Abstract
The proper mechanical properties of resin cements are essential to the longevity of indirect restoration, whereas the 3-point bending test is recommended for measuring the flexural strength. The ISO 4049 specification requires light-curing of specimens in three consecutive points; however, this approach cannot be used for dual-cured resin cements. The aim of this study was to investigate the effect of two different specimen preparation techniques on the flexural strength and elastic modulus of experimental dual-cured resin cements immediately or 5 after minutes light curing. Experimental dual-cured resin cements were formulated, and the specimens of these cements were confectioned with the dimension of ISO 4049 specification. Light-activation was performed at one or three points immediately or 5 minutes after the insertion of cement into the matrix (n=7), resulting in four experimental conditions (2 methods × 2 moments of light-activation). The three-point bending test was performed and the values of the flexural strength and elastic modulus were recorded. Data were individually analyzed using 2-way ANOVA followed by the Tukey’s post hoc test ( P <0.05). Regardless of the points of light-activation, the specimens that were light-cured at 3 points showed the highest values of flexural strength. Only for light-activation at 1 point did the time before the light-activation affect the elastic modulus, whereas delayed light-activation had the highest values. In conclusion, the number of light-curing points on specimen preparation for the 3-point bending test seems to affect the mechanical properties of dual-cured resin cements.
Highlights
Dual-cured resin cements are commonly used to lute indirect restorations and intra-radicular dental posts with the aim of combining the advantages of chemically and light-cured polymerbased materials (FARIA-E-SILVA, et al 2007)
The findings of this study demonstrated that the number of light-curing points significantly affected the σf of the dual-cured resin cement, irrespective of the time before light-activation
Despite the presence of a polymerization reaction activated by a chemical reaction, several studies have demonstrated that dual-cured resin cements require light curing to improve their polymerization potential and mechanical properties (FARIA-E-SILVA, et al 2007; FARIA-E-SILVA, et al 2012; CALGARO, et al 2013; KIM, et al 2013; MAGALHÃES, et al 2014)
Summary
Dual-cured resin cements are commonly used to lute indirect restorations and intra-radicular dental posts with the aim of combining the advantages of chemically and light-cured polymerbased materials (FARIA-E-SILVA, et al 2007). One of the more commonly used laboratory tests for evaluating the mechanical properties of dental resin cements is the 3-point bending test, which is a useful test for determining the flexural strength and flexural modulus (elastic modulus) of the materials (CHUNG, et al 2004; DUYMUS, et al 2013; GONÇALVES, et al 2013). The bar specimen is supported by two rods, 2 mm in diameter and mounted parallel with a 20 mm span between the supports; the load is applied through a rod that is 2 mm in diameter This standardization establishes that the specimen fabrication should be performed with the light-cured resin materials inserted into a mold and followed by lightactivation in three consecutive, overlapping areas in both sides of the specimen. The center of the specimen receives the first light exposure, which is followed by two complementary exposures at equidistant points from the center
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