A comparative evaluation of properties of zirconia reinforced high impact acrylic resin with that of high impact acrylic resin

Poly methyl methacrylate (PMMA) acrylic resin, although being the most popular denture base material, is associated with poor mechanical properties. It has been documented that acrylic resin can be strengthened with an addition of structural component (filler) added in the acrylic matrix, to form a composite structure. To evaluate and compare the transverse strength, impact strength, surface hardness and water sorption of 10% and 20% zirconia (ZrO2) reinforced high impact acrylic resin with that of high impact acrylic resin (Trevalon HI, Dentsply India). There were 30 specimens in each of the four tests, amounting to a total of 120 specimens. Each of the tests had 10 specimens fabricated from high impact acrylic resin (control); 10 specimens fabricated from 10% zirconia (ZrO2) and 10 specimens fabricated from 20% zirconia (ZrO2) reinforced high impact acrylic resin. Specimens were subjected to the test of transverse strength in Universal Testing Machine, impact strength in Izod pendulum impact testing machine and surface hardness by Vickers Microhardness tester according to ISO Specification No. 1567. Water sorption was assessed according to ADA Specification No. 12. Data were analyzed by means of a one-way ANOVA and Bonferroni multiple comparison test. A significant increase in the transverse strength was observed in the reinforced specimens when compared to the control group. Impact strength and surface hardness were found having lesser values compared to the control group. Water sorption was found to increase on the addition of 10% and 20% zirconia (ZrO2) but the value lied below 0.8 mg/cm2 i.e. within the limit of ADA Specification No. 12. Reinforcement of acrylic resin with zirconia powder affects its physical and mechanical properties significantly.