Critical pH for initiation of caries in dentin is:
Critical pH for initiation of caries in dentin is 6.2-6.5.
In addition, the critical pH for dentin is higher than for enamel, so demineralization is likely to start even before the pH reaches the critical level for enamel (pH = 5.5).
4.3-4.5
5.2-5.5
4.9-5.1
6.2-6.5