Disc Derangements

4.2. TMDs related to Disc Derangements

A disc derangement is defined as a displaced disc relative to the condyle and eminence of the temporal bone (5,9,12). Displacement of the disc affects the functional joint movement, can cause movement limitation and gives problems with functional jaw activities such as chewing, mouth opening, yawning, talking, smiling, singing and brushing teeth (92).

Many etiologic factors have been suggested to explain disc derangements (93-99). Direct or indirect trauma to the jaw may cause stretching, tearing, or rupture of the disc, lateral ligament, or capsule. Bruxism has been reported as a potential cause of disc derangements, since compressive overloading may alter the connective tissue of the TMJ. Morphological

In the open mouth position, the intermediate zone of the disc may be positioned between eminence of the temporal bone and head of condyle at the mouth opening position. Due to relocation of the disc in the TMJ during the opening, it is referred as disc placement with reduction (DDwR) (9,12,83,96). During closing of the mouth, a second clicking sound may be heard, which called reciprocal click. The condyle slips posteriorly on the anteromedial displaced disc and the posterior band of the disc slips forward off the condyle. This may result in excessive loading of joint structures, causing injury and inflammation, and pain in the preauricular area. Since the retrodiscal tissue, which is richly innervated, has been stretched progressively due to the anterior disc displacement, an increasing deep stretch pain can be felt in the affected (67,94,96). It has been shown that people who had joint sounds, but do not have pain or dysfunction never progress to more severe impairments joint (9,67,93). A positive history of joint clicking, popping, snapping, palpation of a reciprocal clicks in 1 of 3 trials, and maximum assisted opening of 40 mm or greater are indicative of DDwR (9,83) (Insert

Osteoarthritis (OA) is an inflammatory condition associated with a degenerative process (99). This inflammatory condition clinically manifests as arthralgia, which is defined as pain and tenderness in the joint capsule and/or the synovial lining of the TMJ. In OA, the patient may report joint pain in the preauricular area, crepitus during jaw movements, and limited range of motion, whereas in osteoarthrosis, degenerative changes are similar with OA, but it is a noninflammatory condition (102). Degenerative changes may be unilateral or bilateral and has a strong preference for women. It is estimated that approximately 15 % of the world’s population suffer from osteoarthritis