As a child, the thought of losing your teeth was a fascinating experience. On one hand, you were terrified that your teeth were to going to fall out of your mouth. But on the other hand, the tooth fairy was going to leave you some money under your pillow!
Once you got that dollar under your pillow, you probably wondered if you’d be toothless forever. But slowly and surely your teeth began to grow back larger and stronger.
However, if you did happen to lose a tooth as an adult, it didn’t grow back a second time. Odd. So what’s the deal with human tooth growth?
Baby teeth, otherwise known as deciduous teeth, are the first set of teeth that appear in humans. Baby teeth begin to grow very early on in the development phase.
In fact, baby teeth begin developing as soon as the embryonic stage of pregnancy. And they first become noticeable in early infancy.
So why do we have baby teeth anyway?
Baby teeth are important for the proper growth and development of an infant’s mouth. As well as proper alignment of the jaw.
Baby teeth also have an important connection with our permanent teeth. As they erupt through the gum line, baby teeth provide a guide for the permanent teeth. This way they can slide into the mouth without any complications.
So why do babies lose their baby teeth anyway? Why not just keep them and save the fuss?
The first thing to take into account is a matter of size accommodation. Baby teeth are small, and babies’ jaws are also small.
However, as we all know, babies get big. Fast. Including their jaws. As the jaw grows, the root of the baby tooth gets smaller and smaller until the tooth begins to loosen. And eventually, they fall out.
Finally, as the jaw and facial muscles mature, the permanent teeth grow into their new positions. And become strongly anchored in place.
Once we lose our baby teeth, our 32 permanent teeth begin to erupt into the mouth. Generally, the first permanent teeth begin to appear in the human mouth around 6 years of age. And continue to appear until the last baby looses the last tooth.
Why don’t teeth grow back a second time?
A variety of animals, sharks, in particular, are able to continuously grow teeth over their lifetime as they lose them. These animals are known as polyphyodonts.
A new tooth erupts in a few months, but development can start as soon as a few days after losing the tooth! Unlike sharks, humans are diphyodonts; we only grow two sets of teeth over a lifetime.
So what’s the difference between the two categories?
To understand the difference, we have to take a look at how the teeth develop in both groups.
As we now know, human teeth begin growing during the embryonic stage of pregnancy. When development occurs, a section of tissue known as the dental lamina begins to grow at the gum line.
From this lamina, sections of cells known as tooth buds begin to grow. In humans, we have a predetermined set number of tooth buds: 20. 10 for each side of the jaw for the 20 baby teeth.
In rare cases, humans may have more than 20 tooth buds, resulting in a larger number of teeth. A condition is known as hyperdontia. Researchers believe this may occur because as the bud cell grows, it splits into two distinct buds resulting in multiple teeth.
What about Sharks?
Sharks are able to grow and lose as many as 30,000 teeth over a lifetime! As polyphyodonts, sharks grow teeth in a different way than humans.
Like humans, sharks also have a dental lamina. Where they differ is that sharks grow teeth from stem cells, rather than tooth buds. Stem cells are cells who are able to indefinitely grow cells of the same type. This results in the shark’s ability to grow new teeth over and over again!