Assessing Collagen and Micro-permeability at the Proanthocyanidin-treated Resin-Dentin Interface

Purpose: To establish a fluorescence-based method to simultaneously assess micro-permeability and collagen cross-linking induced by chemical agents at the resin-dentin interface. Materials and Methods: Three chemical agents were investigated (proanthocyanidin-rich grape seed extract: GSE; carbodiimide hydrochloride/N-hydroxysuccinimide: EDC/NHS; glutaraldehyde: GD) along with a control (distilled water) as primers applied on flat occlusal dentin surfaces of 48 teeth and restored with two commercially available etch-and-rinse adhesives. Resin-dentin interfaces were polished and infiltrated with rhodamine-B solution for confocal laser scanning microscopy analysis. Parameters were chosen that would allow acquisition of a simultaneous appearance of collagen and interfacial micro-permeability (rhodamine-B). Fluorescence emission intensity (FEI) was converted into numerals and values were calculated for each group. Data were statistically analyzed using one-way ANOVA and post-hoc Scheffe's and multiple comparisons tests (alpha = 0.05). T-tests with Pearson correlations were used to investigate correlations between collagen cross-linking and micro-permeability. Results: The FEI of collagen was the highest for GD, followed by GSE, with no significant differences between EDC/NHS and the control group (p > 0.05). Micro-permeability was significantly affected by the adhesives (p < 0.05). Micro-permeability was the lowest for GSE groups, regardless of the adhesives (p < 0.001). Weak correlations were found between micro-permeability and collagen auto-fluorescence. Conclusions: Non-enzymatic collagen cross-linking induced by GSE and GD can be detected by increased collagen auto-fluorescence, and results in reduced interfacial micro-permeability. Increased collagen auto-fluorescence was correlated with fluorescent collagen cross-links and decreased micro-permeability at the resin-dentin interface. Collagen auto-fluorescence is a useful tool to detect auto-fluorescent exogenous cross links and their potential impact on the quality of the resin-dentin interface.