How laser irradiation relieves pain induced by orthodontic treatment

Objectives: The aim of the present study was to elucidate how laser irradiation to the foramen mandibulae, foramen infraorbitale and maxillary tubers relieves the pain induced by orthodontic treatment. Methods: The subjects consisted of 24 adults [12: irradiated (LG); 12: control (CG)], all of whom were undergoing orthodontic treatment. When each subject registered their highest pain rating, LG group members were irradiated to the nerve foramens, while CG members were falsely irradiated at the same sites. The laser used in this study was the Ga-Al-As laser.(OLS3000;OSADA) A pain record was kept in which the subjects rated their pain level using the visual analog scale (VAS), both before and after irradiation. A pain reductive score (PRS) was then calculated from these values. Results: Before irradiation, the VAS value was 45.2 ± 16.3 in the LG, and 36.7 ± 23.1 in the CG. After irradiation, the VAS value was 27.4 ± 14.5 in the LG, and 32.3 ± 17.6 in the CG. PRS was 39.1 ± 18.1% in the LG, and 7.2 ± 10.8% in the CG, and this difference was found to be significant (p<0.05) according to the Mann-Whitney U-test. Before and after laser irradiation, several teeth in each subject were subjected to a mechanically produced percussion stimulus, with the response being described as level 2 for pain, level 1 for discomfort, and level 0 for no pain or discomfort. A t test showed a significant difference (p<0.05) for the lower right side first premolar, left side canine and both premolars. Conclusion: Pain resulting from orthodontic pressure was found to be significantly reduced by laser irradiation to these foramens. We believe that the underlying mechanism for this may involve laser irradiation causing inhibition to occur in the regions surrounding the nerve endings.