ULTRASTRUCTURAL AND CHEMICAL STUDIES ON CARIES 199 



TABLE II. The Fluoride Content of Sound and Carious Human Enamel" 

 (Ash weight. From Johanson and Nordback, 1962) 



° Lesions with intact surfaces (white spots). 



^ Pooled sample of 14 teeth. The sound sample was obtained by preparing cavities 

 similar in size and shape to those resulting from removal of white spots. 



"= Pooled sample of 31 teeth. The sample labeled "outer layer" represents the somid 

 enamel from the surface inward to one-half the depth of cavities resulting from re- 

 moval of white spots. The "inner layer" represents the remaining enamel to the full 

 depth of the cavity. 



tion of surface enamel is higher than that of subsurface enamel 

 (Brudevold et al., 1956), it was also of interest to compare the 

 fluoride content of the carious lesion with that of layers of sound 

 enamel. The results of this comparison are presented in study II. 

 Carious lesions again showed a higher concentration of fluoride than 

 corresponding sound tissues. 



Some trace elements other than fluoride were also studied, and the 

 results are presented in Table III. It was found that carious enamel 

 showed a slight increase in lead, iron, and aluminum. 



Studies on the composition of soft carious dentin on a weight basis 



Fig. 13. Section of undecalcified soft carious dentin showing dentinal 

 canals (C) filled with microorganisms (B). The intercanalicular matrix (7C) 

 is largely but incompletely decalcified by the carious process and contains some 

 scattered microorganisms (B) within lacunae. The polystyrene latex spherules 

 (courtesy of Dow Chemical Company) are approximately 0.26 micron in 

 diameter (x approx. 8000.) 



Fig. 14. Undecalcified section of soft carious dentin showing a thick, densely 

 calcified layer interposed between the lumen of the canal (C) and the ex- 

 tensively demineralized intercanahcular matrix (IC). (X approx. 26,000.) 



Fig. 15. Section of embedded, undecalcified sound dentin. A zone of high 

 mineralization (PC), approximately 0.5 micron wide, surrounds the lumen of 

 the canals (C). The intercanahcular matrix (IC) shows an irregular but gen- 

 erally less dense distribution of mineral matter, occasionally displaying a banded 

 appearance. (X approx. 15,000.) 



