Color Stability of Expired Restorative Dental Composite Resins

Abstract

Although expired dental composites should not be used in practice, limited information on their properties is available. The purpose of this study was to evaluate their color stability. 3 composite resins (ice/SDI, rok/SDI, spectrum/Dentsply) from 15 to 146 months after their expiration date and the same materials 23 to 45 months before their expiration date were used to make round specimens. All specimens were finished and polished and after their initial storage in water of 37 o C for 48h, they were immersed in coffee baths simulating 30,60,90,180,360 days of coffee's staining effect. A mean of three measurements of color parameters in the CIELAB system were taken with a portable colorimeter (ShadeEye/Shiofu) at all periods, and data were analyzed statistically by 2way repeated measures ANOVA at a=0.05. Color difference values (ΔΕ*) between base line and staining periods for the investigated materials were 17.7 to 47.6 for the new materials and 13.3 to 38.2 for the expired materials. Statistical analysis indicated significant differences between staining periods (p<0.05) with all materials, but no significant differences between expired and unexpired materials (p>0.05). Although investigated materials had expired for long, their staining behavior within coffee was similar to unexpired. Differences found among materials and immersion time.