Incorporation of EGCG into an etch-and-rinse adhesive system: mechanical properties and bond strength to caries affected dentin

This study evaluated how a matrix metalloproteinase (MMP) inhibitor (EGCG) incorporated into an etch-and-rinse adhesive system (AS) affects the long-term microtensile bond strength (MTBS) to caries affected dentin (CAD) and flexural strength (FS) of AS. Forty CAD surfaces received acid conditioning and were randomly divided into four groups (n = 10): EGCG-PRE – dentin treatment with 200 μg/mL EGCG solution; EGCG-INC – 200 μg/mL EGCG solution incorporated into SA; CHX-PRE – dentin treatment with 2% digluconate solution; NT – no treatment. The AS (Adper Single Bond 2, 3M ESPE) was applied and resin composite blocks were built on the dentin. Beam-shaped specimens (0.8 mm2) were obtained submitted to MTBS testing following 24 h, 6 months or 1 year of water storage (WS). Adhesive interface was analyzed by SEM. FS testing was performed by preparing specimens with the adhesive system, with or without the EGCG solution (200 μg/mL) (n = 10). Tests were carried out in a universal machine (0.5 mm/min). MTBS data were submitted to two-way ANOVA and Tukey’s test, whereas FS data, to the Student’s t-test (α = 0.05). MTBS values were not affected by EGCG application, either incorporated or used as a dentin treatment agent, regardless of the WS period; however, CHX negatively affected MTBS to CAD (p < 0.001). WS significantly reduced MTBS values (p < 0.001) from the 6-months time point. FS was not affected by EGCG incorporation into the SA (p = 0.2527). EGCG incorporation into AS was unable to maintain bond stability to CAD over time, whereas it did not compromise adhesive’s property.