The correct term for the final tooth is second molar. Root canal treatment that pierces the second molar is usually a perforation of the pulpal wall, and the treatment is to repair the perforated area. If the perforation is large or located near the root apex, which is difficult to repair, it can be extracted and then restored with a prosthetic tooth. For perforation of the pulpal wall caused by root canal treatment, the perforation can be located through a surgical microscope and the filling material can be placed in the perforation to effectively block the connection between the root canal and periodontal tissues and to prevent stimulation of the periodontal tissues. Absorbable collagen can be used to place into the tissue surrounding the perforation and then glass ions can be used to repair the perforation, or non-absorbable materials such as biocement MTA can be used directly to repair the perforation. Larger perforations and perforations located at the root apex are more difficult to repair and the prognosis is uncertain, so the affected tooth can be extracted and then restored with an implant denture or fixed partial denture. It is recommended to visit a regular medical institution to receive professional treatment.