188 E. JOIIANSKX 



process. Similar zones were used for the chemical analyses of dentin, 

 whereas technical difficulties introduced some variation in the sam- 

 pling of enamel. 



Observations on the ultrastructure and composition of carious 

 lesions in various stages of development have been reported by other 

 investigators. Hohling (1961) and Lenz (1961) noted morphological 

 changes in cr\'stallites from advanced carious lesions in enamel, and 

 Scott and Albright (1954) compared the matrix of different zones 

 within enamel lesions. In dentin, the distribution of mineral within 

 zones of advanced lesions was studied bv Takuma and Kurahashi 

 ( 1962), and Bernick et ah ( 1954) noted the presence of cross-striated 

 collagenous fibrils in carious matrix. These and other electron micro- 

 scopic studies of carious tissues have recentlv been comprehensively 

 considered bv Helmcke ( 1962 ) . Chemical studies by Coolidge and 

 Jacobs ( 1957 ) of carious lesions of enamel with intact surfaces 

 (white spot lesions) showed a decrease in the amount of calcium, 

 phosphorus, and carbonate on a volume basis. Stack (1954) and 

 Bhussry (1958) reported an increase in organic material in such 

 lesions. In carious dentin, Manly and Deakins (1940) described 

 three physically and chemically distinct zones and noted that volume 

 loss of organic and inorganic constituents (from these zones) was 

 associated with gain in moisture. The amino acid composition of 

 carious dentin and its mucopobsaccharide content have been in- 

 vestigated by Armstrong (1961rt, 1961Z?). 



Comparable studies on sound tissues have recentlv been reviewed 

 in detail bv Brudevold (1962), Frank et ah (1960), and Johansen 

 (1963, 1964). Even though areas of controversy and incomplete 

 knowledge remain in this field of investigation, the information 

 available provides a basis for comparison with conditions in altered 

 tissues. 



Materials and Methods 



Fully formed permanent human teeth with active carious lesions 

 and extracted in the citv of Rochester, New York,* were used for 

 both the chemical and the ultrastructural studies. For observations 



^ The watt'i" supply of Hoch(\ster contains 1 ppni of fluoride. 



