The secret to strong beaver teeth 21.02.2015

The frightening sound of a drill is known to almost everyone. Unlike sharks, whose teeth are renewed throughout their entire fish life, in humans and most mammals, they change only once - from dairy to molars. Although here in rodents teeth grow all their lives. This is due to the fact that, no matter how trite it may sound, rodents gnaw, which is why they grind their teeth evenly. In order for these animals not to be left without the main tool for existence, nature gave them a mechanism for the constant growth of teeth, compensating for abrasion. But what about those who are given teeth once and for life? Researchers from the Department of Materials Science and Engineering at Northwestern University have identified which elements increase the durability of tooth enamel and figured out why beavers can cut trees like a chainsaw.

Tooth enamel is the hardest tissue in our body. It is based on thin long threads of hydroxyapatite. The thickness of one such thread is only 50 nanometers, and the length is a thousand times greater. For clarity, if the height of a birch was a thousand times greater than the diameter of the trunk, then the tree would have a height of about a kilometer. Thousands of such threads are combined into bundles, but still very thin - twenty times thinner than a hair. These bundles are arranged in a certain direction, forming a kind of reinforcing frame of tooth enamel, and the space between them is filled with crystalline hydroxyapatite.

Hydroxyapatite is a mineral containing calcium ions, phosphate and hydroxyl ions. And although enamel is almost entirely composed of a mineral base, even very small amounts of other ions can greatly change its properties. For example, if part of the calcium, even the smallest, is replaced by magnesium ions, the enamel will become more susceptible to the action of acids. Simply put, it will dissolve faster. The same effect will be caused by the replacement of phosphate ions with carbonate. But if phosphate ions replace fluorine ions, the enamel will noticeably improve its properties. That is why toothpaste contains fluoride.

Where does the acid come from in the mouth, which has such a detrimental effect on the teeth, and why is it harmful to eat sweets, although they are not sour at all? The fact is that bacteria live in the mouth, and although they do not pose a threat to the body, they can harm tooth enamel. The remaining sugar serves as food for these bacteria. Everything would be fine if these same microorganisms did not process sugar into lactic acid, thereby increasing the acidity of the environment. The more acidic the environment, the faster the tooth enamel will break down. Yes, yes, the same acid-base balance. As far as we know, beavers do not abuse sweets, but nature still rewarded them with an additional mechanism that makes their teeth stronger. All the essence lies in the very ions that change the properties of enamel.

The researchers took tooth enamel samples from mice, rabbits, rats and beavers and subjected them to rigorous analysis using sophisticated equipment. They literally atom by atom studied the structure of the threads that make up the enamel, and found out an interesting thing. It turns out that the strength and resistance to acids is mainly affected by the amorphous substance, which contains minerals rich in iron or magnesium. Despite the fact that the proportion of such a substance is extremely small, it radically changes the protective properties of enamel. For example, beaver tooth enamel was found to be six times more resistant to acid than rabbit tooth enamel. All this is due to iron compounds, mainly ferrihydrite. It gives not only chemical resistance, but also increases the mechanical strength of tooth enamel. We can say that yes, the beaver really has iron teeth!

However, why hasn't toothpaste been made with iron minerals yet? Although we do not need to gnaw on aspen branches, it would be very nice to reduce visits to dentists. If you look at the teeth of a beaver, you will see that they are far from white - yellow, or even brown. These are absolutely healthy strong teeth, and iron compounds give them color. Not very aesthetically pleasing from a human point of view, but beavers don't seem to care too much about it.