Light-activation through indirect ceramic restorations: does the overexposure compensate for the attenuation in light intensity during resin cement polymerization?

Abstract

ObjectivesThis study evaluated the effects of light exposure through simulated indirect ceramic restorations (SICR) on hardness (KHN) of dual-cured resin cements (RCs), immediately after light-activation and 24 h later.Material and Methods Three dual-cured RCs were evaluated: eco-Link (Ivoclar Vivadent), Rely X ARC (3M eSPe), and Panavia F (Kuraray Medical Inc.). The RCs were manipulated in accordance to the manufacturers’ instructions and were placed into cylindrical acrylic matrixes (1-mm-thick and 4-mm diameter). The RC light-activation (Optilux 501; Demetron Kerr) was performed through a glass slide for 120 s (control group), or through 2-mm or 4-mm thick SICRs (IPS empress II; Ivoclar Vivadent). The specimens were submitted to KHN analysis immediately and 24 h after light-activation. The data obtained at the 2 evaluation intervals were submitted to 2-way ANOVA repeated measures and post-hoc Tukey’s test (pre-set alpha of 5%).ResultsLower KHN was observed when light-activation was performed through SICRs for eco-Link at all evaluation intervals and for Rely X ARC 24 h later. For Panavia F, no significant difference in KHN was observed between control and experimental groups, regardless of evaluation interval. Most groups exhibited higher KHN after 24 h than immediately after light-activation, with the exception of Rely X ARC light-activated through SICR, as no significant difference in KHN was found between evaluation intervals.ConclusionLight overexposure did not compensate for light intensity attenuation due to the presence of SICR when Rely X and eco-Link were used. Although hardness of such RCs increased over a 24-h interval, the RCs subjected to light overexposure did not reach the hardness values exhibited after direct light exposure.

Early Hardness and Shear Bond Strength of Dual-cure Resin Cement Light Cured Through Resin Overlays With Different Dentin-layer Thicknesses

“…12,15,[19][20][21][22][23] However, there are no studies on the shade combinations of a resin inlay simulating the clinical situation including all the dentin, enamel, and translucent layers. In our previous study with the same indirect composite resin used in this study, we measured the power density of LCUs through resin overlays with various layer thickness combinations.…”

Effect of energy density and delay time on the degree of conversion and Knoop microhardness of a dual resin cement

“…Poor monomer conversion of these materials might lead to low bond strength and high water sorption, compromising their physical properties. 8 The immediate light curing of dual-cured resin cements might cause a reduction in the degree of conversion. 9 The reason is that immediate light curing causes the rapid formation of cross-linked polymer chains, entrapping ª 2014 Wiley Publishing Asia Pty Ltd unreacted monomers and free radicals into the polymeric network, and thus jeopardizing the chemical curing.…”

Effects of layering technique on the shade of resin overlays and the microhardness of dual cure resin cement

“…Polymerization of resin cement is usually assessed by hardness tests, 12,13 and many studies on hardness measurements of DCRCs that were light cured through various indirect restorations were performed with one single shade. 14,15 However, in clinical situations, resin inlays are usually fabricated with a layering technique. Studies on the hardness of DCRCs light cured through resin overlays with a layering technique are difficult to find.…”