Suspensions of hydroxyapatite or carbonated apatite stabilized in gelatin gels were exposed to hydrochloric acid solutions containing calcium and/or phosphate and/or fluoride. Initial apatite dissolution occurred at and near the surface of the gel and partial dissolution took place below the surface. A remineralization band subsequently appeared just below the surface when either Ca or PO4 was present in excess. A mathematical theory of demineralization of porous solids predicts this behavior for the apatite case.
- Subsurface demineralization