Clinicostatistical study of bilateral temporomandibular joint disorders.

Clinico-statistical observations on 104 cases of bilateral TMJ disorders are presented. The proportion of bilateral TMJ disorders (BTMJD) to the total patients of TMJ disorders was 23.1 percent. BTMJD occurred most frequently in the twenties and was predominant among female patients. The most common chief complaint was TMJ pain or TMJ sound. There were no significant differences in the age and sex distribution and the chief compaint between BTMJD and unilateral TMJ disorders. Among the initial symptoms of BTMJD, muscle symptoms mostly occurred bilaterally, but TMJ pains occurred unilaterally. TMJ sounds occurred equally in the bilateral and unilateral groups. The period from the onset of BTMJD symptoms to the initial visit to a clinic was longer than that for unilateral TMJ disorders. As for the present condition, most patients of BTMJD had several composit symptoms, TMJ pains+TMJ sounds or TMJ pains muscle symptoms. They rarely presented a similar symptom on both sides. Bilateral TMJ pains and bilateral TMJ sounds were concurrently recognized only in 11 cases. Bilateral TMJ pains and bilateral muscle symptoms were simultaneously recognized only in 11 cases as well. Most of the unilateral TMJ pains were accompanied with TMJ sound on the other side, but many of unilateral TMJ pains were recognized on the same side as that showing unilateral muscle symptoms. Difficulty in opening the mouth wide (<39mm) in unilateral TMJ disorders was severer than in BTMJD.From these analyses it is thought that BTMJD have bilateral derangement of the TMJ disc and condyle or tenderness of the masticatory musculature that were acquired under a persisted abnormal condition of the masticatory system. Furthermore, many of the symptoms of BTMJD are mild in general but BTMJD may be resistant against an ordinary treatment for TMJ disorders.