A comparative study of the fracture resistance of different overdenture base materials. An invitro study

Abstract
Objectives: The objective of this study was to compare the fracture resistance of conventional acrylic resin versus reinforced and unreinforced thermoplastic resin as a denture base material of an implant supported mandibular overdenture.
Materials and Methods: A completely edentulous epoxy mandibular model was used in this study with two root form implants installed bilaterally at the canine areas. The model was duplicated 15 times into dental stone according to the sample size calculation. The 15 dentures were divided into three groups, five model in each. In the first group an implant retained overdenture was constructed with conventional heat cured acrylic resin denture base. In group two the overdenture was constructed from thermoplastic resin material, while the denture base of the third group was thermoplastic resin reinforced with 5% nano-zirconium oxide powder. The universal testing machine was used to evaluate the fracture resistance of the three types of overdenture. The recorded data was collected, tabulated and statistically analyzed.
Results: The results of the present study revealed that the mean values of maximum fracture resistance were much higher in the reinforced thermopress with 5% nano-zirconium oxide powder group followed by the unreinforced thermopress and finally the lowest mean values were the conventional acrylic resin.
Conclusion: the thermoplastic resin material either reinforced or not showed higher fracture resistance and could be used as an alternative to conventional acrylic resin material as a denture base in implant supported overdentures.
Key words: Conventional acrylic resins, denture base, mandibular overdenture; denture fracture, fracture resistance.