Estabilidade de cor de resinas compostas com diferentes valores de croma : correlação do grau de conversão com ΔE e eluição de monômeros

Abstract

Objectives: To evaluate the color stability of three commercial brands of composite resins when immersed in distilled water, within 24 hours, 30 days and 180 days, as well as the degree of monomer conversion and BisGMA and UDMA component elimination. Methods: Five specimens of each resin chroma were made for color stability evaluation, and three specimens for degree of monomer conversion evaluation. Each increment of resin in the specimens was light cured for 20s using a polywave LED and these were then stored in eppendorfs with distilled water after photoactivation. A color scale pattern was made from the material studied, following the Vita (Vita) scale. For color analysis an Easyshade 4.0 (Vita) spectrophotometer was used, while the degree of monomer conversion was assessed by FTIR and the elution of the UDMA and BisGMA components was analyzed by liquid chromatography with mass spectrometer. The following time periods were studied, immediately, 24h, 30 days and 180 days. Results: All resins studied showed a color change from the standard. The 3-way analysis of variance revealed that the interaction between time/color/brand was sisgnificant (p=0,0001). Empress Direct was the only one to display ∆E≥2,7over the 180 days period on chromas B1 and A1. There was a significant direct correlation between degree of conversion and ∆E in 30 days and inverse in 180 days. There is a highly significant correlation between degree of conversion and UDMA elution. Conclusion: The degree of conversion of the studied composites has a significant direct correlation with color stability in the period of 30 days and inverse in the period of 180 days, suggesting a stabilization of the material over time. There is a significant inverse correlation between UDMA elution and degree of conversion of monomers. Clinical Significance: The degree of monomer conversion of composite resins has a significant correlation with color stability over time and with the elution of UDMA.