Prevalence of dental caries in 7-13yr-oid cliildren in Morogoro District, Tanzania, in 1984,1986, and 1988

J. E. Frencken\ G.-J. Truin\ M. A. van't Hof', K. G. KomV, L. Mabelya', J. Mulder"" and H. M. H. M. Ruiken^ 'Department of Cariology and Endodontoiogy ^Department of Mathematical Statistical Consultation, ^Insfifute of Preventive and Community Dentistry, Universify of Nijmegen, Nijmegen, The Netherlands, and ''Department of Preventive and Community Dentistry, Division of Dentistry, University of Dar es Salaam, Dar es Salaam, Tanzania

Frencken JE, Truin G-J, van't Hof MA, Konig KG, Mabelya L, Mulder J, Ruiken HMHM: Prevalence of dental caries in 7-13-yr-old children in Morogoro District, Tanzania, in 1984, 1986, and 1988. Community Dent Oral Epidemiol 1990; 18: 2-^8. Abstract - A 4-yr mixed-longittidinal study to determine the prevalence of caries in 7-13-yr-old Tanzanian children was started in 1984. The parameters considered were age, locality, ^ocio-.£'conomic flatus, and sex. Locality was composed of urban (Morogoro town), rural (Morogoro District), and rural areas in the District with an average fluoride level of 0.5 ppm or more in all drinking water present. SES was established based on the occupation of the father or mother and on housing conditions. Overall, the reproducibility of the dental conditions studied (DjMT/S and D3MT/S) was high, with lower seores for the conditions including early enamel lesions (DjMT/S). The reproducibility of the SES scoring system was high (x = 0.96 and x = 0.90), but the association over the 2 yr of measurement (1984 and 1988) was weak (r = 0.50). There were no restorations found. The percentage of children with caries increased with increasing age from 12-17% at age 7 to 37% at age 13. The statistical tests (ANOVA) revealed an age effect for all conditions studied in 1984, 1986, and 1988 and a locality effect in 1988 only. The mean DjMT-scores varied between 0.15 and 0.24 at age 7 to 0.76 at age 13, while the mean DjMS-scores varied between 0.27 and 0.31 at age 7 to 1.18 at age 13. In general, the caries prevalenee observed was low. Children living in naturally fluoridcited rural areas had significantly lower caries scores than children in non-fluoridated areas.

In developing countries wilh limited resources caries prevalence is generally low in comparison with highly developed countries (1-3). On the African continent increases in income have been shown to be associated with increased consumption of sugar-containing beverages and sweets, and consequently with an increase of caries prevalence, for instance in Ghana (4). Correspondingly, differences in socio-economic status within a population also have an influence on caries experience; in Ethiopia and Nigeria caries was reported to be more prevalent in children from high socio-economic classes, who consumed more luxury food, than in children from low socioeconomic classes (5-7). In recent years a number of authors have suggested that there has been a rapid increase in caries in developing coun-

tries generally (2, 3, 8). If an increase in caries does occur in a low-prevalence population, il is never explosive such as in the case of infectious epidemic diseases, but shows a very slow shift. Trends in caries activity can be measured only by long-term observations in one of the following ways: a pronounced secular trend is observed over periods of move than 10 yr; as an early sign, occasional transverse sampling may show an unexpectedly higher prevalence in the lowest age group, surpassing (he prevalence in the adjacent higher age group(s). Such a sign emerged from the results of the Tanzanian National Dental Health surveys, carried out in 1983, where the mean DjMFS seore was reported to be higher in urban 0-9-yr-olds than in (he older age group of 10-14 yr (9). This early signal was the start ofa specific investiga-

Key words: denfal caries; dental fluorosis; developing countries; fluoride; epidemiology,^ oral J. Frencken, TNO Institute for Preventive Health Care, Department of Community Denli, Health and Epidemiology, PO Box 124, 2300 AC Leiden, The Netherlands Accepted for publication 31 May 1989

tion centered on changes in caries prev, alence in Tanzania, which included, b^ sides a mixed-longitudinal component an investigation into the predictive valu^ of early enamel lesions, S. mutan.s, an^ lactobacillus counts combined for use i| a low-risk child poptilation (10). The aim of the present paper is t^ report on the prevalence of caries in \ child population in Tanzania in 1984 1986, and 1988. Material and methods Description of research area

Morogoro district is situated in the cen^ tral-eastern part of the country witlj Morogoro town as the only big urbai area. In Morogoro (own the University of Dares Salaam, Dental Division, start, ed a teaching unit (field rotation) forden.

Dental earies in Tanzanian children PERIOD

method, and in The Netherlands, using gas chromatography. Examination procedure

The examinations were carried out in a classroom by three calibrated examiners. In 1984 and 1986 the examiners were the same but one of them was replaced in 1988. The examinees were seated on a 1988 kitchen chair with a portable headrest and the oral cavities were illuminated by '85 artificial standardized light powered by a car battery. Each examination was started by the assistant recording the personal particulars of the child and the results of the interview into her/his dietary history and socio-economic background. Fig. 1. Mixed-longitudinal design of the presenl Thereafter, the card was given to the •78 'I'i ^80 •81 1975 •77 study. COHORT I BIRTH YEAR) child who was sent randomly by the assistant to one of the examiners for intraoral examination. The dental observatal students in primary oral health care goro town was 2743, and 13445 children tions were recorded by the examiners in 1983 (11). It was expected that changes of the same age attended the 237 district themselves. Caries was diagnosed acin caries prevalence (cohort effects), primary schools (Education Officers cording to the criteria described by MARcaused by increased consumption of re- Morogoro. personal communication). THALER (13). However, X-rays were not fined snacks and beverages, purchasable Sampling in Morogoro town was carried taken and the approximal surfaces were a s part of a slightly improving national out as follows. A list of 22 primary examined clinically. In 1984 caries was economy, would be detectable in this schools was obtained from the educa- diagnosed at surface level for first molars town. In 1984 the town was estimated to tional authorities. Twenty of them were only. The teeth were cleaned with a have 80400 inhabitants. used to form the satripling frame from toothbrush by the examiners before the oral inspection started. The dental probe Morogoro District covers an area of which six schools were randomly chosen. was used only in cases of doubt. The 19316 km^ and is surrounded in the Two schools participated in the field rotooth surfaces were dried with a hand north and in the south by large mountain tation program and were excluded from balloon. The following dental conditions ranges. The area betweeti the mountains selection for that reason. A slightly difwere studied: D^: early enamel lesions; consists of large plains with isolated hills. ferent sampling procedure had to be folDy. dentinal lesions; D^-MF: early enamel In 1984, 402 090 people were living in the lowed in the rural area. Schools which lesions, dentinal lesions, filled and missDistrict, and most of them were subsis- were included in the Dental School teaching surfaces; DjMF; dentinal lesions, tence farmers. ing program and schools which were infilled and missing surfaces. Enamel nonaccessible by car were excluded from secarious defects and extrinsic staining lection. Through this procedure 67% of were classified into: absent; light; mild Study design the schools (= 159 schools) remained, and severe. The score "severe" indicated To be able to demonstrate cohort effects from which eight were randomly se- that the examiner was unable to make regarding the development of caries in lected. the diagnosis early enamel lesion reliably. Tanzanian children, as well as for predicChildren with score "severe" were extion of future caries activity, it was decidcluded from the DiMFT/S analysis. Fiuoride analyses ed to select children 7-9-yr-old at the beginning of the study. The mixed-longi- In 1978 a shallow wells construction protudinal design of the present study was gram was itnplemented in all districts of based on the age of the children and the Morogoro Region. wells were re- Background parameters measurement interval of 2 yr (Fig. 1). ported to contain water with a fluoride The background paratrveters studied There were seven cohorts, all born be- level up to 7 ppm (12) (published after were age, locality, socio-econoinic status tween 1975 and 1981, and three examina- completion of the 1984 investigation). (SES), and sex. The ages of the children tion periods (1984, 1986, 1988). The chil- This high level necessitated the analysis were obtained from the schools • registradren examined were 7-13 yr old. ::,-.. of all drinking water in the rural areas tion books. Locality was determined as under study. Water samples were taken follows: urban (Morogoro town), rural in the dry season of 1984, 1986, 1988, (Morogoro District), and naturally fluoSampling procedure and in the rainy season of 1985. The ridated rural (villages in the district with In 1984 the number of 7-9-yr-olds at- analyses were carried out in Tanzania, an average fluoride concentration of 0.5 tending the 22 primary schools in Moro- using the selective fluoride ion electrode ppm or more in all water sources pres-


fluoride concentration of 0.5 ppm or more in all drinking water sources (Mgudeni, 0.23-^0.66 ppm; Milama, 0.23 0.81 Duplicate error Test-retest correlation Total, ppm; Kipera, 0.34-1.21 ppm). No signifiUnit intra inter inter intra n cant differences were found between the DjMT 0.4 toolh 0.9 0.76 0.94 582 mean fluoride concentrations in water DjMS surface 0.7 1.5 0.86 0.95 415 samples analyzed at the two laboratories, D,MT tooth 0.3 0.2 0.91 0.96 582 between (hose taken in the dry season of surface D,MS 0.5 0.2 0.96 0.98 415 1984 and 1986, and between those taken at the rainy and the two dry seasons. ment measured in 1984 and 1988 and the In 1988 the number of water samples Table 2. Number of children examined by age in 1984, 1986, and 1988 association over the 2 yr were assessed collected was lower than in previotis using the kappa-coefficient and correla- years (31 only). Paired /-tests showed sigAge 9 10 11 12 13 Total 7 8 tion tests (Spearman), respectively. The nificant differences between the mean 1984 184 309 229 722 kappa-coefficient values were high: 0.96 fiuoride concentration of these 31 sam1986 122 204 135 221 151 833 (1984) and 0.90 (1988), but the associa- ples for the three dry seasons {F

Prevalence of dental caries in 7-13-yr-old children in Morogoro District, Tanzania, in 1984, 1986, and 1988.

A 4-yr mixed-longitudinal study to determine the prevalence of caries in 7-13-yr-old Tanzanian children was started in 1984. The parameters considered...
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