Epidemiological analysis for the influences of plaque and calculus deposition on prevalence of pocket formation.

The influence of plaque and calculus deposition on the prevalence of pocket formation was studied using cross-sectional data from 615 Japanese manual workers aged 18-49. A periodontal pocket with a depth of 4 mm or more from gingival margin to bottom of the pocket was coded as presence of pockets. The oral hygiene status at the specified site was classified into four hygiene patterns as no deposition, deposition of plaque only, deposition of calculus only and deposition of both plaque and calculus. The percentages of six specified tooth types with pocket formation were analyzed according to the local hygiene condition. The results indicate that local oral hygiene produces significant differences in the proportion of teeth with pocket formation in the examined tooth types. The frequency of site-specific hygiene condition were no deposition, deposition of plaque only and deposition of both plaque and calculus, except for the lower central incisors. The teeth without plaque and calculus show no pocket formation in most of the examined tooth types in the subjects aged 18-39, while teeth with plaque and/or calculus indicate high prevalence of pocket formation. It is also revealed that the teeth with both plaque and calculus tend to show higher percentages of pocket formation than those with plaque only. These findings suggest that promotion of a plaque free state would reduce risk for pocket formation to negligible level, and that calculus deposition increase the risk for pocket formation around the teeth with plaque.