Backscattered electron imaging of dental tissues

New findings concerning the processes and results of the mineralization of the dental tissues have been made using new technical developments in scanning electron microscopic specimen-preparation and operation of the instrument. Anorganic preparations have been made with oxygen plasma ashing in the dry state, and with deproteinising solutions and very careful washing and drying for wet specimens: these were imaged with backscattered electrons (BSE) to provide charge-free, topographic images. Methacrylate embedded samples were diamond micromilled to provide flat surfaces: in the absence of topography, BSE images could be used to study even small density differences. The technological advances described here have greatly improved the ability to image tenuously linked, microscopic mineral particles in dental tissues. Additionally, we now have a technique providing atomic number contrast of topographically flat, calcified tissues so that minor variations in the level of mineralization can be detected and regions compared. The advances in the interpretation of the structure of the three dental tissues that these methods have yielded are: the variation in mineral density of the enamel prisms coincident with the pattern of cross-striations seen by light microscopy; the identification of a dense centre of mineralization at the initiation point of calcospherites in dentine; and the relative mineralization of the acellular cement compared with dentine.