Answer:
Human teeth do not grow, once you have them. There are a number of species whose teeth never stop growing, such as rabbits, because they are constantly gnawing on things and their teeth would wear away if they did not keep growing. But human teeth don't do that.
This is a common misconception. Teeth don't grow, gums diminish. This is where the phrase "Long in the tooth" comes from. ~Katantunoro