Influence of a microwave cycle on microhardness and glass transition temperature of some acrylic denture base resin

Abstract

The aim of this study was to evaluate the effect of a microwave cycle, used as a disinfection me- thod, on the Knoop microhardness and glass transition temperatu- re of one heat-polimerized acrylic resin (Clássico), a self-curing one (Jet) and a microwave-polimerized one (Onda-Cryl), all of them ma- nufactured by Artigos Odontológi- cos Clássico Ltda. For the micro- hardness testing, four specimens were used of each denture base materials (2,2 x 2,2 x 2mm). A one minute exposure to microwaves, at 850W, was used as desinfection procedure. For the glass transition temperature (°C), determined by the Differencial Scanning Calori- metry (DSC), six specimens were fabricated, where three were used as controls and the other half, ir- radiated with a microwave cycle for one minute at 850W (micro- hardness - linked Student’s t test and glass transition temperature – not-linked Student’s t test). The results showed a significant incre- ase on the mean microhardness values for the microwave-polime- rized acrylic resin and a signifi- cant decrease of the glass transi- tion temperature for the heat-po- limerized group. According to the results, it is possible to conclude that a microwave cycle increased the microhardness of the micro- wave-polimerized acrylic resin and decreased the glass transition temperature of the heat-polimeri- zed acrylic resin. Key words: acrylic resin, microwa- ves, microhardness, glass transi- tion temperature, desinfection.