Microradiographic Observation of Acidic Subsurface Decalcification in Synthetic Apatite Aggregates

A system was developed for the in situ microradiography of the formation of subsurface demineralization in sections of a synthetic apatite aggregate. Demineralization was achieved using gelatin acidified with lactic acid at pH 2.7, 3.1 and 3.3. The rate of progress of the lesion was approximately 20 μm/day with a gradual decrease with increasing time. The surface layer overlying the region of subsurface demineralization, which often had a greater radio-opacity than the original section, was built up by a remineralization process and did not consist entirely of the original surface. This surface layer reached a constant thickness of about 100 μm after 3–7 days.