A wisdom tooth (or third molars) refers to one of the four molars in humans, including mandibular third molars and maxillary third molars. Wisdom teeth usually appear between the ages of 17 and 25. Most adults have four wisdom teeth, but it is possible to have more, in which case they are called supernumerary teeth. Wisdom teeth commonly affect other teeth as they develop, becoming impacted or “coming in sideways”. They are often extracted when this occurs.