In vitro evaluation of the microhardness of glass ionomer, glass carbomer, and resin-based restorative materials

Objective: This study aimed to compare the microhardness values of restorations placed in Class I cavities prepared in primary molar teeth using high-viscosity glass ionomer cement, glass carbomer, glass carbomer with surface coating, and bulk-fill composite resin. Methods: A total of 48 extracted primary molar teeth were used in the study. After the preparation of standardized Class I cavities, the teeth were randomly divided into four groups (n = 12). The first group was restored with high-viscosity glass ionomer cement. The second group received bulk-fill composite resin. The third group was restored with glass carbomer. In the fourth group, glass carbomer was applied followed by a surface coating. Microhardness measurements were performed in all groups. Results: Among the groups, the highest microhardness values were observed in the composite resin group. This was followed by the high-viscosity glass ionomer group and the group where glass carbomer was applied with surface coating. The lowest microhardness values were recorded in the group restored with glass carbomer alone. Pairwise comparisons using the Games–Howell post hoc test revealed statistically significant differences between all groups (p < 0.001 for all comparisons). Conclusion: Composite resin is more suitable for Class I cavity restorations in primary molars compared to glass ionomer and glass carbomer. However, applying a surface coating over glass carbomer significantly improves its microhardness. Therefore, in cases where resin-based materials are not preferred, glass carbomer with surface coating may be considered a viable alternative. Keywords: Glass ionomer, glass carbomer, microhardness, surface coating, primary molar tooth