Aging Teeth: How Fluoride Quietly Reshapes Our Enamel Over Time
The Enigma of Aging Enamel
As we grow older, our teeth—though remarkably strong—become more brittle. Dentists and researchers have long noticed that enamel, the hard outer shell of our teeth, changes subtly with age. It gets stiffer, harder, but also more prone to cracking. Yet, no one really knew what happens at the atomic level inside enamel to cause this.
A team of scientists from the University of Washington and the Pacific Northwest National Laboratory decided to dig deeper—literally down to the atoms—to find out how age and fluoride exposure alter the nanostructure of tooth enamel.
Peering Into the Atomic World of Enamel
Dental enamel is made up of countless hydroxyapatite nanocrystals—tiny mineral structures only a few nanometers wide. These crystals are the true backbone of our teeth, arranged in complex layers that resist everyday wear and tear.
The researchers compared enamel from two adults: one aged 22 years and another 56 years. Using a cutting-edge imaging method called atom probe tomography (APT)—a tool capable of mapping individual atoms in 3D—they visualized how elements like fluoride (F), magnesium (Mg), and sodium (Na) are distributed within these nanocrystals.
Fluoride Finds a Home in Aging Teeth
What they discovered was striking:
Older enamel contained significantly more fluoride, but the increase was not uniform.
The outer “shells” of the nanocrystals had higher fluoride levels than their cores.
This layering, or “stratification,” suggests that fluoride slowly infuses the enamel surface through daily cycles of demineralization and remineralization—for example, from acidic foods followed by saliva repair.
While this process strengthens enamel against acid attacks, it might also contribute to embrittlement, making the surface harder but less flexible. In other words, fluoride protects enamel from decay but may also make it more prone to tiny cracks over a lifetime.
What Happens Beneath the Surface
The study also revealed that older enamel nanocrystals are smaller and more densely packed than those in younger teeth. Using electron microscopy, researchers found more lattice strain—tiny internal stresses—in senior enamel. These could interfere with how heat or mechanical forces spread through the tooth, possibly explaining why older teeth can chip more easily.
Interestingly, the study found no major difference in organic content (such as proteins) between young and old enamel, suggesting that the key age-related changes occur mostly in the mineral phase—not in organic residues.
Aging Gracefully, Atom by Atom
The findings open new doors for dental research. If we understand how and where fluoride accumulates, scientists could design better fluoride treatments—ones that strengthen enamel without making it brittle. This could have big implications for lifelong dental care and preventive dentistry.
However, the study’s authors also caution that their findings are based on only two samples. Larger studies are needed to confirm these atomic-level patterns across different people, lifestyles, and diets.
Still, this research marks a leap forward in understanding what really happens to our teeth as we age—not just on the surface, but deep within their crystal structure.
Reference
Grimm, J. R., Renteria, C., Mukhopadhyay, S., Devaraj, A., & Arola, D. D. (2024). Stratification of fluoride uptake among enamel crystals with age elucidated by atom probe tomography. Communications Materials, 5(270).
DOI: 10.1038/s43246-024-00709-8