Fluoride Studies Bring International Distinction to John Bartlett, PhD
Professor John Bartlett, the College of Dentistry’s Associate Dean for Research, has received international acclaim for his groundbreaking research on dental enamel and factors related to its development.
In July, at the 2018 International Association for Dental Research meeting in London, England, Dr. Bartlett was presented with the Distinguished Scientist Award for Pharmacology, Therapeutics, Toxicology Research. The award recognizes work that “contributes to the understanding of the mechanisms, efficacy, and safety of drugs used to treat dental disease and associated symptoms.”
Dr. Bartlett’s research has focused on understanding dental enamel development and the cellular interactions that are required for healthy enamel formation. He has published nearly 90 scholarly papers on the biological aspects of enamel, including the effect of excessive amounts of fluoride.
“What we’ve found is that excessive amounts of fluoride stresses the ameloblasts. It doesn’t actually kill them, but it stresses them so they don’t make enamel in the proper way.”
-- John Bartlett, PhD
This most recent honor specifically recognizes Dr. Bartlett’s work studying the impact of fluoride toxicity on ameloblasts—cells that are responsible for the enamel formation process. “We’ve looked at the molecular biology of how excessive levels of fluoride can affect cells in enamel formation,” he said.
Too much fluoride can lead to fluorosis, which is most commonly manifested as white spotting on adult teeth. “You can actually get brown and mottled enamel if you get high enough levels of fluoride.” The cause, Bartlett and his team have found, is stress.
“What we’ve found is that excessive amounts of fluoride stress the ameloblasts. It doesn’t actually kill them, but it stresses them so they don’t make enamel in the proper way.” Fortunately, the response and its effects can be halted. If fluoride levels are reduced, the ameloblasts return to their unstressed state and form unaffected enamel.
There are many factors that can have an impact on enamel formation, which is why anthropologists study teeth to learn about events in a person’s life. “Enamel is more susceptible because the cells that make it are more sensitive to stress,” Dr. Bartlett said. “Even a high fever can affect enamel when it is forming on unerupted teeth.”
Dr. Bartlett’s discoveries have not put him off fluoridating water. “In general, fluoride is good for enamel. It packs the crystals tightly. If there’s too much, however, the enamel can get brittle and break.”
In the U.S., the generally low levels of fluoride in drinking water don’t pose a threat. High doses are the issue. In China and India, for example, fluoride levels in drinking water can be high enough to cause bone fluorosis and other damage, since the crystals in bone formation are the same as in dental enamel.
Dr. Bartlett’s MS is in microbiology and his PhD is in cell and molecular biology. He first began studying fluoride in 2002, after learning about stress responses during his days as a postdoctoral student. Today, his five-person lab has shifted from focusing on genetics to looking at epigenetics—changes in gene expression that don’t affect the underlying DNA—to help understand cellular responses to fluoride. “We’ve found not only how cells are adversely affected, but also gene pathways that help cells overcome exposure,” he said.
This year’s Distinguished Scientist award is Dr. Bartlett’s second time for receiving this honor. In 2012 he was recognized with this award for his work on Basic Research in Biological Mineralization, which included the first discovery of the matrix metalloproteinase named enamelysin, which has become known as MMP20. It is an enzyme that is critical to the formation of healthy dental enamel.
Dr. Bartlett’s award this year included a $3,500 monetary prize, which he shared with his co-investigator, Maiko Suzuki, PhD, a frequent collaborator and co-author whom he called a “truly outstanding researcher.”
Having been named a Distinguished Scientist once before did not lessen the experience this year for Dr. Bartlett. “One scientist is picked per year, and a lot of people are there when you receive the award,” he said. “It is an honor for any scientist and I am very grateful.”