Marginal leakage of bulk fill composites in Class II restorations: A microCT and digital microscope analysis

PurposeTo assess the marginal leakage of experimental resin composites for bulk filling in direct comparison with their precursors for conventional layering technique.MethodsClass II cavities were prepared on 36 sound human molars. Teeth were randomly assigned to 6 equal groups based on the type of resin composite to be used for the restoration. Three resin composites for conventional layering technique, G-aenial Flo, G-aenial Universal Flo, Kalore (GC), and their experimental counterparts for bulk application, G-aenial Flo bulk fill, G-aenial Universal Flo bulk fill, Kalore bulk fill (GC), were tested. The marginal leakage of the materials was separately evaluated at enamel and dentin margins by assessing interfacial infiltration of silver-nitrate through micro-computerized tomography (microCT) and digital microscope analysis. A score system was defined to quantify the extent of the infiltration. Between-group differences in leakage scores were statistically analyzed using Kruskal–Wallis Analysis of Variance. The Cohen's Kappa coefficient was calculated to measure the inter-rater agreement between microCT and digital microscope observations. In all the statistical tests the level of significance was set at α=0.05.ResultsWith any of the tested materials, at the interproximal margin silver nitrate infiltration never progressed beyond the cervical wall into the axial walls of the box. At the occlusal margin and in the majority of the specimens, the infiltration did not extend over the enamel–dentin junction. No statistically significant difference in microleakage scores emerged among the tested materials either at the occlusal or the cervical margin, both on microCT and digital microscope images (p>0.05). The calculated Kappa coefficients indicated that the agreement between microCT and digital microscope observations was very good both at the occlusal (k=0.915) and at the cervical margin (k=0.810).ConclusionThe marginal leakage demonstrated in Class II restorations by new bulk fill resin composites was similar to that of their precursors for conventional layering technique. Similar findings were obtained when assessing interfacial leakage either with microCT imaging or digital microscopy.