In addition LED units have an extended life and produce less heat thus respecting pulp and gingival tissue.25,31 selleckbio Dental resins cured with blue LEDs show a larger depth of cure, a higher DC and more stable three-dimensional structures than those cured using halogen lamps.32 In this experiment the values of conversion of the EndoREZ + Accelerator system were the highest of all materials tested, both with UltraLume LED 5 and Mini LED lamp. In addition, among the materials tested with the same lamp, EndoREZ + Accelerator showed the highest values of enthalpy after the first irradiation time (20 s). With regard to the groups where EndoREZ + Accelerator was tested, the type of LED light unit employed did not influence the experimental results in terms of polymerization rate when compared to the other resin materials tested.
According to our results relative DC progressively increased in all the specimens tested from the first to the fourth irradiation. Further irradiations after the first light exposure of 20 s contributed to increase the percentage of cured monomers. EndoREZ with or without Accelerator and RealSeal polymerized with the Mini LED showed a better behaviour than the same sealers polymerized with the UltraLume LED 5: this was probably due to the major intensity of the light source. RealSeal polymerised with the UltraLume LED 5 showed values of conversion from the second to the fourth irradiation that were higher than those obtained from the EndoREZ polymerized with the same lamp, but these differences were not statistically significant.
In the group RealSeal + Mini LED at each irradiation time the conversion was significantly lower than that recorded for the group EndoREZ + Mini LED, and the values of enthalpy were almost constant during all the polymerization. The different behaviour among the materials tested may be due to their different components, such as photo initiators, that allow a different response of the material to the irradiation. It was not possible to use the same curing mode for the two light units. However in consideration of the exponential increase of the DC as a function of irradiation time, we did not expect significant differences among the two curing modes. In this study we evaluated the differences in DC of the sealers considering the overall characteristics of the LED light units.
During the interval between each irradiation the materials did not exhibit significant exothermic signals, thus indicating that the auto-polymerization was very slow and did not influence this experiment. The sample preparation consisting of ER with the accelerator was meant to reflect the situation that occurs in the endodontic system where the contact of the activator with ER interests Drug_discovery only the interface of the sealer with the gutta-percha cones that are immersed into the accelerator before their placement in the canal previously filled with the EndoREZ.