Color Stability, Surface Roughness and Flexural Strength of an Acrylic Resin Submitted to Simulated Overnight Immersion in Denture Cleansers

• Published in: Brazilian dental journal 2013-04, Vol.24 (2), p.152-156
• Main Authors: Paranhos, Helena de Freitas Oliveira, Peracini, Amanda, Pisani, Marina Xavier, Oliveira, Viviane de Cássia, Souza, Raphael Freitas de, Silva-Lovato, Cláudia Helena
• Format: Article
• Language: English
• ISSN: 0103-6440; 0103-6440
• DOI: 10.1590/0103-6440201302151

This study evaluated color stability, surface roughness and flexural strength of acrylic resin specimens after immersion in alkaline peroxide and alkaline hypochlorite, simulating a period of one and a half year of use of overnight immersion. Sixty disc-shaped (16X4 mm) and 80 rectangular specimens (65X10X3.3 mm) were prepared from heat-polymerized acrylic resin (Lucitone 550) and distributed into 4 groups (n=20): C1: without immersion, C2: 8 h immersion in distilled water; AP: 8 h immersion in alkaline peroxide effervescent tablet; SH: 8 h immersion in 0.5% NaOCl solution. Properties were evaluated at baseline and after the immersion. Color data were also calculated according the National Bureau of Standards (NBS). Results were analyzed statistically by ANOVA and Tukey's HSD test (α=0.05). AP (2.34 ± 0.41) caused color alteration significantly higher than C2 (0.39 ± 0.30) and SH (1.73 ± 0.52). The mean ΔE values were classified as indicial for C2 (0.36 ± 0.29) and noticeable for AP (2.12 ± 0.39) and SH (1.59 ± 0.48). SH (0.0195 ± 0.0150) caused significantly higher ΔRa (p=0.000) than the C2 (0.0005 ± 0.0115) and PA (0.0005 ± 0.0157) groups. There was no statistically significant difference (p=0.063) among the solutions for flexural strength (C1: 105.43 ± 14.93, C2: 100.30 ± 12.43, PA: 97.61 ± 11.09, SH: 95.23 ± 10.18). In conclusion, overnight immersion in denture cleansing solutions simulating a year and a half of use did not alter the flexural strength of acrylic resin but caused noticeable color alterations, higher for alkaline peroxide. The 0.5% NaOCl solution caused increase in surface roughness. Resumo O estudo avaliou a alteração de cor, rugosidade de superfície e força de flexão de espécimes de resina acrílica após imersão em peróxido alcalino e hipoclorito alcalino, simulando um ano e meio de uso seguindo a imersão noturna. Sessenta espécimes circulares (16 X 4 mm) e oitenta retangulares (65 X 10 X 3,3 mm) de resina acrílica termopolimerizável (Lucitone 550) foram distribuídos em 4 grupos (n=20): C1: sem imersão, C2: 8 h de imersão em água destilada; PA: 8 h de imersão em pastilhas efervescentes de peróxido alcalino; HS: 8 h de imersão em hipoclorito de sódio a 0,5%. As propriedades foram avaliadas antes e após as imersões. Os dados de alteração de cor também foram calculados de acordo com o National Bureau of Standards (NBS). Os dados foram analisados estatisticamente pelo teste ANOVA e Tukey HSD (α=0,05). O PA (2,34 ± 0,41) causou alteração de