Pain relief effects of semiconductor laser irradiation

The purpose of this study was to evaluate the pain relief effects of continuous wave and chopper pulsed wave by semiconductor laser irradiation. The irradiation conditions were as follows: Group A, continuous wave (laser energy 1 w, irradiation time 60 s); Group B, chopper pulsed wave of 20 ms (laser energy 2 w, irradiation time 60 s); Group C, chopper pulsed wave of 20 ms (laser energy 1 w, irradiation time 120 s); and Group D, dummy irradiation. The pain relief effects were evaluated on pulp thermal sensitivity and surface anaesthetic effect. (1) Evaluation of pulp thermal sensitivity: the degree of pulp thermal sensitivity was measured by a pain thermometer on irradiation sites and control sites. (2) Evaluation of surface anaesthetic effects: the mucobaccal holds were penetrated with a 30-gauge cartridge needle, and each subject reported an immediate response to needle penetration on irradiation sites and control sites. For these results of pain relief effects on pulp thermal sensitivity and surface anaesthetic effects, there was statistically significant difference in pain relief effects between the irradiation conditions of chopper pulsed wave and control (P<0.05: paired t-test). Also, the irradiation conditions of Group C were significantly more effective than those of Group A. And there was no significant difference between dummy irradiation and control. This study suggests that semiconductor laser irradiation may be useful for pain relief.