Review| Volume 58, ISSUE 9, e16-e24, November 2020

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A systematic review of the complications of high-risk third molar removal and coronectomy: development of a decision tree model and preliminary health economic analysis to assist in treatment planning

Published:August 13, 2020DOI:


      Coronectomy is an alternative surgical technique for the management of high-risk third molars. It involves the removal of the crown of a tooth and the deliberate retention of the roots, thereby avoiding injury to the inferior alveolar nerve (IAN). Previous studies have suggested that it reduces the risk of nerve injury when compared with surgical extraction. The purpose of this study was to systematically review the incidence of complications following coronectomy such as IAN injury, pain, dry socket, infection, root migration, and need for re-operation. A comparative cost analysis of coronectomy and surgical extraction was done based on the results of the review. This provides an insight into the economic implications of the two procedures. A search through the MEDLINE database via Ovid, PubMed, Scopus, EMBASE via Ovid, and Web of Science, was carried out to extract randomised and non-randomised controlled trials. Four studies fulfilled the inclusion criteria. A meta-analysis was conducted to measure the overall effect of each outcome. The pooled odds ratio (OR) for IAN injury was 0.16 (95% CI 0.01 to 0.39). Coronectomy reduced this risk by 84%. Dry socket may occur less frequently following coronectomy whereas infection did not show a higher incidence with either intervention. Root migration was found to occur in 13%–85% of cases and the average incidence of re-operation was 2.2%. The ratio of the average costs was 1.12 favouring coronectomy if cone-beam computed tomography (CBCT) was not done prior to the procedure. If a scan was taken routinely for coronectomy, the cost ratio marginally favoured extraction. Coronectomy reduced the risk of nerve injury in high-risk third molars. Definitive conclusions, however, cannot be made for outcomes such as the need for re-operation, which may alter the cost ratio of coronectomy:extraction, as higher quality studies with longer follow-up are needed.


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        • Tompkins R.L.
        Human population variability in relative dental development.
        Am J Phys Anthropol. 1996; 99: 79-102
        • Breik O.
        • Grubor D.
        The incidence of mandibular third molar impactions in different skeletal face types.
        Aust Dent J. 2008; 53: 320-324
        • Celikoglu M.
        • Miloglu O.
        • Kazanci F.
        Frequency of agenesis, impaction, angulation, and related pathologic changes of third molar teeth in orthodontic patients.
        J Oral Maxillofac Surg. 2010; 68: 990-995
        • Leung Y.Y.
        • Cheung L.K.
        Safety of coronectomy versus excision of wisdom teeth: a randomized controlled trial.
        Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2009; 108: 821-827
        • Renton T.
        • Hankins M.
        • Sproate C.
        • et al.
        A randomised controlled clinical trial to compare the incidence of injury to the inferior alveolar nerve as a result of coronectomy and removal of mandibular third molars.
        Br J Oral Maxillofac Surg. 2005; 43: 7-12
        • Lopes V.
        • Mumenya R.
        • Feinmann C.
        • et al.
        Third molar surgery: an audit of the indications for surgery, post-operative complaints and patient satisfaction.
        Br J Oral Maxillofac Surg. 1995; 33: 33-35
        • Frafjord R.
        • Renton T.
        A review of coronectomy.
        Oral Surg. 2010; 3: 1-7
        • Rood J.P.
        • Shehab B.A.
        The radiological prediction of inferior alveolar nerve injury during third molar surgery.
        Br J Oral Maxillofac Surg. 1990; 28: 20-25
        • Smith W.P.
        The relative risk of neurosensory deficit following removal of mandibular third molar teeth: the influence of radiography and surgical technique.
        Oral Surg Oral Med Oral Pathol Oral Radiol. 2013; 115: 18-24
        • Fareed K.
        • Khayat R.
        • Salins P.
        Vital root retention: a clinical procedure.
        J Prosthet Dent. 1989; 62: 430-434
        • Dachi S.F.
        • Howell F.V.
        A survey of 3,874 routine full-mouth radiographs. I. A study of retained roots and teeth.
        Oral Surg Oral Med Oral Pathol. 1961; 14: 916-924
        • Ecuyer J.
        • Debien J.
        Surgical deductions.
        Actual Odontostomatol. 1984; 38 ([Article in French]): 695-702
        • Renton T.
        Update on coronectomy. A safer way to remove high risk mandibular third molars.
        Dent Update. 2013; 40 (366–8): 362-364
        • Gleeson C.F.
        • Patel V.
        • Kwok J.
        • et al.
        Coronectomy practice. Paper 1. Technique and trouble-shooting.
        Br J Oral Maxillofac Surg. 2012; 50: 739-744
        • Leung Y.Y.
        • Cheung L.K.
        Long-term morbidities of coronectomy on lower third molar.
        Oral Surg Oral Med Oral Pathol Oral Radiol. 2016; 121: 5-11
        • Goto S.
        • Kurita K.
        • Kuroiwa Y.
        • et al.
        Clinical and dental computed tomographic evaluation 1 year after coronectomy.
        J Oral Maxillofac Surg. 2012; 70: 1023-1029
        • Kohara K.
        • Kurita K.
        • Kuroiwa Y.
        • et al.
        Usefulness of mandibular third molar coronectomy assessed through clinical evaluation over three years of follow-up.
        Int J Oral Maxillofac Surg. 2015; 44: 259-266
        • Monaco G.
        • Vignudelli E.
        • Diazzi M.
        • et al.
        Coronectomy of mandibular third molars: a clinical protocol to avoid inferior alveolar nerve injury.
        J Craniomaxillofac Surg. 2015; 43: 1694-1699
        • Kouwenberg A.J.
        • Stroy L.P.
        • Rijt E.D.
        • et al.
        Coronectomy of the mandibular third molar: respect for the inferior alveolar nerve.
        J Craniomaxillofac Surg. 2016; 44: 616-621
        • Higgins J.P.
        • Altman D.G.
        • Gøtzsche P.C.
        • et al.
        The Cochrane Collaboration's tool for assessing risk of bias in randomised trials.
        BMJ. 2011; 343: d5928
        • Huedo-Medina T.B.
        • Sánchez-Meca J.
        • Marín-Martínez F.
        • et al.
        Assessing heterogeneity in meta-analysis: Q statistic or I2 index?.
        Psychol Methods. 2006; 11: 193-206
        • Hatano Y.
        • Kurita K.
        • Kuroiwa Y.
        • et al.
        Clinical evaluations of coronectomy (intentional partial odontectomy) for mandibular third molars using dental computed tomography: a case–control study.
        J Oral Maxillofac Surg. 2009; 67: 1806-1814
        • Cilasun U.
        • Yildirim T.
        • Guzeldemir E.
        • et al.
        Coronectomy in patients with high risk of inferior alveolar nerve injury diagnosed by computed tomography.
        J Oral Maxillofac Surg. 2011; 69: 1557-1561
        • O’Riordan B.C.
        Coronectomy (intentional partial odontectomy of lower third molars).
        Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2004; 98: 274-280
        • Frenkel B.
        • Givol N.
        • Shoshani Y.
        Coronectomy of the mandibular third molar: a retrospective study of 185 procedures and the decision to repeat the coronectomy in cases of failure.
        J Oral Maxillofac Surg. 2015; 73: 587-594
        • Dolanmaz D.
        • Yildirim G.
        • Isik K.
        • et al.
        A preferable technique for protecting the inferior alveolar nerve: coronectomy.
        J Oral Maxillofac Surg. 2009; 67: 1234-1238
        • Hutton G.
        • Rehfuess E.
        Guidelines for conducting cost-benefit analysis of household energy and health interventions.
        World Health Organization, 2006
        • Drummond M.F.
        • O’Brien B.
        • Stoddart G.L.
        • et al.
        Methods for the economic evaluation of health care programmes.
        2nd ed. Oxford University Press, 1997
        • Podgorelec V.
        • Kokol P.
        • Stiglic B.
        • et al.
        Decision trees: an overview and their use in medicine.
        J Med Syst. 2002; 26: 445-463
        • Werner E.F.
        • Wheeler S.
        • Burd I.
        Creating decision trees to assess cost-effectiveness in clinical research.
        J Biom Biostat. 2012; 7: 004
        • Petersen L.B.
        • Olsen K.R.
        • Christensen J.
        • et al.
        Image and surgery-related costs comparing cone beam CT and panoramic imaging before removal of impacted mandibular third molars.
        Dentomaxillofac Radiol. 2014; 43: 20140001
      1. Radiation protection No. 172: cone-beam CT for dental and maxillofacial radiology (evidence-based guidelines).
        European Commission, 2012
        • Renton T.
        Risk assessment of M3Ms and decisions on ordering a CBCT and prescribing a coronectomy.
        Dent Update. 2017; 44: 957-976