Color stability, nanohardness and elastic modulus of denture base acrylic resins with various polymerization techniques

Abstract

The objective of this study was to evaluate color stability, nanohardness and elastic modulus of denture base acrylic resins with various polymerization techniques after storing in coffee, distilled water or dark chamber. Ninety disc-shaped (9X2 mm) specimens of heat-cured (TRX), microwave-cured (BTC) and light-cured (TRD) were fabricated, and randomly divided in three conditions (n=10). The color difference (DE*) was measured using a spectrophotometer at 1, 7, 28 and 56 days; The nanohardness and the elastic modulus were measured from three randomly selected of each group at day 1 and day 56 after color measurement. The repeated mixed analysis of variance following with Tukey’s HSD multiple comparison and paired samples t-test were statistically analyzed at the confidence level of 95%. The interaction among material groups, storage media over the period of time were observed in the DE* (p<0.001). The DE* of the coffee storage group showed the greatest color change since day 7; TRD was greater color change than BTC and TRX both in coffee and distilled water. All specimens in coffee storage group were darker, less red and more yellow. Moreover, the interaction among three factors of nanohardness and elastic modulus showed no significant difference (p=0.103, 0.138). Those of TRX demonstrated the lowest nanohardness and elastic modulus while BTC and TRD showed almost similar. The nanohardness and the elastic modulus of coffee storage group showed the greatest reduction at 56-day storage, following by those in water.