In vitro Evaluation of Dentin Surface Irradiated by Neodymium-doped: Yttrium Aluminum Garnet Laser (Nd: YAG) Using Scanning Electron Microscopy

Introdouction: Dentinal hypersensitivity (DH) is one of the most painful chronic problems reported in dental offices. Various methods have been applied for the treatment of DH. However, majority of them are either ineffective or last for a short period of time. It has been reported that lasers, particularly Neodymium- doped: Yttrium Aluminum Garnet laser (Nd: YAG), can be helpful in the treatment of this disease. However, systematic reviews have shown that the available evidence for its effectiveness is weak. The aim of this study was to evaluate the Nd: YAG laser-prepared dentine surface with different powers and energies. Fifteen extracted human molars were randomly divided into five groups receiving different powers and energies of Nd:YAG laser (Group A: power: 0.7 W, energy: 70 mJ; Group B: power: 0.9 W, energy: 90 mJ; Group C: power: 1.1 W, energy: 110 mJ; Group D: power: 1.3 W, energy: 130 mJ; and Group E: power: 1.5 W, energy: 150 mJ) in three pulse modes. The surfaces of the specimens were then studied using scanning electron microscopy (SEM). With output power of 0.7 W in single, double and triple radiation modes, sealed dentinal tubules and absence of smear layer were observed. The surfaces prepared by using higher powers of 0.9, 1.1, 1.3, and 1.5 W showed the same features as those prepared with 0.7 W power in single and double pulse modes. In addition, carbonization centers were observed when single pulse mode with power of 1.5 W was employed. All combinations of power and energy tested in this study were found to have produced sealing of the dentinal tubules. However, 0.7 W power in double and triple radiation modes is suggested to be the best option for the clinician, due to having the lowest energy, fewer side effects and lower risk of physical dangers, as well as decreasing the occurrence of unwanted carbonizations. Experimental and clinical studies, especially randomized clinical trials, comparing the effects of Nd: YAG lasers with conventional methods are recommended.