Mythili Kalladka, BDS, MSD/Andrew Young, DDS, MSD/Davis Thomas, BDS, DDS, MSD, MSc Med, MSc/ Gary M. Heir, DMD/Samuel Y.P. Quek, DMD, MPH/Junad Khan, DDS, MSD, MPH, PhD
Objective: The term temporomandibular disorders (TMDs) encompasses a variety of disorders of the temporomandibular joint (TMJD) and the associated musculature (MMD). Occlusion and its role in the genesis of TMDs is one of the most controversial topics in this arena. The objective of the narrative review was to summarize the implications of TMDs and its relationship to dental occlusion in two scenarios: 1) TMD as an etiologic factor in dental occlusal changes; 2) The role of dental occlusion as a causative factor in the genesis of TMDs.
Data Sources: Indexed databases were searched from January 1951 to August 2021 using the terms TMJ, TMD, temporomandibular disorders, temporomandibular joint, and dental occlusion.
Conclusion: There is lack of good primary research evaluating true association and showing the cause-and-effect relationship between dental occlusion and TMD. Systematic reviews suggest that the role of occlusion as a primary factor in the genesis of TMDs is low to very low. However, a variety of TMDs can lead to secondary changes in dental occlusion. Distinction between the two is paramount for successful management.
Temporomandibular disorders (TMDs) are one of the most prevalent orofacial pain disorders, and may be arthrogenous and/or myogenous in origin. It is estimated that 5% to 12% of the population may be affected by these disorders.The etiopathogenesis of TMD has shifted from early gnathologic concepts to the current biopsychosocial model.TMDs and occlusion thus became one of the most controversial topics in dentistry. Evidence-based dentistry today has challenged some of the previously held views, by closely scrutinizing the studies and clinical reports from the past. However, it is well documented that certain TMDs can lead to occlusal changes. Thus,many occlusal changes, especially those that manifest with acute changes in occlusion, may be sequelae to TMDs rather than the causation of TMDs.4,5 These changes may be subsequent to developmental, degenerative, systemic, adaptive, benign, and malignant disorders. These patients may often present to the dental practitioner with subjective, and sometimes objective, signs and symptoms of a change in occlusion. Determination of the underlying TMD responsible for the occlusal changes is crucial for treatment planning and successful management.The objective of this narrative review was to familiarize oral health care providers with the scientific evidence on: 1) TMD asan etiologic factor in dental occlusal changes; and 2) the role of dental occlusion as a causative factor in the genesis of TMD.
Data source and resource selection
Indexed databases (PubMed, EMBASE, Scopus, ISI Web of Knowledge, Medline, OVID, Scopus, Cochrane Library) were searchedfrom January 1951 to August 2021 using the terms (“dental occlusion” [MeSH Terms] OR (“dental”[All Fields] AND “occlusion”[All Fields]) OR “dental occlusion”[All Fields]) AND (“temporomandibular joint disorders”[MeSH Terms] OR (“temporomandibular”[All Fields] AND “joint”[All Fields] AND “disorders”[All Fields]) OR “temporomandibular joint disorders”[All Fields] OR (“tem poromandibular”[All Fields] AND “disorders”[All Fields]) OR “temporomandibular disorders”[All Fields]).
Changes in occlusion secondary to TMD
Changes in occlusion may occur secondary to TMDs of the temporomandibular joint (TMJD) or the associated musculature (MMD). The DC-TMD is the most commonly accepted classification for TMDs.6 It subclassifies TMJD into joint pain, joint disorders, joint diseases, fractures, and congenital or developmental disorders. MMDs include muscle pain, contracture, hypertrophy, neoplasm, movement disorders, and masticatory muscle pain attributed to central or systemic pain disorders.In addition, certain TMD-related conditions like bruxism (sleep and awake) may also cause changes in occlusion.
Changes in occlusion secondary to TMDs may be acute (when it develops suddenly) or chronic (when occlusal changes are gradual over a period of months to years). The changes in occlusion include posterior open bite, anterior open bite, facial asymmetries, midline deviations, crossbites, and miscellaneous (such as loss of vertical dimension, and heavier occlusal contacts). These changes may occur as a consequence of TMJ- related pathologies or muscle-related conditions, and may manifest as acute or chronic changes in occlusion. Changes in occlusion may follow increased intraarticular pressure, loss of bone support or MMD resulting from muscle fatigue, electrolyte imbalance, or deep pain inputs. Muscle contraction may also cause positional changes in the jaw, which may vary depending on the muscle involved.
The subsequent section discusses changes in occlusion secondary to TMDs. The specific types of occlusal changes are listed as categories, and the causative TMDs are listed as subcategories, following the taxonomic classification and diagnostic criteria of TMDs (DC-TMD). Additional causes of occlusal changes, such as iatrogenic causes, have also been included wherever applicable. A list of the TMDs and the changes in occlusion secondary to TMDs are shown in Table 1.
Posterior open bite
This may be seen in TMJD subcategories such as joint pain (arthritis), joint disorders (disc disorders such as acute anterior disc displacement without reduction), joint diseases (synovial chondromatosis), fractures, and MMD subcategories.
Terms such as synovitis or capsulitis have been previously used to describe this condition. The expanded taxonomy of DC-TMD describes it as pain originating in the TMJ accompanied with clinical features of localized infection/inflammation and not associated with any systemic condition.
On clinical examination, palpation of the lateral aspect of the TMJ and range of movements may result in reproduction of the pain complaints. This may be accompanied by signs of inflammation such as redness, swelling, or increased temperature in the area of the TMJ. The intraarticular swelling, and effusion of the inflammatory exudate may result in a unilateral ipsilateral/ bilateral posterior open bite with deep anterior teeth contacts depending on whether the condition is unilateral or bilateral.
Since this condition is localized to the TMJ and excludes systemic arthritides and rheumatologic diseases, blood tests/lab studies including rheumatoid panel, erythrocyte sedimentation rate (ESR), complete blood count (CBC) with differential, C-reactive protein (CRP), and anti-nuclear antibody (ANA) may be advised to rule out these conditions
Disc displacement without reduction with limited opening (DDW/O R) is an intracapsular biomechanical disorder involving the disc condyle complex. In in stances of acute DDW/O R the articular disc is most commonly displaced anteriorly and medially, and less commonly laterally and posteriorly
On clinical examination, the maximum assisted mouth opening is less than 40 mm. Contralateral excursive movement is also limited. Loading test may be positive for pain on the same side. In instances of acute anterior DDW/O R, the disc is dislocated anteriorly and the condyle sits heavily on the retrodiscal tissue immediately. This may cause mild changes in occlusion which may manifest as heavier occlusal contacts on the affected side. Subsequently, the retrodiscal tissue may
become inflamed, which may cause posterior open bite on the affected side.
The diagnosis is confirmed through magnetic resonance imaging (MRI). A systematic review correlating clinical findings to MRI reported low to moderate correlation in diagnosing internal derangements through the clinical examination, and suggested that the clinical examination may be utilized for screening, and advanced imaging like MRI should be reserved for accurate diagnosis in cases that are symptomatic12 and not responding to treatment. A systematic review and meta-analysis suggested that ultrasound, especially high-resolution dynamic and static ultraosund, may be used as adjunct tools to the clinical examination and prior to MRI to enable a fast, simple, and cost-effective option for diagnosis.
Fig 1. Changes in dental occlusion secondary to TMDs
This is a benign lesion characterized by numerous calcifications within the joint subsequent to cartilaginous metaplasia occurring in the synovial membrane.
On clinical examination, the patient may exhibit preauricular swelling, and reproduction of the pain complaints with TMJ palpation.
MRI or CBCT may be used for diagnosis. Histopathologic examination reveals cartilaginous metaplasia.
A displaced or non-displaced fracture may involve the bony components of the joint and may cause occlusal changes such as contralateral posterior open bite.
On clinical examination, the patient may exhibit preauricular swelling, and reproduction of the pain complaints with TMJ palpation.
Orthopantomography may be used for initial evaluation.CT/CBCT may be used for diagnosis.
This is pain of muscular origin affected by function, parafunction, and jaw movement. Myofascial pain may be characterized by trigger points, which are hyperirritable spots in taut bands of muscle. Trigger points in the inferior lateral pterygoid may cause mild occlusal changes presenting as disoccluded ipsilateral posterior teeth and premature contact of the contralateral anterior teeth.
Chairside tests such as loading tests, and tests of provocation, may be used. In addition, diagnostic local anesthetic blocks can be used if necessary to distinguish the source and site of pain.
Spasm is a sudden, reversible, involuntary tonic contraction of a muscle. Myositis is a pain of muscular origin, generally secondary to infection, inflammation, or autoimmune conditions. Contracture occurs secondary to trauma, infection, or radiation therapy, and may result in fibrosis of muscle fibers, tendons, and ligaments. These conditions may alter the postural position of jaws; the type of occlusal change produced depends on the muscle involved.16 The most common masticatory muscles involved are the medial and lateral pterygoid, and the masseter. Complete spasm of the elevator muscles causes limitation of opening. Partial spasm causes acute malocclusion, which may sometimes not be visible clinically, but has the potential to cause patient discomfort and a report of their bite “feeling different.” Occasionally occlusion is detectably heavier on the ipsilateral side. Unilateral inferior lateral pterygoid spasm/contracture causes loss of contact on the ipsilateral posterior teeth and heavy contact on the contralateral canines. Bilateral inferior lateral pterygoid spasm/contracture may manifest as bilateral posterior open bite and heavy anterior occlusal contacts. Unilateral medial pterygoid spasm/contracture may result in slight ipsilateral posterior open bite and contralateral accentuated vertical overlap (overbite). Unilateral superficial masseter spasm/ contracture may result in mild posterior open bite on the contralateral side. Myostatic contracture, or shortening of the resting length, of lateral pterygoid muscles (causing posterior open bite) may also occur as a consequence of mandibular advancement device usage, or a protrusive night guard. An early form of open bite is hypo- occlusion.
Additional chair side tests such as loading tests, tests of provocation, and diagnostic blocks can be used as necessary. Intramuscular electromyography (EMG) may be elevated in myospasm.17 Serologic tests may be advised for myositis and may reveal elevated inflammatory markers and elevated creatinine kinase. Serological testing may also be advised to rule out autoimmune disorders.
The immediate postoperative period of TMJ surgeries may also exhibit changes in occlusion.
This may occur secondary to joint diseases (including degenerative joint diseases, systemic arthritides, condylysis/idiopathic condylar resorption, osteonecrosis), bilateral degenerative changes secondary to rheumatoid arthritis/ other autoimmune arthritis, and bilateral idiopathic condylar resorption. Anterior open bite secondary to TMD must be distinguished from anterior open bite due to non-TMD causes such as tongue thrusting habit.
Degenerative joint disease
The expanded taxonomy of DC-TMD describes degenerative disorders not associated with rheumatologic diseases and affecting the joint with damage/degradation of the articular tissues and changes in the osseous structures such as the articular eminence and condyle. Progressive open bite may occur due to resorption of condylar structures.
These conditions are attributed to an underlying systemic inflammatory/rheumatologic disease resulting in pain, inflammation, and structural changes to the TMJ.
Systemic arthritic disorders include inflammatory arthritis (eg, rheumatoid arthritis, juvenile rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis), degenerative arthritis (osteoarthritis), infectious arthritis (Lyme associated, gonococcal arthritis, syphilitic arthritis, tuberculous arthritis), metabolic arthritis (pseudogout, gout), and traumatic arthritis. Among these, juvenile rheumatoid arthritis and rheumatoid arthritis are most commonly associated with anterior open bite. Children with juvenile idiopathic arthritis present with a remarkable prevalence of condylar destruction, which is correlated to the type and duration of the disease. Patients with rheumatoid arthritis often present with rapid onset anterior open bite and often present with class II occlusion. This is secondary to destruction of the mandibular condyles resulting in progressive loss of ramus height. CBCT has been shown to have high diagnostic accuracy in detection of bony changes and may be helpful in evaluating progression of DJD over time. However, care should be exercised owing to radiation exposure, and it should not be used as a screening tool in healthy individuals. Positron emission tomography (PET) scan in combination with CT is the most reliable modality to determine active rheumatoid TMJ arthritis. Laboratory studies include serologic testing for various systemic conditions such as arthritis, and may include rheumatoid panel, CBC with differential, ESR, C-reactive protein, anti- nuclear antibody (ANA), and complete metabolic panel with electrolytes. These should be advised only when necessary, keeping in mind radiation exposure and financial implications.
Idiopathic condylar resorption
This idiopathic condition is seen in adolescents and young females and leads to degeneration of the TMJ condyle with progressive loss of condylar height. It is associated with progressive anterior open bite.
Benign and malignant neoplasms
A variety of benign and malignant neoplasms may affect the TMJ and cause a variety of occlusal changes such as facial asymmetry and midline shift. Primary benign and malignant neoplasms of the TMJ are rare. In these instances, the malignancy may affect the hard and soft tissues of the TMJ including cartilage and bone. Metastasis to the condyle is rare and mainly involves malignancy from the lung. Peripheral osteoma of the mandibular condyle can cause anterior cross bite and mandibular deviation.25 Benign and malignant neoplasms and cysts may cause unilateral open bite.
MRI or CT/CBCT may be used to aid diagnosis. PET scanning may be used to rule out distant metastasis. Biopsy may be used for definitive diagnosis.
Untreated condylar fracture secondary to trauma results in lower midline deviation coinciding with the side of the unilateral fractured condyle.27 In general, plain radiographs serve as basic screening aids to rule out gross morphologic changes in the osseous structure and fractures. Advanced radiographic aids such as CBCT or CT may be advised for accurate diagnosis.
This grouping includes aplasia, hypoplasia, and condylar hyperplasia. Aplasia is a congenital condition characterized by the absence of the mandibular condyle and hypoplasia of the glenoid fossa and articular eminence. It may be associated with syndromes such as Treacher Collins or Goldenhar syndrome, and has associated changes in occlusion including crossbite, open bite, posterior open bite, and facial asymmetry. Hypoplasia is a less severe form of aplasia and may be congenital or secondary to trauma. It may be associated with facial asymmetry, occlusal changes such as a non-horizontal occlusal plane, and posterior open bite on the contralateral side. Bilateral cases may result in anterior open bite.
Hyperplasia is a developmental disorder characterized by facial asymmetry as a result of continued growth of the mandibular condyle
Occlusal changes commonly occur after TMJ arthroscopic disc repositioning and suturing. It may be characterized by heavier contacts or premature contacts, posterior open bite on the surgery side, mandible midline deviations, and incisal prematurity. One study suggested that the majority of the changes in occlusion resolve in 28 days, and treatment should be considered in cases that do not resolve in this time.
Injection of contrast agent during arthrography
Heavier contact may occur on contralateral posterior teeth.Intracapsular edema subsequent to early-stage arthritis also results in premature occlusion of teeth on the opposite side.
Chronic unilateral bruxism
This often causes ipsilateral collapsed bite with severe attrition.
Limitation of mouth opening
This may be seen in conditions such as acute disc displacement without reduction (as previously described), ankylosis, hypoplasia, and adhesions.
This includes adhesions and ankylosis (bony or fibrous). Adhesions are conditions are associated with limitation of opening due to restriction of disc condyle movement by fibrous adhesions. Ankylosis may be bony or fibrous and there may be complete or partial limitation of mouth opening. When unilateral, both conditions cause uncorrected jaw deviation to the involved side on opening.
Inability to close mouth
TMJ hypermobility allows the disc condyle complex to slide beyond the articular eminence. In dislocation, the disc condyle complex cannot return to the fossa (often referred to as an “open lock”) without maneuver either by the patient or by a clinician. In subluxation, such manual reduction is not necessary to return to closure.
Controversy has existed for decades on the role of occlusion in TMDs. The current review summarizes the evidence from systematic reviews and meta-analysis on the role of occlusion in TMD
An early systematic review (2004) on population- based studies in adults, addressing the association of malocclusion, functional occlusion parameters (such as nonworking-side occlusal contacts and occlusal interference), and TMDs, concluded that there were very few associations. The associations were not uniform, and the authors found no particular functional occlusal or malocclusion feature to be apparent. The strength of correlation was not mentioned in studies in two
positive associations (number of rotated lateral teeth, excessive abrasion, and signs and symptoms of TMD). In addition, patients with Angles Class II malocclusion, anterior crossbite and deep bite had fewer symptoms of clinical dysfunction. In view of the limited number of RCTs, methodologic quality, and discrepancies in study design, the authors suggested confirmation of results through validated representative studies in future.
In 2005, a systematic review by the Swedish Council on Health Technology Assessment concluded that the scientific evidence until then was insufficient to enable definite conclusions on the correlation between TMD and specific untreated malocclusion. There was also limited scientific evidence to show the connection of TMD with orthodontic treatment. A systematic review by Mohlin et al31 in 2007 reconfirmed these findings, reporting a lack of association between specific malocclusion or orthodontic treatment and signs and symptoms of TMD.
A systematic review on attrition, occlusion, and masticatory system dysfunction reported that few studies reported a correlation between anterior spatial relationships and attrition. One study reported that a smaller number of teeth may lead to higher tooth wear index, but no study reported loss of posterior teeth contributing to enhanced attrition; it instead appeared to be co-existent with self-reported bruxism. However, there was no definite conclusion regarding the relationship between TMD and attrition.
A systematic review on posterior crossbite and functional changes on the masticatory muscles in the primary and mixed dentition concluded that the malocclusion in these instances could lead to asymmetric muscle function.33 There was also a significant association between posterior crossbite in primary and mixed dentition and TMD that deserved further investigation. A study by Iodice et al34 suggested that it was not possible to draw an association between posterior crossbites, muscle pain, and disc displacement with reduction because the distribution of studies supporting and refuting were similar, and hence the authors suggested more rigorous scientific studies were needed to draw conclusions. Another systematic review in 2018 on TMJ positional and dimensional changes following correction of posterior crossbites in children concluded that there is insufficient evidence for a firm conclusion.
A systematic review by Abduo et al concluded that there was no association between lateral occlusal schemes and TMD development. Another systematic review on centric relation–intercuspal position discrepancy and TMD concluded that due to the low quality of articles and varied methodology, it was difficult to establish definite correlations.37 Further well-designed longitudinal studies with validated diagnostic criteria and strict, standardized methodology were required.
Manfredini et al conducted a systematic review on association studies to determine if there is an association between TMD and features of occlusion, and concluded that there was no disease-specific association between the two, and that there is no role of dental occlusion in the pathogenesis of TMD.
Fig 1. Diagnosis and management of TMDs causing changes in dental occlusion
The shift in the role of occlusion from one of causation to being one of sequelae warrants a change in management. Targeting the pathologic process through mechanism-based approaches is necessary for long-term success, especially in instances where changes in occlusion are secondary to TMDs
The leading professional societies across the world concur on the use of conservative measures as the first line for most TMJD and MMD. Since most TMDs are self-limiting, the first line of management should begin with conservative, reversible procedures. These include home care, pharmacotherapy, shortterm splint therapy, physiotherapy, psychologic counselling, and behavioral modification techniques. These modalities are applicable to several TMDs including arthralgia, arthritis, DDW/O R, DJD, and MMDs. The diagnostic criteria, diagnostic aids, and management of changes in occlusion secondary to TMDs has been detailed in Table 2. The clinical presentation is based on Peck et al.
Manual reduction may be attempted in cases of acute DDW/ O R with auriculotemporal or twin block nerve blocks. Systematic reviews on various treatment modalities (conservative, minimally invasive, and surgical) for DDW/O R found heterogeneity in the included studies and unclear risk of bias, and suggested that the different modalities had comparable therapeutic effects. Therefore, the simplest, least invasive modalities should be tried first for initial management of DDW/O R, especially in simple cases without major psychologic symptoms.
Hypoplasia/aplasia may require distraction osteogenesis, autologous reconstruction, or total alloplastic joint replacement if the jaw function or esthetics are not acceptable to the patient.
Condylar hyperplasia may be treated with high condylectomy (preferred in unilateral condylar hyperplasia) or proportional condylectomy in active condylar hyperplasia. However further studies are needed on the efficacy.
In TMJ luxation, manual reduction may be used chairside, followed by physiotherapy strengthening modalities/exercises. In recurrent cases, dextrose prolotherapy may cause significant reduction in mouth opening and pain. Autologous blood injection alone and in combination with intermaxillary fixation has been reported to be effective in recurrent TMJ luxation. However, concerns on its effect on articular cartilage and possibility of ankylosis have yet to be studied in detail. Surgical interventions for management of TMJ luxation are still unclear and have low quality of evidence for recurrent luxation
Regarding joint diseases (DJD, systemic arthritides, ICR), management of underlying systemic disorders is critical in managing systemic arthritides. Interdisciplinary management is often required in complex cases.
A majority of TMJ neoplasms and cysts require surgical procedures.Accurate diagnosis and distinguishing the original source is critical to success. TMJ chondrosarcoma has been studied systematically and is associated with lower recurrence and higher survival in comparison with other chondrosarcomas. Local recurrence and distant metastasis may be associated with poor prognosis.
Synovial chondromatosis cases may be managed by arthroscopy or open surgery. Open surgery is the recommended modality of treatment. Arthroscopy may be effective in casesless than 3 mm or without extra articular extension.
Adult condylar fractures may be treated by open reduction and rigid internal fixation (ORIF) and closed treatment. A systematic review comparing the two modalities suggested ORIF may have better clinical and functional outcomes. In unilateral displaced subcondylar fractures both modalities provide si milar results for protrusive and maximum mouth opening. However closed treatment resulted in better lateral excursive movements.
Management of underlying infection or systemic autoimmune disorder may be required in addition to conservative modalities for management of myositis. Physiotherapy modalities may be required in management of MMD contracture and myofascial pain.
p class=”pad-top”>Current evidence is insufficient to suggest irreversible procedures like extensive oral rehabilitation for preventative or management purposes of TMDs. A systematic review by Manfredini and Poggio suggested there was an absence of RCTs on the topic related to TMD, bruxism, and prosthodontic planning, and based on the best available current evidence suggested that prosthetic changes in occlusion as a management strategy for TMD and bruxism were not yet acceptable. Another systematic review concluded that at present there was insufficient evidence to demonstrate a cause-and-effect relationship between orthodontics and occlusion, and that orthodontics may not prevent or treat TMDs.
Systematic reviews suggest that the role of occlusion as the primary factor in the genesis of TMD is low to very low. However, a variety of TMDs can lead to secondary changes in occlusion. Distinction between the two is paramount for successful management.
The authors deny any conflicts of interest.