Initial gingivitis induced by topical application of plaque extract

The present study was undertaken to examine if soluble substances in human dental plaque were able to induce structural alterations in the marginal gingiva characteristic of initial gingival inflammation. Four‐day old plaque was sampled from dental students; the plaque material was pooled, suspended in saline, homogenized, centrifuged and filtered. The supernatant, the plaque‐extract, was then, during an eight hour period, topically applied to the gingival margin of the upper jaws of five Beagle dogs. In control regions saline was applied in an identical manner. One and a half hour before sacrifice the animals were given i.v. injections of colloidal carbon. Biopsies of test and control regions were taken according to a technique described by Schroeder et al (1973). The biopsy specimens were embedded in Epon. Semithin sections (2‐3 μm) were examined in the microscope regarding 1. amount of vascular units subjacent to the junctional epithelium containing carbon particles 2. number of polymorphonuclear and mononuclear leucocytes within the junctional epithelium. The examinations revealed that the gingival units exposed to plaque extract in comparison to controls harboured larger numbers of carbon labelled vascular units and larger numbers of leukocytes within the junctional epithelium. The data also showed that the main reaction occurred in the marginal portion of the gingival tissue. The observations of this study indicate that soluble substances from human dental plaque when applied topically in the gingival sulcus may give rise to structural alterations similar to those developing in the gingival tissues in response to plaque accumulation.