The influence of surface resin coating on the color stability of restorative glass-ionomer / glass hybrid cements

Objectives: The advances of glass-ionomer cements granted their employment in anterior restorations. The question regarding color stability is still not answered for these new marketed materials. Thus, the aim of the present study was to assess the color stability of restorative glass-ionomer / glass hybrid cements, in the presence and absence of surface resin coating.
Methods: The restorative glass hybrid cements tested were Equia Forte and Equia Forte HT (GC) and the glass-ionomer cement tested was Ketac Universal (3M ESPE). Eighteen specimens of each material were fabricated. Dimensions of species were 1mm in thickness and 6mm in diameter. Specimens were immersed in ADA staining broth for 14 days. Color measurements according to the CIELab system were performed at the baseline, and after 1, 7, and 14 days of staining. ANOVA requirements and assumptions were met. Data were submitted to three way repeated measures ANOVA (5%).
Results: Overall Ketac Universal presented greater color alterations (p<0.001). Color changes increased with time and the surface coating resulted in less color changes (p<0.001). There were interactions among the three factors (p<0.001). After 1 day, the only difference was detected for Equia Forte in which the surface protection resulted in lower color changes. After 7 days, the same observation was noticed for Equia Forte HT. After 14 days in the staining solution, both Equia products presented greater color alteration in the absence of surface protection. No influence of color alteration was detected for the surface protection with Ketac Universal. Ketac Universal presented greater color alterations after 14 days.
Conclusions: The surface coating improved color stability overtime considering the testing methodology and that the efficiency of surface protection is material dependent.