Improvement of maximum occlusal forces after orthognathic surgery

Purpose: A number of studies have reported that maximum voluntary bite forces increase after orthognathic surgery. This study determined rates of long-term improvement in bite forces and looked for both sex-related differences in improvement and for any differences among surgical procedures. Patients and Methods: The study tested 117 patients before surgery and between 6 months and 3 years after surgery. At each trial, unilateral maximum voluntary bite force was measured at four different tooth positions using a standard transducer. Forty-three control subjects were similarly tested. The rate of increase in maximum bite force was calculated separately for male and female patients in various groups of patients and the controls. Results: The patients had significantly lower maximum bite forces than the controls before surgery and for as long as 2 years after surgery. Within 6 months after surgery, patients' bite forces were already greater than their presurgical forces. Patients generally showed steady improvement in bite force thereafter, with male patients improving more quickly than female patients. There were no clear differences among surgical procedures. Conclusions: Any temporary reduction in maximum voluntary bite force disappears less than 6 months after orthognathic surgery. Orthognathic surgery improves patients' bite forces, but this improvement may be gradual, requiring many months.