A rare mental foramen variation and the role of cone-beam computed tomography in preventing nerve injury: A case report.

Abstract

Background: The interforaminal space is frequently used for dental implant placement due to its strategic location between the bilateral mental foramina. However, neurosensory disturbances following surgical intervention near the mental foramen (MF) can occur in up to 43% of cases. Understanding anatomical variations of the MF is crucial to preventing surgical complications. Traditional two-dimensional radiographs have limitations in accurately visualizing anatomical structures, whereas cone-beam computed tomography (CBCT) provides high-resolution three-dimensional imaging that enhances diagnostic accuracy and clinical decision making. This case report highlights such a scenario.

Methods: A 54-year-old male referred for implant placement underwent preoperative evaluation with CBCT, which revealed a rare anatomical variation: the MF was positioned distal to the right mandibular second incisor (distal to #25) roughly 3 mm from the crest of the ridge, rather than its typical between the apices first and second premolars. The mental nerve exhibited an aberrant course, traversing in a superficial, buccal direction along the alveolar crest of site #25. This variability placed the neurovascular bundle at an extremely high risk for intraoperative injury. Consequently, the implant treatment plan was modified to reposition the implants away from the nerve pathway, and a customized CBCT-based surgical guide was utilized to facilitate accurate implant placement while preserving neurovascular integrity.

Results: The patient exhibited no neurosensory disturbances postoperatively, and a 2-week follow-up showed normal healing. The adjusted implant placement strategy successfully avoided nerve injury.

Conclusion: Conventional radiographs are limited in detecting neurovascular structures and anatomical variations. CBCT serves as an essential diagnostic tool for identifying rare variations of the MF, ensuring precise implant placement, and preventing surgical complications.

Plain language summary: Before placing dental implants, its important to know exactly where key structures are located to avoid causing injury. This case reports on a 54-year-old man who needed dental implants in his lower front jaw. The mental nerve was not identified with conventional radiography, but this was not a crucial issue since the implants planned were lower front teeth. Cone-beam computed tomography (CBCT) revealed that the mental foramen was in an unusual spot-closer to the front teeth, where the implant was planned. If this had gone unnoticed, the surgery could have certainly damaged the nerve, potentially causing permanent numbness. Thanks to the detailed imaging from the CBCT scan, the treatment plan was changed to avoid the nerve. The surgery went smoothly, the patient had no nerve problems afterward, and healing was normal.