Effect of fluorosis on etching of human enamel.

To investigate the effect of fluorosis on the pattern and depth of etch of human enamel, 420 enamel specimens classified according to the Thylstrup and Fejerskov index (TFI) were etched with 37% phosphoric acid for varying times. The mean depths of etch for mildly fluorosed enamel (TFI = 1-3) were generally dependent on etching time (r = 0.55-0.76), and were not significantly different from the depth obtained for non-fluorosed (TFI = 0) specimens. The enamel specimens with more severe fluorosis (TF = 4) required longer etching time which showed little correlation with the mean depth of etch (r = 0.15-0.16). Furthermore, the etched specimens showed typical enamel etching patterns, independent of the severity of fluorosis. When the specimens with TFI = 4 were etched for 45 s, the subsurface organic network was evident, but this disappeared and typical etching patterns could be seen again when etching time was increased to 75-90 s. It is therefore concluded that the diagnosis of the severity of fluorosis must first be made whenever etching of fluorosed enamel is contemplated.