The Influence of Saliva pH on the Fracture Resistance of Three Complete Denture Base Acrylic Resins.

Methods: Ten prosthesis bases prepared with each brand of resin were subjected to neutral and low pH conditions (pH 7 and pH 4) by submerging them in artificial saliva for 30 days. After exposure, the fatigue resistance of the resins was tested using a Dental CS® Testing Machine. . The data sets were described quantitatively in terms of mean () and standard deviation (SD). Shapiro-Wilk tests and unilateral analysis of variance (ANOVA) were performed and complemented by Tukey's multiple comparison tests. The effect size (2), whose cohort points followed Cohen's recommendations: 0.01 (low), 0.06 (medium), and 0.14 (high), was calculated. The results were considered significant if < 0.05 and marginally significant if < 0.10.

Results: One-way ANOVA showed that Megacryl® had the highest fracture resistance at pH 7 (52.23 Kgf), compared with Triplex Hot® ( < 0.001) and RS Vertex® (=0.034). Two-way ANOVA confirmed the interaction between brand and pH (=0.022), also revealing that brands comparison is significant or marginally significant, when pH is not considered (Megacryl® versus Triplex Hot®, < 0.001, and RS Vertex®, =0.058; Triplex Hot® versus RS Vertex®, =0.051), and pH 7 results were significantly higher (=0.003), even when brands are not considered. Hence, Megacryl® at pH 7 was found to have the highest fracture resistance, detached from other brands and pH values.

Conclusion: It can be concluded within the limitations of this study that there are differences in the fracture resistance among the three brands of acrylic resin. Megacryl® was found to have the highest fracture resistance, and Triplex Hot® was the lowest. The results also show that exposure to a low pH environment decreases the fracture resistance of the Megacryl® and RS Vertex® resins.