How Fluoride Changes Your Teeth as You Age — Seen Atom by Atom
A Closer Look at Tooth Enamel
Tooth enamel — the shiny white outer layer of your teeth — is the hardest material in the human body. It protects teeth from daily wear, temperature changes, and acidic foods. But despite its strength, enamel isn’t indestructible. Over a lifetime, it undergoes countless cycles of “demineralization” (when acids erode minerals) and “remineralization” (when minerals are restored by saliva or fluoride treatments).
As we age, enamel tends to become harder but more brittle, meaning it resists wear yet cracks more easily. Scientists have long wondered what happens inside enamel at the atomic level to cause these changes.
Zooming In: The Power of Atom Probe Tomography
In this new study, researchers from the University of Washington and the Pacific Northwest National Laboratory used a cutting-edge technique called atom probe tomography (APT).
This method lets scientists map the position of individual atoms in a material — giving a true 3D “atomic fingerprint.” They compared enamel from a 22-year-old donor and a 56-year-old donor to see how composition changes over time.
What They Found Inside Aging Enamel
Under the microscope, enamel is made of tightly packed hydroxyapatite nanocrystals, the mineral form of calcium phosphate. These crystals have a core, a surrounding shell, and tiny “intergranular” spaces in between — like microscopic tiles cemented together.
APT revealed a clear pattern:
Older enamel had more fluoride atoms in the shell layer of these crystals.
The core and the spaces between crystals didn’t show major changes.
The older enamel’s crystals were smaller and packed more tightly, signs of long-term wear and mineral exchange.
This suggests that over time, fluoride ions gradually accumulate in the outer shell of enamel crystals, likely through countless cycles of acid exposure and repair in the mouth.
Why That Matters
Fluoride is famous for protecting teeth from cavities. It strengthens enamel by replacing hydroxyl ions in hydroxyapatite, forming a tougher compound called fluorapatite, which is more resistant to acid.
But the study reveals a more complex story: as fluoride builds up over decades, it might also make enamel more rigid and brittle — a trade-off that helps resist decay but could make older teeth more prone to cracks.
In short: Fluoride both protects and ages your teeth.
Implications for Dental Health
Understanding exactly where fluoride settles — and how it alters enamel structure — could help dentists design better fluoride treatments that protect enamel without making it too brittle.
This research also shows how advanced materials science can uncover secrets hidden within our teeth, atom by atom — offering new insights into lifelong oral health and the aging process of biominerals.
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, Article 270.