Changes in Mean Fluorosis Scores from Age 9 to 23

Objectives: A few studies suggest that mild dental fluorosis declines in severity from late childhood to adolescence. This study examined changes in mean person- and tooth-level fluorosis from ages 9 to 23 in a birth cohort.
Methods: Fluorosis exams were conducted at 9, 13, 17, and 23 years in the longitudinal Iowa Fluoride Study. Fluorosis Risk Index(FRI) scores (ranging from 0 to 3) were determined for each buccal zone and then averaged at the tooth- and person-levels for early-erupting, late-erupting, and maxillary incisor teeth. Mean scores were categorized(0, 0.01 – 0.50, 0.51 – 1.00, 1.01 – 3) and compared over time. Goodman and Kruskall’s gamma statistic quantified the trends in mean fluorosis severity and tested for significant declines in mean FRI category with age. Wilcoxon signed-rank tests assessed whether the probability of having a lower follow-up mean FRI score was significantly greater than having a higher score.
Results: Comparing mean person-level scores over time for the 282 participants completing all 4 examinations showed that the percentages with scores of 0.51 or greater declined with increasing age. Specifically, the percentages were 18%(age 9), 10%(age 13), 5%(age 17), and 3%(age 23) for early-erupting teeth, 16%(at 13), 6%(17), and 5%(23) for late-erupting teeth, and 33%(at 9), 19%(13), 14%(17), and 10%(23) for maxillary incisors. Mean tooth-level scores also declined. Percentages with means 0.51 or greater were 18%(age 9), 11%(13), 7%(17), and 6%(23) for early-erupting teeth(n=3,269), 14%(at 13), 7%(17), and 5%(23) for late-erupting teeth(n=4,251), and 29%(at 9), 17%(13), 12%(17), and 9%(23) for maxillary incisors(n=1,068). Gamma statistics for all tooth groups at the person- and tooth-levels indicated significant declines in categorized means (P<0.0001). All Wilcoxon signed-rank tests were significant(P< 0.05), except for maxillary incisors (baseline category 0.01–0.50) from 17–23 (person-level) and from 9–13 (tooth-level).

Conclusions: Fluorosis severity(mean FRI scores) at both the person- and tooth-levels declined throughout adolescence and early adulthood.