Scanning electron microscopic observations of the pulsed carbon dioxide laser effect on human enamel support microradiographic findings and indicate that this laser is significantly more efficient than the ruby laser within the limits of this investigation. Surface changes which were suggestive of fusion occurred between energy densities of 13 to 50 joules per square centimeter.There may be several potential applications of laser energy to dentistry. Initially, the use of the laser as a replacement for the dental drill was a popular idea,' but because of the high energy densities required this does not seem practical and has not been explored scientifically. Laser application to spectroscopic analysis of the chemical composition of substances related dentally has been attempted2?3 but still seems to be premature. The dental laboratory use of laser energy to solder and weld is in an early stage of development.4 In studying the effect of low laser energy densities, our interest has been ap-
A preliminary survey of age changes in human teeth by Nalbandian,1 2 utilizing the multifactorial point system proposed by Gustafson,3 suggested that the relative transparency of root dentin-generally known as "sclerosis"-might be among the more reliable dental aging characteristics, presumably least affected by the superimposed pathology to which the crown portion of teeth is prone. It seemed worthwhile, therefore, to examine the nature of the age changes in the root dentin more closely.In the present study structural alterations associated with sclerotic root dentin have been observed by means of optical and electron microscopy as well as by high-resolution microradiography. While similar techniques have been employed individually as applied to studies on crown dentin, there does not appear to be any previous study comparing the combined results of these several approaches in the study of typical sclerotic age changes in the root dentin of human teeth.The classical studies of W. D. Miller,4 Beust,5-7 and Bodecker and Lefkowitz,8 9 demonstrated alterations in the optical appearance of ground sections of dentin as well as a decrease in permeability to dyes coincident with aging. These changes could be the result of intratubular calcification, which would inhibit the diffusion of dyes and cause the refractive index of the tubules to approach that of the intertubular dentin, thus modifying the relative transparency.Recently a number of microradiographic investigations of crown dentin'0-'6 have revealed areas of considerably greater X-ray absorption in relation to the dentinal tubules than in the general dentin matrix, suggesting deposition of highly concentrated minerals. For example, J. Miller'0 demonstrated a highly mineralized zone around the odontoblastic processes in microradiographs of dentin from unerupted teeth. Similar observations were made by Blake" in sound teeth from eleven-to thirteen-year-olds. Bergmann and Engfeldt12 studied by microradiography the transparent dentin under superficial caries. Their material showed, in addition to hypercalcified zones around many tubules, other tubules which appeared to be completely obliterated by highdensity material. The following year Rbckert13 reported complete tubular obliteration in the crown dentin of young and old non-carious teeth, stating that there was a greater tendency toward tubular obliteration with increasing age. Downloaded from
SCLEROTIC AGE CHANGES IN ROOT DENTIN 5Bradford'4 15 has studied the structure and "maturation" of dentin by optical microscopy of ground sections and sections of decalcified material, noting various stages in a progression of tubular "maturation," culminating in complete tubular obliteration.The most conclusive demonstration of a hypercalcified peritubular zone was recently made by Frank'6 in electron-microscopic studies of undecalcified sections of crown dentin from unerupted third molars.It appears that the hypercalcified peritubular zone is a normal structure in dentin, with the possible exception of areas near the preden...
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