Physical properties of polyamide-12 versus PMMA denture base material.

OBJECTIVES: Polyamide-12 (PA) is a flexible material suited for denture bases and clasping. This study investigated its potential aging effects with a focus on surface roughness, color stability, and elasticity. METHODS: PA specimens (Valplast) of 40x10x2 mm and equally measuring PMMA specimens (Palapress) as control were fabricated. Color changes after storage in air, water, coffee, and red wine (n=10) were measured using the CIE L*a*b* color specification. Elasticity after thermocycling (1000, 3000, and 7000 cycles, n=15) was measured by three-point bending testing. Mean surface roughness (Ra) was determined after storage in the liquids mentioned above and thermocycling (n=10). RESULTS: Tukey's HSD test (P<0.05) revealed statistically significant color changes of PA in red wine (DeltaE=4.27 after 12 days, DeltaE=6.90 after 12 days) and coffee (DeltaE=3.93 after 36 days) but no color changes in PMMA. Elastic modulus of PA was 845 MPa and not affected by thermocycling (Tukey's HSD test, P>0.81). Dry specimens showed significantly decreased elasticity (P<0.001). Mean surface roughness (PA 0.20 mu m, PMMA 0.28 mu m) did not change significantly after thermocycling or storage (Mann-Whitney U-test, 0.16<P<0.65). SIGNIFICANCE: PA exhibited a higher susceptibility to discoloration than PMMA. Neither surface roughness nor elasticity of PA was altered by artificial aging.