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Study: Dental fluorosis generally less noticeable over time

University of Iowa researchers include ADA National Fluoridation Advisory Committee member

March 06, 2020

By David Burger

Iowa City, Iowa — Results from a University of Iowa College of Dentistry study suggest that mild and moderate dental fluorosis is generally less noticeable over time, validating the beliefs of some supporters of community water fluoridation that there have been overestimates of fluorosis prevalence made by anti-fluoridation activists.

The Journal of Dental Research, a peer-reviewed journal published by Sage Publications on behalf of the International Association for Dental Research and American Association for Dental Research, published the study Feb. 24.

 Photo of Steve Levy
Dr. Levy
The researchers included Dr. Steven Levy, the Wright-Bush-Shreves-endowed professor of research in the University of Iowa's College of Dentistry Department of Preventive & Community Dentistry, and a member of the ADA National Fluoridation Advisory Committee, a subcommitee of the ADA Council on Advocacy for Access and Prevention.

“Our study supports that fluorosis is less of a concern than some have stated,” Dr. Levy told the ADA News in an joint email interview with his fellow researchers Dr. John J. Warren, professor and director of the College of Dentistry’s Dental Public Health graduate program, and Alexandra Curtis, Ph.D. candidate in biostatistics at the University of Iowa College of Public Health. “Our data support the continued use of community water fluoridation as the best and most efficient way to prevent dental caries on a population basis. Our results also suggest that many statements, and photographs used, by opponents of community water fluoridation that present data on fluorosis prevalence probably exaggerate the true severity.”

The study, titled “Decline in Dental Fluorosis Severity during Adolescence: A Cohort Study,” builds on data collected from 1992-2019 in the Iowa Fluoride Study and Iowa Bone Development Study concerning fluoride exposures and intakes from birth to age 23.

“We collected data on dental fluorosis and dental caries patterns and investigated associations of these with fluoride exposures and other factors,” the researchers said. “We also investigated the esthetic perceptions of dental fluorosis and other oral conditions, and how a number of factors, including fluoride intake, affected bone development.”

The researchers said there are only four prior studies of fluorosis patterns across two time points, and that this is the first study to present results with more than two time points for the same individuals.

 Photo of John Warren
Dr. Warren
"Our results show clearly that the level of fluorosis seen on early-erupting teeth around age 9 is generally less noticeable at ages 13, 17, and 23, and that fluorosis on late-erupting teeth around age 13 is generally less noticeable at ages 17 and 23,” the researchers said. “The data show that early presentation of dental fluorosis soon after eruption will generally be less noticeable later, presumably due to post-eruptive maturation, tooth wear, mastication, toothbrushing, demineralization and remineralization.”

Drs. Levy and Warren and Ms. Curtis said that they were surprised by some of the study results.

“We were aware of the few previous studies which suggested that the presentation of dental fluorosis might lessen over time, and our examiners commented that they didn’t seem to be seeing as much fluorosis during the latter stages of our study,” they said. “On the other hand, it was surprising to see that our data clearly indicated that the level of fluorosis seen shortly after eruption seemed to decline substantially after a few years. Based on the conventional dental wisdom, we and most other investigators had always assumed that fluorosis remained pretty much unchanged over time, so the clear decline did surprise us.”

The researchers said that further study is needed.

“Additional research is warranted to assess patterns of dental fluorosis as children get older in study samples from other geographical regions and with different levels of fluoride exposures,” they said.

Dr. Levy said that the study’s findings should buoy supporters of community water fluoridation.

“Hopefully these results are able to help some people who are fighting in the trenches,” he said.

 Photo of Alexandra Curtis
Ms. Curtis
The research was supported by National Institutes of Health grants, the Roy J. Carver Charitable Trust and the Delta Dental of Iowa Foundation.

Dr. Leon Stanislav, National Fluoridation Advisory Committee chair, said the committee is proud to have Dr. Levy as a member and was pleased with the study’s findings.

“Dr. Levy’s work is world-renowned and he is widely published,” Dr. Stanislav said. “In the most recent study on fluorosis, his research team demonstrated that the vast majority of cases of fluorosis are mild to moderate, which diminishes as one ages toward adulthood. It’s nice to have proof of what most dentists who have practiced for a couple of decades see within their own patient population. Anti-fluoridationists typically overstate the effects of fluorosis in arguments against water fluoridation. This body of work and the volumes of research Dr. Levy and his colleagues have provided the academic and scientific communities have been an invaluable service to the oral health of the community. Community water fluoridation is the most cost-effective and safe way to address the problems of tooth decay irrespective of race, age, gender or socioeconomic status.”  

More information on fluoride can be found at ADA.org/fluoride.