Recent uses of electron microscopy in the study of physico-chemical processes affecting the reactivity of synthetic and biological apatites.
Studies which used scanning electron microscopy (SEM) to investigate subsurface demineralization of dental enamel have recently been well reviewed. The purpose of the present paper was to review several studies, carried out in our laboratories, which have used electron microscopy to examine physicochemical properties of synthetic and biological apatites, to relate these results to previous studies, and to present new data. Aspects of the ultrastructure of hydroxyapatite and carbonated-apatites have been observed by high resolution transmission electron microscopy, and related to shape and growth of these crystals. Surface morphologies of discs prepared from precipitated carbonated-apatites and from ceramic carbonated-apatites were examined by SEM and the information was used in the interpretation of apatite dissolution studies relevant to dental caries. Improvements in the technique of backscattered electron imaging of demineralized enamel have enabled better interpretation of enamel caries experiments. SEM examination of enamel and dentin treated by low energy lasers of specific wavelengths have shown that lasing conditions can be chosen that produce surface fusion of the apatite which inhibits caries-like lesion progression. SEM examination of crystals formed on and in enamel during high concentration fluoride treatments implies that calcium fluoride-like crystals are formed and they may act as a slow-release fluoride reservoir in the mouth.