Influencia do tempo pos-prensagem (imediato e 24 horas) na porosidade, rugosidade, dureza de superficie e resistencia ao impacto de resinas acrilicas

AUTOR(ES)

Mauricio Tanji

DATA DE PUBLICAÇÃO

2002

RESUMO

This study investigated the influence of the post-pressing time (immediate and 24 hours) on the porosity, roughness, hardness of surface and impact strenght variables in Clássico, QC-20 and Onda-Cryl thermo-cured acrylic resins. Sixty specimens were made with a retangular aluminium die (65xl0 and 64x9 x 3,0 mm) attached to a wooden plate with Super Bonder adhesive (Loctite). The die were moulded with Zetalabor condensation silicone (Labordental Ltda.) used for laboratory purposes and the molds were included into metal flasks or reinforced fiberglass flasks. The powder/liquid proportion and mixture, as well as acrylic resin pressing were made according to manufature s instructions. The acrylic resins were cured in heat water (74°C) for 9 hours, boiling water for 20 minutes or by microwave energy with 1100W for 10 minutes. The specimens were removed afier flasks cooling at room temperature and submetted to polishing by conventional procedure. Subsequently, were submetted to: a) porousness test by specimens immersion into Nankin ink (Acrilex) for 12 hours, washed into running water for 10 seconds and thererafter the porous was counted and photographed in. pre-determined areas; b) superficial roughness with Surfcorder SE 1700; c) hardness with Shimadzu microdurometer with load of25 grams by 10 seconds; d) impact strenght test with Charpy system in a Wolpert machine. The results submetted to ANOVA and Tukey s test showed that: 1 - porosity: the best porosity was promoted by Onda-Cryl in the immediate post-pressing time, and the QC-20 in the 24 hours one. When the post-pressing time was compared, alI acrylic resins showed statistical significative difference. 2 - roughness: no statistical significative difference was observed among materials when the post-pressing time was considered. When the post-pressing time was unfoqued, only Clássico acrylic resin showed values with statistical significative difference. 3 - hardness: in the immediate post-pressing the best hardness was showed by the Onda-Cryl and the smallest by QC-20 both with statistical significative difference. In the 24 hours post-pressing, Onda-Cryl showed great hardness values with statistical significative difference when compared to QC-20. Clássico resin showed statistical similarity with both. When the post-pressing time compared, only Onda-Cryl do not presenting statistical significative difference. 4 - impact strength: no statistical significative difference was observed among resins in the immediate post-pressing. In the 24 hours postpressing, the Clássico and Onda-Cryl resins do not showed statistical significative difference, however both were statistically diferent ITomthe QC-20 resin with the smaller value. When the post-pressing time compared, only the QC-20 resin showed value with statistical significative difference

ASSUNTO(S)

resistencia de materiais materiais dentarios

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