Caries and fluorosis prevalence and fluoride exposure in Vietnamese children

Objectives: To assess fluoride exposure of preschool children, and caries and fluorosis status of school children to consider the appropriateness of introducing salt fluoridation. Methods: School children in Hanoi (n=524) and in rural LaoCai (n=566) were examined using National Institutes of Health caries guidelines and Dean's Fluorosis Index. Children were randomly selected from the schools visited in the 1999 National Oral Health Survey that had employed a multistage stratified random sampling strategy. Morning spot urine samples were taken from 190 Hanoi and 200 LaoCai 3-5 year old children. Fluoride excretion rates were determined using an ion specific electrode and adjusted based on creatinine excretion as per Zohouri et al 2006. The fluoride concentration in drinking water was determined using a fluoride specific electrode. Results: Caries prevalence in Hanoi and LaoCai was – 6-8 year olds dmft 5.70 and 6.05, 12-14 year olds DMFT 2.08 and 1.56. The Unmet Restorative Index (d/dmft, D/DMFT) in both age groups was over 94%. Fluorosis prevalence in Hanoi 12-14 year olds was 46.9%, predominantly questionable (26.2%) or very mild (12.3%). Fluorosis prevalence in LaoCai was 9.5%. Fluoride excretion in 3-5 year olds was 0.35 mgF/24h in Hanoi and 0.25mgF/24h in LaoCai. The LaoCai mean is below the optimal range of 0.35-0.40mgF/24h proposed by Marthala and Schulte 2005. The mean fluoride concentration range in water was 0.23-0.87ppm in Hanoi districts and 0.10-0.33ppm in LaoCai districts. The district with the highest mean fluoride concentration in water (0.87ppm) had the highest mean fluoride excretion level (0.43mgF/24h). Conclusions: Caries prevalence in 6-8 year olds was relatively high in Hanoi and LaoCai with 12-14 year olds caries and fluorosis prevalence higher in Hanoi. Fluoride excretion rates were below the proposed optimal range in LaoCai. Salt fluoridation could be an appropriate prevention intervention for LaoCai.