The relationship between temporomandibular joint disk displacement and mandibular asymmetry in skeletal Class III patients.

OBJECTIVE To investigate the relationship between temporomandibular joint disk displacement (TMJ DD) and facial asymmetry in skeletal Class III patients. MATERIALS AND METHODS The subjects comprised 97 skeletal Class III adult patients seeking orthodontic treatment. In addition to the routine lateral and posteroanterior (PA) cephalograms, and regardless of the TMJ status, each subject consented to magnetic resonance imaging (MRI) to evaluate their TMJs. According to MRI readings, subjects were classified into four groups: group 1, bilateral normal disk position; group 2, bilateral DD with or without reduction; group 3, DD more advanced on the right side; and group 4, DD more advanced on the left side. PA and lateral cephalometric variables were analyzed to compare the four groups. RESULTS When the TMJ DD was more advanced on one side than on the other, the chin point usually deviated to the advanced side. When the TMJ DD status was equal or bilaterally normal, the amount of mandibular deviation was not significant. CONCLUSIONS If a skeletal Class III patient has an asymmetric face, especially in the mandibular region, careful examination is necessary with regard to the status of the TMJ during orthodontic diagnosis and treatment planning.