Chewing movements in near ideal occlusion with and without TM symptoms

Orthodontic models hand-articulated into maximum intercuspation of 720 untreated subjects were evaluated by 17 criteria for grading an ideal anatomic occlusion including good dental interdigitation and alignments. Of the 720 subjects screened, the best 17 subjects were divided into three groups that contained 11 near ideal occlusions scored with 92-98%, three lower evaluated occlusions scored with 86-88% and three near ideal occlusions with TM signs or symptoms scored with 90-94%. Border and chewing movements were recorded using incisor tracking instrument (Visitrainer, model 3). Border movements in asymptomatic subjects demonstrated a well-defined intercuspal position, smooth and equal lateral excursions, and straight opening/closing movements. However, one subject with pain of right joint recorded an inconsistent intercuspal position, restricted excursions and a deviated path corresponding to a reciprocal click in opening/closing movements. Chewing movements in asymptomatic subjects with near ideal occlusion demonstrated either no or a lower rate of opening gliding tooth contact along the lateral border movement on non-working side, and a higher rate of closing gliding tooth contact along border movement on the working side. Chewing movements in symptomatic subjects with near ideal occlusion showed opening and closing without gliding along the lateral excursions, and closing point was inconsistent with maximum intercuspal position in the pain subject. In examining these near ideal occlusion subjects, the different characteristic chewing and border movements were defined for subjects with and without TM symptoms, respectively. Asymptomatic subjects with near ideal occlusion and lower evaluated occlusion showed almost the same chewing function. The goal of orthodontic treatment might be anatomic ideal occlusion with good chewing and border movements indicated in this study.