Root canal treatment is pierced, if it is from the apical foramen generally have no effect, if it is the lateral perforation may need to repair or extraction of the affected tooth, it is recommended to go to the hospital for specific examination and treatment. Root canal treatment process requires the use of mechanical preparation of the root canal, in the process of probing the length of the root canal may occur in the instrument through the apical foramen lodged through the phenomenon, this in the measurement of the length of the root canal, the normal preparation of the root canal for the treatment, and the later has no effect on the subsequent treatment can be normal. If the lateral wall is pierced during the root canal process, small perforations can be repaired with biomaterials and then re-search for root canal access for proper treatment. If the root canal is pierced through the lateral wall and the perforation is large and cannot be repaired, it is recommended to extract the affected tooth and wait for prosthetic restoration.