[Effect of Neodymium-Doped Yttrium Aluminum Garnet Laser Combined With Desensitizing Toothpaste on Dentinal Tubule Occlusion Against Acid Challenge].

Objective To assess the effects of different application sequences of neodymium-doped yttrium aluminum garnet(NdratioYAG)laser and the desensitizing toothpaste containing stannous fluoride on dentinal tubule occlusion.Methods Twelve intact third molars freshly extracted from human were selected and prepared into dentin slices with a thickness of 0.8 mm.Each dentin slice was subdivided into four small slices,three of which were etched with 6% citric acid and randomly assigned to the following three groups(n=12):(1)control group:no treatment;(2)NdratioYAG+toothbrushing(TB)group:first irradiated with NdratioYAG laser and then brushed with desensitizing toothpaste;(3)TB+NdratioYAG group:first brushed with desensitizing toothpaste and then irradiated with NdratioYAG laser.The NdratioYAG laser irradiation were carried out at 1 W,15 pulses/s,and the pulse width of 150 mus for 10 s(for a total of 6 cycles).After the above treatment,the 12 dentin slices from the NdratioYAG+TB and TB+NdratioYAG groups were randomly assigned to four subgroups(n=3)and subjected to acid etching in the Coca-Cola solution for 0,5,10,and 15 min.A scanning electron microscope was used to observe and photograph the dentin slices in each group,and eight single-blinded examiners scored the slices according to uniform criteria.The analysis of variance was carried out to compared the scores between groups.Results Before acid etching,the dentin tubule occlusion scores of the NdratioYAG+TB and TB+NdratioYAG groups were(4.83+/-0.09) scores and(3.85+/-0.66) scores,respectively,which had no significant difference between each other(P=0.0590)and were higher than that[(0.10+/-0.07)scores]of the control group(both P<0.0001).The dentin tubule occlusion scores of the NdratioYAG+TB group after acid etching for 5,10,and 15 min were(4.33+/-0.60)scores,(4.27+/-0.24)scores,and(3.63+/-0.07)scores,respectively,which were not significantly different from those[(4.04+/-0.10)scores,(3.76+/-0.59)scores,and(3.17+/-0.29)scores,respectively]of the TB+NdratioYAG group(all P>0.05).In the NdratioYAG+TB subgroup,the dentin tubule occlusion score after acid etching for 15 min was significantly lower than that before acid etching(P=0.0011).In the TB+NdratioYAG group,there was no statistically significant difference in the score between before and after acid etching(P>0.05).Conclusions NdratioYAG laser irradiation with appropriate parameters combined with the use of desensitizing toothpaste could produce an excellent occluding effect on dentinal tubules regardless of the sequence.However,brushing with desensitizing toothpaste followed by NdratioYAG laser irradiation produced more consistent dentin sealing after acid etching.