Influência da transmitância de luz na profundidade de polimerização de compósitos fotoativáveis / Influence of light transmission on the depth of cure of composite resin

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The purposes of this study was: (1) to examine the light transmittance characteristics of two light-cured resin composites, for different thickness, as a function of the wavelenght. (2) to determine the penetration depth of the light, as a function of the wavelength, and (3) to evaluate the polymerization depth of resin composites submitted to two curing sources, by analyzing the depht of cure and Knoop hardness number. Two resin composites (Filtek Z250, shade A2 and Filtek Supreme XT, shade A2E) were used. Specimens of six different thicknesses (0.15, 0.25, 0.30, 0.36, 0.47 and 0.75 mm). The transmittance at wavelengths from 400 to 800nm was measured using a UVvisible spectrophotometer, before and after light polymerization. Transmittance data of 1.5 mm thickness was used to de determine the penetration depth of the light, as a function of the wavelength. For depht of cure, two curing sources were employed: a halogen light source (Optilux 501 - Demetron) with 25 s of exposure time and a 20 s exposure time for a LED (Radii SDI). Specimens were prepared using ISO 4049 dimensions: 4.0 x 6.0 mm (n=5). The same samples were submitted to Knoop hardness test, so that measurements were performed at the irradiated surfaces and at each 1.0 mm, up to 3.0m of depth. Significant differences were found in the wavelength dependence of transmittance between the two materials, and between the unpolymerized and polymerized stages of each resin composite. Before polymerization, at lower wavelengths, the light transmittance of the Filtek Supreme XT resin composite was lower than the Filtek Z250. At the higher wavelengths, however, Filtek Supreme XT presented higher light transmittance. For both resin composites, the penetration depth was higher after polymerization. However, Filtek Supreme XT showed a higher gain in penetration depth at the 0.15 mm thickness. Depht of cure and Knoop hardness numbers was higher for FilteK Z250 and for halogen light source Knoop hardness numbers decreased with increasing depths. The difference in light transmittance characteristics of the resin composites may affect their depth of cure.

ASSUNTO(S)

luz (odontologia) - transmissão compósitos poliméricos light (dentistry) - transmission polymerization odontologia materiais dentários composite resin dental materials polimerização

ACESSO AO ARTIGO

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