Accuracy of the simplified Thylstrup & Fejerskov index in rural communities with endemic fluorosis

The aim of the present study was to compare the values of the Thylstrup & Fejerskov Index (TF index) for the determination of the prevalence of dental fluorosis using either all teeth (gold standard) or six upper anterior teeth (simplified TF index). The sample was made up of 396 individuals aged six to 22 years from three Brazilian cities with endemic fluorosis caused by the ingestion of water with high fluoride concentration. The prevalence of dental fluorosis was evaluated by a single trained examiner with excellent intraexaminer agreement (kappa = 0.95). Intraexaminer reproducibilities were calculated at tooth level. Sensitivity, specificity, positive and negative predictive values of the simplified TF compared to gold standard were 90.6 (95%CI: 86.6 to 93.6), 100 (95%CI: 95.3 to 100), 100 (95%CI: 98.3 to 100) and 77.5 (95%CI: 69.8 to 83.5), respectively. The ROC value was 0.953 (95%CI: 0.933 to 0.973). The simplified TF index proved suitable for determining the prevalence of dental fluorosis in regions with endemic fluorosis caused by the ingestion of water with high concentrations of fluoride.