A Prospective Study on the Effect of Coronal Tooth Structure Loss on the Survival of Root Canal‐Retreated Posterior Teeth Restored With Metal Ceramic Crowns With up to 10‐Year Follow‐Up

ABSTRACT Aim The primary aim of this study was to evaluate whether the volume of residual coronal tooth structure influences the survival of root canal‐retreated posterior teeth with up to 10‐year follow‐up. Secondary aims were to assess whether 12‐month radiographic findings and the Dental Practicality Index (DPI) could predict long‐term survival. Methodology A total of 156 posterior teeth in 140 patients underwent clinical examination, baseline CBCT and PA prior to retreatment in a postgraduate endodontic unit under specialist supervision. Residual coronal tooth volume was quantified using intraoral scans following the completion of root canal retreatment and before core build‐up and placement of metal–ceramic crowns. The metal–ceramic crowns were cemented using RelyX Luting Plus (3 M ESPE, St. Paul, MN, USA). Follow‐up assessments were conducted at 12, 24, 36, 48, and 120 months (T12–T120). Periapical radiograph (PA) and cone beam computed tomography (CBCT) were obtained at T12, with additional periapical imaging at T48. Outcomes were categorized as ‘survived’ or ‘extracted’. The optimal cut‐off value for residual volume was identified using receiver operating characteristic (ROC) analysis and Youden's index. Associations between survival and clinical variables were analysed. Results The 10‐year recall rate was 66.4%, with a Kaplan–Meier estimated 10‐year cumulative survival of 85.4%. The optimal threshold for residual tooth volume was 41%, with 58 teeth (40.8%) below this threshold and 84 (59.2%) at or above it. Teeth with < 41% volume had an extraction rate more than three times higher than those with ≥ 41% (20.7% vs. 5.9%; p = 0.016). Teeth with an unfavourable 12‐month CBCT result had a 4.5‐fold increased risk of extraction compared to those with favourable outcomes ( p = 0.004). DPI scores were not significantly associated with extraction risk ( p = 0.67). Conclusion Root canal‐retreated posterior teeth demonstrated favourable long‐term survival. A residual coronal tooth volume ≥ 41% was strongly associated with improved survival. In addition, favourable PA and CBCT findings at 12 months were associated with improved long‐term outcomes. These findings support root canal retreatment as a reliable and biologically favourable treatment option for posterior teeth with persistent apical periodontitis.