MICROSTRUCTURAL CHANGES IN EARLY CARIES 



175 



Fig. 3. Microradiograph of a ground section ot earl\" caries of human dental 

 enamel cut parallel to prisms. (X 350.) (Reproduced by kind permission of 

 the editor of the Brifisli Dental Joiinuil.) 



late stage just before surface breakdown. Mortimer (1962) has seen 

 a similar appearance in the surface zone of occlusal lesions, where 

 he finds that radiolucent striae of Retzius are rarely seen. Gustafson 

 ( 1961 ) has pointed out that variations in the degree of mineraliza- 

 tion of the enamel and its minute structures may play an important 

 part in producing patterns of demineralization. 



There can be little doubt that this pattern indicates a selective 

 demineralization of certain structures of the enamel by caries, but 

 whether this is caused b\' variations in the chemistry of these struc- 

 tures (Brudevold, 1961), variations in their physical properties, e.g. 

 orientation of crystallites (Poole, 1962), variations in their accessi- 

 bility to the demineralizing agent and its paths of entry (Poole, 

 1962), variations in the degree of mineralization (Gustafson, 1961), 

 or variations in their inorganic-organic complex, is not yet clear. 

 Each has its supporters. 



One major point of diflPerence between observers lies in the demon- 



