Early dental plaque morphogenesis. A scanning electron microscope study using the hydroxyapatite splint model and a low-sucrose diet.

Abstract

Bacterial colonization of hydroxyapatite splint segments attached to buccal surfaces of maxillary molar and premolar teeth, were studied at intervals of 2, 4, 6, 12, 24 and 48 hr in six subjects given a low‐sucrose diet. Bacteria were first encountered in 4 or 6 hr specimens and considerable variation existed between subjects regarding time of appearance, rate, and extent of microbial growth. Individual organisms were seen attaching to a pellicle surface with or without intervening thread‐like or coat‐like structures. Similar thread‐like structures were sometimes seen connecting individual organisms. The colonization started frequently in grooves or pits in the surface and the bacteria spread as monolayered cells from these starting points. Bacteria were also seen colonizing on epithelial cells. Cocci dominated in numbers in all phases of this study although rods and filaments appeared in increasing amounts in 24 and 48 hr specimens. Structures resembling corncobs were seen in 48 hr specimens. The gross morphology of plaque development was characterized by patches or strands of bacterial growth and a heterogeneous pattern of apparently freshly colonized areas interspersed between areas of more extensive colonization. Except for a few bacterial clumps, no aggregates or hemispherical globules appeared on the splint surface. These findings warrant a revision of how the salivary aggregating factors are functioning in vivo: Their importance may be to mediate attachment between individual cells in the early monolayer as well as between cells and pellicle, and later contribute to the cohesion of the plaque, rather than by forming bacterial aggregates that settle down on the tooth surface.