ULTBASTRUCTUEAL AND CIIFIMICAL STUDIES ON CARIF:S 201 



TABLE III. Trace Elements of Sound and Carious Human Enamel" 

 (Ash weight.'' From Johansen, Steadman, and Steadman, to be published) 



" Soft carious enamel without surface layer; samples removed with pj con excavator. 

 '' Pooled sample of 25 teeth. 



revealed an increase in water and organic material and a decrease in 

 ash (Table IV). Analysis of the ash fraction for major elements 

 showed a marked decrease in magnesinm with relatively minor 

 changes in calcium and phosphorus contents. The calcium phos- 

 phorus ratio was somewhat lower in the carious tissue than in sound 

 dentin. On a dry weight basis, carious dentin also contained about 

 50 per cent less carbonate than sound dentin (Fig. 27), and the 

 difference in rate of release at temperatures below 600 °C might in- 



FiG. 16. Section of undecalcified soft carious dentin embedded in methac- 

 ryhite. Crystallites (AC) seen in edge view present thin, dark profiles; those 

 seen in broad surface view are wider and less dense. At left is the lumen of a 

 dentinal canal (C). (X approx. 74,650.) 



Fig. 17. Undecalcified soft carious dentin, showing the somewhat crumbled 

 edge of a section taken from unembedded material. Most crystallites appear in 

 broad surface view. ( X approx. 96,800. ) 



Fig. 18. Section of undecalcified sound dentin embedded in methacrylate. 

 Crystallites (AC) seen in edge view present thin, dark profiles; those seen in 

 broad surface view are wider and less dense. ( X approx. 74,650.) 



Fig. 19. Undecalcified sound dentin, showing the somewhat crumbled edge 

 of a section taken from unembedded material. In the thinnest parts, the crys- 

 tallites appear in broad surface view; in the thicker parts they are seen in edge 

 view. (X approx. 96,800.) 



Fig. 20. Isolated collagenous fibril from homogenized preparation of carious 

 dentin. A few crystallites (AC) in both broad surface view and narrow profile 

 view are seen associated with the fibril. Very faint indication of banding is seen. 

 ( X approx. 69,600. ) 



Fig. 21. Isolated collagenous fibrils from homogenized preparation of sound 

 dentin. The crystallites are oriented with their long axes parallel to the long 

 axis of the fibrils. The alternating light and dark transverse bands are seen to 

 be in register where the two fibrils join to form a single unit. (X approx. 

 70,000.) 



