Influence of storage period and effect of different brands of acrylic resin on the dimensional accuracy of the maxillary denture base.

The aim of this study was to evaluate the dimensional changes of denture bases made from different resins after different storage periods. For this purpose, 25 sets of plaster models/resin bases were prepared using 4 acrylic resins submitted to two types of polymerization: 1--QC-20 submitted to polymerization by microwave energy; 2--QC-20 submitted to polymerization by water hot bath; 3--Vipi Cril submitted to polymerization by water hot bath; 4--Vipi Wave submitted to polymerization by microwave energy; and 5--Onda Cryl submitted to polymerization by microwave energy. After polymerization, the specimens were sectioned for accuracy readings using a comparison microscope. Readings were taken at 3 points: the crests of the right (A) and left (B) ridges, and the median region of the palate, in 4 different periods. The data obtained were submitted to two-way ANOVA and Tukey's test at 5% significance level. The greatest distortions were found in the posterior palatal region of the base (M), with statistically significant difference (p<0.05) for the studied resins. All acrylic resins presented dimensional changes and the storage period influenced these alterations.