Effect of transcutaneous electrical nerve stimulation on pain, edema, and trismus after surgical removal of impacted third molars: a split-mouth randomized clinical trial

Background: The transcutaneous electrical nerve stimulation (TENS) stimulus inhibits the activity of nociceptive neurons of the central nervous system. Pain relief is achieved by increasing the pulse amplitude of TENS to induce a non-painful paranesthesia beneath the electrodes. This study aimed to assess the effect of TENS on acute pain, edema, and trismus after surgical removal of impacted third molars. Material and Methods: This randomized, double blind, split-mouth clinical trial was conducted on 37 patients with bilaterally impacted mandibular third molars. The angle and body of mandible at the site of surgery in one randomly selected quadrant underwent TENS immediately after surgery (50 Hz, 100-µs short pulse, 15 minutes for 6 days). The TENS stimulator device was used in off mode for the placebo quadrant. The pain score (primary outcome) was measured for 7 days postoperatively, and edema and trismus (secondary outcomes) were assessed at 2, 4 and 7 days, postoperatively. The results were analyzed by repeated measures ANOVA using R software (alpha=0.05). Results: The overall mean pain score was significantly lower in the TENS than the placebo group (P<0.05). The number of taken analgesics in the first 3 days was significantly lower in the TENS group (P<0.001). Postoperative edema in the TENS group was lower than the placebo group but only the difference was not statistically significant (P>.05). The inter-incisal distance, as an index to assess trismus, was not significantly different between the two group at day 2, but it was significantly higher in the TENS group after the second day (P<0.001). Conclusions: TENS effectively decreased pain and trismus following impacted third molar surgery, and may be recommended as a non-pharmaceutical method to relieve postoperative symptoms.