Use of microwave energy for processing acrylic resin near metal

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOThe conventional method to process acrylic resin is a time consuming step to construct removable prosthodontics. Microwave energy could provide a solution, but there are still questions regarding this process taking place in the presence of metal. The aim of this study was, therefore, to compare residual monomer, microhardness and porosity of two acrylic resins cured by different methods in the presence of a metal framework. The conditions evaluated were: Group 1 - Acrylic resin Clássico, short cycle heatcured for 3 h; Group 2 - Acron MC resin cured in microwave oven for 3 min at 500 W; Group 3 - Acrylic resin Clássico cured in microwave oven for 3 min at 500 W. For each group 12 specimens measured were prepared, measuring 30 X 4 mm (diameter X thickness) and containing inside a metal framework of 28 X 8 X 0.5 mm. After curing the samples were individually imersed in 6.0 ml of deionized water. Residual monomer released in the water, which was changed daily, was measured spectrophotometrically for 12 days. The specimens were polished in order to measure microhardness at the distances of 50 to 800 mm of the metal framework. The specimens were cross-sectioned to evaluate the internal and external porosity under the naked eye and using a X100 magnification. Porosity under the naked eye was observed in all of the Group 3 samples and in 50% of those from Groups 1 and 2. Under magnification, porosity was found externally and internally in all of samples. It was concluded that microwave energy can be effectively used to polymerized removable partial denture, and that, when polymerized with microwave energy, conventional resin presents higher porosity.Com o objetivo de verificar a efetividade da energia de microondas na polimerização da resina acrílica próxima ao metal, foram confeccionados 36 corpos-de-prova cilíndricos com 30,0 mm de diâmetro x 4,0 mm de espessura, contendo no seu interior uma sela metálica com 28,0 mm x 8,0 mm x 0,5 mm, divididos aleatoriamente em 3 grupos e submetidos aos seguintes processamentos: G1) resina Clássico polimerizada em ciclo curto; G2) resina Acron-MC polimerizada em forno de microondas por 3 minutos a 500 W; G3) resina Clássico polimerizada em forno de microondas por 3 minutos a 500 W. Após a polimerização, cada amostra foi dividida em duas partes aproximadamente iguais, sendo que uma das partes foi utilizada para a avaliação de monômero residual, enquanto a outra foi submetida aos testes de dureza e porosidade. A dosagem de monômero liberada na água durante doze dias consecutivos foi avaliada através da espectrofotometria. A dureza Knoop foi verificada nas distâncias de 50, 100, 200, 400 e 800 mm da sela metálica, e a porosidade interna e externa foi avaliada a olho nu e com auxílio de microscópio com aumento de 100 X. Diante dos resultados obtidos, concluiu-se que a energia de microondas pode ser utilizada para a polimerização da resina acrílica contendo sela metálica no seu interior e que as resinas acrílicas convencionais, quando polimerizadas através da energia de microondas, apresentaram maior quantidade de poros122173181FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO1996/4814-5The conventional method to process acrylic resin is a time consuming step to construct removable prosthodontics. Microwave energy could provide a solution, but there are still questions regarding this process taking place in the presence of metal. The aim of this study was, therefore, to compare residual monomer, microhardness and porosity of two acrylic resins cured by different methods in the presence of a metal framework. The conditions evaluated were: Group 1 - Acrylic resin Clássico, short cycle heatcured for 3 h; Group 2 - Acron MC resin cured in microwave oven for 3 min at 500 W; Group 3 - Acrylic resin Clássico cured in microwave oven for 3 min at 500 W. For each group 12 specimens measured were prepared, measuring 30 X 4 mm (diameter X thickness) and containing inside a metal framework of 28 X 8 X 0.5 mm. After curing the samples were individually imersed in 6.0 ml of deionized water. Residual monomer released in the water, which was changed daily, was measured spectrophotometrically for 12 days. The specimens were polished in order to measure microhardness at the distances of 50 to 800 mm of the metal framework. The specimens were cross-sectioned to evaluate the internal and external porosity under the naked eye and using a X100 magnification. Porosity under the naked eye was observed in all of the Group 3 samples and in 50% of those from Groups 1 and 2. Under magnification, porosity was found externally and internally in all of samples. It was concluded that microwave energy can be effectively used to polymerized removable partial denture, and that, when polymerized with microwave energy, conventional resin presents higher porosit