title: Coronectomy of the lower third molar is safe within the first 3 years.
abstract: OBJECTIVE
  There is no long-term evaluation on the safety of coronectomy of the lower third molar. The aim of this study was to investigate the 3-year morbidity of coronectomy of the lower third molars and to monitor the behavior and migration pattern of the retained roots after coronectomy.
  
  
  METHODS
  This was a prospective cohort study. Patients with lower third molars with specific radiographic sign(s) showing proximity of the roots to the inferior alveolar nerve who underwent coronectomy in a previous randomized clinical trial were reviewed postoperatively in the first week and the third, sixth, 12th, 24th, and 36th months. The morbidities of infection, pain, root eruption, reoperation to remove the root, and the development of any pathology were recorded. The pattern of any root migration was analyzed.
  
  
  RESULTS
  Ninety-eight patients (35 men and 63 women; mean age, 25.7 yrs; standard deviation, 7.9 yrs) with 135 coronectomies completed the 36-month review. None presented with infection or pain from the postoperative third month onward. Root eruption causing sensitivity occurred in 3% (4/135) of the sample and the erupted roots were removed. None of the reoperated cases presented with a postoperative inferior alveolar nerve deficit. No pathology developed in any of the retained roots after coronectomy. Root migration was noted in most cases in the first 12 months, and all roots stopped migrating from the 24th month onward. The mean root migration at 36 months was 2.8 mm (standard deviation, 1.4 mm).
  
  
  CONCLUSIONS
  This study confirms that retained roots after coronectomy in the lower third molars produce no complications in terms of infection, pain, or the development of pathologies within the first 3 years. Root eruption can occur in a very small percentage of patients and may require reoperation to remove the root.
authors.affiliation: Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Hong Kong, Hong Kong.
authors.forename: Yiu Yan
authors.initials: YY
authors.lastname: Leung
authors.forename: Lim Kwong
authors.initials: LK
authors.lastname: Cheung
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008334:Mandible; D008340:Mandibular Nerve / Q000473:pathology; D008964:Molar, Third / Q000473:pathology / Q000601:surgery*; D010149:Postoperative Pain / Q000209:etiology; D011446:Prospective Studies; D012449:Safety; D013530:Surgical Wound Infection / Q000209:etiology; D019228:Tooth Crown / Q000601:surgery*; D014078:Tooth Eruption / Q000502:physiology; D014081:Tooth Extraction; D014085:Tooth Migration / Q000209:etiology; D014092:Tooth Root / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D014095:Tooth, Impacted / Q000601:surgery; D016896:Treatment Outcome