Questions & Answers

People holding up hand-written questions

Why do we have two stages of teeth?

Hi, my name is Dr. Peter Fritz. I am a periodontist and adjunct professor in the Faculty of Applied Health Sciences at Brock University. Today I’m answering the question, “Why do we have two stages of teeth?”

Humans have two sets of teeth in their lifetime, the primary (or baby) teeth and the permanent teeth. There are 20 primary teeth that appear at 6 months of age followed by 32 permanent teeth that appear between 7 and 12 years of age. Both sets are important for chewing and talking. The primary teeth also act as placeholders so the permanent teeth can erupt in the correct position.

The reason for two stages of teeth, is likely size. Permanent teeth are bigger and there are more of them. A full set of permanent teeth would be too big to fit in a child’s mouth. In contrast, the primary teeth are smaller and fit nicely in the smaller jaw of a child. The primary teeth, however, are not able to simply grow into permanent teeth. Unlike other parts of the human body, erupted teeth cannot grow any bigger. Therefore, the only way to have bigger teeth to fit an adult jaw is to replace the primary teeth. So as the jaw grows and more space becomes available, the primary teeth will fall out and they will be replaced by the permanent teeth. These permanent teeth must then last the rest of a person’s life.


Are you an Ontario university researcher who'd like to answer Curiosity Shop questions?

Ask a question