Chlorhexidine Release and Water Sorption of Chlorhexidine-Incorporated Dental Adhesive Resins

OBJECTIVE: This study evaluated chlorhexidine release from unfilled, non-solvated, methacrylated-based resins of increasing hydrophilicity, and to examine relationships among Hoy's solubility parameters, water sorption, solubility and the rate of chlorhexidine release. METHODS: Resin disks were prepared from light-cured, experimental resin blends (R1, R2, R3, R4 and R5) containing 0.0 wt%, 0.2 wt%, 1.0 wt% and 2.0 wt% chlorhexidine diacetate (CDA), and immersed in deionised water at 37 ºC. Mass changes and chlorhexidine release were recorded at different periods. After a 28-day period, water sorption, solubility and the cumulative chlorhexidine release data were obtained. Additionally, antibacterial property of the resin disks was evaluated by observing the dimensions of inhibition zone against S. mutans. RESULTS: The most hydrophilic resin (R5) exhibited the highest chlorhexidine release rate. The most hydrophobic resin (R1) exhibited the lowest rate. However, no inhibition zone was produced by any specimens after one week. The addition of CDA increased solubility significantly but with no effect on water sorption. Significant positive correlations were seen between water sorption and the cumulative chlorhexidine release. CONCLUSION: Chlorhexidine release from resins may be attributed to the presence of channels/pathways in the polymer due to water-induced swelling, which in turn is enhanced by the hydrophilicity of cured polymer matrix.