Survival of retained permanent canines after autotransplantation: A retrospective cohort study

Introduction: After third molars, canines are the teeth most commonly affected by displacement and impaction. Although orthodontic surgical treatment represents the standard method for realignment of canines, autotransplantation (autoTX) functions as the second-line therapy if orthodontic alignment does not succeed in treating impaction and severe displacement. This retrospective cohort study aimed to identify clinical predictors for postoperative survival and endodontic treatment needs after autoTX of severely displaced and impacted canines.

Methods: The study cohort comprised patients who received canine autoTX in a single surgical center between 2006 and 2018. Canines with severe displacement and retention were surgically treated using a standardized protocol. Statistical analysis of survival probability was performed with the Kaplan-Meier method, and bivariate data were analyzed using logistic regression and the Pearson chi-square test. Nonparametric continuous variables were analyzed using the Mann-Whitney U test.

Results: Data from 319 patients with 378 canine grafts were available for analysis after a mean follow-up of 54.7 ± 36.5 months on the patient level (range, 0.3-181.8 months). With 25 lost autotransplants, the cumulative survival rate was 93.4%. Patient age at surgery, the state of the apical foramen, endodontic treatment need, and persistence of deciduous teeth at the implantation site had a significant negative impact on autotransplant survival (P <0.05). Endodontic treatment need was significantly related to the patient's age at surgery, the state of the apical foramen, and preoperative orthodontic traction (P <0.05). Thus, these independent variables were identified as clinical predictors for the survival of both the autotransplant and the dental pulp. Gender, ischemia time, postoperative ankylosis, or site of autoTX did not influence any of the outcome variables.

Conclusions: The high survival rates of autotransplanted permanent canines make this treatment a promising option, especially in patients with severe tooth displacement, in which orthodontic treatment alone cannot provide predictable alignment, irrespective of the patient's age. Interpreting age and preoperative orthodontic traction as delaying the onset of autoTX and state of apex, time-dependent aspects seem to be of great importance for postoperative complications leading to endodontic treatment or graft loss. Therefore, early implementation of autoTX as a treatment modality for impacted, severely displaced, and vain exposed canines in daily surgical practice should be encouraged.