ROLE OF CHELATION IN DECALCIFICATION SYSTEMS 653 



although the concentration of dissolved calcium did not change 

 during the incubation of teeth with saliva (or saliva sediment), 

 there was a fairly consistent rise in the inorganic phosphate as com- 

 pared with control media containing saliva but no teeth (Jenkins, 

 1959; Jenkins and Dawes, 1963). To determine whether this was 

 a loss of phosphate from the tooth or a breakdown of organic phos- 

 phates in saliva, total phosphate (i.e. organic plus inorganic) was 

 estimated in many of the experiments, and in most cases it showed 

 no change. It was concluded that the presence of the tooth surface 

 favored the breakdown of organic phosphate in the same way as 

 White and Hess ( 1956 ) had found that ashed bone appeared to act 

 as though it contained phosphatase. The explanation of the few 

 experiments in which total phosphate in solution did rise (again 

 with no evidence of a rise in calcium) is not clear; but possibly 

 adsorbed phosphate was released. How it entered a medium al- 

 ready saturated with calcium phosphate and whv it should be re- 

 leased in some experiments and not others is unexplained. These 

 experiments provide no evidence for the formation of chelating 

 agents either from salivary constituents or from enamel. It is possi- 

 ble, of course, that chelators might have formed but in too low 

 a concentration to dissolve detectable quantities of calcium. In any 

 case, this negative evidence in no way disproves the proteolysis- 

 chelation theory, but merelv makes it somewhat less probable. 



Quantitative Considerations 



An obvious difficultv of proteolysis-chelation as a mechanism of 

 enamel caries arises from the low concentration of organic matter 

 in enamel. Could 0.6 per cent of organic matter (excluding lipid), 

 even if it were broken down as Schatz suggests and even if the 

 whole of it had chelating properties, dissolve the 99.4 per cent of 

 mineral matter? Bibbv et ah (1958) considered this to be one in- 

 superable difficultv in the theor\'. It has been answered by Schatz 

 et al. in several ways. First, they speculate that small areas of de- 

 struction of enamel may open up pathways through which other 

 chelators from plaque or food can enter and extend the ca\ity. 

 Secondly, they have calculated from the amount of bone dissolved 

 during 2 hours in their in vitro experiments that 11 mg of enamel 



