050 



G. N. JENKINS AND C. DAWES 



800 - Gelatin-grown 



600 - 



o 



Q. 



O 



400 - 



200 - 



Hours 



Fig. 2. Respiration ot a strain of proteolytic bacteria isolated from a human 

 mouth and later grown in the presence of autoclaved human tooth (1), un- 

 treated human tooth (2), hair (3), rat molar dentine (4), rat incisor dentine 

 (5), human dentine (6), human enamel (7), no addition (autorespiration) 

 (8). (Courtesy of Dr. Albert Schatz and the New York State Dental Journal.) 



Experiments on somewhat similar lines were carried out b\ 

 Hashimoto (1958, I960), who incubated cow and human teeth with 

 bacteria and detected a rise in concentration of nonprotein nitrogen, 

 calcium, magnesium, and phosphate in the medium. The parallel- 

 ism between the rise in nonprotein nitrogen and in mineral matter 

 was interpreted as evidence for proteohsis followed b\- chelation 

 of the metallic ions by the products of proteolysis. 



Although these conclusions are quite reasonable, they are by no 

 means the only possible explanation of the results, and in anv case 

 their relevance to caries is speculative. In particular, the media in 

 which these incubations were carried out were not saturated with 

 calcium phosphate, unlike saliva at neutrality and probabh plaque 

 at neutralit\' (Dawes and Jenkins, 1962). It is therefore very prob- 

 able that at least some of the mineral matter was dissolved in the 

 media without involving chelation, and exposed the organic matrix, 

 which was then attacked by bacteria. These experiments did not, 



