Effects of aluminum oxide addition on the flexural strength, surface hardness, and roughness of heat-polymerized acrylic resin

Background/purpose: Acrylic dentures frequently fracture during service due to their poor strength characteristics. The aim of this study was to evaluate the effects of adding 0.5–5 wt% aluminum oxide (Al2O3) powder on the flexural strength, surface hardness, and roughness of a conventional heat-polymerized acrylic resin. Materials and methods: In total, 50 specimens were prepared for each test. Specimens were divided into five groups (n = 10) coded A to E. Group A was the control group (without adding Al2O3). Specimens in the other four groups (B–E) were reinforced with Al2O3 at loadings of 0.5, 1, 2.5 and 5 wt%. Flexural strength was assessed with a three-point bending test using a universal testing machine. Hardness testing was conducted using a Vickers hardness tester. A surface-roughness test was performed with a profilometer. Results: Data analyses using analysis of variance and Tukey'shonest significant difference tests showed that adding 2.5 wt% Al2O3 significantly increased the flexural strength compared to the control group (P = 0.000). The Vickers hardness significantly increased (P < 0.05) after incorporation of 2.5 and 5 wt% Al2O3. No significant difference (P > 0.05) was detected in surface-roughness levels between the reinforced and control groups. Conclusion: Reinforcement of the conventional heat-cured acrylic resin with 2.5 wt% Al2O3 powder significantly increased its flexural strength and hardness with no adverse effects on the surface roughness.