Fracture strength of restorations in proximal cavities of primary molars

This study evaluated the fracture strength of various restorative materials for primary molars in dovetail and box-only class II cavity designs. Eighty extracted noncarious human primary molars were used. The teeth were randomly divided into two groups for either dovetail or box-only preparations. The teeth were then divided into four subgroups for each restorative material: glass ionomer cement (GIC), resin-modified glass ionomer cement (RMGIC), compomer, and composite. The restorations were tested for fracture strength. The loads at fracture and fracture mode were recorded and a scanning electron microscopy analysis was performed to observe the micromorphology of the borders between the teeth and the materials. The nonparametric Kruskal-Wallis and Mann-Whitney U-tests were used. Although there were significant differences between the restorative materials (p < 0.05), there were no differences between the fracture strength of the box-only and the dovetail cavity designs in any of the groups (p > 0.05) except the composite group. The fracture strength of the compomer and composite groups was significantly higher than that of the GIC and RMGIC groups (p < 0.05). A class II cavity could be selected as dovetail or box-only and compomer and composite are more resistant to fracture than GIC and RMGIC.