comparative evaluation of dentine surface changes following nd:yag laser irradiation by sem

introduction dentine hypersensitivity is a common clinical problem in dental practices. so several methods such as, nd: yag laser have been used to treat this problem. previous studies reported that nd:yag laser irradiation on root surface makes some thermal changes, like dentine melting and some other side effects which are related to power of laser irradiation. the aim of our study was to compare two different settings of nd: yag laser to evaluate their efficacy in occluding dentinal tubules and their side effects by means of sem. methods 15 newly extracted mandibular molars were selected and the specimens with certain dimensions from buccal surface and below cej were prepared. specimens were divided in 3 groups: group 1 (control), were not irradiated by laser; group 2, irradiated by nd:yag laser (0.5w, 10hz, 60sec, 2 times); and group 3, irradiated by nd:yag laser (1w, 10hz, 60sec, 2 times). after preparation and gold coating of specimens, the photomicrographs were seen by sem in magnification of 100 and 1500. finally, the number and diameter of dental tubules, crater and microcraks were determined in each group. after that, the data was analyzed using anova test. results results of this study showed that diameter of dentinal tubules were reduced in nd: yag irradiated groups, compared with control group. also there were no significant differences in the mean number of open dentinal tubules between nd:yag (0.5 watt) and control group. on the contrary, there were significant differences between nd:yag (1 watt) and the other groups . meanwhile, no group showed micro cracks or craters. conclusion the results of this study show that nd:yag laser irradiation can cause thermal effects such as decrease in dentinal tubules diameter or their occlusion. also 1 watt power nd:yag laser is more effective than 0.5 watt power in tubules occlusion which is a necessary factor in dentine desensitization. key words dentine hypersensitivity, nd:yag laser, dentinal tubules, scanning electron microscope (sem).