Abstract
Infrared spectra of light-cured composite materials were obtained from microareas(100μm×100μm each)of the thin composite film by a Fourier transform infrared spectrometer equipped with a microscopic unit.To allow transmission IR measurement, the thin composite films were prepared by cutting out a cured composite mass perpendicular to the photoirradiated surface.The variation of degree of conversion(DC)determined spectroscopically was examined along the distance from an irradiated surface, and then compared with that of Knoop hardness.The results are as follows:1)Individual maximum in DC of the materials Palfique Light and Silux appeared at ca .1.0mm deep from the photo-irradiated surface.2)The material P-30 kept nearly constant its DC at ca.70% in the 0.4-3.0mm depth range.The DC rapidly decreased with the increase in the depth.3)The maximum in DC of Palfique Light and Silux increased by prolonging photoirradiating time up to 60s.On the other hand, the maximum in DC of P-30 was constant at ca.70% DC after the 10-60s irradiation.4)The inhibition of polymerization by oxgen extended to 1.0mm deep from the irradiated surface of each material.5)Knoop hardness was proportional to DC for each material.The slope of the regression line was considerably influenced by inorganic filler content.The slopes for the materials P-30, Palfique Light and Silux decreased in that order.The results indicate that, especially for highly filler-loading composites, the hardness may be considerably varied by a slight change of the DC.
