Methacrylated epigallocatechin gallate functionalized dental adhesives: Antiproteolytic activity and dentin bonding studies

OBJECTIVES: To assess the antiproteolytic effect of EGCG-methacrylate monomers and its inhibitory effect on gelatinolytic activity in the hybrid layer. Also, to investigate the effect of an adhesive material functionalized with EGCG-methacrylate monomers on immediate and long-term dentin-resin bond strength. METHODS: Neat EGCG (E0) was reacted with three different ratios of methacryloyl ester and dissolved in ethyl acetate to obtain EGCG-methacrylates with hydroxyl functionalization at 33 % (M-E33), 67 % (M-E67) and 100 % (M-E100) levels. Resin composite blocks were built on human dentin surfaces using self-etching adhesive containing E0, M-E33, M-E67, and M-E100 at 1 wt%. Demineralized human dentin disks were immersed in deionized water (DW) or lactic acid (LA) and subsequently treated with DW, acetone (as controls), E0, M-E33, M-E67 and M-E100 diluted in acetone. Concentrations of solubilized type I collagen C-terminal (CTX and ICTP) and N-terminal (NTX) telopeptides were determined from 7-day extracts of dentin matrix specimens by ELISA assays. In situ zymography of adhesive-dentin interface slices from restored teeth was performed by confocal microscope after 24 h dentin treatment. Microtensile bond strength (µTBS) and failure pattern were evaluated after 24 h and 6 months. Data were analyzed using two-way ANOVA and Tukey post hoc test (p < 0.05). RESULTS: All experimental groups statistically reduced the release of solubilized telopeptides from dentin samples in DW and LA. E0 and M-E100 incorporated into the adhesive system reduced the gelatinolytic activity within the hybrid layer. The lowest µTBS values for restored teeth were observed for E0 and M-E100 groups, after 24 h and 6 months, respectively. The most prevalent failure observed was classified as type 4, except for M-E100. SIGNIFICANCE: EGCG-methacrylate monomers effectively protected collagen from degradation. When incorporated into adhesive systems, EGCG-methacrylates reduced gelatinolytic activity within the hybrid layer, and did not affect immediate and long-term bond strength values of restorations.