Effect of fluoridated salt intake in infancy: a blind caries and fluorosis study in 8th grade Hungarian pupils

Salt fluoridation is effective at inhibiting caries, but fluorosis prevalence data are deficient.

The purpose was to undertake a blind study of caries and tooth mottling in 8th grade school pupils from south-east Hungary who had resided (test) or not resided (control), until November 1985, in a 350 ppm F-/kg domestic salt-fluoridated area during their early years of life.

In Szeged, blind clinical caries and anterior tooth mottling scoring (+10% repeats) of 49 previously salt-fluoridated (mean age 14.14 years) and 59 non-salt-fluoridated subjects (mean age 14.08 years) were undertaken by one examiner, in June 1997. In addition, radiographic and photographic recordings were taken. In Glasgow, four dental and two lay staff scored the projected 35 mm colour transparencies (+10% repeats) of each pupil's six upper anterior teeth, for tooth mottling. All clinical, radiographic and photographic data were then analysed.

Mean DMFS scores were 9.18 (SD=10.72) for test users and 4.51 (SD=6.24) for control users (P<0.01) and, based on repeat observations, clinical reliability=0.99; X-ray reliability=0.95. Clinically, three test children had fluorosis of 10 teeth, with eight teeth in two controls. Photographic scoring by the clinical examiner gave a 97.2% clinical match, while photographic agreements for all four dentist pairs were 92.5%-97.2%, with lay observers' agreements at 89.8%. For both groups, 10% repeats produced 98.5% agreements. In a sole test case "fluorosis" photographic unanimity was obtained, and non-unanimous "possible fluorosis" was recorded by two to four panel members for only three other test and two control subjects.

No evidence was found that significant anterior tooth fluorosis resulted in subjects exposed previously to 350 ppm F-/kg domestic salt from birth to 2.3-4.8 years of age. However, no caries benefit was demonstrated after the 11.5-year salt fluoridation gap. Caries differences seemed social class-related, city-based controls having less disease than rural test subjects, in spite of an identical F- tablet regimen in all schools from 1987, until subjects were 10 years old. These data emphasise (a) the superiority of sustained community-delivered fluoridation and (b) the need to maintain constant fluoride delivery to tooth surfaces, certainly well beyond 10 years of age.