Teeth are the only body part that cannot repair themselves. Repairing means either regrowing what was lost or replacing it with scar tissue. Teeth cannot do that because they are made of enamel, which is the hardest substance in the entire human body and has a very high percentage of inorganic material within it. It doesnt contain many proteins and cells, which are present in ample amounts in other parts of the body. Although some parts of the tooth such as parts of pulp and periodontal ligaments can be regenerated, the major structures such as enamel cannot repair themselves. They are replaced or repaired artificially with the help of synthetic components and made to function alike.

It is important to note that while some organs can regenerate themselves, others cannot. For example, the liver is the only organ in the human body that can regenerate. The brain cannot regenerate itself well because when it is damaged, its cells find it harder to make new ones. This is because the brain has very few of the special cells called "stem cells" that can multiply and turn into other cells.