EFFECT OF REINFORCEMENT OF HIGH-IMPACT ACRYLIC RESIN WITH ZIRCONIA ON SOME PHYSICAL AND MECHANICAL PROPERTIES Efeito do reforço de resinas acrílicas de alto impacto com zircônia em algumas propriedades físicas e mecânicas

OBJECTIVES: To evaluate the effect of reinforcing high-impact acrylic resin (Metrocryl HI) with zirconia powder in two different concentrations on the transverse strength, impact strength, surface hardness, water sorption and solubility. MATERIALS AND METHODS: Fifteen specimens were prepared for each test, five from Metrocryl HI resin as control, five others were prepared from the 5% zirconia-modified Metrocryl HI resin, and another five specimens were prepared from the 15% zirconia-modified Metrocryl HI resin. Transverse strength was assessed with a 3-point bending test using a screw-driven testing machine. For the impact strength, a Charpy tester was used. Surface hardness testing was conducted using Vickers tester. The water sorption and solubility test was performed according to International Standards Organization specification No. 1567 for denture base polymers. Micro-structural examination of two specimens, one representing each ZrO 2 concentration group, was carried out using scanning electron microscopy. RESULTS: As determined by ANOVA and Bonferroni multiple comparison tests, the addition of zirconia resulted in a highly significant increase in transverse strength of high-impact acrylic resin (P 0.05). Although a significant increase in water sorption was demonstrated (P< 0.05), still its mean value lies within the specification limits. CONCLUSIONS: Reinforcement of high-impact acrylic resin with zirconia powder increases its transverse strength significantly.