Lifetime Fluoride Exposures and Fluoride Content of Primary Tooth Dentin

A valid biomarker for lifetime fluoride exposure would facilitate population-based research but currently does not exist. Previous studies indicate that primary tooth dentin may be a promising candidate. Objectives: This study examined the association between primary tooth dentin fluoride content and fluoride exposures. Methods: We collected 99 children's exfoliated primary central incisors and first molars from 2 fluoridated and 2 non-fluoridated communities in North Carolina. Dentin was isolated by micro-dissection and analyzed for fluoride content using the micro-diffusion, ion-specific electrode technique. Information on children's fluoride exposures from drinking water, toothpaste, supplements and rinses was collected by a self-reported questionnaire administered to caregivers. The data were used to create variables estimating lifetime fluoride exposure (in mg/kg of body weight) and exposures for pre- and post-eruption periods. These variables and others for dietary factors (tea, fish and soda), geographic location, race and sex were included in a linear regression model (OLS) to predict dentin fluoride levels in ppm. Results: Statistically satisfactory exposure models consistently included variables estimating pre- and post-eruptive exposures to a variable for combined toothpaste, supplements and drinking water, but other variables differed for incisor and molar models. Only a small portion of the variance (10%) in incisor dentin fluoride (mean=792.3; SD=402.3 ppm) was accounted for by the best model as evaluated by the adjusted R-squared. A large portion of the variance (63%) of molar dentin fluoride (mean=767.5; SD=489.4 ppm) was predicted by the pre- and post-eruptive fluoride exposures (p<.05 and .01, respectively), as well as school fluoride rinse (p<.01), fish consumption (p<.01) and geographic location (p<.001). Conclusion: Results for molars suggest that primary tooth dentin may prove to be a satisfactory biomarker for fluoride exposure. Supported by NIDCR Grant #R01-DE11294-04.