• (n.) The act of retreating; specifically, the Hegira.
The therapy of the same disease in a patient, with the same agent or procedure repeated after initial treatment, or with an additional or alternate measure or follow-up. It does not include therapy which requires more than one administration of a therapeutic agent or regimen. Retreatment is often used with reference to a different modality when the...
Re·treat'ment noun The act of retreating; specifically, the Hegira. [ R.] D'Urfey. 
The process of repeating the root canal treatment.