question: My 13 year old son has a bad tooth and the dentist keeps telling me that we need to wait until his teeth are done growing until he can fix it. I thought that once your permanent teeth came in that is the size they will be. I have never herd of your teeth growing or getting bigger. Also I have been having him use toms of maine sensitive tooth paste the dentist said this was too abrasive for kids teeth. What would make kids teeth be prone to an abrasive toothpaste as compared to adult teeth. What is in the tooth paste that makes it abrassive?