The radiographic and electromyographic study on masseter muscle following mandibular angle ostectomy in monkeys

Objective To investigate the morphological and functional changes of masseter muscle after mandibular angle astectomy. Methods 12 adult rhesus monkeys were used in this study and equally divided into 3 groups (n=4). Lateral mandibular angle astectomy was performed in each animal and the controlateral side was used as controls. The masseter muscle thickness, cross-section area and peak values of electromyography (EMG) were recorded before operation and at 3, 6, 12 months after operation, respectively. Results The masseter muscle thickness, cross-section area and peak values of EMG in the operated side were significantly lower than those in the unoperated side. The largest difference between two sides was observed at 3 months after operation. Although a recovering tendercy was found in the operated side with time, the values of masseter muscles from the operated side was lower than those from the unoperated side even at 12 months after operation. Conclusion Masseter atrophy and functional contraction decrease occurred following mandibular angle ostectomy, however it seems to be reversible with time passing.