The root surface: an illustrated review of some scanning electron microscope studies.

This review paper highlights how the advent of a new type of surface microscopy in the late 1960s, scanning electron microscopy (SEM), was responsible for a fresh appraisal of the structure of the root surface. Details of the formation, resorption and repair of cementum, all surface phenomena, and the varied relationships and mineralization patterns of the two sets of fibres within cementum - the hall mark of the tissue - could be seen in a way and at a range of magnifications hitherto impossible. The major interpretational advances were made rapidly using secondary electron imaging of anorganic normal, exposed, carious and instrumented root surfaces. SEM made an important contribution to our knowledge of the composition of the microbial flora overlying the root surface by enabling the survey of plaque still kept intact on the whole tooth. It was possible to appreciate better the existence of distinct microenvironments within the plaque with their unique populations of interacting bacteria, and to see the location and prevalence of regions with special relationships between bacterial forms, such as "corn-cob" arrangements. Aspects of the structure of calculus, and its relationship to the cementum, were revealed in anorganic preparations. More recently, SEM cathodoluminescence and backscattered electron imaging have been applied to the study of normal and diseased root surfaces. The latter technique has proved particularly apt for detecting, in topography-free specimens, small variations and changes in the mineral content of roots and their acquired coatings.