Purpose:  This study aimed at  evaluation of the masseter muscle electromyographies (EMGs)  after mandibular third molar surgery and the relationships between clinical variables and EMG results.

Patients and methods:  Sixty patients were included in the study. Masseter muscles parameters were measured using EMG prior to operation and 1 week and 3 weeks  post–operation. Before and after the third molar surgery the clinical variables were also recorded.

Results:  Significant differences in the areas of voltage, power spectral densities and median frequencies (p=0.010, 0.018 and 0.043, respectively) were found 1 week  postoperatively when comparing the EMG results of the masseter muscle from the extraction site and non extraction side. Significant associations in clinical variables     (postoperative swelling, bone reduction and pericoronitis) and the EMG results 7 days postoperatively, (p<0.05) were also noted. However, there were no significant differences 21 days postoperatively.

Conclusion: Barring the controversies about the reliability of EMG, this study showed that some EMG variables could be used to evaluate postoperative changes in masseter muscle activity as the postoperative changes in EMG activities were transient.