<p>Surgical extraction of mandibular third molars (MTM) is one of the most common procedures in oral and maxillofacial surgery. One of the most widely-known complications of removing MTM is the disturbance to the inferior alveolar nerve (IAN). Coronectomy is a technique used for MTM surgery where only the crown is extracted and the roots are left in situ to reduce the risk of nerve disturbances in cases where the MTM is in close-proximity to the mandibular canal. The aim of this study was to evaluate the clinical effectiveness of surgical coronectomy for MTM extractions in close proximity to the IAN. Four males and nine females were included in this study. They had an average age of 31 years, ranging from 22 to 49 years. The right side was 6 cases and the left side was 7 cases. Postoperative follow up period was average of 26 months, ranging from 6 to 52 months. Almost every case had an uneventful postoperative course. Neither pulpitis, localized alveolar osteitis, postoperative infection, wound dehiscence, delayed healing, nor eruption of roots was observed. However, nerve disturbances appeared after a coronectomy in just one case. Two of 13 cases (15%) underwent reoperation to remove the retained root despite favorable prognosis. Postoperative radiograph or dental CBCT revealed migration of the root in twelve of the 13 cases (92%). The mean root migration distance after coronectomy was 0.95 mm at 1 month, 1.83 mm at 5-6 months, 2.2 mm at 9-12 months, 3.0 mm at 24-28 months, and 3.4 mm at 36-52 months. Although coronectomy does not remove the roots in principle, the option to remove roots in accordance with prognosis may be specific advantage to use coronectomy procedures. We would suggest that coronectomy is a useful oral surgical procedure in certain complicated cases of mandibular wisdom tooth extraction. (J Osaka Dent Univ 2024; 58: 7-12)</p>