Discussion
CAVITY
This in-vitro study investigated the effect of a high-irradiance light curing (3 s @ 3000 mW/cmTML strains the adhesive interface between the cavity walls and the restoration and provokes the formation of marginal gaps. As marginal gaps could also form immediately after light-curing due to shrinkage stress of the restorative material, marginal analysis was carried out at two different time points (before and after TML) in the present study. The first attempts to evaluate dental restorative materials with regard to their marginal integrity date back to the 1970s [The here used loading force and frequency (1.7 Hz, 49 N) is reported to be most frequently used to simulate the mechanical degradation of resin composite restorations in vitro [Taking the margins of the whole restoration (enamel and dentine) into consideration, employing the high-irradiance light-curing mode resulted in similar marginal integrities as the regular 10-s light-curing mode, regardless of the tested RBC. As for Power Fill, this result could be attributed to the presence of the AFCT reagent, which allows a step-like progression of the polymer chain and enhances the thermal and mechanical properties of RBCs, and to the fact that this RBC was actually developed to be compatible with high-irradiance light curing [The bulk-fill RBC “Power Fill” showed better marginal integrity than the conventional RBC “Prime” regardless of the used light-curing mode. This is in contrast to the results of a recent study, which compared the same RBCs and concluded that both achieve similar marginal integrity in primary molars [The conventional RBC “Prime” was not especially developed for high-irradiance light curing and does not contain an AFCT reagent. This makes the observed similar marginal integrity between both applied light-curing modes rather interesting. The fact that the radiant exposure in case of the high-irradiance light-curing mode is less than the regular light-curing mode (9.0 vs. 12.0 J/cm