Wisdom teeth, the third molar, usually erupt around the age of 17~21 years old, located at the distal end of the second molar, often with abnormal morphology and position, and there may be pain, swelling and other symptoms at the time of eruption, and the presence of wisdom teeth that have not erupted can be clarified through X-rays, as follows. The third molar usually erupts around the age of 17~21 years old, which is normally the eighth tooth back from the mesial incisor, located at the distal end of the second molar, often with abnormal morphology and position, and the morphology may be similar to that of the first or second molar. The third molar may erupt with symptoms such as pain and swelling, and the gingival flap around the crown forms a blind pocket during eruption, which may lead to wisdom tooth pericoronitis. Wisdom teeth that have not erupted or are unable to erupt due to obstruction may be examined by X-ray to clarify their presence and exact location. It is recommended to visit a hospital for examination and professional treatment.