Fate of mandibular canals displaced by enlarged cystic lesions: does the inferior alveolar neurovascular bundle relocate to its original position?

Our aim was to identify the positional changes of the inferior alveolar neurovascular bundle and evaluate the relocation of the displaced mandibular canal after enucleation of a cyst. Seventy patients (72 sites) who had had cysts enucleated were divided into three groups based on the degree of encroachment of the cystic lesion into the mandibular canal and whether a bone graft had been inserted after the cyst had been enucleated. The mean (range) of patients' ages was 45 (18-75) years, and there were 29 male and 41 female patients. Group A comprised cysts with encroachment on the mandibular canal that were enucleated without a bone graft; Group B consisted of cysts with no encroachment of the mandibular canal, but were enucleated without a bone graft; and Group C comprised cysts with encroachment of the mandibular canal that were enucleated with a bone graft. The displacement of the mandibular canal was identified from analysis of computed tomographic (CT) images. Changes in the position of the mandibular canal were measured on panoramic radiographs. The mandibular canal was repositioned superiorly by a mean (SD) of 2.4 (1.65)mm after enucleation of the cyst, which was significant in Group A (p<0.001), but not in Groups B and C. These results indicate that the displaced inferior alveolar neurovascular bundles that were not surrounded by bony canal tended to relocate towards a supposedly normal position, and after enucleation of the cyst the mandibular canal was remodelled in this new location. This tendency to relocate was blocked by bone grafting. Bone grafts are therefore recommended in cases where enough bony height is required for future insertion of implants.