Effect of different light curing methods on mechanical and physical properties of resin-cements polymerized through ceramic discs

Abstract

ObjectiveThe aim of this study was to compare the polimerization ability of three different light-curing units (quartz tungsten halogen, light-emitting diodes and plasma arc) and their exposure modes (high-intensity and soft-start) by determination of microhardness, water sorption and solubility, and diametral tensile strength of 5 dual-curing resin cements. Material and methodsA total of 720 disc-shaped samples (1 mm height and 5 mm diameter) were prepared from different dual-curing resin cements (Duolink, Nexus, Bifix-QM, Panavia F and RelyX Unicem). Photoactivation was performed by using quartz tungsten halogen (high-power and soft-up modes), light-emitting diode (standard and exponential modes) and plasma arc (normal and ramp-curing modes) curing units through ceramic discs. Then the samples (n=8/per group) were stored dry in the dark at 37ºC for 24 h. The Vickers hardness test was performed on the resin cement layer with a microhardness tester (Shimadzu HMV). For sorption and solubility tests; the samples were stored in a desiccator at 37ºC and weighed to a constant mass. The samples were weighed both before and after being immersed in deionized water for different periods of time (24 h and 7 days) and being desiccated. The diametral tensile strength of the samples was tested in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by nonparametric Kruskal Wallis and Mann-Whitney U tests at 5% significance level. ResultsResin cement and light-curing unit had significant effects (p<0.05) on microhardness, diametral tensile strength, water solubility and sorption. However, no significant differences (p>0.05) were obtained with different modes of LCUs. ConclusionThe study indicates that polymerization of resin cements with different light-curing units may result in various polymer structures, and consequently different mechanical and physical properties.

Effect of Different Thicknesses of Pressable Ceramic Veneers on Polymerization of Light-cured and Dual-cured Resin Cements

“…17–25 Microhardness (MH) is defined as the resistance of a material to indentation or penetration and has been used as a valid correlation with degree of polymerization, indicating that microhardness values increase as degree of polymerization increase. 26,27 Another method used to evaluate polymerization is degree of conversion (DOC) by using infrared spectroscopy, also known as FTIR (Fourier Transform InfraRed Spectroscopy).…”

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

“…11 Microhardness is one of the most important properties of dental materials 12 and might be used to predict the degree of conversion; the higher the microhardness, the higher the degree of conversion is expected to be. However, this correlation might be contradictory, 13 as polymers are dependent on different polymerization modes, which might affect the hardness, but not the degree of conversion of a resin cement.…”

Thermal analysis of bulk filled composite resin polymerization using various light curing modes according to the curing depth and approximation to the cavity wall

“…Similarly, pulse-delay polymerization is initiated by a short flash of curing light followed by a waiting time of several minutes before the final cure is performed 1,13,20,23 . Soft-start curing is initiated with a reduced power density during the first part of the polymerization period in order to reduce polymerization shrinkage stress 1,4,6,29 . These methods have been reported to reduce the gap formation between the tooth structure and the composite resin without compromising the mechanical properties or degree of conversion 17-19,27 .…”