244 



J. A. GRAY AND M. D. FRANCIS 



TOTAL ACID CONCENTRATION (moles/liter) 

 [H+] + [UNDISSOCIATED BUFFER] 



Fig. 33. The enamel dissolution rate was a straight-line function of total 

 acid concentration for a medium at 37°C containing lactic acid plus 6 per cent 

 hvdroxyethyl cellulose with or without 0.03 m CaCL added. The CaCL in- 

 hibited the rate proportionally across all acid concentrations and pH values. 

 The dashed line is taken from Fig. 32. 



appeared to be excellent examples of incipient carious lesions, but 

 again surface attack was nev^er completely arrested. However, the 

 character of the subsurface dissolution was completely different from 

 that in the lesions produced in vivo or in vitro with the organic 

 polymer-acid systems (Fig. 3j). The lesion was continuous to the 

 surface with no relatively sound outer layer, and had no birefrin- 

 gence, conditions indicative of very advanced decalcification as de- 

 fined by Gustaf son ( 1957 ) . Nevertheless, further studies of such 

 systems should provide additional valuable information concerning 

 the dynamics and equilibria of incipient carious lesion formation 

 once correlation with the organic polymer-acid svstem has been 

 established. 



The decalcification rate of enamel during incipient carious lesion 



