Purpose: The objectives of the present study were to determine the changes in the ultrastructure of human dentine resulting from simulated cavity preparation by an Er:YAG Laser, and to investigate the optimal parameters of that laser for ablating dentine. Materials and Methods: Whole extracted caries-free human molars were used in this experiment. A slice of coronal enamel was removed to expose dentine above the pulp chamber. Irradiation was carried out using an Er:YAG laser with different combinations of energy levels, frequencies and pulse modes. Samples were then prepared for SEM analysis. Results: Within the Er:YAG laser parameters tested, several characteristic features were evident on the dentine surface. The features included absence of smear layer, open dentinal tubules, microroughness, and crater-like appearance. It was also demonstrated that intertubular dentine is more prone to ablation compared to peritubular dentine. SEM analysis also indicated that the optimal parameters, which produced the cleanest and smoothest treated dentine surface, were around 250 mJ energy level, variable square pulse (VSP) mode, and 10 Hz frequency. Conclusion: This study reported on some of the visible effects of Er:YAG laser treatment of dentine. Features such as open dentinal tubules, absence of smear layer and crater like appearance were similar to those effects noted in previous reports. However, other characteristics such as microirregularities and microprojections have not been previously described. The clinical relevance of the paper is that its findings validate the optimal performance parameters recommended by the manufacturer (Fotona Laser Systems).
Keywords: laser, dentine, surface morphology, SEM, optimal parameters