Effects of denture cleansers on heat-polymerized acrylic resin: A five-year-simulated period of use

Abstract

This study evaluated color stability, surface roughness and flexural strength of acrylic resin after immersion in alkaline peroxide and alkaline hypochlorite solutions, simulating a five-year-period of use. Sixty disc-shaped (16x4 mm) and 60 rectangular specimens (65x10x3.3 mm) were prepared from heat-polymerized acrylic resin (Lucitone 550) and assigned to 3 groups (n=20) of immersion (20 min): C1: distilled water; AP: warm water and one alkaline peroxide tablet; SH: 0.5% NaOCl solution. Color data (ΔE) were determined by a colorimeter and also quantified according to the National Bureau of Standards units. A rugosimeter was used to measure roughness (μm) and the flexural strength (MPa) was measured using a universal testing machine. Data were evaluated by Kruskal-Wallis followed by Dunn tests (color stability and surface roughness) and by one-way ANOVA and Bonferroni test (flexural strength). For all tests was considered α=0.05. AP [0.79 (0.66;1.42)] caused color alteration significantly higher than C1 [0.45 (0.37;0.57)] and SH [0.34 (0.25;0.42)]. The mean ΔΕ values quantified by NBS were classified as “trace” for C1 (0.43) and SH (0.31) and “slight” for AP (0.96). SH [-0.015 (-0.023;0.003)] caused significantly higher ΔRa than the C1 [0.000 (-0.004;0.010)] and AP [0.000 (-0.009;0.008)] groups. There was no statistically significant difference among the solutions for flexural strength (C1: 84.62±16.00, AP: 85.63±12.99, SH: 84.22±14.72). It was concluded that immersion in alkaline peroxide and NaOCl solutions simulating a five-year of 20 min daily soaking did not cause clinically significant adverse effects on the heat-polymerized acrylic resin.