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

objective: the 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 methods: a 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 37°c 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 37°c 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. results: resin 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. conclusion: the 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.