BACKGROUND In atrophic posterior mandibular areas, where the bone height superior to the inferior alveolar nerve (IAN) is less than 6 mm, short implants are not applicable. Conventional alternatives such as IAN transposition and various alveolar bone augmentation approaches are technically demanding and prone to complications. CASE SUMMARY Computer-guided dynamic navigation implantation improves the accuracy, predictability, and safety of implant placement. This case report presents a dynamic navigation system-guided trans-IAN implant placement technique, which can successfully treat a posterior mandibular dentition defect when the bone height is only 4.5 mm. The implant was inserted into the buccal side of the IAN and was 1.7 mm away from the IAN. The implantation deviations were controlled within a satisfying range, and the long-term restoration outcome was stable. CONCLUSION Dynamic navigation system-guided trans-IAN implant placement might be a recommended technique for patients with extremely insufficient residual bone height and sufficient bone width in the posterior mandibular area.

BACKGROUND Implant fracture is one of the most serious mechanical complications of dental implants. Conventional treatment necessitates visibility of the apical portion of the fractured implant, whereas for deep and invisible implant fractures, the traditional trephine method has been ineffective. Surgical removal of the marginal bone to expose the fracture surface would be a time-consuming and extensively damaging procedure. Here, we propose a novel technique to address invisible implant fractures. CASE SUMMARY A 50-year-old woman was referred to our department with the chief complaint that her right mandibular implant tooth had fallen out 3 mo earlier. Cone-beam computed tomography examination showed an implant fracture with a fracture surface 5.1 mm below the crestal ridge. The patient was treated with osteotomy combined with the trephine technique to expose the surgical field and remove the implant. The invisible fractured implant was successfully removed, with minimal trauma. A modified Wafer technique-supported guided bone regeneration treatment was then administered to restore the buccal bone wall and preserve the bone mass. Six months later, fine regenerative bone and a wide alveolar crest in the edentulous area were observed, and a new implant was placed. Four months later, restoration was completed using a cemented ceramic prosthesis. Clinical and radiographic examinations 12 mo after loading fulfilled the success criteria. The patient reported no complaints and was satisfied. CONCLUSION Osteotomy combined with the trephine technique can be effectively used to address deep and invisible implant fractures.