Subsurface demineralization in dental enamel and other permeable solids during acid dissolution

Subsurface demineralization of dental enamel during acid dissolu-tion has been reported many times, but its cause remains obscure. At first, the phenomenon was thought to result from the physical structure of enamel. More recent studies have shown that subsur-face demineralization occurs in other permeable solids, indicating that there must be more fundamental factors involved in this curious effect. In order for this phenomenon to be investigated, dissolution experiments were carried out by means of real-time scanning microradiography in various systems, including enamel, or aggregates ofhydroxyapatite (calcium, strontium, or barium), or hydroxides (calcium or magnesium). These were chosen to discrimi-nate between effects ofstructure and composition. It was found that it was not possible for the demineralization observed in these systems to be attributed to a common feature. From this, it is concluded that subsurface demineralization in enamel and other mineralized tissues should not be ascribed to a single cause