Impregnation with antimicrobials challenge bonding properties and water sorption behaviour of an acrylic liner

Objectives: To investigate the effect of impregnation of poly(ethyl methacrylate) and tetrahydro-furfuryl methacrylate (PEM/THFM) polymeric delivery system with chlorhexidine or fluconazole on its shear bond strength (SBS) and water sorption. Methods: For SBS testing, 16 PEM/THFM discs impregnated with chlorhexidine (CHX), pure fluconazole (FLUp) or fluconazole from capsules (FLUc) and 16 drug-free control discs were prepared and bonded to heat-cured acrylic blocks. All discs were allowed to set for 24 h at room temperature. After setting, half the discs (n = 8) were tested immediately (Group 1). The other half was further incubated in water for 28 days at 37°C before testing (Group 2). To evaluate water uptake, five PEM/THFM discs impregnated with CHX, FLUp or FLUc and five drug-free control discs were prepared and incubated in water. Mass changes were measured up to six months. Results: The mean SBS for control, FLUp, CHX and FLUc discs were 4.01, 3.85, 3.29 and 2.26 MPa, respectively for Group 1. Group 2 showed significantly lower SBS (P ≤ 0.05). All failures were adhesive. The percentage mass change due to water sorption ranged significantly from 12% for control to 27% for FLUc (P ≤ 0.05). A strong negative correlation between the extent of water absorption and the SBS was detected (R = 0.94, P = 0.05). Significance: Impregnation with antimicrobials presents a challenge to the physical and mechanical properties of a polymer. However, despite increased water uptake SBS remained acceptable for a temporary lining material and comparable to drug-free long-term lining materials. Moreover, the enhanced water uptake could contribute to improved leaching. © 2012 Elsevier Ltd. All right reserved.