Bite forces after open or closed treatment of mandibular condylar process fractures

Purpose: This study compared maximum voluntary bite forces in patients who received either open or closed treatment for fractures of the mandibular co ndylar process. Patients and Methods: One hundred fifty-five patients (127 male. 28 female) with unilateral fractures of the mandibular condylar process (91 treated c losed and 64 treated open) were included in this study. Maximum voluntary b ite forces were measured at 6 weeks, 6 months, and 1, 2, and 3 years after fracture. At each trial, unilateral maximum voluntary bite force was measur ed at 4 different tooth positions bilaterally using a standard transducer. Electromyography (EMG) of the masseter muscles was also recorded during the bite force measurements, and ratios of the working/balancing side EMG were calculated. Analysis of the data was performed using standard statistical methods. Results: The only significant difference between the 2 samples was in the l evel of fractures on the condylar process. No patients treated open had fra ctures of the "head" of the condylar process, whereas there were 11 in the group treated closed. No differences were observed in maximum voluntary bit e forces between the 2 treatment groups at any time period, or were there c orrelations between bite force magnitude and location of the fracture, disp lacement of the fracture, or any other variable studied. Both groups showed a significant recovery of maximum bite force from the 6-week to the G-mont h testing session. For both groups, working/balancing EMC ratios were signi ficantly greater when subjects were biting on the side opposite the fractur e. When biting on that side, the working/balancing EMG ratios were higher i n the closed treatment group, but the difference did not reach significance . Conclusions: Maximum voluntary bite forces in patients treated for mandibul ar condylar process fractures do not differ significantly when treatment is open or closed. Neuromuscular adaptations to the fractured mandibular cond ylar process occur in both groups. (C) 2001 American Association of Oral an d Maxillofacial Surgeons.