Effect of adhesive application techniques on microtensile bond strength to dentin

This in-vitro study aims to investigate the effects of applying two different universal adhesives in self-etch mode using various techniques on dentin microtensile bond strength (µTBS) and the resindentin interface, both immediately and after aging with 10000 thermal cycles. In this thesis, 80 caries-free human molars were used. The dentin surfaces were prepared using a diamond disc and sandpaper. Two different universal adhesive systems (Nova Compo B Plus, AllBond Universal) were applied in self-etch mode using the following five different techniques: 1-Adhesive application according to the manufacturer's instructions 2-Adhesive application with a sonic applicator 3-Bioactive glass application followed by adhesive application 4-Adhesive application with a sonic applicator after bioactive glass application 5-Double-layer adhesive application with separate polymerization for each layer Composite resin was applied to the adhesive-treated surfaces. Half of the specimens were subjected to 10,000 thermal cycles, while the other half was stored in distilled water for one week. All specimens were then subjected to a microtensile bond strength (µTBS) test, and failure types (adhesive, cohesive, mixed) were evaluated under a light microscope. The resin-dentin interface was examined with a scanning electron microscope (SEM). The data were analyzed using JAMOVI 2.3.21, and the normality of the data distribution was assessed with the Shapiro-Wilk test. Robust ANOVA was used to compare non-normally distributed values according to application technique, adhesive system, and aging, with multiple comparisons analyzed using the Bonferroni test. Results were presented as trimmed mean ± standard error (T-Mean ± SE). The level of significance was set at p < 0.05. For both universal adhesives, the double-layer application technique showed significantly higher values compared to other techniques. Among these, the AB2KT group (94.58 ± 5.71) demonstrated higher values than the NC2KT group (60.54 ± 5.21). After aging, a decrease in µTBS values was observed in almost all groups. The relatively lower bond strength of universal adhesives compared to multi-step systems is a disadvantage. However, the double-layer application technique, which does not present any challenges in clinical use and positively affects bond strength, appears to have high potential for routine practice. Keywords: universal adhesive; bioactive glass; double-layer application; microtensile, SEM.