The Bond Strength of a Highly Cross-linked Denture Tooth to Denture Base Polymers: A Comparative Study

Purpose: This study compared shear bond strength and type of bond failure between a highly cross-linked tooth and different denture base polymers. Materials and Methods: Cross-linked denture teeth were bonded to either a heat-, an auto-, a microwave-polymerized denture base resin or a relatively new injection-molded, microwave-polymerizable polyurethane-based resin. Six experimental groups were established for each of the shear and peel tests. In four of the groups, teeth were used as received and bonded to each of the denture base resins; in the remaining two groups, they were treated with dichloromethane to determine its effect on the bonding with heat or auto-polymerized denture base resins. Bond strength was determined by compressive load applied at 45 degrees on the palatal surface of each tooth until fracture; the type of bond failure was assessed by the peel test. Results: The results showed that heat-cured PMMA groups failed cohesively and demonstrated significantly higher bond strengths than the other resins used. The application of dichloromethane on the ridge lap areas of teeth resulted in a significant improvement of bond strengths in heat- and auto-cured resins. Conclusion: Within the limitations of this experimental study, the results suggest that type of denture base material and processing methods may have an influence upon the bond strength between interpenetrating polymer network (IPN) denture teeth and base materials. Treatment of denture teeth with dichloromethane could provide substantial improvement in the bond strength of teeth with heat and auto-cured denture base resins; however, this finding should be validated in further investigations on the long-term effect of such treatment on the bond strength. Keywords: adhesion, IPN (interpenetrating polymer network) denture teeth, mechanical test, mechanical properties, polymethylmethacrylate