Intentional replantation for refractory apical periodontitis in mandibular first molars: a 2-year retrospective cohort study

Background/purpose Refractory chronic apical periodontitis (CAP) of mandibular first molars has a high conventional treatment failure rate, and effective tooth-preserving strategies are clinically urgent. This study evaluated the clinical efficacy and prognostic factors of intentional replantation for this condition. Materials and methods This 2-year retrospective cohort study enrolled 42 patients (mean age: 28.6 ± 5.3 years; 54.8% male, 45.2% female) with refractory CAP in mandibular first molars who underwent standardized intentional replantation. Overall treatment success at 2 years was strictly binarized based on established criteria: the complete absence of clinical symptoms (including persistent pain, swelling, or sinus tracts) and radiographic evidence of complete or partial bone healing of the periapical lesion on cone-beam computed tomography (CBCT). Univariate chi-square test and multivariate Logistic regression (interpreted as exploratory analysis due to the low number of failure events) were performed to identify prognostic factors for treatment failure. Results The overall clinical success rate was 88.10% (37/42). Preoperative periapical lesion size >5 mm (OR = 4.23, 95%CI:1.15-15.58, P = 0.015), periodontal ligament (PDL) damage during extraction (OR = 5.17, 95%CI:1.28-20.89, P = 0.008), and no postoperative microscopic root canal treatment (RCT) (OR = 6.02, 95%CI:1.36-26.59, P = 0.005) were independent risk factors for treatment failure. Conclusion Intentional replantation of mandibular first molars with refractory chronic apical periodontitis offers a predictable and effective tooth-preserving strategy, providing a reliable alternative to extraction and implant therapy in carefully selected clinical cases.