Impact strength and dimensional accuracy of heat-cure denture base resin reinforced with ZrO2 nanoparticles: An in vitro study

Background: Polymerization shrinkage and fracture are the two common trouble shoots with denture base resins. Polymerization shrinkage affects the dimensional accuracy and fit of the prosthesis. The effect of zirconia (ZrO2) nanoparticles on polymerization shrinkage is not documented yet. Purpose: The aim and objective of this study were to evaluate the impact strength and dimensional accuracy of heat-cured poly methyl methacrylate (PMMA) on reinforcement with ZrO2 nanoparticles. Materials and Methods: Conventional heat-cure denture base resin (control) and the polymer reinforced with 3, 5, and 7 wt% of ZrO2 nanoparticles were prepared and used in this study. Forty bar-shaped specimens were prepared and tested for impact strength using Charpy's type impact tester. Forty denture bases were fabricated and checked for dimensional accuracy by measuring the distance between the denture base and the cast in two different sections using the travelling microscope. Results: The impact strength decreased with increased concentration of ZrO2 and found to be least at 7 wt% concentration (2.01±0.26 J/mm2). The distance between the denture base and the cast significantly decreased both in the posterior palatal seal region (0.060±0.007cm) and mid-palatine section region (0.057±0.006cm) with ZrO2 nanoparticles reinforcement and was found to be least at 7 wt% concentration. Conclusion: Reinforcement of heat-cured PMMA with ZrO2 nanoparticles significantly increased the dimensional accuracy and decreased the impact strength.