The effect of polymerization cycles on color stability of microwave-processed denture base resin.
OBJECTIVE
This study evaluated the effect of different microwave polymerization cycles on the color changes of a microwave-processed denture base resin after accelerated aging and immersion in beverages.


METHODS
Specimens of light pink acrylic resin were divided into three groups according to polymerization cycle: (A) 500 W for 3 minutes, (B) 90 W for 13 minutes + 500 W for 90 seconds, and (C) 320 W for 3 minutes + 0 W for 4 minutes + 720 W for 3 minutes. Control groups were a heat-processed acrylic resin (T) and a chemically activated denture repair resin (Q). Eight specimens per group were aged in an artificial aging chamber and evaluated at 20, 192, and 384 hours. Another series of 40 specimens per group were immersed in water, coffee, tea, cola, or red wine and evaluated at 1, 12, and 36 days. Color was measured by a spectrophotometer before and after aging or immersion. Color changes (DeltaE) were analyzed by ANOVA/Bonferroni t-test (alpha = 0.05).


RESULTS
Mean DeltaE (+/- SD) after 384 hours of accelerated aging were (A) 2.51 +/- 0.50; (B) 3.16 +/- 1.09; (C) 2.89 +/- 1.06; (T) 2.64 +/- 0.34; and (Q) 9.03 +/- 0.40. Group Q had a significantly higher DeltaE than the other groups. Color changes of immersed specimens were significantly influenced by solutions and time, but the five groups showed similar values. Mean DeltaE at 36 days were (water) 1.4 +/- 0.8; (coffee) 1.3 +/- 0.6; (tea) 1.7 +/- 0.5; (cola) 1.4 +/- 0.7; and (red wine) 10.2 +/- 2.7. Results were similar among the five test groups.


CONCLUSIONS
Color changes of the microwave-polymerized denture base resin tested were not affected by different polymerization cycles after accelerated aging or immersion in beverages. These changes were similar to the conventional heat-polymerized acrylic resin test, but lower than the repair resin after accelerated aging.
Department of Dental Materials and Prosthodontics, University of São Paulo, Ribeirão Preto Dental School, Ribeirão Preto, São Paulo, Brazil.
Marília Rodrigues
MR
Bonatti
Tatiana Ramirez
TR
Cunha
Rômulo Rocha
RR
Regis
Cláudia Helena
CH
Silva-Lovato
Helena Freitas Oliveira
HF
Paranhos
Raphael Freitas
RF
de Souza
D000180:Acrylic Resins / Q000737:chemistry / Q000528:radiation effects*; D001628:Beverages / Q000009:adverse effects; D003116:Color; D003819:Denture Bases; D003779:Denture Design; D008872:Microwaves; D017797:Prosthesis Coloring
D000180:Acrylic Resins