[Scanning electron microscopy of dental plaque and tartar on the surface of human cementum].

Supragingival plaque covering cementum, exposed through withdrawal of the epithelial attachment, presented the same bacterial polymorphism as nature dental plaque. Rounded, filamentous and rod-shaped organisms were observed. In some areas, the presence of extracellular material corresponded to plaque matrix. Corn cob configurations consisting of central filamentous bacteria associated with peripheral cocci were often seen in the supragingival plaque overlaying the cementum. The observation of cementum calculus allowed the differentiation of supragingival and subgingival calculus. The first consisted mostly of calcified dental plaque. The calcification started more often in the interbacterial matrix, but sometimes an initial calcification of the bacterial bodies was noted. Beside this calcified bacterial plaque, crystalline inorganic deposits devoid of micro-organisms were observed. The same differences were noted in subgingival calculus but the proportion was clearly reversed. Amicrobial crystalline deposits were more frequent and calcified bacteria were more uncommon.