Introduction: Dental fluorosis has been assessed only 3 times in nationally representative oral health surveys in the United States. The first survey was conducted by the National Institute of Dental Research from 1986 to 1987. Subsequently, the National Health and Nutrition Examination Survey (NHANES) conducted fluorosis assessments from 1999 to 2004 and more recently from 2011 to 2012. A large increase in prevalence and severity of fluorosis occurred between the 1986–1987 and 1999–2004 surveys. Objectives: To determine whether the trend of increasing fluorosis continued in the 2011–2012 survey. Methods: We analyzed publicly available data from the 2011–2012 NHANES, calculating fluorosis prevalence and severity using 3 measures: person-level Dean’s Index score, total prevalence of those with Dean’s Index of very mild degree and greater, and Dean’s Community Fluorosis Index. We examined these fluorosis measures by several sociodemographic factors and compared results with the 2 previous surveys. Analyses accounted for the complex design of the surveys to provide nationally representative estimates. Results: Large increases in severity and prevalence were found in the 2011–2012 NHANES as compared with the previous surveys, for all sociodemographic categories. For ages 12 to 15 y—an age range displaying fluorosis most clearly—total prevalence increased from 22% to 41% to 65% in the 1986–1987, 1999–2004, and 2011–2012 surveys, respectively. The rate of combined moderate and severe degrees increased the most, from 1.2% to 3.7% to 30.4%. The Community Fluorosis Index increased from 0.44 to 0.67 to 1.47. No clear differences were found in fluorosis rates among categories for most of the sociodemographic variables in the 2011–2012 survey. Conclusion: Large increases in fluorosis prevalence and severity occurred. We considered several possible spurious explanations for these increases but largely ruled them out based on counterevidence. We suggest several possible real explanations for the increases. Knowledge Transfer Statement: The results of this study greatly increase the evidence base indicating that objectionable dental fluorosis has increased in the United States. Dental fluorosis is an undesirable side effect of too much fluoride ingestion during the early years of life. Policy makers and professionals can use the presented evidence to weigh the risks and benefits of water fluoridation and early exposure to fluoridated toothpaste.
A paper published in this journal, "Measuring the short-term impact of fluoridation cessation on dental caries in Grade 2 children using tooth surface indices," by McLaren et al had shortcomings in study design and interpretation of results, and did not include important pertinent data. Its pre-post cross-sectional design relied on comparison of decay rates in two cities: Calgary, which ceased fluoridation, and Edmonton, which maintained fluoridation. Dental health surveys conducted in both cities about 6.5 years prior to fluoridation cessation in Calgary provided the baseline. They were compared to decay rates determined about 2.5 years after cessation in a second set of surveys in both cities. A key shortcoming was the failure to use data from a Calgary dental health survey conducted about 1.5 years prior to cessation. When this third data set is considered, the rate of increase of decay in Calgary is found to be the same before and after cessation of fluoridation, thus contradicting the main conclusion of the paper that cessation was associated with an adverse effect on oral health. Furthermore, the study design is vulnerable to confounding by caries risk factors other than fluoridation: The two cities differed substantially in baseline decay rates, other health indicators, and demographic characteristics associated with caries risk, and these risk factors were not shown to shift in parallel in Edmonton and Calgary through time. An additional weakness was low participation rates in the dental surveys and lack of analysis to check whether this may have resulted in selection biases. Owing to these weaknesses, the study has limited ability to assess whether fluoridation cessation caused an increase in decay. The study's findings, when considered with the additional information from the third Calgary survey, more strongly support the conclusion that cessation of fluoridation had no effect on decay rate. Consideration of the limitations of this study can stimulate improvement in the quality of future fluoridation effectiveness studies.
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