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 threedifferent light-curing units (quartz tungsten halogen, light-emitting diodesand plasma arc) and their exposure modes (high-intensity and soft-start) bydetermination of microhardness, water sorption and solubility, and diametraltensile strength of 5 dual-curing resin cements.

Material and methods

A total of 720 disc-shaped samples (1 mm height and 5 mm diameter) wereprepared from different dual-curing resin cements (Duolink, Nexus, Bifix-QM,Panavia F and RelyX Unicem). Photoactivation was performed by using quartztungsten halogen (high-power and soft-up modes), light-emitting diode(standard and exponential modes) and plasma arc (normal and ramp-curingmodes) 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 hardnesstest was performed on the resin cement layer with a microhardness tester(Shimadzu HMV). For sorption and solubility tests; the samples were storedin a desiccator at 37ºC and weighed to a constant mass. The sampleswere weighed both before and after being immersed in deionized water fordifferent periods of time (24 h and 7 days) and being desiccated. Thediametral tensile strength of the samples was tested in a universal testingmachine at a crosshead speed of 0.5 mm/min. Data were analyzed statisticallyby nonparametric Kruskal Wallis and Mann-Whitney U tests at 5% significancelevel.

Results

Resin cement and light-curing unit had significant effects (p<0.05) onmicrohardness, diametral tensile strength, water solubility and sorption.However, no significant differences (p>0.05) were obtained with differentmodes of LCUs.

Conclusion

The study indicates that polymerization of resin cements with differentlight-curing units may result in various polymer structures, andconsequently different mechanical and physical properties.