Computer-Assisted CBCT Evaluation of Inferior Alveolar Nerve Canal Regeneration One Year Following Nerve Transposition.

Background

Rehabilitation of the severely atrophic posterior mandible remains surgically challenging, and inferior alveolar nerve (IAN) repositioning is a well-established technique that enables implant placement in anatomically compromised cases. Although neurosensory outcomes following nerve relocation have been extensively investigated, the regenerative capacity of the mandibular canal itself has not been previously evaluated. This study presents the first computer-assisted, cone-beam computed tomography (CBCT)-based assessment of bony canal regeneration after IAN transposition.

Methods

Twenty-two patients who underwent unilateral IAN transposition were evaluated using standardized CBCT one year postoperatively. A semi-manual segmentation workflow was performed using Mimics Core Medical software version 27.0 (Materialise), and regenerated canal walls were identified according to four strict criteria: (1) canal continuity across sequential CBCT sections, (2) defined canal walls demonstrating high-density bone (>800 HU, or >400 HU), (3) ≥270° circumferential bony enclosure, and (4) morphology consistent with the native mandibular canal. Regeneration was quantified as the proportion of the surgically disrupted canal segment exhibiting a fully, or near fully, reconstructed canal.

Results

Mandibular canal regeneration was observed in all patients. The mean regeneration at one year was 72.7% ± 13% when applying strict >800 HU criteria, with 20 patients demonstrating substantial (>70%) reformation and 2 patients showing partial regeneration (<40%). When a lower density threshold (>400 HU) was applied to include early or less mineralized bone, the mean regeneration increased to 78.1% ± 11%, indicating the presence of maturing bone structures that did not yet meet full-density criteria.

Conclusions

Computer-assisted CBCT analysis demonstrates that partial to extensive regeneration of the mandibular canal occurs within one year following IAN transposition. This study provides the first quantitative evidence of this phenomenon, highlighting the intrinsic regenerative potential of the mandibular canal and suggesting a possible association with postoperative neurosensory recovery.