Bond Strength of Denture Teeth to Injection-molded Thermoplastic Resin

Objectives: Recently, the removable partial dentures (RPDs) without metal clasp have been used for patients who, for esthetic demands, do not prefer conventional RPDs with metal clasps.
It was essential to provide mechanical retention for denture teeth and injection-molded thermoplastic resins.
The purpose of this study is investigate the bond strength of denture teeth to injection-molded thermoplastic resin.
Methods: Composite resin teeth (CR), acrylic resin teeth (AR) were chosen to be bonded to three types of injection-molded thermoplastic denture base resins and as a control, heat-polymerized resin. The ridge-lap surfaces of the denture teeth were divided into four groups according to type of surface treatment given (n=10):
no treatment group (NO), ethyl-acetate group (EA), T-shaped connected channels 1.6mm group (TS)and, T-shaped connected channels 2.1mm group (TL). A vertical load was applied using load testing machine at a crosshead speed of 1 mm/min.
Results: All group of EA were not significantly different from all group of NO. In the group of VP, EB and RN, each group of TL generally possessed significantly higher bond strengths than the other surface treatment. Furthermore, almost all group of CR were significantly higher than all group of AR. Additionally, in all group of TL, the RN were significantly higher than the VP and the EB. The RN-TL-CR was the highest bond strength value in this study. However, the RN-TL-CR were significantly lower than the AC-NO-CR.
Conclusions: 1. Chemical surface treatment for denture teeth was not effective in improving bond strength.
2. The diameter of the connected channels was approximately 1/3 of the width of the ridge-lap surfaces, which was the most effective in improving the bond strength.
3. Group of Polycarbonate has the highest bond strength in this study.
4. In the group of TL, the bond strength of composite resin teeth was higher than that of resin teeth.