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 0.5e5 wt% aluminum oxide (Al 2 O 3 ) 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 Z 10) coded A to E. Group A was the control group (without adding Al 2 O 3 ). Specimens in the other four groups (BeE) were reinforced with Al 2 O 3 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% Al 2 O 3 significantly increased the flexural strength compared to the control group (P Z 0.000). The Vickers hardness significantly increased (P < 0.05) after incorporation of 2.5 and 5 wt% Al 2 O 3. 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% Al 2 O 3 powder significantly increased its flexural strength and hardness with no adverse effects on the surface roughness.

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Different sintering times did not alter the marginal fit of the zirconia copings. The mean values of the marginal gap were within the clinically acceptable level for all three groups.

Food simulating agents did not adversely affect the shear bond strength of Hard GC Reline; however, ethanol and heptane decreased the bond strength of Tokuyama and TDV, respectively. These findings may provide support to dentists to recommend restricted consumption of some foods and beverages for patients who have to use dentures relined with certain hard liners.

The contact of home bleaching agents with esthetic restorative materials is unavoidable. Therefore protecting these restorations from bleaching agents and reglazing or at least polishing the restorations after bleaching is recommended.