Abstract:

Objective To explore the effects of Er: YAG lasers with different pulse energies and of Er: YAG lasers combined with Duraphat on dentine surface morphology and the dentinal tubule exposure rate, thereby providing a theoretical basis and parameters for clinically treating dentine hypersensitivity with Er: YAG lasers.Methods Dentinal tubule exposure models were divided into five groups, namely, group A (single Er: YAG laser exposure), group B (Duraphat+ Er: YAG laser), and group C (Er: YAG laser+Duraphat), which were exposed to 6 levels of pulse energy (80 mJ/P- 250 mJ/P), and experimental control group D (Duraphat group) and blank control group E. Scanning electron microscopy was used to observe dentine surface morphology and dentinal tubule closure in these groups, and Image-Pro Plus 6.0 software was used for image analysis to measure the exposure rates of the five groups of dentinal tubules.Results The dentinal tubule exposure rates for the A-D groups were significantly lower than that of the E group (P < 0.001); when the Er: YAG laser pulse energy was less than 250 mJ/P, the dentinal tubule exposure rates for the A-C groups were all lower than that of the D group, but when the pulse energy was higher than 250 mJ/P, the dentinal tubule exposure rates for the A-C groups were higher than that of the D group, showing significant differences (P < 0.001); under the same handling method, when the pulse energy was 80~200 mJ/P, the dentinal tubule exposure rate decreased as the pulse energy increased. If the pulse energy reached 250 mJ/P, the exposure rate of the dentinal tubules increased instead. There were apparently no significant differences between 80 mJ/P, 100 mJ/P, 160 mJ/P and 200 mJ/P in the A and C groups or between 80 mJ/P and 100 mJ/P in the B group (P > 0.05), while significant differences existed among the other groups (P< 0.05). Under the same pulse energy, the dentinal tubule exposure rates were A group > C group >B group; under different pulse energies, there existed significant differences between the A and B groups (P < 0.05); when the pulse energy was 120~250 mJ/P, there were significant differences between the B and C groups (P < 0.05), while there were no significant differences among other groups (P＜0.05).Conclusion Er: YAG lasers can close the dentinal tubules and play a cooperative role if combined with Duraphat; the effects of laser exposure are better if fluorine is applied beforehand; and dentinal tubule closure is positively correlated with the pulse energy of Er: YAG lasers within a certain energy scope, but when the pulse energy reaches 200 mJ/P, the dentine surface is excessively fused and injured.

Key words: Er: YAG laser, Pulse, Duraphat, Dentin surface morphology, Dentinal tubule, Exposure rates