Effect of the physical properties of acrylic resin of overnight immersion in sodium hypochlorite solution.

OBJECTIVES: This study evaluated colour stability, surface roughness and flexural strength of microwave-polymerised acrylic resin after overnight immersion in sodium hypochlorite, simulating 180 days use. MATERIALS AND METHODS: Forty disc-shaped (15 mm x 4 mm) and 40 rectangular specimens (65 mm x 10 mm x 3 mm) were prepared from microwave-polymerised acrylic resin. The specimens were immersed in 0.5, 1% sodium hypochlorite, Clorox/Calgon and distilled water. Colour measurements (ΔE) were determined by a portable colorimeter. A surface analyser was used to measure roughness (µm). The flexural strength (MPa) was measured using a three-point bending test in a universal testing machine. Data were evaluated by one-way anova, followed by Student-Newman-Keuls test (α = 0.05). RESULTS: Statistical analysis found significantly higher colour changes (SNK, p < 0.001) for the 1% sodium hypochlorite, but mean ΔE value quantified by National Bureau of Standards was classified as slight. When comparing the surface roughness, no statistical significance was found among the solutions (anova, p = 0.637). The 1% sodium hypochlorite presented significantly lower flexural strength compared with the control group (SNK, p = 0.034). CONCLUSION: It was concluded that immersion in 1% sodium hypochlorite solutions for 8 h does influence the colour stability and flexural strength of microwave-polymerised acrylic resin, during the simulated period of 180 days.

Comparison of physical and mechanical properties of microwave-polymerized acrylic resin after disinfection in sodium hypochlorite solutions.

This study evaluated the color stability, surface roughness and flexural strength of a microwave-polymerized acrylic resin after immersion in sodium hypochlorite (NaOCl), simulating 20 min of disinfection daily during 180 days. Forty disk-shaped (15 x 4 mm) and 40 rectangular (65 x 10 x 3 mm) specimens were prepared with a microwave-polymerized acrylic resin (Onda-Cryl). Specimens were immersed in either 0.5% NaOCl, 1% NaOCl, Clorox/Calgon and distilled water (control). Color measurements were determined by a portable colorimeter. Three parallel lines, separated by 1.0 mm, were registered on each specimen before and after immersion procedures to analyze the surface roughness. The flexural strength was measured using a 3-point bending test in a universal testing machine with a 50 kgf load cell and a crosshead speed of 1 mm/min. Data were analyzed statistically by ANOVA and Tukey's test (alpha=0.05). There was no statistically significant differences (p>0.05) among the solutions for color, surface roughness and flexural strength. It may be concluded that immersion in NaOCl solutions simulating short-term daily use during 180 days did not influence the color stability, surface roughness and flexural strength of a microwave-polymerized acrylic resin.

Comparison of physical and mechanical properties of microwave-polymerized acrylic resin after disinfection in sodium hypochlorite solutions

This study evaluated the color stability, surface roughness and flexural strength of a microwave-polymerized acrylic resin after immersion in sodium hypochlorite (NaOCl), simulating 20 min of disinfection daily during 180 days. Forty disk-shaped (15 x 4 mm) and 40 rectangular (65 x 10 x 3 mm) specimens were prepared with a microwave-polymerized acrylic resin (Onda-Cryl). Specimens were immersed in either 0.5 percent NaOCl, 1 percent NaOCl, Clorox/Calgon and distilled water (control). Color measurements were determined by a portable colorimeter. Three parallel lines, separated by 1.0 mm, were registered on each specimen before and after immersion procedures to analyze the surface roughness. The flexural strength was measured using a 3-point bending test in a universal testing machine with a 50 kgf load cell and a crosshead speed of 1 mm/min. Data were analyzed statistically by ANOVA and Tukey's test (?=0.05). There was no statistically significant differences (p>0.05) among the solutions for color, surface roughness and flexural strength. It may be concluded that immersion in NaOCl solutions simulating short-term daily use during 180 days did not influence the color stability, surface roughness and flexural strength of a microwave-polymerized acrylic resin.

Este estudo avaliou a estabilidade de cor, rugosidade superficial e resistência à flexão de resina acrílica polimerizada por microondas após desinfecção em hipoclorito de sódio, simulando 20 min de desinfecção diária durante 180 dias. Quarenta espécimes circulares (15 x 4 mm) e 40 retangulares (65 x 10 x 3 mm) foram preparados em resina acrílica polimerizada por microondas (Onda-Cryl). As amostras foram imersas em hipoclorito de sódio a 0,5 por cento, hipoclorito de sódio a 1 por cento, Clorox/Calgon e água destilada (controle). Medidas de cor foram determinadas por um espectrocolorímetro portátil. Três linhas paralelas, separadas por 1,0 mm, foram registradas em cada amostra antes e depois dos procedimentos de imersão para analisar a rugosidade superficial. A resistência à flexão foi medida utilizando um teste de flexão por 3 pontos em uma máquina universal de ensaios com uma célula de carga de 50 Kgf e uma velocidade de 1 mm/min. Os dados foram analisados estatisticamente por ANOVA e teste de Tukey (?=0,05). Não houve diferença estatisticamente significante (p>0,05) entre as soluções para cor, rugosidade superficial e resistência à flexão. Pode-se concluir que a imersão em soluções de hipoclorito de sódio, simulando um uso diário de curta duração durante 180 dias, não influenciou a estabilidade de cor, rugosidade superficial e resistência à flexão de resina acrílica polimerizada por microondas.