Abstract
This study evaluated the Knoop hardness of a dual-cured resin cement (Rely-X ARC) activated solely by chemical reaction (control group) or by chemical / physical mode, light-cured through a 1.5 mm thick ceramic (HeraCeram) or composite (Artglass) disc. Light curing was carried out using conventional halogen light (XL2500) for 40 s (QTH); light emitting diodes (Ultrablue Is) for 40 s (LED); and Xenon plasma arc (Apollo 95E) for 3 s (PAC). Bovine incisors had their buccal face flattened and hybridized. On this surface a rubber mold (5 mm in diameter and 1 mm in height) was bulk filled with the resin cement. A polyester strip was seated for direct light curing or through the discs of veneering materials. After dry storage in the dark (24 h 37 degrees C), the samples (n = 5) were sectioned for hardness (KHN) measurements, taken in a microhardness tester (50 gF load 15 s). The data were statistically analyzed by ANOVA and Tukey's test (alpha = 0.05). The cement presented higher Knoop hardness values with Artglass for QTH and LED, compared to HeraCeram. The control group and the PAC/Artglass group showed lower hardness values compared to the groups light-cured with QTH and LED. PAC/HeraCeram resulted in the worst combination for cement hardness values.
Highlights
The use of resin cements has grown in the last few years due to an increased application of esthetic indirect restorative materials such as ceramics and resin composites
Onlays, laminate veneers and all-ceramic crowns are commonly luted with dual-cured resin cements because light transmission through the indirect restorative is reduced, so the chemical reaction should theoretically guarantee a satisfactory degree of conversion
The control group and the plasma arc (PAC)/Artglass group showed lower hardness values compared to the groups light-cured with quartz tungsten halogen (QTH) and light emitting diodes (LED)
Summary
The use of resin cements has grown in the last few years due to an increased application of esthetic indirect restorative materials such as ceramics and resin composites As advantages, these cements present adhesion to substrates due to compatibility with silane agents and adhesive systems, low solubility, easy handling properties and favourable aesthetics when used with metal-free ceramic systems. The final quality of the restoration can be influenced by factors such as light-curing method and exposure time, type of indirect restorative material and by the luting agent.[3,4,5] Inlays, onlays, laminate veneers and all-ceramic crowns are commonly luted with dual-cured resin cements because light transmission through the indirect restorative is reduced, so the chemical reaction should theoretically guarantee a satisfactory degree of conversion. The null hypotheses tested were: (1) there is no difference in the degree of cure of the resin cement promoted by different curing units; (2) there is no difference in the degree of cure obtained by means of light activation through different veneering materials and (3) the light activation mode does not influence the microhardness values of the resin cement
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