Validation of Fingernail Fluoride Concentration as a Predictor of Risk for Dental Fluorosis

The aim of this study was to validate the use of fingernail fluoride concentrations at ages 2–7 years as predictors of the risk for developing dental fluorosis in the permanent dentition. Fifty-six children of both genders (10–15 years of age) had their incisors and premolars examined for dental fluorosis using the Thylstrup-Fejerskov index. Fingernail fluoride concentrations were obtained from previous studies when children were 2–7 years of age. Data were analyzed by unpaired t test, ANOVA, and Fisher’s exact test when the fingernail fluoride concentrations were dichotomized (≤2 or >2 µg/g). Children with dental fluorosis had significantly higher fingernail fluoride concentrations than those without the condition, and the concentrations tended to increase with the severity of fluorosis (r 2 = 0.47, p < 0.0001). Using a fingernail fluoride concentration of 2 µg/g at ages 2–7 years as a threshold, this biomarker had high sensitivity (0.84) and moderate specificity (0.53) as a predictor for dental fluorosis. The high positive predictive value indicates that fingernail fluoride concentrations should be useful in public health research, since it has the potential to identify around 80% of children at risk of developing dental fluorosis.