Approach
The Diagnostic Criteria for TMD (DC/TMD) is an evidence-based diagnostic system that has been developed on the basis of extensive multi-centre studies.[5] DC/TMD comprises a physical domain called Axis I, which evaluates the temporomandibular joint and associated joints physically, and a psychological domain called Axis II, which assesses psychosocial comorbidities. Axis I evaluates the subjective symptoms and requires patient history, whereas Axis II identifies the barriers to treatment response, factors that contribute to chronic pain (psychological and social aspects), and targets for further interventions. Questionnaires developed based on these domains help diagnose TMDs.[1][2][5]
Diagnosis is based on history and physical examination. The 4 characteristic features are pain, joint noise, masticatory muscle tenderness, and limited mandibular function.[11] Patients may present with a single feature or with a combination of these features.
History
All patients should be asked about pain location, onset, duration, and exacerbating or mitigating factors; joint noise to distinguish between clicks and crepitus; para-functional habits such as nail biting or bruxism; and stress, depression, anxiety, and a history of inflammatory joint disease.[44][45]
Patients may complain of pain on using their jaw, their jaw locking (the opening pathway stops either opening or closing and can be manipulated to open/close further), or their bite not feeling right. Patients with myofascial pain and dysfunction complain of cyclic pain and possibly tooth pain from night-time bruxing (teeth grinding or clenching). Pain is the most important feature and if it is not related to using the jaw is unlikely to be due to TMDs.
Patients with internal derangement often complain of pain that is worse with mandibular movement.[11] These patients have clicking as well as possible locking and restriction of opening of the jaw.
Patients with osteoarthrosis are usually older adults. These patients complain of joint noise that is defined as crepitus.[11]
Physical examination
On examination, the area just anterior to the tragus should be palpated for tenderness at rest and on opening the jaw. The patient should open and close the mouth as an index finger is slightly depressed into the anterior tragal area and over the lateral portion of the joint to palpate within the joint for clicks or crepitus and tenderness. A stethoscope can be placed on the anterior tragal area to hear clicks; however, if a patient describes clicks, they are more likely to hear them as the joint lies just in front of the ear. The jaw should be evaluated as the patient opens and closes his/her mouth. Deviation of the jaw to either side or jerky movements should be sought. These are most often seen in internal derangement. The teeth should be evaluated for wear facets, the cheeks for lines of thickened tissue, and the tongue for crenulations, which are indicative of bruxism.[11] Normal range of mouth opening is over 35 mm between the upper and lower incisors in 97% of the population. Lateral movement of over 6 mm should be expected to each side.
Tests
No diagnostic tests are usually necessary. An orthopantomogram may be a useful first-line investigation to exclude dental causes and is easier to obtain if the patient presents to their dental practitioner first.
MRI can be used to evaluate disc morphology and internal derangement.
CT may be used to evaluate fractures and abnormalities of bone and to determine the traumatic and arthritic subtypes of TMDs.[17][46] Cone-beam CT has lower dose radiation than traditional CT and produces a superior image.[47][48]
If rheumatoid arthritis is clinically suspected, inflammatory markers, rheumatoid factor serology, and anti-cyclic citrullinated peptide antibody should be obtained to help confirm or exclude a diagnosis. See Rheumatoid arthritis (investigations).
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