Changes in masticatory patterns after bilateral fracture of the mandibular condylar process

Because the morphology of the temporomandibular joint is thought to 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 such fractures, and 2) to determine whether and when normal masticatory patterns are recovered.

Twenty-two patients (15 men and 7 women) were examined at 6 weeks, 6 months, 1 year, 2 years, and 3 years after bilateral condylar process fractures. Patients were age and sex matched to a control sample. Incisor movements in three dimensions, along with muscle activity from the anterior temporalis, posterior temporalis, and superficial masseter, were recorded at 500 Hz during mastication of a gummy candy.

Although the patients showed no reduction of interincisal opening during mastication, the opening was achieved with reduction of anterior translation of the condyles. Patients had significantly narrower chewing cycles, with significantly lower adductor muscular effort during the closing phases of mastication. Differences from controls were no longer detectable 1 year after the fractures.

The amount of opening during mastication may appear clinically normal in patients with bilateral condylar process fractures. However, disruption 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 may reduce loads on the fractured condylar processes. In general, these patients recover normal masticatory cycles within 1 year.