Suggested Modification of the Technique Coronectomy for Lower Third Molar To the Editor: The extraction of unerupted third molars is the most frequently performed procedure in clinical practice. The procedure has been associated with risk of damage to the inferior alveolar nerve (IAN) ranging from 0.35%1 to 1.3%,2 increasing to approximately 5% when there is a close relationship with the tooth mandibular canal.3 Coronectomy or intentional partial odontectomy is a surgical technique indicated for teeth free of pathology (caries, periodontal disease, cysts, and tumors) that need to be removed and come in close relation to important structures (mandibular canal and maxillary sinus). This technique involves the removal of the tooth crown and maintenance of dental roots in the socket without further treatment.4,5 Pogrel et al4 found a success rate of approximately 94% at a mean postoperative period of 22 months when coronectomy was performed for the treatment of third molars retained. This paper aims to describe a modification of the technique of coronectomy through a clinical case.

CLINICAL REPORT A 26-year-old healthy female patient was attended at the School of Dentistry, Federal University of Campina Grande for extraction of the lower right third molar tooth with orthodontic indication. During the clinical examination, there was absence of the element in question. In panoramic radiography, the tooth was in mesioangular position and was able to view deletion and absence of apical root canal mandibular cortex, suggesting a close relationship of the tooth with MC (Fig. 1A). To assist surgical planning, computed tomography (CT) was performed and confirmed the close relationship of the tooth with MC (Fig. 1B). Then the patient was proposed for the realization of coronectomy, emphasizing the advantages and limitations of the technique, and the possibility of a second surgery.

FIGURE 1. A, Panoramic radiograph showing the proximity of the roots of the tooth 48 and the mandibular canal. B, Axial computed tomography demonstrating the buccolingual extent on tooth 48 region.

FIGURE 2. A, Drill Zecrya as indicated by computed tomography. B, Intraoperative clinical image after cleavage and removal of the tooth crown 48.

The patient signed an informed consent and informed view of the ethical regulation of research involving humans in Brazil. The surgical technique was performed according to Gleeson et al6 and Gady and Fletcher.5 After local anesthesia, a flap was made, and peripheral osteotomy and exposure of the tooth were performed. During planning, a stop of endodontic file was inserted into a drill-type Zecrya according to the width of the cementoenamel junction obtained in measuring CT (Fig. 2A). This procedure aimed to avoid an excessive deepening of the drill, which could cause damage to the lingual bone plate region and hence to the lingual nerve. Then the separation between the crown and the root was made at right angles, preserving approximately 1 to 2 mm width labiolingual, cleaving finished with a delicate instrument (7 spatula), avoiding excessive force and the possibility of mobilizing the remaining root. With the aid of a diamond bur, one remaining tooth wear was done so that the roots stay 3 mm below the buccal and lingual bone crest (Fig. 2B). Simple suture with interrupted stitches was made to obtain primary healing. Postoperatively, antibiotic (azithromycin 500 mg once a day for 5 days), analgesic (acetaminofen 500 mg of 6/6 hours for 2 days), and anti-inflammatory (ibuprofen 400 mg every 8 hours for 3 days) were prescribed. After 2 weeks, the patient was reevaluated and did not report any symptoms (Fig. 3A). The panoramic radiograph after 24 months shows no radiographic signs of pathology and migration 2 mm of remaining root. The patient was monitored without any complaints.

FIGURE 3. A, Postoperative clinical image showing good healing of the tooth 48 region without signs of inflammation and infection, and patient with good oral opening, without limitation of mandibular movements. B, Postoperative panoramic radiograph showing the presence of tooth roots, with good healing aspect.

The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014

Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.


The Journal of Craniofacial Surgery • Volume 25, Number 6, November 2014


DISCUSSION Coronectomy is a technique indicated for the treatment of unerupted teeth whose removal might be associated with an increased risk of damage to the IAN. The absence of cortical MC, deletion apical root of the mandibular canal, and diversion signs are commonly found on panoramic radiographs that are suggestive of the intimate relationship between the third molar with IAN,3,7 but only CT provides confirmation. Pogrel et al4 describe a technique in which the court shall include the entire width of the buccolingual tooth crown, using specific tools to retract the lingual tissues, preventing damage to the lingual nerve. But according to Gleeson et al,6 lingual tissue retraction may damage the lingual nerve; therefore, an incomplete cut with the surgical drill crown and cleavage with specific remaining tooth is less traumatic. The use of “stop” endodontic features low cost, is easy to purchase, effective, and does not contribute to the occurrence of complications. However, the measurement of CT in the buccolingual width of the tooth crown is essential before the use of the drill. In a study,8 52 patients underwent coronectomy and 3 patients required another surgery to remove the remaining root due to the presence of pain or infection. Dolanmaz et al9 found that in 43 procedures, no root needed to be removed. The time of postoperative control of these studies is 10 years and 24 months, respectively, which may explain the difference in results. In fact, the major complications associated with the coronectomy technique are migration of the remaining radicular tooth mobilization during cleavage and paresthesia.8,10 Regarding the remaining root retained in the socket, there may be a migration toward occlusal.3,9 This fact is particularly limited in dental roots that are transfixed by NAI and/or root submersion obtained by means of root wear by keeping tooth roots 2 to 3 mm below the alveolar crest. Dolanmaz et al9 found that migration is greater in the first 6 months, noting a gradual decrease of 3.4 mm in 6 months, 3.8 mm in 12 months, and 4.0 mm in 24 months. The authors believe that the formation of hard tissue on the occlusal surfaces is critical in reducing the root movement. Migration root may indicate the need for further surgery and such conduct is favorable by distancing the roots of CM, limiting the possibility of damage to the IAN. This approach should be performed when infection occurs or exposure of the root remaining in the oral cavity causes inflammation of the surrounding tissues. The mobilization of the tooth during cleavage is a likely factor in the use of inadequate instrument, incorrect cutting, and excessive force to separate the crown of the tooth roots. When the mobilization occurs, root remnants must be removed due to the possibility to become a site for the development of infection. The mobilization of the remaining root varies between 3% and 9%, but when there is proper planning and coronectomy technique is properly employed, this value is 1%.10 The use of the cleavage technique using light force limits the possibility of mobilization. When attempting cleavage is performed unsuccessfully, the assessment of depth of cut in the crown must be reevaluated before a second attempt cleavage.10 The use of endodontic stop is to determine the measurement obtained by CT, depth of cut, thus contributing to the use of force for lighter cleavage. Although coronectomy can be employed to prevent damage to the IAN, paresthesia is possible, though unusual. Hatano et al7 found a percentage of 1% paresthesia employing this technique and 5% in conventional extraction techniques. When the attempt is made to divide without success, the use of excessive force can move the tooth roots and compress the IAN, contributing to the


development of neuropraxia. Thus, the tooth should be cleaved with minimum force possible. The technique described presents low cost and easy implementation. Prospective studies need to be developed to determine the rate of complications and success of this technique. Julierme Ferreira Rocha, DDS, MSc Júlio César Silva de Oliveira, DDS, MSc Department of Surgery and Integrated Clinic Araçatuba Dental School Universidade Estadual Paulista Júlio de Mesquita Filho Araçatuba—UNESP Araçatuba, Brazil [email protected] José Wilson Noleto Ramos, DDS, MSc Department of Surgery Patos Dental School Campina Grande University Campina Grande, Brazil Idelmo Rangel Garcia Júnior, DDS, MSc Eduardo Hochuli-Vieira, DDS, MSc Department of Surgery and Integrated Clinic Araçatuba Dental School Universidade Estadual Paulista Júlio de Mesquita Filho Araçatuba—UNESP Araçatuba, Brazil

REFERENCES 1. Cheung LK, Leung YY, Chow LK, et al. Incidence of neurosensory deficits and recovery after lower third molar surgery: a prospective clinical study of 4338 cases. Int J Oral Maxillofac Surg 2010; 39:320–326 2. Valsameda-Castellon E, Berine-Aytes L, Gay-Scoda C. Inferior alveolar nerve damage after lower third molar surgical extraction: a prospective study of 1117 surgical extractions. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;92:377–383. 3. Leung YY, Cheung LK. Correlation of radiographic signs, inferior dental nerve exposure, and deficit in third molar surgery. J Oral Maxillofac Surg 2011;69:1873–1879 4. Pogrel MA, Lee JS, Muff DF. Coronectomy: a technique to protect the inferior alveolar nerve. J Oral Maxillofac Surg 2004;62:1447–1452 5. Gady J, Fletcher MC. Coronectomy: indications, outcomes, and description of technique. Atlas Oral Maxillofac Surg Clin North Am 2013;21:221–226 6. Gleeson CF, Patel V, Kuok J, et al. Coronectomy practice. Paper 1. Technique and trouble-shooting. Br J Oral Maxillofac Surg 2012;50:739–744 7. 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 8. O’Riordan BC. Coronectomy intentional partial odontectomy of lower third molars). Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2004;98:274–280 9. 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 10. Patel V, Glesson CR, Kuok J, et al. Coronectomy practice. Paper 2: complications and long term management. Br J Oral Maxillofac Surg 2013;51:347–352

© 2014 Mutaz B. Habal, MD

Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.

Suggested Modification of the Technique Coronectomy for Lower Third Molar.

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