Objectives: this study was conducted to compare the fracture resistance of three different denture base materials for implant overdentures. The three materials tested in this study were heat cured polymethyl methacrylate (PMMA), heat cured PMMA reinforced with 5% zirconium oxide powder, and thermoplastic resin.
Materials and Methods: Two implants were installed in the canine areas bilaterally in an epoxy resin model of a completely edentulous mandible. Duplication of the model was done according to sample size calculation to produce 15 stone models on which overdentures were constructed. The 15 models were divided equally into three groups. Overdentures were made from conventional heat cured PMMA in group I, and conventional heat cured PMMA reinforced with 5% zirconium oxide powder in group II and thermoplastic resin in group III. Fracture resistance of the overdentures was measured using a universal testing machine, and measurements were collected and statistically analyzed.
Results: The highest mean value for fracture resistance was recorded in group III, while the lowest mean value was recorded in group I. A statistically significant difference was found between group I and group III. Group II showed higher fracture resistance than group I, but the difference was not statistically significant.
Conclusions: reinforcement of heat cured PMMA with 5% zirconium oxide powder increases the fracture resistance of implant overdenture denture bases. Thermoplastic resins can also be used as a denture base material for implant overdentures, with a fracture resistance comparable to that of conventional PMMA.