Color Stability and Degree of Conversion of Light-cured Resin Cements

To evaluate the color stability and degree of conversion of light-cured resin cement with different activator-initiator systems using LED lights with different wavelengths (polywave x monowave).

Sixteen resin cement samples were made using a circular silicone matrix (7 mm diameter, 0.5 mm thickness) for each of the following tested materials: Variolink Esthetic LC (Ivoclar, color Light+); RelyX Veneer (3M ESPE, color A1); Filtek Z350XT flow resin (3M ESPE, color A1); Allcem Veneer APS (FGM, color A1); NX3 Light cure (Kerr, color A1). Half of the samples were photocured with a monowave LED light (Elipar Deep Cure), and the other half with a polywave LED light (Valo Grand). The initial color of each cement was measured using a high translucency ceramic sample simulating ceramic venner. Color measurements were performed with a reflectance colorimetric spectrophotometer and the data was collected according to the CIE L* a* b* system in two steps. The degree of conversion was measured using an infrared spectrometer by Fourier transform (FTIR / ATR) and the absorbance method. Statistical analysis was performed using ANOVA repeated measures and Tukey’s post hoc tests (p <0.05).

For the color analysis, there were no significant differences between the cement related to time versus light curing (p = 0.084) and also related to time versus cement versus light curing (p = 0.142). Among the factors, there was only a statistically significant difference for the type of cement (p <0.01). In contrast, for the photocuring device (p = 0.504) and the interaction between them (p = 0.738), there was no significant difference. For the degree of conversion analysis, it showed a statistically significant difference for both factors, resin cements (p <0.01) and light curing units (p <0.01).

The color stability of RelyX cement is low compared to other cements, while Variolink cement presented the best degree of the conversion value.