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This study compares the results of a full mouth examination with the results of examining only the CPITN selection of 10 index teeth 17/16, 11, 26/27, 47/46, 31 and 36/37 for estimates of prevalence and severity of the conditions assessed with the CPITN, i.e. gingival bleeding, dental calculus, pockets 4-5 mm deep and pockets 6+ mm deep. The mean number of sextants recorded with bleeding or with calculus was generally overestimated when examinations were based on the CPITN selection of index teeth, whereas the mean number of sextants with pockets, whether moderate or deep, were generally underestimated. Similarly, the prevalence of pockets, whether moderate or deep, was underestimated in virtually all age groups while the prevalence of calculus was overestimated in all age groups and the prevalence of bleeding was overestimated among persons below 30 yr of age. We conclude that the partial recording approach of the CPITN methodology is reasonably well suited for identifying persons who are relatively healthy according to the hierarchy of the CPITN parameters. There is, however, a considerable risk that persons presenting with the more severe conditions, i.e. pockets, will be overlooked if only partial recordings are performed.

In order to study the validity of the hierarchical principle of the CPITN we used data originating in a cross-sectional study of periodontal disease in a random sample comprising 1131 Kenyans aged 15-65 yr to determine, for each tooth present in each individual, the absence or presence 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 for bleeding, calculus, pocket 4-5 mm and pocket 6+ mm. According to the hierarchical principle of CPITN a tooth with pockets as the most severe finding is assumed positive also for calculus and bleeding, and a tooth with calculus as the most severe finding is assumed positive also for bleeding. Our analysis showed that calculus as the most severe finding of a tooth overestimates the occurrence of bleeding by up to 18%, depending on age of the individuals and the set of teeth examined. Pockets as the most severe finding in a tooth overestimates the occurrence of bleeding by up to 13%, and overestimates calculus by up to 54%, most pronounced in the younger age groups. The effect of these overestimations on prevalence and severity estimates was the most pronounced for the severity measures, particularly regarding the severity of bleeding, whereas prevalence estimates remained relatively unaffected. Undoubtedly, this result should be seen in the light of a very high prevalence and severity of both bleeding and calculus in this population.

We describe a random effects model for caries lesion development and progression based on considering the effects of the pH fluctuations over time in microbial dental plaque as a Wiener process with a single absorptive barrier. The model predicts that the period of greatest risk to developing caries occurs shortly after eruption, but thereafter the longer a surface survives without developing a lesion, the less likely will it be that a lesion will subsequently develop. The model is able to anticipate why the effect of water fluoridation on caries prevalence is most pronounced when caries is diagnosed at cavity level. This model offers one way in which the variability which characterizes the complex ecosystem associated with dental caries may be considered a subject of interest for enhancing our understanding of its pathogenesis and epidemiology.

This paper presents a method for the analysis of data originating from studies of destructive periodontal disease. The proposed method is an extension of the Mantel-Haenszel technique for the analysis of case-control studies and allows for expression of the site-specificity of destructive periodontal disease while maintaining the individual as the unit of analysis. Using data originating from a cross-sectional study of periodontal breakdown and oral hygiene parameters in a random sample of adult rural Kenyans, the proposed method is illustrated and the results compared with results obtained when two alternative analytical methods are used. The results demonstrate that the choice of analytical strategy may have profound implications for the conclusions to be drawn. Depending on the strategy chosen, one may draw conclusions which are qualitatively different and the present study indicates that the direction of these differences is not predictable.

It is commonly believed that the prevalence of dental caries in developing countries is increasing, though in Kenya and Tanzania there is insufficient information to confirm such trends. In order to test the hypothesis, therefore, 762 children in Dar es Salaam and 802 children in Nairobi aged 12 yr in 1984 were examined for dental caries as part of a baseline study to monitor changes of prevalence with time. Dental caries was recorded by surfaces using the criteria recommended by the WHO and examinations were performed by standardized examiners. The mean DMFT in Dar es Salaam of 0.67 (SD 1.20) was significantly higher than that for Nairobi, 0.51 (SD 1.23). No differences were found in the mean DMFS index. Nairobi children had a greater number of filled teeth and surfaces. Although a greater proportion of children were caries-free in Nairobi than in Dar es Salaam, amongst those with caries, Nairobi children had significantly higher DMFS scores, and a greater proportion with DMFS greater than 4. The possible reasons for such findings are discussed. The mean DMFT and DMFS reported here are amongst the lowest reported in the recent literature from both countries.

In this report on the findings of a baseline study designed to monitor changes in the prevalence of dental caries in 12-yr-old children in Dar es Salaam and Nairobi, the details relating to the pattern of carious attack on particular tooth and surface types are described. In both populations molars accounted for over 90% of all affected teeth and in both groups first molars were more affected than second molars. Very few anterior teeth were affected in either population, though caries of the incisors and canines accounted for a greater proportion of affected teeth in Nairobi (3.4%) than in Dar es Salaam (0.6%). Significantly more mandibular first and second molars were affected in Dar es Salaam than in Nairobi, though in Nairobi the maxillary first molars were more affected than in Dar es Salaam. Occlusal surfaces were the most common site for caries in both populations. With the exception of buccal surfaces, smooth surface caries tended to be higher in Nairobi than in Dar es Salaam. Dar es Salaam children had, however, a significantly higher mean DFS score for occlusal surfaces. The preponderance of occlusal caries indicates that relatively simple restorative care is required to meet the needs of the two populations, and it is suggested that such care could be largely provided by auxiliary dental personnel.

608 12-yr-old children in Harare, and 556 in rural areas of Mashonaland and Central Province, Zimbabwe, were examined for dental caries in 1985. 27.6% of children in the urban area, and 20.9% in the rural, had caries (P less than 0.01). The mean DMFT in urban and rural areas was 0.57 (+/- 1.13) and 0.49 (+/- 1.42), respectively (P = 0.29). Girls had higher levels of caries than boys. Most of the caries occurred on occlusal surfaces, and first molars were the most affected of all teeth. Caries experience was similar to that reported 10 yr previously in Zimbabwe, and similar to that found recently in 12-yr-olds in Kenya and Tanzania. The authors question whether in fact developing countries having high or increasing levels of caries in 12-yr-olds constitute the exception or the rule with regard to trends in dental caries prevalence.