Changes in masticatory patterns after bilateral fracture of the mandibularcondylar process

Purpose: Because the morphology of the temporomandibular joint is thought t o control movements of the mandible during mastication, bilateral fractures of the condylar process should disrupt masticatory patterns. The purposes of this study were 1) to document changes in masticatory patterns after suc h fractures, and 2) to determine whether and when normal masticatory patter ns are recovered. Patients and Methods: Twenty-two patients (15 men and 7 women) were examine d at 6 weeks, 6 months, 1 year, 2 pears, and 3 years after bilateral condyl ar process fractures. Patients were age and sex matched to a control sample . Incisor movements in three dimensions, along with muscle activity from th e anterior temporalis, posterior temporalis, and superficial masseter, were recorded at 500 Hz during mastication of a gummy candy. Results: Although the patients showed no reduction of interincisal opening during mastication, the opening was achieved with reduction of anterior tra nslation of the condyles. Patients had significantly narrower chewing cycle s, with significantly lower adductor muscular effort during the closing pha ses of mastication. Differences from controls were no longer detectable 1 y ear after the fractures. Conclusion: The amount of opening during mastication may appear clinically normal in patients with bilateral condylar process fractures. However, disr uption of controlling structures and lateral pterygoid function appears to reduce the amount of anterior translation and lateral excursion during the chewing cycle. Reduced adductor muscle activity during the closing phases m ay reduce loads on the fractured condylar processes. In general, these pati ents recover normal masticatory cycles within 1 year.