Coronectomy is a procedure intentionally aiming to remove only the crown of an impacted mandibular third molar, leaving the root undisturbed, and thus avoiding possible direct or indirect damage to the IAN. This technique was first described by Knutsson et al. in 1989 in a retrospective study of 33 patients. 6 more papers about coronectomy were published to date, with 3 case reports and 2 retrospective studies, and one randomized controlled trial by Renton et al. in 2005.In this last study, 128 patients were randomized to undergo either extraction or coronectomy of wisdom teeth. The group undergoing extraction was found to be significantly more common in experiencing IAN deficit after surgery than the coronectomy group, while no significant differences could be concluded in terms of other surgical morbidities. The other studies also drew similar conclusions. One common finding, however, was the slow superficial migration of the wisdom tooth root after coronectomy. It had been suggested the root is only indicated to be removed only if it is exposed intraorally, but the risk of IAN damage of the second surgery is reduced as the root has migrated away from the nerve.