It absorbs the light in a broad wavelength selleck chem spectrum of 360 to 510 nm, with a absorption peak of approximately 468 nm.15 Figure 1 show the spectral distribution and irradiance of the two light cure units, which were used in this study. It should be noted that they both overlap the required wavelength necessary to achieve the correct curing of the resin composite tested. Figure 1. The light spectrum emitted by the light units that were evaluated. The wavelength of the QTH lamp was between 380 and 515 nm, with the peak of emission at 496 nm. The LED device presents a wavelength between 380 and 510 nm, with the emission peak at 453 … However, the highest mean values were observed with the QTH lamp.

The Ultralume 5, used in this study, present a central LED, with four peripheral additional LEDs that emit light in the UV-Vis area (the smaller peak), with maxim light emission at 454 nm (BRANDT 2010). The four additional lights increase the spectrum of wavelength of this light-curing device, however, at distance of 2 mm, these LEDs probably were underused, compromising the optimal performance of the LED device tested.16 The degree of the conversion measurements was lower at the bottoms of the samples than at the top surface. This reduction probably occurred due to the decrease in the irradiance incident on the region. When the light emitted reaches the composite resin, all the specimens is irradiated. The light transmittance through the resin increment is reduced, influencing negatively the degree of conversion of the bottom of the increment.

This results are similar to procedures where the indirect restorations compromise the degree of conversion of resin cement, due to the light attenuation through the restoration.17 These results are relevant, since they demonstrate that insufficient curing can compromise the bottom of the sample. Therefore, the region that sometimes is in contact, in direct restorations, with the adhesive layer may be affected. This problem can be aggravated in deep cavities, where a distance of a few millimeters that separate the tip of the light source and the resin increment can drastically reduce the intensity of the light incident at the bottom of resin increment. The results of the microhardness test were somewhat similar to those of the degree of conversion evaluation.

Reflecting the outcome of similar studies12, 8 in each of the situations we noted the top of the sample presents higher results than the bottom. The results are probably due to the reduction in Cilengitide the light intensity on the region, similar the degree of conversion. Polymerization at reduced rate, as bottom of the specimen, may lead to a more linear polymer structure because relatively few growth centers are formed.19,20 At a higher rate of polymerization, as top of the increment, caused by a higher power density, a multitude of growth centers are formed, leading to a more branched and cross-linked polymer structure.