Abstract
Dental decay may be closely related to disturbances in calcium-phosphorous metabolism. There has been little evidence to indicate the mechanism by which such systemic factors operate on the fully erupted tooth. One possibility in this connection is that the tooth can undergo post-eruptive changes in calcification in response to such systemic changes. To determine whether such intradental changes do occur, Bodecker and Applebaum 1 made roentgenological study of teeth in ground section, 1 mm. thick. The radiation was obtained from an X-ray machine which operates at about 40,000 volts. By this method, only gross differences in radiolucency were recognizable—such as that between dentin and enamel, or the partial decalcification associated with a lesion of incipient caries. In no case was it possible to distinguish any minute structural detail. Similar results have been obtained by Heiwinkel. 2
Recently, Fricke 3 found that excellent radiographs of insects can be obtained by means of soft X-rays (Grenz or Boundary rays). He employed a specially constructed X-ray tube which operates at potentials as low as 4,000 volts. With the generous cooperation of Dr. Fricke, we were able to examine several thin sections of teeth with his apparatus. Since minute structural variations in teeth have never before been observed by this method, we report our technique.
Ground sections of teeth are prepared by means of a special planing machine. 4 The thickness of these sections is in the neighborhood of 0.15 mm.; for any one section it is constant to ± 0.01 mm., at least in the region of the crown. Such uniformity is greater than can be obtained by hand grinding. The section is mounted in Canada balsam, between 2 layers of black paper; this prevents its drying and generally facilitates its manipulation.
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