Fluoride exposure, dental fluorosis and caries among South Australian children.

Abstract

The use of fluoride involves a balance between the protective effect against caries and the risk of having fluorosis. Fluorosis in Australian children was highly prevalent in the early 1990s. Policy initiatives were introduced to control fluoride exposure so as to reduce the prevalence of fluorosis. Objective: The study aimed of describing the prevalence, severity and risk factors for fluorosis, and to escribe the trend of fluorosis among South Australian children. The study also aimed of exploring the effect of the change in fluoride exposure on dental fluorosis and caries. Methods This research project was nested in a larger population-based study, the Child Oral Health Study (COHS) in Australia 2002-2005. The parent study's sample was chosen using a multistage, stratified random selection with probability of selection proportional to population size. Fluoride exposure history was retrospectively collected by a parental questionnaire. This nested study sample (n=1401) was selected from the pool of South Australian (SA) COHS participants. Children were selected by year of birth to form three birth cohorts: those born in 1989/90; 1991/92; and 1993/94. Children were approached in two further stages: a dental health perception questionnaire, and a clinical examination for fluorosis. Some 898 children took part in the first stage. Among those, one trained dentist examined 677 children for fluorosis under clinic conditions using two indices (the Fluorosis Risk Index (Pendrys, 1990) and the TF Index (Thylstrup and Fejerskov, 1978)). The Dental Aesthetic Index score (DAI) was also recorded. Caries experience extracted from dental records of all previous visits to school dental linics was used to enable calculation of dmfs/DMFS scores at different anchor ages. Data were re-weighted age and sex to represent the South Australian child population. Per cent lifetime exposure to fluoride in water and patterns of discretionary fluoride use were calculated. Fluorosis data were used to calculate the prevalence and severity of fluorosis. Caries dmfs/DMFS scores were calculated at different anchor ages to enable comparison between birth cohorts. Results A higher proportion of children in the later birth cohorts used low concentration fluoride toothpaste, and a smaller amount of toothpaste was used when they commenced toothbrushing. There was a significant decline in the prevalence of fluorosis across the three successive birth cohorts. Risk factors for fluorosis, defined by the two indices, were use of standard fluoride toothpaste, an eating and/or licking toothpaste habit, and exposure to fluoridated water. Means (SD) of the deciduous caries dmfs scores at age six and eight were 1.45 (3.11) and 2.46 (3.93) respectively. Evaluation of the "trade-off" between fluorosis and caries with fluoride exposure indicated that the use of low concentration fluoride toothpaste and preventing an eating/licking of toothpaste habit could reduce the prevalence of fluorosis without a significant increase in caries experience. Conclusion There was a marked decline in the prevalence of fluorosis across the three successive birth cohorts. The decline was linked with the reduction in exposure to fluoride. Exposure to fluoridated water and several components of toothpaste use were risk factors for fluorosis. Establishing an appropriate use of fluoride toothpaste could be successful in reducing fluorosis without a significant increase in caries experience.