Effect of natural collagen cross-linker concentration and application time on collagen biomodification and bond strengths of fiber posts to root dentin

Proanthocyanidin-rich plant-derived agents have been shown to increase dentin biomechanical properties and resistance of dentinal collagen to degradation. This study investigated the effects of proanthocyanidin-rich extract (grape seed extract, GSE; Vitis vinifera) on the mechanical properties of demineralized dentin matrix, and the bond strength and stability of the adhesion of fiber posts to the root dentin. Demineralized dentin beams (n = 15) were incubated with 6.5% or 10% GSE for 30, 60, or 120 s. The modulus of elasticity (E) and the fold increase in E were determined by comparing specimens at baseline and after treatment. The data were analyzed by two-way ANOVA and Tukey post hoc tests (α = 0.05). For the bond strength test, single-rooted human teeth were randomly divided into seven groups: control group, no treatment; and experimental groups as described for the modulus of elasticity. Fiber posts were cemented with RelyX U200. Each group was randomly divided into two subgroups: 24 hours of water storage and 12 months of water storage. All roots were sectioned transversely in the coronal, middle, and apical regions, producing 1-mm thick slices, and the push-out test was performed. The failure modes were observed, and the bond strength means were analyzed by ANOVA (α = 0.05). For E test, no significant difference was observed among the incubation times (P > 0.05); however, high concentration of GSE (10%) resulted in a statistically higher fold increase in E compared to 6.5% (P < 0.05). For the push out test, the immediate and stored for 12 months groups showed similar bond strength values with or without pretreatment with GSE (P > 0.05), irrespective of the GSE concentration, time of treatment, and root regions (P > 0.05); however, the use of GSE contributed to a significant reduction in adhesive failure mode. The results indicate that 10% GSE exhibits a high cross-linking potential for dentin extracellular matrix. Moreover, the bond strength of fiber posts luted to root dentin with RelyX U200 remained stable after 12 months of water storage, with or without pre-treatment with GSE.