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Effect of titanium oxide and zirconium oxide nanoparticle incorporation on the flexural strength of heat-activated polymethyl methacrylate denture base resins – An in vitro experimental study

Introduction: Flexural strength is one of the most important properties which determine the clinical success of dentures. Even though titanium oxide nanoparticles (nano-TiO2) and zirconium oxide nanoparticles (nano-ZrO2) are extensively used to modify the properties of polymethyl methacrylate (PMMA) resin, there is negligible documentation in the literature comparing these two. Aim: The aim of the study is to find out and compare the effect of incorporation of 1 weight % nano-TiO2 and nano-ZrO2 on the flexural strength of heat-activated PMMA resin. Materials and Methods: 1 weight % of TiO2 and ZrO2 nanoparticles were weighed using a digital weighing balance and mixed with PMMA resin powder using the geometric dilution method. Sixty “35 mm × 10 mm × 3 mm” rectangular-shaped specimens fabricated were divided into three different groups, each containing twenty samples each. The specimens were loaded to failure at a crosshead speed of 1 mm/min and with 500 N load cell in a Universal Instron Testing Machine, Model 3345. Flexural strength was registered by the machine with 0.001 MPa precision. Results: PMMA with nano-TiO2 group had the maximum flexural strength, load at maximum flexure, and load at break followed by unreinforced PMMA and PMMA with nano-ZrO2. Statistically significant difference was noted between the three groups (P < 0.001). Post hoc analysis using Tukey's post hoc test showed a statistically significant difference for all three pair-wise comparison. Conclusions: Within the limitations of this study, it can be concluded that nano-TiO2 greatly enhanced the flexural strength, load at maximum flexure load, and load at break of PMMA resin, whereas nano-ZrO2 significantly reduced these properties of PMMA.