Influence of re-using reversible hydrocolloids on the linear alteration of coating models.

Reusing reversible hydrocolloids too many times may cause alterations of the coating model and produce unsatisfactory RPPs. The aim of this study was to analyze the linear alterations of coating models reproduced from molds obtained with two commercial brands of reversible hydrocolloid (RH) with 15 reuse cycles of the material. A metal model was used with 4 marks (A, B, C and D) on which the distances AB, BC, CD, DA, BD and AC could be measured lineally.

Influence of mechanical and chemical polishing in the solubility of acrylic resins polymerized by microwave irradiation and conventional water bath.

Objectives: The aim of this work was to evaluate the solubility of acrylic resin activated by microwave irradiation (MI) or water bath (WB), when submitted to chemical (CP) or mechanical (MP) polishing.

Methods: Forty acrylic resin samples were made and processed either by water bath (74 +/- 1 degrees C, 9 h) or microwave irradiation (500 W, 3 min). After deflasking, the samples were finished with aluminum oxide sandpapers in decreasing granulations till reaching similar dimensions.