The influence of experimental gingivitis on plaque formation.

The rate of plaque growth was assessed using daily Plaque Index measurements over a 7-day period in eleven dental students with an initial mean Gingival Indes of 1.21 (+/- 0.05). The mean Gingival Index was then reduced to 0.27 (+/- 0.04) and the rate of plaque growth assessed in the same way. Bacterial smears were taken from the teeth at intervals during both experimental periods and percentage counts of various morphological types of bacteria made. The rate of plaque growth was found to be significantly greater when the Gingival Index was high compared with when the Gingival Index was low (P less than 0.001). There was also an earlier development of a complex bacterial flora when the Gingival Index was high. The hypothesis is presented that gingival exudate has no inhibitory action on the formation of dental plaque, but contains substances which enhance bacterial aggregation and the colonization of the tooth surfaces by these aggregates.