7 



Ultrastructural and Chemical Observations 

 on Dental Caries 



ERLING JOHANSEN, Department of Dentistry and Dental Research, 

 School of Medicine and Dentistry, University of Rochester, Rochester, 

 New York 



CARIOUS lesions are manifestations of a complex disease phenome- 

 non affecting the calcified tissues of teeth. It is known that numerous 

 factors including the saliva will influence the course of the disease, 

 and that the basic process by which lesions develop is generated by 

 microbial metabolism in localized areas on external tooth surfaces. 

 The acid environment thus created by metabolism of carbohydrates 

 favors dissolution of dental tissues. Enamel and dentin do not re- 

 spond to this injury by cellular regeneration or repair, but by a de- 

 fensive obliteration of dentinal canals and development of secondary 

 dentin between the lesion and the pulp. These formations at the 

 same time constitute a barrier to the penetration of pulpal fluids into 

 the lesion. On these grounds it can be assumed that the ultrastruc- 

 tural and chemical changes which have occurred in dental caries are 

 mainly the results of the carious process with modifying influences 

 primarily limited to factors associated with the fluid environment of 

 the oral cavitv. 



The original ultrastructural studies on carious lesions of enamel 

 and dentin to be summarized in the present report were carried out 

 on zones of advanced destruction. This part of the tissue was chosen 

 in order to observe maximal changes brought about bv the carious 



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