OBJECTIVE The purpose of the present study was to evaluate the effect of modified Widman flap (MWF) surgery (as a periodontal treatment procedure) on maximum bite force (MBF; as an indicator of patient function). METHODS In this clinical trial, 24 patients were examined for their MBF before and at one, four and eight weeks after their MWF surgery. These recordings along with the patients' demographics were analyzed using repeated measures ANOVA at a significance level of 0.05. RESULTS Males had a significantly higher MBF than female patients. Repeated measures ANOVA revealed a significant difference in MBF among the four time points (P<0.001) in each gender group. The MBFs recorded at baseline, and at four and eight weeks were not significantly different (P=0.148). Also, MBF showed a slight increase in male patients while it decreased in females over time. CONCLUSIONS The MWF surgery does not eventually decrease patients' MBF, which is a relief for patients. This procedure is therefore advised in order to save the maximum number of teeth as it remains the most significant factor determining MBF. However, this surgery has more favorable results in male patients. At four weeks after surgery, the patients will regain their baseline bite force.