In the 1450 ppm F ( n = 218 ) , 440 ppm F ( n = 226 ) and control ( n = 259 ) groups the prevalence of dental fluorosis ( TF > 0 ) was 17 % , 15 % and 12 % for the wet ( p > 0.05 ) and 26 % , 24 % and 25 % for the dry ( p > 0.05 ) photographs respectively .
