The Influence of Thermocycling on the Flexural Strength of a Polyamide Denture Base Material

OBJECTIVE: The aim of the present study was to evaluate the influence of thermocycling on the flexural strength of a polyamide base denture material. MATERIALS AND METHODS: A polyamide denture base material (Valplast) was tested, whereas a PMMA material (Vertex) was used as a control. Thirty specimens of each material were fabricated for flexural strength testing according to ISO 1567. They were prepared and stored in water at 37°C for 48 hours. The specimens of each material were divided into three equal groups (n=10). Flexural strength testing was performed immediately after water storage and after thermocycling (5°C / 55°C, 2 c/min) for 3000 and 5000 cycles. A three point flexural test was performed on a universal testing machine at a crosshead speed of 5 mm/min. The final flexural strength was calculated using the formula: F(S) = 3 PL/2 bd(2). A two-way ANOVA with post-hoc analysis using Tukey's procedure was applied at .05 level of statistical significance. RESULTS: A statistically significant reduction in flexural strength was recorded after thermocycling at 3000 cycles for PMMA and at 5000 cycles for both materials. The flexural strength of PMMA was significantly higher compared to polyamide for all the conditions tested (p<0.05). CONCLUSION: Thermocycling had a significant adverse effect on the flexural strength of polyamide and PMMA denture base materials.