Prevalence of chronic periodontal disease using probing depth as a diagnostic test

The prevalence of chronic periodontal disease was investigated using the occurrence of diseased pocket sites as the diagnostic criterion. The study group comprised 250 dentally aware subjects aged 21-60 years, with a high number of teeth remaining in all age groups. The % of sites with a probing depth of greater than or equal to 4 mm was 16% for the total sample. Most diseased sites (69%) were in the 4-mm class, with only 4% at depths greater than or equal to 7 mm. 82% on the subjects had 1 or more sites greater than or equal to 4 mm. With probing depth as the sole criterion for diagnosis of chronic periodontal disease, prevalence in a sample is heavily dependent on the critical levels selected for probing depth and cut-off point. With critical levels of 4 mm for probing depth and 1 diseased site for the cutoff point, prevalence was 49% in the 21-30 year age group and 95% in the 51-60 year age group. A shift in cutoff point to 40 diseased sites gave a prevalence of 2% and 41%, respectively, in the 2 age groups. For a critical depth of 7 mm and a cutoff point of 1 diseased site, the prevalence was 2% and 43% for the 2 age groups, respectively. Aspects of importance for the decision-making process on disease are discussed.