Diagnoses

Temporomandibular joint dysfunction

Establishing this diagnosis

Relative movement of the two bony components in a joint is called "articulation". This movement should be fluid, and without popping, clicking, grating or locking. There should not be pain on closing the teeth together (from the teeth, jaw muscles or jaw joints). Presence of joint pain is a symptom of inflammation in the area.

Diagnosing TMD involves a review of the patient's medical, dental and social history and certain specific examination steps. History of the painful symptoms is important. Frequent questions include the following:

• Was there an injury to the jaw? Forceful blows can cause fractures (most commonly at the "neck" or narrowest part of the condyle), tears in the fibrous joint capsule, or merely inflammation in the joint capsule.
• Has the patient experienced recent sinus congestion or ear ache? Due to the close proximity of these anatomical areas to the TMJs, pain in one can be felt in another.
• Does the patient clench or grind their teeth? Heavy jaw muscle contraction forces can injure the joint capsules, and/or cause inflammation in the joints.
• Is the patient experiencing stress? Sometimes a stressful lifestyle causes the patient to clench and grind their teeth. Often the patient is not even aware they do it, and sometimes they may do it at night.
• Is the patient having difficulty sleeping? This question has the same implications as stress.
• Is the patient missing some or all of the back teeth on the affected side? Back teeth help to support the jaw muscle closing forces, and if they are missing, the joints take all of the force.
• Did the patient recently undergo dental treatment requiring the mouth to be opened wide, or for a prolonged period? If so, inflammation in the joints can result.
• Are the jaw muscles tired or sore? If so, the patient is likely clenching or grinding the teeth.
• Is the patient experiencing headaches? If the headaches originate in the temples, or radiate from the jaw closing muscles, clenching or grinding may be producing muscle fatigue and headache.

Examination involves evaluation of the teeth: are there signs of heavy muscle activity, such as wear planes, chips, cracks/craze lines, or notches (abfractions) at the gum line?; feeling ("palpation") for pops, clicks or grating (also called crepitus); listening, either unaided or with a stethoscope, for popping, clicking or crepitus; using electronic devices to "listen" to the joint as it articulates; using electronic devices that measure electrical activity in the muscles; using advanced imaging techniques, such as injection of dye into the joint and producing an "arthrogram".

Clicking may be an early derangement of the joint capsule, the smooth crescent-shape of which may be slightly wrinkled. It can also be a sign of "ligament laxity", in which case the ligaments attaching the joint capsule to the condyle may have been stretched, and are now snapping over the edge of the condyle. This may be caused by forcing the mandible to open past its ideal maximum opening, or by trauma to the mandible. Clicking may accompany any stage of jaw joint dysfunction.

Popping is a sign that the joint capsule has changed shape, which generally requires a significant amount of time to occur (i.e. a sign of a more chronic problem).

An "opening pop" suggests that a bulge in the joint capsule (disk) has developed in the anterior (forward) portion of the joint compartment, and is blocking the forward slide of the mandible needed to fully open the jaw.

A "closing pop" suggests that a bulge in the joint capsule has developed in the posterior (back) portion of the joint compartment, and is blocking the rearward return of the mandible. A "reciprocal pop" is one that occurs both on opening and closing, implying that the disk has bulged both forward and rearward, and instead of being crescent-shaped, now has a dumbbell shape.

Crepitus (grating) may be a sign that a hole has been worn through the fibrous joint capsule/disk, and the condyle is now rubbing directly on the glenoid fossa of the skull base. This would generally represent a long-standing derangement of the joint.

Examination also involves an assessment of pain. The dentist will generally place inward and forward pressure on the condyles when the teeth are closed to see if it causes pain. This will include placing the finger tips into the ear hole, which may seem unusual. A painful response supports a diagnosis of "capsulitis", or inflammation of the fibrous joint capsule. If there is no clicking, popping, grating, or locking, this is usually the earliest sign of trouble in the joints. Capsulitis may also accompany a more advanced (chronic) problem.

The patient's "envelope of motion" will be evaluated—can they open their mouth fully? Does the jaw deviate significantly to the left or right when opening? Is the opening restricted? Does the jaw lock, either open or closed?

Electronic devices can detect sounds in the joint which may not be detectable audibly or by auscultation (i.e. with a stethoscope).

The dentist will evaluate the patient's occlusion, or how the upper teeth and lower teeth line up when the jaw muscles are at rest, and the condyle of the mandible is in a stable position in the glenoid fossa. Teeth which are improperly aligned may cause greater forces to be placed on the jaw joints, which can lead to TMD. Improper alignment of the teeth is called "malocclusion".

Advanced imaging techniques for evaluating the jaw joints include tomograms, arthrograms, CT scans, Magnetic Resonance Imaging (MRI) and iCAT scans (cone beam scans).