Water/ethanol and water/acetone proanthocyanidin solutions enhance the mechanical stability and sealing ability of resin-dentin bonds produced by the cross-linked dry bonding technique

Objectives: To evaluate the influence of solvents on the mechanical stability and dentin sealing ability of adhesive interfaces produced on dry dentin after collagen biomodification with a proanthocyanidin-rich grape seed extract (GSE). Methods: Flat dentin surfaces (N = 120) were initially divided into 10 groups. After phosphoric acid etching for 15s, the etched dentin was treated with: water (control), 5 % ethanol, 90 % ethanol, 5 % acetone, 90 % acetone, and the same groups added with 5 % GSE. The treatments were kept on the etched dentin for 60s. Then, the teeth of each treatment were further divided into two groups. Thus, after rinsing, the dentin was kept moist (wet bonding) or air-dried for 60 s (dry bonding). A water -free two-step etch -and -rinse adhesive system (Optibond S, Kerr) was applied, and composite blocks were built up. The teeth were tested for bond strength (mu TBS) immediately or after 12 months of aging. Considering the mu TBS results, additional teeth were prepared for qualitative analysis of nanoleakage (NL; SEM) and hybrid layer permeability (CLSM). The mu TBS data were analyzed with three-way RM ANOVA and Tukey (alpha = 0.05). Results: The immediate mu TBS did not differ among treatments for wet dentin. For dry dentin, GSE in 5 % ethanol or acetone presented the highest mu TBS values, the latter similar to wet control. After 12 months, mu TBS of GSE in 5 % ethanol or acetone were comparable to the immediate results for wet and dry techniques. These reduced NL and improved dentin sealing for both dentin wetness conditions like the immediate wet control. Conclusions: The application of 5 % GSE to etched dentin, either in 5 % ethanol or 5 % acetone, resulted in enhanced mechanical stability and dentin sealing of interfaces produced on dry dentin. Significance: Dentin biomodification with proanthocyanidin in the presence of ethanol or acetone makes bonding procedures less sensitive by eliminating the need to keep dentin wet and increasing the quality and stability of hybrid layers produced on dry etched dentin.