at least one sign of TMD, and about one third of individuals reported at least one symptom of TMD.²⁹⁶ Mongini and colleagues documented a prevalence of TMD symptoms in children and teenagers of 12% and 20%, respectively.²¹⁰ Wanman and colleagues showed an incidence of joint noise in young adults in their late teens to be as high as 17.5% over a 2-year period.³⁴⁵ TMDs remain a frequent cause of visits to primary care physicians, otolaryngologists, internists, and pediatricians. Despite the high incidence of TMDs, their natural history suggests that, in up to 40% of patients, symptoms resolve spontaneously.²⁹⁶

TMD includes various signs and symptoms of the temporomandibular joint (TMJ), the masticatory muscles, and related structures (Figs. 9-1 through 9-8). These may include a spectrum of referred head and neck pain; joint noise (e.g., popping, clicking, crepitus); reduced or altered mandibular range of movement as a result of muscle spasm or disc displacement; condylar head erosion; and direct pain on palpation of either the TMJ or the masticatory muscles. The signs and symptoms associated with TMDs can also lead to misdiagnosis.^{16,112,171,216,342}

Figure 9-1 A, Intraoral frontal view of dentition juxtaposed with the underlying alveolar bone. B, Intraoral lateral view of dentition juxtaposed with the underlying alveolar bone. From Okeson JP: Management of temporomandibular disorders and occlusion, St. Louis, 2012, Elsevier, p 3, Figures 1-1, A and B, 1-3, and 1-4.

Figure 9-2 Lateral view of the craniofacial skeleton. From Okeson JP: Management of temporomandibular disorders and occlusion, St. Louis, 2012, Elsevier, p 4, Figure 1-5.

Figure 9-3 Bony structures (components) of the temporomandibular joint. MF, Mandibular fossa; AE, articular eminence; STF, squamotympanic fissure. From Okeson JP: Management of temporomandibular disorders and occlusion, St. Louis, 2012, Elsevier, p 4, Figure 1-12.

Figure 9-4 Anterior cross-sectional view of the articular disc, the fossa, and the condyle. A, Illustration. B, Cadaver specimen. The disc adapts to the morphology of the fossa and the condyle. LP, Lateral pole; MP, medial pole. From Okeson JP: Management of temporomandibular disorders and occlusion, St. Louis, 2012, Elsevier, p 8, Figure 1-14.

Figure 9-5 A, Lateral view illustrations and B, cadaver specimen views of normal movement of the condyle and disc during vertical mouth opening. As the disc moves out of the fossa, it rotates posteriorly on the condyle. First, rotational movement occurs (predominantly in the lower joint space). After that, translation takes place (predominantly in the superior joint space) as mouth opening continues. A from Okeson JP: Management of temporomandibular disorders and occlusion, St. Louis, 2012, Elsevier, p 17, Figure 1-30. B courtesy Terry Tanaka, MD, San Diego, Calif.

Figure 9-6 Illustrations of the normal functional movement of the condyle and disc during the full range of opening and closing. The disc is rotated posteriorly on the condyle as the condyle is translated anteriorly out of the fossa. The closing movement is the exact opposite of the opening movement. From Okeson JP: Management of temporomandibular disorders and occlusion, St. Louis, 2012, Elsevier, p 19, Figure 1-31.

Figure 9-7 Illustration of rotational movement of the mandible. This movement occurs with the condyles in the terminal hinge position. This pretranslation opening will occur until the anterior teeth are approximately 20 to 25 mm apart. From Okeson JP: Management of temporomandibular disorders and occlusion, St. Louis, 2012, Elsevier, p 64, Figure 4-7.

Figure 9-8 The second stage of movement during mouth opening is illustrated. Note that the condyle is translated down the articular eminence as the mouth rotates open to its maximum limit. From Okeson JP: Management of temporomandibular disorders and occlusion, St. Louis, 2012, Elsevier, p 64, Figure 4-8.

A wide variety of often contradictory “conservative” treatment modalities (i.e., non-invasive or potentially reversible) have been recommended to alleviate the symptoms of TMD and to prevent recurrence.* Enthusiasm by clinicians for the direct surgical alteration of the structures that comprise the TMJ to treat TMD have waxed and waned over the past half century.^{60,71,141,143,200,222,241,344} Occlusal factors (i.e., degrees of malocclusion) are often claimed to be associated with TMD. Although it is sometimes stated that orthodontic treatment increases the prevalence of TMD, it is also claimed that orthodontic maneuvers (for at least some types of malocclusion) may reduce the signs and symptoms of TMD. Studies document that the correction of a baseline jaw deformity with malocclusion through orthodontics and orthognathic surgery improves the presenting TMD in the majority of the treated patients, whereas a minority get worse.^{6,29,31,67,102,131,152,232,236,347,349,356,359} This is described in greater detail later in this chapter.

Mandibular Range of Motion

The expected normal mandibular range of motion and inter-incisor mouth opening is discussed periodically in the literature.9,70,93,115,146,179,197,234,235,249,308,309,311–313,315,316,318 Even a 6-year-old child can often open the mouth to a maximum 40 mm or more. Measurements of maximum vertical mouth opening with and without discomfort are considered useful parameters of TMJ health. A restricted mouth opening is considered by many to be a distance of less than 40 mm. Only 1.2% of young adults open their mouths less than 40 mm. However, 15% of the healthy elderly population open their mouths less than 40 mm. Any lateral or protrusive movement of less than 8 mm is considered restricted, although the significance of this measurement is unclear.

Review of Occlusal Factors and Association with Temporomandibular Disorders

Clinicians from a spectrum of medical and dental specialties often consider malocclusion to be the major etiologic factor of TMD.^† An assumed strong association between TMD and the malpositioning of the teeth serves as one reason why the diagnosis and treatment of TMD is generally considered within the purview of dentistry. Many of the therapeutic options for the treatment of TMD are based on the idea of “normalizing” or “neutralizing” the occlusion.^135,355 Common treatment approaches to do so include the reversible use of an occlusal appliance or definitive techniques such as occlusal adjustment (equilibration), restorative dentistry, orthodontics, and orthognathic surgery. Concurrently, it is also true that either the onset of TMD or the worsening of current symptoms is frequently blamed on any one of the previously mentioned treatment regimens.

The dental literature contains clinical studies and reports that claim there are causal relationships between occlusal factors and the symptoms and signs associated with TMD. Egermark-Eriksson and colleagues examined 402 children and reported an association between signs and symptoms of TMD, specific malocclusions (i.e., Class II, Class III, anterior crossbite, and anterior open bite), and occlusal supra-contacts.⁸⁷ Brandt studied 1342 children and found a correlation between TMD and degrees of overbite (deep and open) and overjet.³³ Nilner examined 749 teenagers and young adults and reported an association with centric relation (CR)–centric occlusion (CO) discrepancies (i.e., slides), balancing-side contact slides, and symptoms and signs of TMD.²²⁰ Confusion in the literature arises as independent research studies have drawn contrary conclusions. DeBoever and colleagues examined 135 individuals with signs and symptoms of TMD and found no specific associations with malocclusion.⁵⁹ Gunn and colleagues similarly found no association between TMD and occlusion in 151 migrant children that they studied.¹²¹ Dworkin and colleagues examined 592 individuals within a specific health maintenance organization and found no association between TMD signs and symptoms and specific occlusions.⁸⁰

In their review article, Seligman and Pullinger pointed out that the majority of existing clinical research (up to that point in time) did not support a clear relationship between occlusion and TMD symptoms.³⁰² They further clarified that the majority of published research relied on symptom-based data rather than discrete disease classifications. Seligman pointed out that symptoms like joint sounds (e.g., popping, clicking, crepitus) and pain (e.g., in the TMJ region and the masticatory system) lack specificity.³⁰³ In addition, most published studies did not differentiate between TMD diagnostic categories (e.g., disc displacement, myalgia, TMJ osteoarthritis). Most published studies also suffered from a lack of or an inadequate control group. Seligman and colleagues attempted to avoid these shortcomings by completing a multifactorial analysis of the risks and relative odds of an individual having a TMD as a function of 1 of 11 common occlusal features.^259,304 They looked for correlations between each of these 11 specific occlusal factors (Box 9-1) and 1 of 6 TMJ diagnostic categories (Box 9-2), including asymptomatic normal controls without TMD.²⁵⁹

Box 9-2 Temporomandibular Joint Diagnostic Categories to Consider in TMD *

1. Disc displacement with reduction (N = 81)

2. Disc displacement without reduction (N = 48)

3. Temporomandibular joint osteoarthrosis with disc displacement history (N = 75)

4. Primary osteoarthrosis (N = 85)

5. Myalgia only (N = 124)

6. Asymptomatic normals (N = 147)

^*Data from Pullinger AG, Seligman DA, Gornbein JA: A multiple logistic regression analysis of the risk and relative odds of temporomandibular disorders as a function of common occlusal features. J Dent Res 72:968–979, 1993.

The asymptomatic control subjects (N = 147) were considered the reference standard because they were without current symptoms or signs of TMD and because they had no history of TMD. Occlusal findings in the symptomatic group showed wide variations, including the following:

• Overjets ranging from –1 to +6 mm

• Overbites ranging from –2 to +10 mm

• Midline discrepancies of up to 5 mm

• Anteroposterior molar relationships from –6 to +6 mm

• Molar asymmetries of 0 to 6 mm

• CR–CO slides of up to 2 mm

There were also a wide variety of crossbites, asymmetrical slides, posterior contacts, and severe attrition facets in the control group. Interestingly, no anterior open bites were found in the control group.

The authors concluded that what have been traditionally considered malocclusions cannot be used to define or predict either individuals with TMD or those who are or will become asymptomatic. No single occlusal factor was able to differentiate a TMD patient from a healthy subject. The authors did identify four specific occlusal features that occurred mainly in individuals who were symptomatic with TMD (see diagnostic categories 1 through 5) and that were rarely found in those who were asymptomatic for TMD (see diagnostic category 6). The occlusal features that primarily occurred in individuals with symptomatic TMD included the following:

1. The presence of a skeletal anterior open bite

2. CR-CO slides of more than 2 mm

3. Overjets of more than 4 mm

4. Five or more missing and unreplaced posterior teeth

Pullinger and colleagues concluded that occlusion cannot be considered the most important factor in the definition of TMD but that specific occlusal factors do make biologic contributions to TMD and thus cannot be ignored.254–261 In most individuals, they observed that the human biologic system will adapt to a variety of malocclusions in an attempt to achieve TMJ stability. The authors surmised that some occlusal features will place greater adaptive demands on the individual’s biologic system than others. Although most individuals are able to compensate for their occlusal disharmony without problems, adaptation for others may lead to a greater risk for TMD. On the basis of this data, the authors stressed the importance of five occlusal conditions, which in isolation or combination are more likely to reach the threshold that exceeds adaptation for an individual and therefore results in TMJ dysfunction. The high-risk malocclusions are discussed later in this chapter.

Occlusal Conditions More Frequently Associated with Temporomandibular Disorders

Anterior Open Bite

Research by Pullinger and colleagues showed a strong relationship between osteoarthritis of the condylar head with a loss of condylar height and an anterior open-bite malocclusion.254–261 Interestingly, anterior open bite was not commonly associated with disc displacement disorders with or without reduction. Myalgia (i.e., masticatory muscle discomfort) was also a frequent symptom among patients with an anterior open bite. It is not stated in what percentage of individuals the anterior open-bite malocclusion occurred only secondarily as a result of osteoarthritis followed by a loss of condylar height with clockwise rotation of the mandible. Therefore, it is unclear what percentage of the examined individuals with anterior open bites had these finding as part of a developmental jaw deformity.

Overjet (>6 to 7 mm)

In the patients that were studied, an overjet of more than 4 mm was more likely to be associated with osteoarthritis. Only when the overjet was more than 6 mm was there an association with disc displacement. The occurrence of a progressive overjet in adults would be suggestive of active condylysis. It was not stated in what percentage of those individuals with significant overjet (i.e., >6 to 7 mm) the occlusal feature was part of a developmental jaw deformity rather than occurring secondarily only after condylysis with a loss of condylar height.

Centric Relation–Centric Occlusion Slides

Limited occlusal slides (i.e., 1 mm) were common in all patient groups, including the normal controls. CR–CO slides of more than 2 mm were only found in the patients with TMDs. Pullinger found that larger slides were frequently associated with osteoarthritis of the condylar head. He questioned the advisability of the clinicians’ automatic attempt to “relieve” the occlusal slides in all individuals—whether by irreversible (e.g., occlusal equilibration, orthodontics, surgery, restorative dentistry) or reversible (e.g., occlusal splints) means—because the observed slide may be either adaptive or inconsequential.²⁶⁰

Note:

The studies by Pullinger and colleagues seem to confirm that the occlusal features of anterior open bites; overjets of more than 6 mm; and CR–CO slides of more than 2 mm are frequently seen in conjunction with osteoarthritis (i.e., loss of condylar height) and less commonly seen with disc displacement disease. Unfortunately, it is not clearly stated which came first: a developmental deformity with malocclusion and then osteoarthritis or condylysis with the loss of posterior facial height that results in a secondary jaw deformity with malocclusion.

Unilateral Maxillary (Lingual) Crossbite

The occlusal feature of unilateral maxillary crossbite occurs in about 10% of the adult population, and it is frequently found in association with TMJ disc displacement with or without disc reduction. Approximately 25% of the patients with non-reducing disc displacements were found to have unilateral maxillary lingual crossbites. This indicated to Pullinger and colleagues that disc displacement may be a biologic adaptive response of the individual to a unilateral maxillary lingual crossbite.²⁶⁰ The investigators theorized that these individuals may later be prone to osteoarthritis. They suggested that the orthodontic treatment of a unilateral crossbite discovered during childhood should be considered as a preventative measure to reduce the adaptive demands on the masticatory system. They did not come to the same conclusion for the correction of a longstanding unilateral posterior crossbite in an adult, because skeletal adaptation would have already occurred. Unfortunately, the investigators did not clarify if the crossbites in their study patients were the result of developmental jaw deformities (e.g., asymmetrical mandibular excess) or simply due to the malpositioning of the teeth. They did not specifically comment on whether orthognathic surgery should be carried out in conjunction with orthodontics (if needed) in young adults to correct the presenting malocclusion as a way to prevent the progression of TMD.

Missing Posterior Teeth (≥5)

The investigators found that, when five or more posterior teeth were missing, the incidence of TMD increased. This includes TMD categories of both osteoarthritis and disc displacement with or without osteoarthritis. Pullinger and colleagues further claimed that, when two or four of the “posterior teeth” (bicuspids) were removed as part of an orthodontic treatment protocol, there was a negligible effect on TMD.²⁶⁰ Other studies carried out by Kayser¹⁵⁶ and Witter³⁵⁴ have also documented acceptable masticatory function after bicuspid extractions and orthodontic treatment without increased signs and symptoms of TMD.

Note:

The multifactorial analysis of occlusal factors and TMD disease categories carried out by Pullinger and colleagues showed that, except for the few clearly defined occlusal features described previously, there was a low probability of a malocclusion being associated with TMD. Seligman and colleagues estimated that the overall contribution of occlusal factors for the defining of patients with TMD was only in the range of 10% to 20%.³⁰² The corollary is that 80% to 90% of the causative factors cannot be explained by patients’ presenting malocclusions.

In the Pullinger and Seligman study, it must be assumed that many of the significant overjets observed in the adult subjects were secondary deformities after condylar resorption (i.e., condylysis).²⁶⁰ The authors did not present evidence to suggest that the presence of significant overbite or overjet plays a role in the pathophysiology of non-arthritic disorders of the TMJ, and they did not show that it was a causative factor in the observed osteoarthritis. They do believe that a combination of unilateral retruded centric position in the presence of a clinically apparent retruded centric position–inter-contact position slide may encourage TMJ disc displacement but that unilateral retruded centric position per se is not associated with TMD. They found that lost molar support (i.e., 4 or 5 posterior teeth) may be associated with osteoarthrosis. They concluded that a dental midline discrepancy is not a predictor of TMD development during adulthood. Anterior open bite is frequent in the presence of condylysis or osteoarthritic changes in the TMJ, but it is probably the result of (rather than the cause of) the osteoarthritic changes. Interestingly, when open bites are observed in children, they are rarely associated with TMJ symptoms. In the pediatric population, the majority of observed open bites represent a developmental jaw deformity rather than a result of osteoarthritis. Nevertheless, it is recommended that, when either a child or an adult is found to have an anterior open bite, radiographic analysis of the condylar head should be undertaken to check for osteoarthritic changes.

Orthodontic Treatment and Its Effects on Temporomandibular Disorders

Review of the Literature

The relationships among malocclusion, orthodontic treatment to improve the occlusion, and the effects on TMD is discussed frequently in the literature.* A spectrum of orthodontic treatment philosophies has been championed by individual practitioners on the basis of presumed effects on TMD. The longitudinal nature of orthodontic treatment, which is often carried out over several years, means that a changing TMD history would also be expected in a control group that is not simultaneously undergoing orthodontic treatment. Therefore, the occurrence of joint noise (e.g., popping, clicking) or myalgia (i.e., masticatory muscle discomfort) during orthodontic treatment may either be the result of the treatment or consistent with the natural history of the untreated individual.

Sadowsky and colleagues reported on 75 adult study patients who had undergone orthodontic treatment with full appliances during adolescence at least 10 years earlier.²⁹⁰ The treated group was compared with a group of 75 similar adults with untreated malocclusions. The authors also went on to increase both their control and subject groups and to report these additional findings several years later.²⁹¹ In the two sequenced studies, respectively, 15% to 21% of the treated subjects presented with one or more signs of TMD (e.g., joint noise), and 29% to 42% had at least one or more symptoms of TMD. There were no statistically significant differences between the treated and untreated (control) groups.

Larsson and colleagues evaluated 23 individuals who had undergone orthodontic treatment during adolescence at least 10 years earlier.¹⁷² Mild TMD was recorded in 8 out of 23 (35%) of the patients, whereas only 1 (4%) had severe TMD. The authors compared this with published epidemiologic controls and stated that there was no difference in the incidence of TMD in the treated group versus the control group.

Dahl and colleagues examined 51 subjects 5 years after the completion of orthodontic treatment and compared them with an untreated control group.⁵⁴ The authors found no statistical differences in TMD between the two groups. The number of subjects in both groups who had at least one mild TMD symptom was relatively high (70% in the treated group versus 90% in the untreated group). Mild symptoms (e.g., joint noise), masticatory muscle fatigue, and stiffness in the lower jaw were frequently observed in both groups.

A study by Smith and Freer examined 87 individuals who were treated with full orthodontic bracketing during adolescence.³²⁰ The treatment group (N = 87) was compared with an untreated control group (N = 28). Four years after treatment ended, TMD symptoms were found in 21% of the treated group and 14% of the control group; this was not found to be statistically significant. The one symptom that was statistically more common in the treatment group was a “soft click” (64% of the treated group versus 36% of the untreated group).

Rendell and colleagues examined 462 individuals (90% adolescents and 10% adults) who were undergoing orthodontic treatment in a graduate orthodontic dental school clinic.²⁶⁷ With the use of a modified Helkimo Index, only 11 of the patients presented with TMD signs or symptoms before treatment. Of the other 451 patients, during the 18-month study, none developed TMD signs or symptoms. For those with preexisting TMD signs or symptoms (N = 11), there was no consistent change in the level of pain or dysfunction reported during treatment.

Kremenak and colleagues reported pretreatment and posttreatment TMD examination data from 109 patients who were treated with full orthodontics.166,167 The Helkimo Index scores were also compared. No statistically significant differences were noted between the subjects’ pretreatment and posttreatment scores. Ninety percent of the patients had Helkimo Index scores that either remained the same or improved, and 10% of the treated patients had scores that worsened. The authors concluded that the orthodontic treatment provided to their patients was not an important etiologic factor for the development of TMD.

Hirata and colleagues examined 102 individuals before and after orthodontic treatment for signs and symptoms of TMD.¹²⁸ They compared their treatment group with 41 untreated controls who were matched for age. The incidence of TMD for the treatment and control groups was not statistically significantly different.

Studies have also been carried out to evaluate specific orthodontic treatment maneuvers and their relationship to TMD symptoms and signs. The studied orthodontic maneuvers include the type of orthodontic mechanics used; extraction versus non-extraction therapy; orthodontic treatment and posterior condylar displacement; and orthodontic treatment focused on classic gnathologic principles.

Note:

In the studies that were reviewed, no consistent benefits or causative factors of TMD were identified on the basis of any specific orthodontic treatment maneuvers carried out in the treatment group as compared with controls.

Orthodontic Treatment Undertaken Specifically to Relieve Temporomandibular Disorders

In everyday dental practice, the establishment of a preferred intra-arch morphologic relationship of the teeth and then the achievement of a satisfactory inter-arch relationship of the teeth in one jaw to those in the other jaw (i.e., occlusion) serves as the basis of treatment objectives. According to a review of the literature, the establishment of a “normal” occlusion through orthodontic mechanics or via other dental means carried out for the purpose of eliminating or preventing the worsening of TMD does not seem warranted. Pullinger and Seligman have stated five potential exceptions to this, which were described previously in this chapter.255–261 McNamara and colleagues also stated that prudent basic dental treatment objectives will generally include the establishment of the six keys to ideal occlusion as advocated by Andrews, when feasible; the establishment of a limited CR–CO slide (i.e., <2 mm); the limiting of an anterior open bite; the alleviation of significant overjet (i.e., >6 to 7 mm); the limiting of unilateral maxillary lingual crossbites in children; and the establishment of a stable posterior occlusion.

Orthodontic Treatment Undertaken Specifically to Prevent Temporomandibular Disorders

The literature also contains studies that suggest that specific orthodontic maneuvers are effective for the prevention of TMD. The studies by Magnusson and colleagues 187–192 and the study by Egermark and colleagues⁸⁹ suggest preventative TMD advantages related to orthodontic occlusal corrections. At 5 and 10 years, these investigators reevaluated a group of 402 children and adolescents who had originally undergone a full course of orthodontic treatment. The Helkimo Index was used to measure clinical signs of TMD in the now older age group (i.e., ≥25 years old). Interestingly, the Helkimo Index outcome was lower in those who had undergone orthodontic treatment as compared with the control group. The studies by Dahl and colleagues and Sadowsky and colleagues also demonstrated a trend (although not a statistically significant one) toward the decreased prevalence of TMD signs and symptoms in orthodontically treated patients.^53,290,291 These studies would require further confirmation before accepting them as credible indications of a cause-and-effect relationship.

Summary of Effects of Orthodontic Treatment on Temporomandibular Disorders

McNamara, Seligman, and Okeson summarize their understanding of the relationship between orthodontic treatment and TMDs as follows ²⁰³:

1. Signs and symptoms of TMD do occur in healthy individuals.

2. Signs and symptoms of TMD increase with age, particularly during adolescence.

3. Orthodontic treatment performed during adolescence generally does not increase or decrease the odds of developing TMD later in life.

4. The extraction of teeth as part of an orthodontic treatment plan does not increase the risk of TMD.

5. There is no elevated risk for TMD associated with any particular type of conventional orthodontic mechanics.

6. Although a stable occlusion is a reasonable orthodontic treatment goal, the inability to achieve a specific gnathologic ideal occlusion does not result in TMD signs or symptoms.

7. No specific method of TMD prevention has been demonstrated to be effective.

8. When more severe TMD signs and symptoms are present, simple forms of treatment can alleviate them in most patients.

Note:

McNamara, Seligman, and Okeson suggest that until reliable criteria are developed for the treatment of TMD, the dental and medical professions should be encouraged to manage presenting TMJ symptoms with reversible therapies and to only consider permanent alterations in the occlusion (for the specific purpose of treating or preventing TMD) in patients with very unique circumstances. This is in agreement with the National Institure of Health conference guidelines which states that reversible therapies should be used in the primary treatment of TMD²¹⁹

A summary of evidence-based systematic reviews of TMDs was carried out by Rinchuse and McMinn.²⁸³ Their systematic review resulted in the following conclusions:

1. Occlusion, which was once considered the primary and sole cause of TMD, now at best is recognized as having a secondary role in causing it.

2. Conventional orthodontic treatment that improves the occlusion does not cause TMD.

3. The use of occlusal adjustments in orthodontic patients has no evidence-based support for the treatment of TMD.

4. There is evidence-based support for the use of occlusal splints and biofeedback for the treatment of TMD.

Association of Jaw Deformities, Orthognathic Surgery, and Temporomandibular Disorders

Review of the Literature

The association of a jaw deformity with malocclusion and the effects of orthodontic and surgical correction on TMD signs and symptoms have been examined in clinical studies for the past several decades.* The quality of the research and therefore the value of the conclusions vary. There are just three longitudinal prospective controlled clinical trial studies that have been carried out to assess the effects of orthognathic surgery on TMD: the studies by Onizawa and colleagues,²³² Panula and colleagues,²³⁶ and Dervis and colleagues.⁶⁷

The study by Onizawa and colleagues sought to evaluate changes in the symptoms of TMD after orthognathic surgery.²³² TMJ symptoms in preoperative orthognathic patients (N = 30) were compared with those of healthy control volunteers (N = 30). Changes in TMD symptoms were evaluated in both groups at 3- and 6-month postoperative intervals. The authors found no significant differences in the incidence of TMJ sounds, deviation of mouth opening, or tenderness on direct palpation of the TMJ and masticatory muscles between patients who were scheduled to undergo orthognathic surgery and control volunteers. The treatment group did not report TMJ symptoms significantly more often than the control subjects. At both the 3- and 6-month postoperative intervals, half or more of the treatment group showed no change in TMJ sounds, deviation of mouth opening, or tenderness on palpation of the TMJ or masticatory muscles. At each evaluation time frame, some individuals in both the control group and the study group exhibited improvement in TMJ symptoms, whereas others showed a change for the worse. Findings of postoperative TMJ sounds were observed to be associated with a reduction of mandibular mobility (i.e., mouth opening). The authors concluded that TMD symptoms did not always show improvement after surgical correction and that, for some patients, the symptoms changed for the worse.

Panula and colleagues carried out research to study the effects of orthognathic surgery on TMJ dysfunction.²³⁶ They completed a prospective follow-up study to examine the influence of orthognathic procedures for the correction of dentofacial deformities on signs and symptoms of TMJ dysfunction. Sixty consecutive patients with dentofacial deformities were examined preoperatively and then twice after orthognathic surgery. The Helkimo Anamnestic and Dysfunction Indices were also given as a questionnaire, and the results were used as part of the determination. The prevalence of headache was also assessed. The average follow-up was 4 years after the initial preoperative examination. A group (N = 20) with a similar type and grade of dentofacial deformity who elected not to undergo surgical correction or any other occlusal therapy served as the control group. The majority of the treatment group (73%) was found to have signs and symptoms of TMJ dysfunction or TMD during the preoperative examination. At the final postsurgery examination (i.e., 4 years after surgery), the prevalence of TMD had been reduced to 60%. There was also a dramatic improvement in the prevalence of headache, which was initially experienced by 63% of patients and reduced to 25% of patients at the final visit. The authors concluded that signs and symptoms of TMD, including pain (headache) levels, could be reduced with orthognathic treatment. The risk of an orthognathic patient experiencing new TMD was extremely low. No association could be shown between TMD and any specific type or magnitude of dentofacial deformity.

A study was conducted by Dervis and colleagues with the objective of looking at the long-term prevalence of TMD in individuals with a dentofacial deformity who then underwent orthognathic surgery as compared with a control group.⁶⁷ Signs and symptoms of TMD in both the dentofacial deformity patients and the control group were evaluated before surgery, 1 week after release of intermaxillary fixation, and 1 and 2 years after surgery with the use of the Helkimo Anamnestic and Dysfunction Indices. At both the initial preoperative examination and the final examination (i.e., 2 years after surgery), signs and symptoms of TMD in the patients who were undergoing orthognathic surgery were compared with those of healthy control subjects. The lengths of condylar pathways during opening and with lateral and protrusive movements were also evaluated with the use of axiography. A statistically significant reduction of TMD symptoms and signs 2 years after surgery as compared with before surgery was found. Interestingly, at the initial examination, the patients with dentofacial deformities who were scheduled to undergo orthognathic surgery did not report TMD signs and symptoms with a greater frequency than other healthy control subjects. At the final examination (i.e., 2 years after surgery), greater improvements in TMD symptoms in the patients who had undergone orthognathic surgery were found as compared with healthy control subjects. The authors also found a statistically significant decrease in masticatory muscle tenderness after surgery. The authors concluded that the “functional status” of the TMJ can be improved with orthognathic surgery. There was no clear association between TMD symptoms and a specific type or pattern of dentofacial deformity.

When comparing and contrasting the three published longitudinal prospective controlled studies that were conducted to determine the effects of orthognathic procedures on TMD symptoms and signs (i.e., Onizawa and colleagues,²³² Panula and colleagues,²³⁶ and Dervis and colleagues⁶⁷), several observations can be made:

1. Patients with dentofacial deformities who were scheduled to undergo orthognathic surgery were not found to have significant differences in their TMD signs and symptoms as compared with patients in the control groups.

2. After orthognathic surgery and orthodontics, signs and symptoms related to TMD were frequently improved.

3. Despite the trend for diminished signs and symptoms of TMD after orthognathic surgery and orthodontics, individuals did not always show improvement; for some, the symptoms changed for the worse.

4. After orthognathic surgery and orthodontic treatment, a decrease in masticatory muscle tenderness was frequent. A decrease in joint tenderness on palpation was also a common occurrence.

5. In one of the three studies reviewed, a decrease in maximum mouth opening was observed, but this was not found to be of clinical importance.

There are other less rigorous reports and studies that can be found in the literature that also analyze the effects of orthodontics and orthognathic surgery carried out for the correction of dentofacial deformities on TMD, including the following:

Karabouta and colleagues reviewed 280 individuals with different patterns of mandibular deformities (e.g., prognathism, retrognathia, open bite, asymmetry) who underwent orthognathic surgery that included sagittal split ramus osteotomies of the mandible. Before surgery, the patients were found to present subjective or objective TMJ dysfunction symptoms with an incidence of 41%.¹⁵⁴ After surgery, the incidence of such symptoms in the same patients was reduced to 11%. Individuals with no preoperative TMJ dysfunction symptoms developed such symptoms with an incidence of 4% after surgery.

White and colleagues set out to review the prevalence of TMD in patients with dentofacial deformities who were undergoing orthognathic surgery.³⁴⁹ Preoperatively, 49% of their study group presented with TMD. After orthognathic surgery, in the symptomatic patients, 89% had improved temporomandibular function, 3% were unchanged, and 8% developed increased symptoms. Of the preoperative asymptomatic patients, 8% developed TMD after surgery. In the study group, TMD was significantly greater in patients with Class II skeletal deformities as compared with those with Class III tendencies. Overall, temporomandibular function generally improved in both treatment groups (i.e., Class II and Class III) after successful surgery.

Hori and colleagues reported three individual (non-consecutive) cases in which there was a worsening of preexisting TMJ dysfunction after sagittal split ramus osteotomy of the mandible and 6 weeks of intermaxillary fixation.¹³¹ All three of their patients initially presented specifically seeking treatment of malocclusion for the relief of TMD. All three patients had active TMD before and after their orthognathic procedures.

Aghabeigi and colleagues studied the effect of orthognathic surgery on the TMJ of patients who presented with an anterior open bite.⁶ This was a retrospective survey study of patients (N = 83) who presented with an anterior open bite who then underwent orthognathic surgery. The preoperative prevalence of head and neck pain was 32%, TMJ dysfunction was found in 40% of patients, and limited mouth opening was found in 7%. The overall prevalence of TMJ signs and symptoms was not found to be significantly different after orthognathic surgery. In the study group, an abnormal psychological profile was the most significant factor associated with the presence and persistence of TMJ pain. The authors concluded that orthognathic surgery does not significantly influence TMD in patients with anterior open bites. Female patients—particularly those with abnormal psychological profile—were at higher risk for persistent postoperative TMJ pain.

Westermark and colleagues studied a consecutive series of individuals to understand the effects of orthognathic surgery on the signs and symptoms of TMD.³⁴⁷ The authors sent a survey questionnaire to a consecutive series of patients (N = 1516) who initially presented with dentofacial deformities and who then underwent orthognathic surgeries that were performed by a group of experienced surgeons at a single institution. The survey was given at least 2 years after surgery. The questions asked in the survey related to joint pain, chewing pain, joint noise, grinding, daytime headache, and morning headache. Preoperatively, 43% of the patients reported subjective symptoms of TMD; postoperatively, 28% of the patients did. This difference suggested an overall beneficial effect of orthognathic surgery on TMD signs and symptoms. Patients with Class II skeletal deformities did not improve as much as with those with Class III skeletal prognathism.

Yamada and colleagues studied the incidence of condylar morphologic change, disc displacement, and signs and symptoms of TMD in individuals set to undergo orthognathic surgery.³⁵⁹ The study showed preoperative condylar morphologic change (unilateral or bilateral) in 36% of the subjects and in 24% of each joint. Preoperative disc displacement (unilateral or bilateral) was seen in 41% of the subjects and in 30% of each joint. The percentage of condylar morphologic change and disc displacement was higher for individuals with anterior open-bite skeletal Class II growth patterns and lower for patients with skeletal Class III deformities.

Wolford and colleagues studied changes in TMD after orthognathic surgery in a series of 25 patients who were scheduled to undergo bimaxillary surgery.³⁵⁶ They used magnetic resonance imaging and clinical verification of TMJ articular disc displacement. This was a retrospective evaluation with an average follow up of 2.2 years. Presurgically, 16% of the patients had only TMJ pain, 64% had only TMJ sounds, and 20% had both TMJ pain and sounds. Postoperatively, 24% of the patients had only TMJ pain, 16% had only TMJ sounds, and 60% had both TMJ pain and sounds. Thirty-six percent of the patients had TMJ pain preoperatively; this jumped to 84% after surgery. In addition, the authors claimed that 6 out of 25 of their patients (24%) developed condylar resorption postoperatively, thereby explaining the high incidence of observed Class II open-bite malocclusion. The authors demonstrated that patients with preexisting TMJ dysfunction who undergo bimaxillary osteotomies via the techniques that they used have a high probability of the significant worsening of TMJ dysfunction after surgery. This reported high incidence of TMD and condylar resorption after orthognathic surgery is contrary to all other studies reported in the literature.

Borstlap and colleagues reported about a consecutive series of individuals who were scheduled to undergo sagittal split ramus osteotomies for both Class II mandibular retrognathism and Class III mandibular prognathism.³¹ Patients were reviewed preoperatively, immediately postoperatively, and at 3, 6, and 24 months postoperatively. Any signs and symptoms of TMD were documented, including clicking, preauricular pain, maximum mouth opening, protrusive movements, and lateral excursions. The authors documented that 56% of the patients with preexisting TMD had relief of their signs and symptoms. Interestingly, 22% of individuals without preexisting TMD went on to develop clinical signs or symptoms after surgery.

Bock and colleagues studied the importance of temporomandibular function as a factor in the achievement of patient satisfaction after orthognathic surgery.²⁹ The authors’ orthognathic surgery patients (N = 102) were examined at an average of 47 months after surgery. The average age of their patients was 24 years. A patient satisfaction questionnaire and other modalities were reviewed, including the Helkimo Index, clinical findings, nerve function parameters, and the incidence of intraoperative and postoperative complications. The results of their study showed that 91% of patients were satisfied or very satisfied with their overall orthognathic results. Answers to the questionnaires revealed that only 79% of patients would undergo treatment again (i.e., 21% of the patients would not). Statistically significant differences were found in the Helkimo Index and in the pain reported both in the TMJs and with jaw movements between the satisfied and dissatisfied postoperative patients. The authors surmised that the 21% of patients who would not undergo treatment again were more likely to have a greater degree of TMD and limitations with regard to mandibular range of movement. Statistically significant differences were found between those who were satisfied and those who were dissatisfied with surgery on the basis of their Helkimo Indices. Those with pain on palpation in the TMJ region and those with pain experienced during motion of the mandible were more likely to be overall dissatisfied with the treatment. The persistence of postoperative symptoms of TMD, including pain, was the single most important correlation with low patient satisfaction.

Frey and colleagues studied the effects of mandibular advancement procedures and counterclockwise rotation on signs and symptoms of TMD.¹⁰² The study patients were followed for a minimum of 2 years after orthognathic surgery. A series of patients with Angle Class II malocclusions (N = 127) who were undergoing sagittal split ramus osteotomies with advancement and counterclockwise rotation of the mandible were studied to evaluate signs and symptoms of TMD at specific intervals after surgery. The results of the study indicate that counterclockwise rotation of the mandible was associated with more masticatory muscle tenderness early after surgery, especially in those who were undergoing more than 7 mm of advancement. The combination of extensive mandibular advancement with counterclockwise rotation was also associated with increased TMD symptoms early after surgery. Interestingly, all TMJ symptoms declined by 2 years after surgery. The authors conclude that surgical advancement and counterclockwise rotation of the mandible (i.e., sagittal split ramus osteotomy) is associated with a slight increase in masticatory muscle discomfort during initial recovery. All symptomatology tended to decline over time, which suggests that the amount of advancement and the amount of mandibular counterclockwise rotation should not be considered as risk factors for the long-term development of TMD in patients without preexisting symptoms.

Jung and colleagues retrospectively evaluated the effects of bilateral intraoral vertical ramus osteotomies with setback for the management of Class III skeletal patterns on symptoms that are associated with TMD.¹⁵² Patients were evaluated preoperatively and at intervals (i.e., 1, 3, 6, 12, 18, and 24 months) after surgery for specific parameters, including mouth opening, clicking, and TMJ pain. The authors reported that 94% of those with preoperative joint noise achieved resolution. After surgery, 8% of individuals who were free of noise before surgery developed joint noise afterward. On average, mouth opening was 50 mm before surgery and 49 mm 6 months after surgery. Joints that were free of pain before surgery remained so. Those individuals with preoperative TMJ pain remained free of pain at 18 months. The authors concluded that bilateral intraoral vertical ramus osteotomy with setback as a method of managing Class III skeletal deformities was also effective for the relief of undesirable TMJ symptoms (e.g., joint noise, pain) without negatively affecting mouth opening.

Additional thoughts Concerning Effects of Orthodontics and Orthognathic Surgery on Temporomandibular Disorders

It may not be correct to conclude that orthodontic treatment and orthognathic surgery carried out for the correction of a presenting jaw deformity with malocclusion are the responsible factors for any observed reduction or resolution of TMD signs and symptoms.¹⁸ During the decades that have passed since McCarty and Farrar first defined the diagnoses of internal derangement of the TMJ and then described a disc repositioning procedure to treat it, quality research to evaluate their recommended treatment has been scant.²⁰⁰ The experience of orthopedic surgeons with regard to the treatment of derangements of the knee should remind us of the need for clinical practice to be based on sound supporting evidence. Moseley and colleagues carried out a controlled clinical trial of arthroscopic surgery (i.e., lysis and lavage or arthroplasty) for osteoarthritis of the knee that should give us pause when considering irreversible TMD treatment.²¹² Clinician opinions regarding the effectiveness of lysis and lavage or arthroplasty to manage knee pathology in anticipation of improved function and relief of pain have varied but are currently without consensus. Therefore, a randomized clinical trial that included a placebo group was designed by Moseley and colleagues to address this controversy. To blind the placebo group, a sham surgical procedure was designed as part of the study. The placebo subjects were given a general or regional anesthetic, and incisions were made; however, the arthroscope was not inserted into the joint, and no therapeutic procedure was carried out. The results of the study were that neither treatment group (i.e., lysis and lavage or arthroplasty) offered improved clinical outcomes as compared with the placebo group for osteoarthritis. As a consequence of this evidence-based study, many orthopedic surgeons have changed treatment recommendations for their patients. In any case, Medicare (i.e., the U.S. government medical insurance plan for the elderly) made a decision that it would no longer cover arthroscopy for osteoarthritis of the knee. Restorative dentists, orthodontists, and orthognathic surgeons should remain circumspect when advising patients regarding irreversible treatment specifically for the purpose of relieving TMD.

Brief Overview of Okeson’s Thinking About Temporomandibular Disorders and the Effects of Occlusion

Okeson believes that, during the normal use of the masticatory system, either local or systemic events can occur that may influence function.165,227–231 Each individual has a varied ability to tolerate these events without any adverse head and neck effects. It is likely that an individual’s tolerance can be influenced by these local or systemic factors. When an event exceeds the individual’s physiologic tolerance, the system begins to reveal changes. Each component of the masticatory system can tolerate a certain amount of change. When functional change exceeds a critical level, alteration of the tissues begins. The tissue breakdown site is generally seen in the structure with the least tolerance. Therefore, the breakdown site varies from individual to individual. This is influenced by factors such as the individual’s unique maxillofacial morphology, previous head and neck trauma, and local tissue conditions. The weakest link in the masticatory system will break first (i.e. masticatory muscles, TMJs, supporting structures of the teeth, the teeth themselves). Typically, the weakest structures in the system are the masticatory muscles; this is evidenced by muscle tenderness and pain during mandibular movements.

When the TMJs are the weakened structures in the system, the individual may experience joint tenderness and pain. The TMJ can also produce sounds such as clicking or grating. When the individual has increased muscle activity (e.g., bruxism, grinding), then the next weakest link is frequently either the supporting structures of the teeth (i.e., the periodontium) or the teeth themselves. The teeth may show mobility or wear (e.g., loss of enamel, breakdown of restorations, fracture). Emotional stress seems to be a major influence on bruxing activity.

According to Okeson, the occlusal condition can influence TMDs by way of two mechanisms. One mechanism relates to the introduction of acute changes in the occlusal condition (e.g., recent restorative dentistry with an uneven alteration of the occlusal surfaces). Acute changes can lead to a muscle co-contraction response that leads to a condition of muscle pain. Typically, in these circumstances, new muscle engrams are developed, and the patient adapts with little consequence. A second mechanism relates to a more longstanding variation in the occlusal condition. In these conditions, maximum intercuspation (i.e., centric occlusion) results in the instability of the masticatory system (e.g., a CR–CO discrepancy). The orthopedic instability is not likely to withstand significant compressive loading forces on the TMJs. Dental therapy (i.e., the alteration of the occlusion) will only be helpful for the relief of TMDs when it effectively relieves one of these conditions (i.e., the muscle co-contraction response or the orthopedic instability accompanied by loading forces).

Dr. Okeson concludes that, in general, conventional orthodontic treatment is not an effective method for the prevention of TMD. As a corollary, a review of the literature suggests that patients who receive conventional orthodontic therapy are at no greater risk for the development of TMD than those who do not. According to Dr. Okeson’s work, any dental or surgical procedure that produces an occlusal condition that is not in harmony with a musculoskeletal stable position of the joint can—but does not necessarily—predispose the individual to these problems. Alternatively, dental or surgical procedures that reduce one of these occlusal conditions and restore harmony may improve the masticatory system.

Personal Thoughts About the Role of Open Joint Procedures for Temporomandibular Disorders

Unanswered questions remain: What is the appropriate treatment for an individual with a persistent symptomatic intracapsular TMJ disorder that has either not resolved spontaneously or not responded to conservative therapy? In these cases, what are the best studies to use to confirm the diagnosis and then select the appropriate treatment intervention?

A critical review of the literature suggests that outcomes for open TMJ procedures are often unpredictable and may result in further TMD.73–77 The success rate for “redo” open joint surgery is even less favorable. Among the criteria for an open joint procedure are the following: that the clinician must be confident that the source of the pain or dysfunction is arising from within the joint; that the appropriate use of conservative measures has failed; that the current symptoms are intolerable to a patient who is psychosocially stable; and that a significant long-term success rate for the selected open joint procedure in the specific patient can be assured.

Although an intracapsular lavage procedure with or without limited debridement and lysis of adhesions to relieve inflammation and improve function may be relatively benign in experienced hands, disc repositioning and discectomy have generally proven to be of little statistical value as compared with conservative measures. The technical simplicity of disc repositioning and discectomy procedures has lured many clinicians into offering them as standard options; however, a significant long-term success rate has not been documented.

The overall approach to TMD should aim to avoid further harm to the joint and err on the side of appropriate conservative management to relieve symptoms and to achieve or maintain reasonable function for the long term.