Treatment outcome in endodontics: the Toronto study--phase 4: initial treatment.

Outcome 4-6 years after initial treatment was assessed for Phase 4 (2000-2001) of the Toronto Study. Of 582 teeth treated, 430 were lost to follow-up (99 discontinuers, 331 dropouts), 15 were extracted, and 137 (32% recall minus 15 extracted teeth) were examined for outcome: healed (no apical periodontitis, signs, symptoms) or diseased. When pooled with Phases 1-3, 439 of 510 teeth (86%) were healed. Logistic regression identified 2 significant (P < or = .05) preoperative outcome predictors: radiolucency (odds ratio [OR], 2.86; confidence interval [CI], 1.56-5.24; healed: absent, 93%; present, 82%) and number of roots (OR, 2.53; CI, 1.25-5.13; healed: single, 93%; multiple, 84%). In teeth with radiolucency, intraoperative complications (OR, 2.27; CI, 1.05-4.89; healed: absent, 84%; present, 69%) and root-filling technique (OR, 1.89; CI, 1.01-3.53; healed: lateral, 77%; vertical, 87%) were additional outcome predictors. A better outcome was suggested for teeth without radiolucency, with single roots, and without mid-treatment complications. The predictive value of root-filling technique in teeth with radiolucency requires validation from randomized controlled trials.