Abstract
Statement of problem: Addition of zirconium oxide nanofillers to PMMA had improved the mechanical properties of heat polymerized acrylic resin, but it's effect on bond strength to acrylic teeth hadn't been evaluated yet.
Purpose: The purpose of the study was to evaluate the effect of Zirconium oxide (ZrO2) nanofillers powder with different concentrations (1.5%, 3%, 5%) on bond strength of resin denture base to acrylic teeth before and after thermocycling.
Material and methods: Zirconium oxide nanoparticles powder were added to heat cured (PMMA) with different concentrations (0, 1.5% ,3%, 5%). The base surfaces of 16 molar acrylic teeth were flattened, and zirconia reinforced heat-polymerized acrylic resin was applied to them. Thereafter, bar specimens were produced for the microtensile bond strength testing either before or after thermocycling.
Results: The results showed that 5% ZrO2 conc. recorded the highest value of microtensile bond strength. The lowest value was recorded in 1.5%, followed by 3%. Regarding thermocyling, the non-thermocycled groups always recorded higher values of microtensile bond strength either significant (1.5% & 5%) or insignificant (0% & 3%) than thermocycled ones at p < 0.05.
Conclusions: Within the limitation of this study, it was concluded that reinforcement of acrylic denture base with zirconia nanofillers had significantly decreased bond strength with acrylic denture teeth in 1.5 % and 3% concentration; however, 5% had increased the bond strength values insignificantly. Thermocycling had reduced the bond strength in all concentrations.