Comparative Assessment of Different Pre-Treatment Bonding Strategies to Improve the Adhesion of Self-Adhesive Composites to Dentin

The aim of this study is to compare the adhesive interface formed in dentin, using self-adhesive composites applied with different bonding strategies, by testing the microtensile bond strength (mu TBS) and ultramorphology through the use of light microscopy. Permanent, sound human molars were randomly allocated to six experimental groups. The groups included a negative control group, where only etching was performed via EtchOnly; a positive control group where an adhesive was applied, OptiBondFL (OBFL); and an experimental group where a primer was applied using a co-curing strategy together with a composite (Primer_CoCuring). The samples were sectioned into microspecimens for mu TBS (n = 8) and into 1-mm thick slabs for light microscopy using Masson's trichrome staining protocol (n = 3). The statistical analysis included a two-way ANOVA for mu TBS data and Tukey's HSD was used as a post-hoc test (significance level of 5%; SPSS v. 26.0). The results of the mu TBS revealed that the self-adhesive composite (F = 6.0, p < 0.018) and the bonding strategy (F = 444.1, p < 0.001) significantly affected the bond strength to dentin. However, their interactions were not significant (F = 1.2, p = 0.29). Etching dentin with no additional treatment revealed the lowest mu TBS (VF_EtchOnly = 2.4 +/- 0.8 MPa; CC_EtchOnly = 2.0 +/- 0.4 MPa), which was significantly different from using a primer (VF_CoCu = 8.8 +/- 0.8 MPa; CC_CoCu = 6.3 +/- 1.0 MPa) or using the full adhesive (VF_OptiBondFL = 22.4 +/- 0.3 MPa; CC_OptibondFL = 21.2 +/- 0.4 MPa). Microscopy images revealed that the experimental Primer_CoCuring was the only group with no collagen fibers exposed to the dentin-composite interface. Overall, the use of a primer, within the limitations of this study, increased the bonding of the self-adhesive composite and provided sufficient infiltration of the collagen based on light-microscopic imaging.

Automated summary

This study compares the adhesive interface formed in dentin using self-adhesive composites with different bonding strategies. The results indicate that using a primer strategy enhances the bond strength of the self-adhesive composite and provides sufficient collagen infiltration.