The 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 <FONT FACE="Symbol">m</font>m 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.
Acrylic resins; Porosity; Microwaves
