ABSTRACT
Fracture of acrylic resin denture base is a common problem in maxillary dentures. Because the stresses in mouth on the denture base are of flexural type, the aim of this study was to determe the effect of palatal shape combined with acrylic resin thickness on the flexural strength of the denture base. In this experimental study, 48 stone casts in 3 groups [shallow, medium and deep palatal vault] were prepared. Eight casts of each palatal form were covered with a single layer of base-plate wax and eight were covered with two layers. Patterns were invested and processed with Acropars acrylic resin in the same manner. Flexural strength, deflection and fracture load were measured with DARTEC testing machine. Statistical analysis was performed using multivariate ANOVA, Kruskal-Wallis and Mann Whitney tests. The results showed that the flexural strength of shallow bases were significantly different from medium and deep palatal shapes at both thicknesses [P<0.001]. There were no statistically significant differences in flexural strength between the medium and deep palatal shapes [P=0.583]. Increasing the base thickness significantly increases the flexural strength in each palatal shape [P<0.001]. This study revealed that palatal shape and base thickness have significant effects on flexural strength of denture bases. In shallow palates, increasing the thickness of denture base can enhance flexural strength of denture