Fluorosis of the Late-Erupting Teeth and Timing of Fluoride Intake

Introduction: Concerns have been expressed about the increased prevalence of dental fluorosis. Few studies have reported on fluorosis of the late-erupting teeth, and little is known about the timing of fluoride intake to cause such fluorosis. Objectives: To report on the prevalence of fluorosis of late-erupting teeth and importance of different time periods of fluoride intake. Methods: Subjects were participants in the longitudinal Iowa Fluoride Study. Fluoride intake from water, beverages, selected foods, supplements and dentifrice had been estimated longitudinally from birth. Subjects were examined for fluorosis at age 13 by three trained dentist examiners using the Fluorosis Risk Index (FRI). Results were analyzed separately for canines, first and second premolars, and second molars, and related to estimated annual daily fluoride intake (area-under-the-curve in mg F/kg bw/day) using Pearson correlations. Results: Prevalence rates (n=189) for 1+ teeth with fluorosis were 19% (canines), 20% (first premolars), 21% (second premolars), 13% (second molars) and 27% (any of 16 late-erupting teeth). Strongest correlations between fluorosis scores and fluoride intake were at age 48-60 months (correlations= 0.20, 0.25, 0.25; p=0.02, 0.002, 0.002) for canines, first premolars and second premolars, respectively. Second molars were most highly correlated with age 72-84 month intake (r=0.28, p = 0.002). Correlations were also significant (p<0.05) for intakes at ages 36-48 and 60-72 months for canines, for ages 24-36, 60-72 and 72-84 months for first and second premolars and for ages 24-36, 48-60 and 60-72 months for second molars. Conclusion: Results suggest that there are slight differences between canines and premolars or second molars in risk periods for fluorosis. If fluorosis of premolars or second molars is a concern, then fluoride intake up to 84 months (7 years) can be important in fluorosis etiology. Supported in part by NIH grants R01-DE09551, R01-DE12101, and M01-RR00059.