Disk Displacement of Temporomandibular Joint and Dentofacial Asymmetry

Objectives:The purpose of this study was to investigate the relationships between TMJ disk displacement (DD) and amount and direction of facial asymmetry with results of MRI reading in Class III patients.Methods:The subjects comprised 97 patients with skeletal class III patients. TMJ MRI, lateral and postero-anterior cephalograms were obtained. According to the results of MRI, subjects were divided into 4 groups; Group 1: normal disk position in both TMJ, Group 2: disk displacement with reduction in both TMJ or without reduction in both TMJ, Group 3: TMJ ID was more advanced on the right side, Group 4: TMJ ID was more advanced on the left side. Results: The results showed that there were little differences in the lateral cephalograms, but linear measurements in the postero-anterior cephalogrmas evaluating the amount of mandibular asymmetry, L1per, Menper showed significant differences (p < 0.001). the results indicated that there was a right-sided mandibular shift in group 3, left-sided mandibular shift in group 4. Group 1,2 shows relatively little amount of mandibular asymmetry. In the angular measurement evaluating vertical asymmetry, all the variables, Mxcant, FOP, and FMP shows statistical differences. But, in the comparisons of absolute value of angular measurements, only FMP has a statistical significance.Conclusion: If the TMJ DD was more advanced on the one side than the opposite side, the mandible usually deviated to the advanced side, and if the TMJ DD was equal status or bilaterally normal, the amount of mandibular deviation was less.This study showed that associations existed between TMJ DD and facial asymmetry, however, no cause and effect association is made.It is important that if the orthodontic patient had an asymmetric face, especially in the mandibular region, the careful caution should be given to the status of the TMJ during orthodontic treatment planning as is afforded other factors influencing facial balance.