[The influence of polymerization method on the mechanical properties of dental resins composites]

The aim of the study was to asses the influence of the time, method and type of light curing on the compressive strength of dental composites. Dental composite resin (T-Econom, Ivoclar Vivadent) was cured for 10, 30 or 40 sec. with either a commercial conventional halogen light curing unit (LCU)--Hilux, (Benliodlu Dental Inc), or a light emitting diode (LED), LCU-Bluedent LED Smart. The compressive strengths were determined after 72 h on samples 3 mm in diameter and 7 mm high using FPZ 100/1 device.The samples cured with LED LCU for 40 seconds in pulse mode showed the smallest values of compressive strength (245 MPa), while those cured with LED LCU for 40 seconds in ramp mode reached the highest values (295 MPa). Similar values for compressive strength were found for the samples polymerized with conventional halogen LCU and the samples cured with LED LCU in constant mode (283 MPa and 285 MPa, respectively).Compressive strength depends on the light type and method. Tested LED curing light seems to induce similar compressive strengths as the halogen-based light. Using this conventional light curing unit requires at least 40 seconds of exposure in order to achieve adequate compressive strength. The LED light curing unit should be used in the ramp mode for at least 40 sec, followed by 10 sec in fast mode in order to achieve the best results.