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A longitudinal study of occlusal caries among schoolchildren in Dar es Salaam, Tanzania.

OBJECTIVES
To describe the clinical caries status and the radiographic progression of occlusal caries lesions in permanent first and second molars among primary schoolchildren in Dar es Salaam over a 3-year period.


METHODS
Clinical and radiographic diagnosis of caries in first and second permanent molars in 223 children aged 8-16 years were carried out annually from 1994 to 1997. The drop-out rates from the baseline in 1994 to the follow-up examinations in 1995, 1996 and 1997 were 16.6%, 22.0% and 35.4%, respectively. Twenty-one percent of the dropouts were picked up during the study.


RESULTS
Less that 5% of all occlusal surfaces that were sound at the beginning of the study developed new clinical caries lesions over the 3-year study period. The highest rate of new lesions was found in second molars. The mandibular second molars were most frequently affected by new caries lesions followed by the mandibular first molars. Progression of lesions was generally slow. After 1, 2 and 3 years, 30.0%, 47.9% and 52.8% of lesions in occlusal surfaces of first molars had progressed, compared to 47.9%, 71.3% and 100.0% of lesions in second molars.


CONCLUSIONS
Dental caries prevalence was low. New occlusal lesions were more likely to appear in mandibular second molars. Carious lesions were progressing slowly, especially in the first molars. Fissure abrasion may play a role in minimizing the risk of developing new occlusal lesions as well as progression of existing lesions.