Properties of Methacrylate Resins Passively Incorporating EGCG

Objectives: The high incidence of composite-resin restoration replacements due to failures happening at tooth-filling interface reinforce the need for improved restorative that are less susceptible to bacterial deterioration. Epigallocatechin gallate (EGCG) has demonstrated antimicrobial efficacy, collagen crosslinking ability, and inhibitory effect against MMPs and cathepsins. Previous work has also shown that EGCG can be incorporated into polymers in low concentrations (~1%) without detrimentally affecting their properties. This study aims to formulate dental resins passively incorporating increasing concentrations of EGCG and to investigate the resins physical and biological properties.
Methods: Resins were prepared by the addition of 0.5-20wt% EGCG into triethylene glycol dimethacrylate (TEGDMA). Monomers were combined with a co-initiator system consisting of 0.5% CQ and 1% DMAEMA, for light activated polymerization. Fourier Transform Infrared Spectroscopy was used to determine the Degree of conversion (DC%). Glass transition temperatures (Tg) were established using Differential Scanning Calorimetry (DSC). Gel content (GC) and Degree of Swelling (DS) were measured using gravimetric analysis after 48h of incubation of samples in acetone and water, respectively. Antibacterial efficacy was tested against S. mutans and determined by counting the colony forming units and calculating the bacterial survival rate. One-Way ANOVA and Tukey post hoc tests were used to analyze data (α=5%).
Results: Resins incorporating 20% EGCG showed significant decreases in the DC% compared to the control TEGDMA. Increasing the concentration of EGCG did not affect the Tg of the polymers. Reductions to the GC and DS were identified for concentrations of 2% and above. The antibacterial activity of resins increased as the concentration increased, with incorporation of 10% or more EGCG producing almost completely inhibition of bacterial growth.
Conclusions: The passive incorporation of increasing concentrations of EGCG into a dental methacrylate (TEGDMA) produce dental resins with strong biological activity; however, higher concentrations may detrimentally affect their physical properties.