Dental asymmetry in temporomandibular disorders.

In our previous study, it was reported that facial asymmetry due to mandibular lateral displacement (MLD) was significant in patients with temporomandibular disorders (TMD). In this study, dental asymmetry in TMD patients was investigated by means of PA cephalogram and study model. Lateral deviation of the midline of the mandibular occlusal table (PA-mid) and right-left difference of the molar relationship (Molar-Diff.) were examined, and their relationship with MLD was studied. PA-mid and Molar-Diff. were significantly correlated with MLD. In most cases, displaced side of the midline of the lower occlusal table was coincident with that of the mandibular skeletal midline. These results suggest that in TMD patients asymmetries in occlusal relationship of the midline of the mandibular teeth and molars were mainly due to a mandibular skeletal asymmetry and not merely due to a dental malposition on the alveolar basal bone. Many cases had a more distal occlusal relationship of the first molar on mandibular displaced side compared with that on the opposite side. A high incidence of Class II relationship was found (61.8% as a whole) and more remarkable on the mandibular displaced side. Midline discrepancy and right-left difference of the molar relationship seem to be important occlusal characteristics in patients with TMD.