Abstract
Background: The application of Nd:YAG laser on dentin with the adhesive system non-polymerized can influenced the quality of hybrid layer formed. Objectives: The aim of this study is to assess through analysis by scanning electronic microscopy (SEM), the Nd:YAG laser influence on the hybridization quality, using conventional Adper Single Bond (SB) or self-etching Clearfil SE Bond-Kuraray (CSEB) adhesives. Methods: Nine bovine incisors were treated on their incisal with SB and with CSEB in their cervical portion. They were divided into 3 groups with 6 specimens in each and treated as follows; G1- adhesive system and polymerization; G2- adhesive system, laser (60mJ/pulse) and polymerization; G3- adhesive system, laser (140mJ/pulse) and polymerization. All samples were restored with composite resin (Filtek Z350-3M). The thickness, the presence of failures (gap/porosity) and tags/microtags in the hybrid layer were analyzed using the SEM. The data were submitted to ANOVA and Tukey statistical tests 5%. Results: The highest average of hybrid layer thickness (1.89±0.15) was observed for G3 and the smallest was observed for G1-CSEB (1.36±0.14). The multiple comparison of ratio test showed that the smallest prevalence of failures was for G3-CSEB and the best performance for the presence of tags/microtags was found for G2-SB. Conclusion: Independent of the adhesive system used, the Nd:YAG laser, according to the parameter applied, had a positive influence on the hybridization quality.
Highlights
The formation of a good quality of hybrid layer in restorative dentistry is important for the improvement of bond strength and for the sealing of dentinal tubules that can prevent the leakage which increases the treatment longevity [1]
The dentine re-crystallization, with consequent obliteration of some tubules, was reported by Dederich et al [11] and Matsumoto et al [13]. According to this findings about dentin morphology after treatment with Nd:YAG laser, Gonçalves et al [15] studied the application of Nd:YAG laser on dentin with total-etching adhesive non-polimeryzed, believing that a fusion between them could form a hybrid layer more resistant, increasing the bond strength and the dentine re-crystallization. The results proved this hypothesis and leaded Matos et al [16], Matos et al [17], Arisu et al [18], Marimoto et al [19] and Ribeiro et al [20] to reproduce this methodology developed by Gonçalves et al [15] to confirm that the Nd:YAG laser applied after the adhesive, but before their polymerization, increases the immediate bond strength of the composite resins
The application of the two-way ANOVA test revealed that for technique factor, Subgroup Laser 140 mJ showed the hybrid layer thickness higher compared to the other subgroups; for adhesive factor, Single Bond (SB) showed the hybrid layer thickness higher compared to the Clearfil SE Bond (CSEB), and the interaction between the factors were statistically significant
Summary
The formation of a good quality of hybrid layer in restorative dentistry is important for the improvement of bond strength and for the sealing of dentinal tubules that can prevent the leakage which increases the treatment longevity [1]. Several studies [2,3] state the importance of hybrid layer thickness and formation of resin tags for bond strength. The use of total-etching adhesives suggest that the dentinal etching with the phosphoric acid removes the smear layer, opens dentinal tubules, exposes the collagen fibrils promoting the infiltration of the primer and bond [2,3]. These adhesives with this mechanism of action create a thick hybrid layer, but, with greater probability of failure, due to the hydrolysis of collagen that was not penetrated by the bond [4].
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