THE ROLE OF
SUPRAGINGIVAL DENTAL PLAQUE IN THE INITIATION OF GINGIVITIS
Many types of materials
accumulate on teeth. By far the most widespread and important deposit is dental
plaque. Plaque consists primarily of
microorganisms in an organ-ized matrix of organic and inorganic components. Bacteria account for at least 70% of the mass of
plaque. In fact, one cubic millimeter of dental plaque contains more than 100 million
bacteria consisting of more than 400 species. The organic matrix of plaque
consists of polysaccharide, pro-tein, and lipid components, while the inorganic
matrix is composed primarily of calcium and phosphorous ions.
The dental plaque above the
gingival margin of the tooth is designated as supragingival, and the dental
plaque below the gingival margin (i.e., in the gingival sulcus or pocket) is
called subgingival. Gingivitis can be experimentally induced in an uninflamed
periodontium by allowing the unimpeded accumulation of supragingi-val plaque
and is reversed completely by the thorough and complete removal of
supragingival plaque.
Gingivitis is due principally
to the accumulation and retention of plaque at or near the gingival margin. The
accumulation of supragingival plaque is also a prime in-fluence in the
development of subgingival plaque. As undisturbed plaque matures, it changes in
composition and becomes more complex. A bacterial succession oc-curs whereby
microorganisms associated with gingival health, that is, gram-positive rods and
cocci, are re-placed by microorganisms associated with gingivitis, that is,
gram-negative rods and cocci, as well as spiral or-ganisms and spirochetes. As
a consequence of the change in microflora, the inflammation-induced changes in
the gingiva cause an increase in epithelial cell turnover and connective tissue
degradation, resulting in anatomical changes that tend to deepen the gingival
sulcus, causing a gingival pocket to form. This change in gingival architecture
and the subgingival environment provides a new and better protected niche for
bacteria to grow. Here they are continually bathed by exudate from the gingival
crevice and end products from the supragingival plaque. Hence, control of
supragingival plaque will also have a profound influence on the de-veloping
composition of periodontitis-associated sub-gingival plaque.
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