Abstract
In the preceeding paper, influence of YAG laser irradiation on the dental hard tissues was studied and it was reported that cavities were formed more easily in carious enamel than in sound one.In the present paper, the effect of surface glossiness of dental hard tissues on cavity formation by laser was considered;the effect of black staining on the surface has already been established by several authors.The importance of surface glossiness became confirmed for the volume of cavities formed in sound enamel increased greatly when the glossiness was less than a critical value.Furthermore, degree of ease of cavity formation in artificial carious bovine tissues by laser was studied using demineralization period from one to six days.An increasing volume of cavities with time was observed in the enamel.Inversely, in the dentine, the volume of cavities was reduced to about 30% that of sound dentine, presumably due to the fractional increase in organic components in dentine resulting from demineralization.Natural caries in human dental enamel were also irradiated with a defocused beam, and cavities with glassy surface were easily formed.Microradiographic and electron microprobe analyses revealed both a decrease in transmittance and an increase in Ca-Kα and P-Kα X-ray intensities on the cavity surface probably due to the high density of the glassy surface.
