A8 Temporomandibular joint problems

Topic

Temporomandibular disorders are a group of conditions affecting the muscles of mastication, the temporomandibular joint, and associated structures. This group encompasses articular disc displacement—which may occur with or without reduction—osteoarthritis of the mandibular condyle, muscle spasms, and myofascial pain; these are four distinct manifestations that share a common origin in the temporomandibular joint and the muscles that move it.

Within the temporomandibular joint, the articular disc lies between the mandibular condyle and the glenoid fossa; under normal conditions, it acts as a shock absorber and redistributes the loads transmitted between these two bony structures during mastication.

The articular disc shifts anteriorly when the retrodiscal ligaments holding it in place become overstretched, typically due to bruxism or direct trauma to the temporomandibular joint. This anterior displacement moves the disc out of the position required to perform its function as a shock absorber between the mandibular condyle and the glenoid fossa.

The very muscles of mastication whose overactivity—as seen in bruxism—overstretches the retrodiscal ligaments and displaces the articular disc can also undergo muscle spasms as a result of that same overactivity. This spasm of the masticatory muscles is what causes myofascial pain; thus, the same muscular origin can give rise to both articular disc displacement and myofascial pain, conditions that are grouped together under the umbrella of temporomandibular disorders. When the articular disc becomes displaced and no longer occupies its correct position between the mandibular condyle and the glenoid fossa, the pressure it bears during masticatory function can become significantly higher than that borne by a properly positioned disc, as it no longer redistributes the load in the normal manner.

This abnormal pressure on the articular disc also triggers synovial inflammation within the temporomandibular joint, further raising intra-articular pressure and releasing inflammatory mediators—such as interleukin-1 and prostaglandin E2—that degrade the fibrocartilage composing the disc.

During mouth opening, the joint click occurs when the mandibular condyle, moving forward, jumps over the posterior border of the displaced disc and momentarily repositions itself onto it. This sudden jump of the mandibular condyle over the displaced disc is what generates the joint sound perceived as a click.

The joint sound produced by this mechanism and the limited mouth opening that arises when the displaced disc fails to reduce back onto the mandibular condyle are the most common clinical manifestations of temporomandibular disorders; thus, a single mechanical issue involving the temporomandibular joint disc—exacerbated by synovial inflammation and frequently accompanied by masticatory muscle spasm—ultimately manifests as the constellation of signs and symptoms characterizing temporomandibular disorders.

ID:3454