It is generally recommended to only have one root canal treatment per sitting. This is because root canal treatment can be a time-consuming and complex procedure, and it may be more comfortable for the patient to have it done in separate sessions. Additionally, it may be necessary to allow time for the infected or damaged tissue to heal before completing the treatment.
That being said, there are cases where multiple root canals may be performed in one sitting. For example, if a tooth has more than one root or if the tooth is severely damaged and requires extensive treatment, it may be necessary to complete the root canal treatment in one session. However, this is typically not the norm and would be determined on a case-by-case basis by the dentist or endodontist.