Disc displacement of the temporomandibular joint and related factors

Abstract

Temporomandibular joint (TMJ) disc derangement is frequently found in daily clinical dental practice. In fact, anterior disc displacement and deformity are observed on TMJ-MR images in approximately 11% of new patients in our orthodontic department, diagnosed with TMJ disc displacement with or without reduction. If the clinical symptom is limited to TMJ noise and no abnormal findings are encountered in the TMJ hard tissues such as the mandibular condyle on imaging examination, usually no specific treatment for temporomandibular disorders (TMDs) is performed and the patient is just observed. On the other hand, if pain, closed lock, fibrous adhesion or indefinite complaints are observed in the TMJ or related areas, treatment for TMDs will be needed to relieve symptoms. It has been highly recommended to treat TMJ symptoms with conservative and reversible treatments based on scientific evidence. When TMJ disc displacement is caused and treated relatively early, disc replacement may be achieved as a result. Even with similar conservative treatment, replacement of the TMJ disc occasionally fails, therefore, the replacement will not always succeed, and even if replacement is achieved temporarily, recurrence may occur. TMJs with disc displacement or deformation may be accompanied by organic changes in the synovial fluid and joint constituent tissues, resulting in a decline in the lubricating and buffering functions, and so should not simply be considered as morphological problems. Furthermore, although many of the clinical symptoms caused by TMJ disc displacement tend to ease over the long term, the course of the disease varies. Therefore, it is desirable to clarify the detailed aspects and prognosis of abnormalities in the position and morphology of the TMJ disc, which cause disturbance of jaw movement and discomfort symptoms, leading to more accurate diagnoses. Thus, this article reviews changes in the TMJ tissue related to disc displacement based on the results of basic research.