Comparison of two indices of dental fluorosis in low, moderate and high fluorosis Tanzanian populations.

This study aimed at comparing the Thylstrup-Fejerskov index (TFI) and the Dean's Index (DI) which were applied on three communities with different severity of dental fluorosis. A total of 1565 children aged between 11 and 18 yr with a mean age of 14.7 were examined for dental fluorosis with the TFI and 1155 of these children were also examined with the DI. The measurement error for the TFI was 0.50 (10 scale point) compared to 0.53 for DI (6 scale point). The Kappa values and the measurement-remeasurement correlation appeared to be better for the TFI. No difficulties were encountered in applying the TFI in contrast to the DI, which caused uncertainties in assessing the "questionable" and "very mild" scores, and this may explain the relatively better reproducibility of the TFI. The correspondence between both indices was determined. TFI 0 corresponded well with DI 0. The conversion values for TFI 1, 2, 3 and 4 into DI scores were 0.3, 0.8, 1.4 and 2.4 respectively. The TFI 5-9 corresponded with DI score 4. TFI could discriminate the severe forms of dental fluorosis which were categorized in Dean's highest score 4. TFI was able to reveal more dental fluorosis than DI in communities with minor and moderate dental fluorosis. In the community with severe dental fluorosis where more than 85% of all teeth exhibited a DI > or = 1, both indices revealed a comparable prevalence of dental fluorosis. The TFI is considered a near ideal instrument.