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This report is a 2-year follow-up of a baseline study conducted in Tanzania in 1984. 377 and 448 twelve-year old primary school children were examined in Dar es Salaam (urban) and rural areas respectively. The same criteria and examiners were employed to replicate conditions in 1984 as closely as possible. The mean DMFT score has remained stable over the 2-year period in both the urban (1984: 0.67 (s.d. 1.20); 1986: 0.64 (s.d. 1.32) and rural (1984: 0.51 (s.d. 1.07); 1986: 0.40 (s.d 0.93) areas. However, a significant decrease in the mean DMFS score in Dar es Salaam from 1.19 (s.d. 2.71) in 1984 to 0.81 (s.d. 1.96) in 1986, and in rural areas from 0.78 (s.d. 1.98) in 1984 to 0.48 (s.d. 1.44) in 1986 was observed. In 1986 significantly fewer children with caries had more than 5 involved surfaces in both urban and rural areas than in 1984. In the two areas the difference in caries prevalence observed between 1984 and 1986 affected different surfaces types to varying extents. The results do not support the finding that caries is increasing in all developing countries.

Water is a major source of fluoride ions in areas where skeletal and dental fluorosis are endemic. We investigated the capacity of bone char to remove fluoride from water and its effects on selected bio-indicator organisms. Under static and dynamic conditions, the capacity of bone char was in the order of 2.5 mg of fluoride per g of bone char. Bone charcoal did not appear to support growth of yeast and S. aureus. E. coli and S. faecalis counts in the filtrate decreased with time but there was substantive growth in the bone charcoal.