Root migration pattern after third molar coronectomy: a long-term analysis

Coronectomy was introduced as a treatment for impacted lower third molars at high risk of inferior alveolar nerve damage. Root migration is considered one of the common surgical complications of this procedure. This study aimed to investigate the long-term behaviour of retained root(s) after coronectomy. This was a prospective study, with 3-5 years of follow-up, of patients who underwent lower third molar coronectomy. Panoramic radiographs were taken preoperatively and at 1 week, 6, 12, 24, 36, and 60 months postoperative. Root migration patterns were recorded. Factors including age, sex, type and pattern of impaction, and root form were analyzed with respect to the root migration rate. A total of 356 coronectomies were performed in 254 patients. Most root migration was found to occur within 6 months (91.1%) and 12 months (61.4%) postoperative. From 24 months onwards, less than 5% migrated further. Age was found to be a factor affecting root migration: migration decreased with increasing age (by 0.203 mm less per year increase in age). Other factors investigated were found to be unrelated. Therefore, adequate preoperative warning should be given to young patients considering coronectomy as treatment for impacted lower third molars. However, it should also be noted that the incidence of root exposure leading to re-operation is low.