Getting a tooth gem under 18 is possible but often requires parental consent. Tooth gems are a type of body modification that involves attaching a small gemstone to the surface of a tooth. A professional piercer or dentist usually does the procedure, which can be expensive. In order to get a tooth gem under the age of 18, you must have your parent or guardian present to give their consent. This is because tooth gems are considered a form of body modification, and minors are not legally allowed to make decisions about their bodies without parental permission.