What is the critical pH and why does a tooth dissolve in acid?
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Updated: Aug 29, 2026

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Ratiometric Imaging of Extracellular pH in Dental Biofilms
Published on: March 9, 2016
1Department of Oral Biology, Faculty of Dentistry, University of Manitoba, Winnipeg, Manitoba, Canada. Colin_Dawes@umanitoba.ca
Journal (Canadian Dental Association)
|December 5, 2003
Abstract:
This paper discusses the concept of critical pH for dissolution of enamel in oral fluids. The critical pH does not have a fixed value but rather is inversely proportional to the calcium and phosphate concentrations in the solution. The paper also discusses why teeth dissolve in acid, why remineralization of white-spot caries lesions is possible and why remineralization of teeth eroded by acid is not possible.
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The potential of hydrogen (pH) is a measure of the acidity or basicity of a water-based solution determined by the concentration of hydronium ions (H3O+). In one liter of pure water at neutral pH, there are 1×10−7 moles of hydronium ions. However, the extensive range of hydronium ion concentrations present in water-based solutions makes measuring pH in moles cumbersome. Therefore, a pH scale was developed to convert moles of hydronium ions into the negative logarithm of the hydronium ion...
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