TRANSMISSION ELECTRON-MICROSCOPY OF CEMENTUM CRYSTALS CORRELATED WITHCA AND F DISTRIBUTION IN NORMAL AND CARIOUS HUMAN ROOT SURFACES

Root-surface caries, like enamel caries, develops as a subsurface type of mineral loss. Very Little is known about the composition of the su rface zone covering the body of the lesion, and the ultrastructure and composition of carious cementum are not known. The aim of this study was to correlate the ultrastructure and arrangement of the cementum cr ystals with the distribution of fluoride and calcium in root cementum from human teeth with sound, unexposed, or exposed root surfaces as we ll as in early stages of root-surface caries. Microradiographically, u nexposed specimens showed a relatively homogeneous mineral distributio n contrasting with the formation of an apparently highly mineralized s urface layer in exposed and, in particular, in carious cementum. The e lectron-probe findings showed a substantial fluoride peak correspondin g to the surface layers in carious tissues in particular, whereas the calcium profile in the surface did not reflect the apparent increase i n mineralization. A substantial increase in size of the cementum cryst als was found in specimens with formation of the fluoride-rich, well-m ineralized surface zone. The crystal lattice intervals when observed a long the (001) plane showed a hydroxyapatite spacing. The findings ind icated that a significant crystal growth can be achieved in human ceme ntum concomitant with fluoride accumulation.