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Name: Daniel
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Question:
What animals have molars that grow continuously ?



Replies:
No mammals that I or my colleagues are aware of, only some few whose incisors grow continuously.

J. Elliott


Most vertebrates are "polyphyodonts" meaning that they replace teeth continuously through out their lives. All the teeth aren't replaced at once, but in waves so that the animals always have functional teeth around those that are lost.

Most mammals are "diphyodonts", which means that they have only 2 sets of teeth: baby teeth and adult teeth.

The teeth of herbivore mammals, those which eat grasses, seem to grow throughout their lives. But really, the teeth are very long and extend far down into the jaws. They gradually move up in the jaw toward the surface over time, with the area beneath them filling in with bone.

Elephants are especially interesting because they have six molars, or grinding teeth. Only the first 2 come in and are chewed with until they wear out and fall out. Then the next pair and then the last pair. So the elephants' teeth can last the ~70 years of their life span.

Horses often have to have their teeth "floated" because the lower molars are narrower than the upper molars. Sharp points form as the teeth wear on the outside edges of the upper teeth and inside edges of the lower teeth. These are filed off by veterinarians so that the points don't cause pain and interfer with eating.

Some rodents, rabbits and a few other animals have specialized "open-rooted" teeth that can continue to grow through-out their lives. This can include their cheek teeth and incisors. If the front teeth are misaligned, this continual growth can cause the teeth to grow across into the opposite jaw. For pets, veterinarians can trim these front teeth when they start to get too long.

Thanks for Asking NEWTON!

Laura Hungerford



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