Influência da desinfecção por microondas na dureza e resistências à flexão e ao impacto de resinas acrílicas

Este trabalho tem como objetivo comparar a influência da desinfecção por microondas na dureza e resistências à flexão e ao impacto em 30 corpos-de-prova de resinas acrílicas termopolimerizáveis Clássico, Onda-Cryl e QC-20, confeccionados a partir de matrizes retangulares de alumínio, com dimensões de 65x10x3 mm. As matrizes foram incluídas em gesso na parte inferior de muflas metálicas ou de plástico pela técnica convencional de inclusão. A proporção pó/líquido e mistura das resinas acrílicas foram efetuadas de acordo com as recomendações do fabricante. Após a polimerização em água aquecida a 74°C por 9 horas, água em ebulição por 20 minutos e por energia de microondas por 10 minutos, os corpos-de-prova foram removidos das muflas após esfriamento e submetidos aos acabamento e polimento convencionais. Os testes de dureza e de resistências ao impacto e à flexão foram efetuados nos corpos-de-prova com e sem desinfecção (imersos em 150ml de água destilada, em fomo de microondas com 650 W por 3 minutos): dureza Knoop em microdurômetro Shimadzu HMV -2000, com carga de 25g por 10 segundos; resistência ao impacto numa máquina Otto Wolpert Werke (sistema Charpy), com 40 kpcm de impacto; e resistência à flexão de 3 pontos numa máquina Instron com velocidade de 0,5 mm/minuto até fratura. Os resultados submetidos à análise de variância e ao teste de Tukey (5%) mostraram que a desinfecção aumentou a dureza das resinas Clássico e Onda-Cryl, não influenciando as resistências ao impacto e flexão das 3 resinas

Effect of microwave disinfection on physical and mechanical properties of acrylic resins

This study evaluated the effect of microwave energy on the hardness, impact strength and flexural strength of the Clássico, Onda-Cryl and QC-20 acrylic resins. Aluminum die were embedded in metallic or plastic flasks with type III dental stone, in accordance with the traditional packing technique. A mixing powder/liquid ratio was used according to the manufacturer's instructions. After polymerization in water batch at 74°C for 9 h, boiling water for 20 min or microwave energy at 900 W for 10 min, the specimens were deflasked after flask cooling at room temperature, and submitted to finishing. Specimens non-disinfected and disinfected by microwave irradiation were submitted to hardness, impact and flexural strength tests. Each specimen was immersed in distilled water and disinfected in a microwave oven calibrated to 650 W for 3 min. Knoop hardness test was performed with 25 g load for 10 s, impact test was carried out using the Charpy system with 40 kpcm, and 3-point bending test with a crosshead speed of 0.5 mm/min until fracture. Data were submitted to statistical analysis by ANOVA and Tukey's test (α=0.05). Disinfection by microwave energy decreased the hardness of Clássico and Onda-Cryl acrylic resins, but no effect was observed on the impact and flexural strength of all tested resins

Effect Of Microwave Disinfection On Physical And Mechanical Properties Of Acrylic Resins.

This study evaluated the effect of microwave energy on the hardness, impact strength and flexural strength of the Clássico, Onda-Cryl and QC-20 acrylic resins. Aluminum die were embedded in metallic or plastic flasks with type III dental stone, in accordance with the traditional packing technique. A mixing powder/liquid ratio was used according to the manufacturer's instructions. After polymerization in water batch at 74 degrees C for 9 h, boiling water for 20 min or microwave energy at 900 W for 10 min, the specimens were deflasked after flask cooling at room temperature, and submitted to finishing. Specimens non-disinfected and disinfected by microwave irradiation were submitted to hardness, impact and flexural strength tests. Each specimen was immersed in distilled water and disinfected in a microwave oven calibrated to 650 W for 3 min. Knoop hardness test was performed with 25 g load for 10 s, impact test was carried out using the Charpy system with 40 kpcm, and 3-point bending test with a crosshead speed of 0.5 mm/min until fracture. Data were submitted to statistical analysis by ANOVA and Tukey's test (alpha=0.05). Disinfection by microwave energy decreased the hardness of Clássico and Onda-Cryl acrylic resins, but no effect was observed on the impact and flexural strength of all tested resins.19348-5