Association of Mandibular Morphological and Trabecular Bone Characteristics with Long-Term Outcomes Following First Permanent Molar Extraction: A Retrospective Study

Background/Purpose: This study aimed to evaluate mandibular morphological, trabecular, dental, and periapical factors associated with favorable long-term outcomes following early mandibular first permanent molar (FPM) extraction. Methods: This retrospective study included 60 patients with pre-extraction and ≥5-year follow-up panoramic radiographs. Patients were classified into favorable (FO; n = 30) and unfavorable (UFO; n = 30) outcome groups according to residual space and second permanent molar (SPM) axial position. Gonial angle (GA), antegonial notch depth (AND), notch angle (ANA), cortical thickness (ACT), and corpus and angulus fractal dimensions (FD) were assessed. Initial SPM and second premolar (SP)angulations, primary second molar (PSM)–SP status, and FPM periapical index (PAI) scores were also evaluated. Analyses included Bonferroni correction, exploratory multivariable logistic regression, and receiver operating characteristic (ROC) analysis. Results: AND was greater in the FO group (Bonferroni-adjusted p = 0.015) and remained associated with FO after adjustment (OR = 2.22 per millimeter; 95% CI: 1.19–4.15; p = 0.012). An extracted PSM with an unerupted SP was associated with higher odds of FO than a retained PSM (adjusted OR = 9.51; 95% CI: 1.45–62.50; p = 0.019). AND demonstrated moderate discrimination (AUC = 0.728; 95% CI: 0.600–0.856); a ≥2.0-mm threshold yielded 86.7% sensitivity and 53.3% specificity. Other morphological and fractal parameters did not differ significantly between groups; angulations and PAI were not significantly associated with outcome. Conclusions: AND and PSM–SP status were associated with FO. These exploratory findings require validation in larger, independent cohorts before clinical application, particularly given the wide confidence intervals for categorical estimates and the limited specificity of the proposed AND threshold.