Effects of root canal treatment with or without manual-dynamic irrigation on post-operative pain and periapical healing

INTERVENTION: The intervention treatment is called manual‐dynamic irrigation and the control treatment is called passive irrigation. Manual‐dynamic irrigation involved using a syringe and needle to deliver the antibacterial solution (irrigant) into the root canal during treatment and supplemented with pumping (agitation) of the irrigant using a rubber (gutta‐percha) point. Passive irrigation involved using a syringe and needle to deliver the antibacterial solution into the root canal without any agitation of the irrigant. CONDITION: Apical periodontitis ; Oral Health ; Apical periodontitis PRIMARY OUTCOME: The pain experienced at 12‐24, 24‐48, 48‐72 hours after each root canal treatment visit will be measured using a Visual Analogue Scale score (0 = no pain; 10 = worst patient imaginable) SECONDARY OUTCOME: Periapical healing at 12 months after completion of the root canal treatment will be judged to be successful if there is absence of clinical (pain, swelling, presence of a 'gum boil') or radiographic (dark area around the root) signs of disease at follow‐up INCLUSION CRITERIA: Those patients on the waiting list for non‐surgical root canal treatment or root canal retreatment in the Department of Endodontics, Eastman Dental Hospital, London, UK and fulfilling the following inclusion criteria (based on the notes from the New Patient Consultation Clinic and findings from the pre‐treatment assessment session) will be invited to participate. 1. Age 18 years or older 2. Absence of history of diabetes and/or a medical condition which requires long‐term steroid or anti‐inflammatory/analgesic medication 3. Absence of history of chronic orofacial pain, major traumatic injuries, or major maxillo‐facial surgery 4. Absence of persistent or spontaneous pre‐operative pain at New Patient Clinic 5. Able to attend two consecutive appointments for treatment to be completed within 1 month 6. The teeth should be permanent with mature apex (apices) 7. The teeth should have a non‐vital pulp (negative response to pulp testing) and associated