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 surfaceroughness 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. Copyright (c) 2012, Association for Dental Sciences of the Republic of China. Published by Elsevier Taiwan LLC. All rights reserved.