Why don't the teeth of mammals grow back?

Dental technology of the future Berlin researchers breed teeth that grow back

"And the shark has teeth", Mackie Messer begins his famous bank song in the "Threepenny Opera". And he not only wears it "on his face", as it goes on there, but also for a lifetime. Sharks are - just like crocodiles or rodents - one of those animals that keep growing back teeth.

People usually only get teeth twice

Unfortunately, we humans usually only grow teeth twice: As babies, we get 20 milk teeth. And between the ages of six and twelve, these deciduous teeth are replaced by the 32 teeth of the permanent set of teeth. While there are also cases in which people grow teeth or even entire sets of teeth a third time, this is extremely rare. Anyone who loses their second teeth due to poor systems or poor care, fights or accidents will ultimately only be helped by implants or the "third party".

Certain prerequisites are in place

In theory, humans would also have the prerequisite for getting new teeth over and over again. "Basically, science assumes that the human jaw also has the information necessary for the growth of new teeth for a lifetime," explains Dr. Jennifer Rosowski, research assistant at the Medical Biotechnology Department at TU Berlin. The scientist knows what she is talking about. She devoted her doctoral thesis to the topic of regenerative teeth.

Process of human tooth formation

But the key question is: How do you get the human jaw to produce new teeth? A research project of the TU Berlin under the direction of Prof. Dr. Roland Lauster examined this. The scientists investigated the process of human tooth genesis: When our teeth are formed, certain precursor cells collect in our jaw below the outer skin layer. These cells condense and form a kind of tooth germ. This germ interacts with the jaw via messenger substances and begins to develop into a tooth.

Differentiation of different cell types

"Within the tooth bud that is formed in this way, different cell types differentiate: the enamel organ, the dental papilla and the tooth ridge. These tissues gradually differentiate into a complete tooth," explains Lauster's colleague Rosowski the further process. The information as to whether an incisor or molar is now being formed comes from the surrounding jaw tissue.

In humans, the milk teeth are placed in the jaw from the sixth to eighth week and the permanent teeth in the twentieth week after birth. For another set of teeth, which could later replace the permanent teeth that protruded at primary school age, there are usually no attachments.