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

Salt fluoridation is effective at inhibiting caries, but fluorosis prevalen ce data are deficient. Objectives: The purpose was to undertake a blind stu dy of caries and tooth mottling in 8th grade school pupils from south-east Hungary who had resided (test) or not resided (control), until November 198 5, in a 350 ppm F-/kg domestic salt-fluoridated area during their early yea rs of life. Methods: In Szeged, blind clinical caries and anterior tooth mo ttling scoring (+10% repeats) of 49 previously salt-fluoridated (mean age 1 4.14 years) and 59 non-salt-fluoridated subjects (mean age 14.08 years) wer e undertaken by one examiner, in June 1997. In addition, radiographic and p hotographic recordings were taken. In Glasgow, four dental and two lay staf f scored the projected 35 mm colour transparencies (+10% repeats) of each p upil's six upper anterior teeth, for tooth mottling. All clinical, radiogra phic and photographic data were then analysed. Results: Mean DMFS scores we re 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-ra y reliability=0.95. Clinically, three test children had fluorosis of 10 tee th, 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 "po ssible fluorosis" was recorded by two to four panel members for only three other test and two control subjects. Conclusions: No evidence was found tha t significant anterior tooth fluorosis resulted in subjects exposed previou sly to 350 ppm F-/kg domestic salt from birth to 2.3-4.8 years of age. Howe ver, no caries benefit was demonstrated after the 11.5-year salt fluoridati on 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 f luoridation and (b) the need to maintain constant fluoride delivery to toot h surfaces, certainly well beyond 10 years of age.