Root canal treatment filled with paraformaldehyde may leak, usually due to the type of tooth cavity, the doctor’s operation is not closed tightly or chewing with the affected tooth will be temporary sealing destroyed, etc. It is recommended to go to the regular hospital and follow the doctor’s instructions. 1. If the tooth is adjacent to the hole, especially close to the gums of large-scale caries, etc., it is easy to be difficult to solidify when filling the root canal treatment with paraformaldehyde, and close to the gums are prone to gingival sulcus fluid or blood oozing out, which affects the effect of filling. 2. If the doctor’s operation is not standardized, without good moisture barrier, hemostasis, cavity preparation, etc., it may lead to leakage of Paraformaldehyde. 3. During root canal treatment, it is not allowed to chew with the affected tooth, if chewing with the affected tooth may destroy the temporary sealing material and lead to the leakage of Paraformaldehyde.