If your Thanksgiving plans involve cracking eggs for pie, say, or bread pudding, you probably won’t think twice about just chucking the shells into your compost or trash can. But eggshells, being made mostly of calcium, can actually play a role in dental health – at least they can once they’re turned into hydroxyapatite, the mineral compound that forms most of the enamel covering your teeth.
“Eggshell-derived hydroxyapatite,” write the authors of a recent review in Evidence-Based Dentistry, “shows a wide-range of applications in dentistry…marking it as a promising biomaterial in dentistry.”
Using hydroxyapatite in toothpaste or targeted treatments is a very biological idea: Give the tooth what it’s already built from and let the body do what it knows how to do.
Every day, every hour, your enamel naturally goes through tiny cycles of loss and repair. Acids from food or harmful bacteria pull minerals out; your saliva delivers minerals right back. Under normal conditions, saliva is constantly trying to correct the balance.
Hydroxyapatite – HAP for short – simply gives saliva a little help, putting the minerals right where they’re needed. The particles blend into weak spots, settle into microscopic defects in enamel, and support the gentle mineral exchange that keeps your teeth strong.
Eggshell-derived HAP (eHAP) goes a step further by also bringing trace minerals along for the ride – magnesium, sodium, zinc, and more. Trace minerals appear to improve how tooth and bone cells respond – and they’re not naturally included in synthetic HAP. Where synthetic HAP can be thought of as a solo performer, eggshell-derived HAP is more like an ensemble cast.
To our knowledge, most HAP toothpastes currently available still use a synthetic form of the mineral. The only one that clearly doesn’t is Dr. Jen, which is available in a fluoride-free version, but we have to imagine that more will appear in the near future, considering what the science has shown so far.
Which brings us back to that recent review.
The review looked at 17 studies altogether – many in the lab, some in animals, and a few in clinical settings. Analysis revealed a steady pattern of eHAP behaving in ways that the body seems to really appreciate.
When applied to the teeth, the tiny particles of hydroxyapatite slip deep into the dentinal tubules – the microscopic tubes that form the layer of tooth that sits between the enamel and the pulp. There are a lot of nerve endings in those tubules, which is why teeth become sensitive as their enamel gets worn away. HAP stops this by sealing off those tubules, reducing sensitivity naturally.
When applied to early enamel lesions – cavities – eHAP can encourage the formation of dense, stable mineral deposits, essentially helping enamel tighten its structure and stand up better to acids. Some studies even found these deposits richer in calcium and phosphorus than those formed by synthetic HAP.
And because it’s so biocompatible, researchers are exploring it beyond toothpaste: bone grafting, socket preservation, periodontal regeneration, pulp capping. That’s still early-stage research, but the fact that eggshells can play in those spaces at all says something about how harmoniously they mesh with human tissue.
So far, most of the evidence for all this comes from lab-based studies. These tend to show great mineral formation, tight bonding patterns, and encouraging biological responses. On the other hand, real mouths can be chaotic places. Saliva, chewing forces, temperature changes, dietary acids – these things complicate everything.
So while the trajectory is exciting, we’re still more in the “watching closely” phase than crowning eHAP king. But even if it turns out that eHAP’s performance is equal to that of synthetic HAP, it remains an option for those who want something more natural.
Still, it’s hard not to appreciate the elegance of taking something that can be mindlessly tossed away can be transformed into something our teeth recognize as their own. It’s recycling at its finest – and biology at its finest.
