The pH of carious cavities—II: The pH at different depths in isolated cavities

Using a micro-antimony electrode, the pH of a number of cavities, classified into three types according to decay thickness and clinical opening size, was measured both before and after excavation, and isolation from the neutralizing effects of saliva. On excavation, the pH of the bottom layers in cavities, regardless of type, were always lower than the pH of the corresponding surface layers. The pH values of the top and bottom layers in cavities with small clinical openings and thick layers of decay, were lower than in cavities with thin layers and large clinical openings. In most instances, the isolation of cavities from saliva decreased the pH, indicating a possible diffusion of acids from within the depths of the decayed material.