Effects of ethanol on the surface and bulk properties of a microwave-processed PMMA denture base resin.

Purpose: This study evaluated the effect of different concentrations of ethanol on hardness, roughness, flexural strength, and color stability of a denture base material using a microwave-processed acrylic resin as a model system. Materials and Methods: Sixty circular (14 × 4 mm) and 60 rectangular microwave-polymerized acrylic resin specimens (65 × 10 × 3 mm3) were employed in this study. The sample was divided into six groups according to the ethanol concentrations used in the immersion solution, as follows: 0% (water), 4.5%, 10%, 19%, 42%, and 100%. The specimens remained immersed for 30 days at 37°C. The hardness test was performed by a hardness tester equipped with a Vickers diamond penetrator, and a surface roughness tester was used to measure the surface roughness of the specimens. Flexural strength testing was carried out on a universal testing machine. Color alterations (ΔE) were measured by a portable spectrophotometer after 12 and 30 days. Variables were analyzed by ANOVA/Tukey's test (α= 0.05). Results: For the range of ethanol-water solutions for immersion (water only, 4.5%, 10%, 19.5%, 42%, and 100%), the following results were obtained for hardness (13.9 ± 2.0, 12.1 ± 0.7, 12.9 ± 0.9, 11.2 ± 1.5, 5.7 ± 0.3, 2.7 ± 0.5 VHN), roughness (0.13 ± 0.01, 0.15 ± 0.07, 0.13 ± 0.05, 0.13 ± 0.02, 0.23 ± 0.05, 0.41 ± 0.19 μm), flexural strength (90 ± 12, 103 ± 18, 107 ± 16, 90 ± 25, 86 ± 22, 8 ± 2 MPa), and color (0.8 ± 0.6, 0.8 ± 0.3, 0.7 ± 0.4, 0.9 ± 0.3, 1.3 ± 0.3, 3.9 ± 1.5 ΔE) after 30 days. Conclusions: The findings of this study showed that the ethanol concentrations of tested drinks affect the physical properties of the investigated acrylic resin. An obvious plasticizing effect was found, which could lead to a lower in vivo durability associated with alcohol consumption.