Effect of Hard Tissue Modification on Bacterial-Induced Secondary Caries at the Tooth-Resin Interface

Secondary caries at the tooth-resin interface is the primary reason for replacement of resin composite restorations. The tooth-resin interface is formed by interlocking of resin material with hydroxyapatite crystals in enamel and collagen mesh structure in dentin. Efforts have been made to strengthen the tooth-resin interface, and dentin biomodification agents have been previously identified with collagen cross-linking potential and antimicrobial activities. The purpose of the current study was to assess protective effects of dentin biomodification agents against secondary caries development around enamel and dentin margins of a class V restoration, using a bacterial caries model. Class V composite restorations were made on sixty bovine tooth samples (n=15) with pre-treatment of cavity walls with either control buffer solution, an enriched fraction of grape seed extract (GSE-UP), 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide/N-hydroxysuccinimide (EDC/NHS), or chlorhexidine digluconate (CHX). After incubating specimens in a bacterial model with Streptococcus mutans for 4 days, caries lesions were evaluated by microhardness test and confocal laser scanning microscopy with rhodamine B staining. Results of the study revealed that GSE-UP significantly inhibited secondary caries development immediately adjacent to the dentin-resin interface, as indicated by absence of rhodamine B staining around the restoration margin in dentin. Results suggest that incorporation of biomodification agents, specifically GSE-UP, into adhesive systems may inhibit secondary caries and thereby increase the longevity of resin composite restorations.