Significantly more mottling was found in the optimal fluoride area, according to both indices, although the TF index demonstrated the difference more clearly. The social class had no effect on the prevalence of mottling in the optimal fluoride area. A total of 600 children aged 8-10 years, in three groups of 200 each, formed the study group.
The prevalence of enamel mottling in optimal & low fluoride areas of the West Midlands was studied in March 1989 using the Al-Alousi index and the TF index.
Hamdan M, Rock WP., Community Dent Health. 1991 Jul;8(2):111-9. The prevalence of enamel mottling on incisor teeth in optimal fluoride and low fluoride communities in England.