Marginal gap formation of light-activated base/liner materials: effect of setting shrinkage and bond strength

Objectives: The purpose of this study was to compare the effect of setting shrinkage and the shear bond strength on the marginal gap formation in dentin cavities of commercially available light-activated base/liner materials during the early stage of setting, with those of chemical-cured base/liner materials. Methods: The maximum marginal gap width and the opposing width in the dentin cavity was measured 30 min after the start of mixing. The setting shrinkage and shear bond strength to dentin was measured as the same procedure. To estimate the setting shrinkage, the maximum marginal gap width and the opposing width that occurred with materials placed in a Teflon cavity was measured. Results: The two light-activated base/liner materials produced a significantly wider marginal gap than the chemical-cured base/liner materials (p<0.05). There were no significant differences in the width of the marginal gap between the remaining five light-activated base/liner and chemical-cured base/liner materials (p>0.05). The material that produced the smaller marginal gap width in the dentin cavity had a smaller marginal gap width in the Teflon cavity. There was a highly significant correlation between the two findings (r=0.93, p<0.01). However, shear bond strength to dentin had no effect on the marginal gap in the dentin cavity (r=0.04, p>0.50). Significance: It appeared that the setting shrinkage of light-activated base/liner materials in the early stage of setting had a greater effect on the marginal gap formation in the dentin cavity than the bond strength to the dentin structure.