Outcome of Non-surgical Endodontic Treatment: Initial Treatment and Retreatment. The Toronto Study Phase 4

The 4-6 year outcome of non-surgical endodontic treatment was assessed for Phase 4 of the Toronto Study Project, and the data pooled with that of the previous phases. The outcome---"healed" (no radiolucency, symptoms or signs other than tenderness to percussion) or "diseased" (either radiolucency, symptoms or signs)---was assessed by an independent, calibrated examiner. For initial treatment, 439/510 teeth (86%) were healed. Logistic regression revealed an increased risk of disease persistence for pre-operative radiolucency, two or more roots and, in teeth with radiolucency, for presence of complications and root filling with lateral compaction. For retreatment, 187/229 teeth (82%) healed. Logistic regression revealed an increased risk of disease persistence for pre-operative adequate root filling, perforation, radiolucency and, in teeth with radiolucency, for treatment in two or more sessions. The prognostic importance of the technique-related variables (root filling technique and number of treatment sessions) requires validation from randomized controlled trials.