VALIDITY OF CPITNS ASSUMPTIONS OF HIERARCHICAL OCCURRENCE OF PERIODONTAL CONDITIONS IN A KENYAN POPULATION AGED 15-65 YEARS

In order to study the validity of the hierachical principle of the CPI TN we used data originating in a cross-sectional study of periodontal disease in a random sample comprising 1131 Kenyans aged 15-65 Sir to d etermine, for each tooth present in each individual, the absence or pr esence of gingival bleeding, of dental calculus, of a pocket of 4-5 mm or a pocket of 6+ mm, such that each tooth had a separate recording f or bleeding, calculus, pocket 4-5 mm and pocket 6+ mm. According to th e hierachical principle of CPITN a tooth with pockets as the most seve re finding is assumed positive also for calculus and bleeding, and a t ooth with calculus as the most severe finding is assumed positive also for bleeding. Our analysis showed that calculus as the most severe fi nding of a tooth overestimates the occurrence of bleeding by up to 18% , depending on age of the individuals and the set of teeth examined. P ockets as the most severe finding in a tooth overestimates the occurre nce of bleeding by up to 13%, and overestimates calculus by up to 54%, most pronounced in the younger age groups. The effect of these overes timations on prevalence and severity estimates was the most pronounced for the severity measures, particularly regarding the severity of ble eding, whereas prevalence estimates remained relatively unaffected. Un doubtedly, this result should be seen in the light of a very high prev alence and severity of both bleeding and calculus in this population.