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Teeth play a crucial role in the digestive process by breaking down food, safeguarded by enamel that endures the considerable stress of chewing. However, unlike other bodily materials, enamel lacks the ability to self-repair, leaving it susceptible to deterioration as individuals age.
Researchers are delving into the age-related transformations of enamel to devise strategies for prolonging the health and resilience of teeth.
A study conducted by a team from the University of Washington alongside the Pacific Northwest National Laboratory investigated the atomic structure of enamel extracted from two human teeth: one belonging to a 22-year-old and the other to a 56-year-old. Notably, the enamel from the older individual exhibited elevated fluoride levels, a common additive in drinking water and toothpaste, known for its protective properties for enamel. The inclusion of fluoride in drinking water has recently sparked considerable discussion and scrutiny.
The findings from this research were published on December 19 in Communications Materials. While the study serves as a preliminary exploration, it sheds light on how fluoride interacts with enamel over time, particularly in the context of aging, the researchers indicated.
“Teeth tend to become more brittle as people grow older, particularly at the outer layer where cracks typically initiate,” stated Jack Grimm, a doctoral student in materials science and engineering at UW and the study’s lead author. “Multiple factors contribute to this brittleness, one being the mineral composition. Our goal is to understand precisely how these minerals change, which necessitates examination at the atomic level.”
Enamel primarily consists of minerals organized in repetitive structures that are significantly smaller than the diameter of a human hair, measuring ten thousand times less.
“Previously, our research focused on larger scales—about one-tenth the size of a human hair,” said co-senior author Dwayne Arola, a professor at UW in materials science and engineering. “At that size, it’s challenging to discern the distribution of mineral and organic components within the enamel’s crystalline structure.”
To analyze the atomic structure, Grimm and Arun Devaraj, a materials scientist from PNNL, employed a technique known as “atom probe tomography.” This method enables researchers to create a three-dimensional visualization of each atom within a sample.
The researchers crafted three samples from each tooth and compared the elemental composition across three distinct areas within the enamel’s microscopic structures: the core, a “shell” surrounding the core, and the space in between.
In the older enamel samples, elevated fluoride concentrations were detected in most regions, particularly in the shell areas.
“We encounter fluoride through various sources like toothpaste and tap water, but no previous study has effectively traced its integration in a tooth at this atomic detail,” remarked co-author Cameron Renteria, a postdoctoral researcher at UW working across oral health sciences and materials science and engineering. “Ideally, we would study a tooth from someone with a documented history of fluoride exposure, including their dietary habits, but that is impractical. Thus, this serves as an initial step towards understanding the fluoride influence.”
The interdisciplinary approach of this research is deemed vital by the team.
“I initially specialized in metallurgy but transitioned to studying biomaterials after connecting with Dwayne in 2015. Our discussions highlighted the potential synergy in our disciplines, exploring how to study biomaterials at microscopic levels,” explained Devaraj. “Jack joined us in 2019 and contributed significantly to this in-depth exploration. Interdisciplinary research fosters innovation and may illuminate significant questions regarding the changes teeth undergo with age.”
The research team is also keen to investigate how the protein composition within enamel evolves as time progresses.
“Our aim was to chart the distribution of organic material in enamel and determine if the minute protein levels decrease with age. However, our findings prominently highlighted the fluoride distribution around the crystalline structure,” Arola noted. “Currently, there’s a lack of public discourse on how aging affects teeth. Nevertheless, the dental community strongly advocates for the use of fluoride to combat tooth decay.”
Co-author Semanti Mukhopadhyay, a postdoctoral researcher at PNNL, contributed to this paper. The study received funding from the National Institutes of Health, Colgate-Palmolive Company, and a distinguished graduate research program collaboration between PNNL and UW.
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