Coronectomy

Indications, Outcomes, and Description of Technique

Jacob Gady, DMD, MD a, Mark C. Fletcher, DMD, MD a,b,*

KEYWORDS
 Coronectomy  Third molars  Inferior alveolar nerve

KEY POINTS
 Coronectomy is considered a reasonable and safe treatment alternative for patients who demonstrate elevated risk for
injury to the inferior alveolar nerve with the removal of third molars.
 The procedure has been documented in the oral and maxillofacial surgery literature as a treatment alternative to
extraction of third molar in patients considered at elevated risk for permanent nerve injury.
 Coronectomy is particularly appropriate for patients who are older than 25 years and who report low tolerance for the
possibility of posttreatment neurosensory deficit at the consultation.
 Appropriate patient selection for coronectomy is paramount.
 Periodic follow-up assessments are required, and patient compliance is essential.

Coronectomy was first described by Ecuyer and Debien in 1984 dimensions, but is not yet the standard of care, owing to cost
as an alternative procedure to traditional extraction of third and the increased exposure of the patient to radiation. Certain
molars.1 Several reports have been published since regarding radiographic features that depict an increased risk of iatro-
the technique, indications, efficacy, and outcome of this pro- genic IAN damage when extracting third molars include dark-
cedure. Most recently, it has been investigated as an alterna- ening of the root, narrowing of the apices, deflection of the
tive to traditional surgical extraction of third molars, root, diversion of the IAN canal, narrowing of the IAN canal,
particularly for those with an increased risk of damage to the and interruption of the white line of the IAN canal.2,6 Coro-
inferior alveolar nerve (IAN). Several studies have demon- nectomy may decrease the incidence of damage to the IAN in
strated that coronectomy does significantly decrease the risk these cases of increased risk.
of iatrogenic injury to the IAN, with some studies also sug- Pogrel and colleagues7 performed 50 coronectomies on
gesting a lower complication rate. This article discusses the 41 patients who were at significantly increased risk of IAN
indications for coronectomy, the author’s technique, and the damage from panoramic radiographic assessment, and found
complications and outcomes of this procedure. no postoperative cases of inferior alveolar nerve involvement.
Similar results were reported by Leung and Cheung,8 who
Indications performed 171 coronectomies and 178 surgical extractions
(controls) of third molars on 231 patients. Nine patients in the
control group presented with IAN sensory deficit versus 1 pa-
The main indication for performing a coronectomy is to prevent
tient in the coronectomy group, demonstrating a statistically
iatrogenic injury to the IAN when removing a third molar.
significant decrease in IAN damage using coronectomy for
Therefore, the ability to determine whether the IAN is at high
high-risk patients.8
risk is paramount and should be well understood.
The frequency of IAN damage after extraction of a third
molar ranges anywhere from 0.4% to 8.4%.2e5 Panoramic ra- Contraindications
diographs are traditionally used in the preoperative evaluation
of patients who will undergo surgical extraction of mandibular The success of coronectomy depends on the survival of the
teeth. Increasingly, computed tomography scanning is used to retained root fragments with the successful formation of
evaluate the relationship of the tooth to the IAN in 3 osteocementum and bone over the roots. Any tooth with active
caries into the pulp, or demonstrating periapical abnormality
should not be considered for coronectomy. Horizontally im-
pacted teeth and teeth associated with tumors or large cysts
Disclosures: The authors have nothing to disclose. should be excluded. The coronectomy procedure can otherwise
a
Department of Craniofacial Sciences, Division of Oral and Maxillo-
be accomplished with vertically positioned, mesially tilted,
facial Surgery, University of Connecticut School of Dental Medicine, 263
Farmington Avenue, Farmington, CT 06030, USA
and distally angulated teeth. Other local factors excluding
b
Avon Oral and Maxillofacial Surgery, 34 Dale Road, Suite 105, Avon, coronectomy are patients scheduled for an osteotomy in the
CT 06001-3659, USA future. Patients excluded for systemic reasons from undergoing
* Corresponding author. 34 Dale Road, Suite #105, Avon, CT 06001, USA. coronectomy include immunocompromised patients (chemo-
E-mail address: markcfletcher@att.net therapy, AIDS, radiation therapy, immunomodulating drug

Atlas Oral Maxillofacial Surg Clin N Am 21 (2013) 221–226

1061-3315/13/$ - see front matter ª 2013 Elsevier Inc. All rights reserved.
http://dx.doi.org/10.1016/j.cxom.2013.05.008 oralmaxsurgeryatlas.theclinics.com
222 Gady & Fletcher

therapy, and so forth), poorly controlled diabetics, and those tooth using a straight elevator. Effort is directed at mini-
patients who are to undergo radiation therapy.7e9 mizing any mobilization of the residual roots. On removal
of the crown, any sharp fragments of retained tooth
Technique structure are smoothed down with a 2.3-mm diameter
diamond round bur with simultaneous copious saline irri-
The technique used by the authors and described here is gation. The remaining enamel is typically reduced
similar to that described in the literature, for example by approximately 3 mm below the buccal crest of alveolar
Pogrel and colleagues.7 bone (Fig. 2AeJ).
a. Root canal treatment is not indicated during coro-
1. First the patients are evaluated radiographically for root nectomy. Sencimen and colleagues10 found that pa-
proximity to the IAN. If the patient is at significant increased tients having coronectomy with root canal treatment
risk for damage to the IAN, the option of coronectomy is had a much higher infection rate than those patients
discussed as an alternative to third-molar extraction. who underwent coronectomy without root canal
Criteria for selection involves the degree of root develop- treatment. Seven of the 8 patients undergoing root
ment, the degree of associated abnormality, the age of the canal treatment developed postoperative infections,
patient, and patient tolerance for the potential of sustain- whereas only 1 of 8 patients in the control group
ing permanent neurosensory disturbance (Fig. 1AeD). developed an infection. The investigators suggested
2. Once coronectomy has been decided upon for treatment, that mobilization of the root during root canal therapy
informed consent is obtained. Included in the consent and/or prolonged procedure time may contribute to
process is a thorough discussion of the rationale for coro- the higher infection rate in the study group.
nectomy. Risks including, but not limited to, infection, 4. After the coronectomy is completed, a dental curette is used
neurosensory disturbance, coronal migration of retained for removal of any and all follicular soft tissue in the surgical
root fragments requiring surgical retrieval, and the po- bony defect. Any grossly visible exposed pulpal soft tissue is
tential need for additional surgical procedures are dis- curetted. A bone file is used to smooth the bone edges along
cussed. The possibility that extraction of the tooth may be the socket defect and buccal bone trough. The incision is
necessary in the event of extensive decay, active infection, copiously irrigated with saline, and a small amount of
and mobility of retained roots is also included in the con- doxycycline powder (doxycycline hyclate, 50 mg capsules;
sent process. Watson Laboratories, Corona, CA) is applied topically to the
3. IAN blocks including long buccal infiltration are accom- surgical site before closure with chromic suture. Primary
plished with 2% lidocaine with 1:100,000 epinephrine and closure is desirable whenever possible, and may involve
0.5% bupivacaine with 1:100,000 epinephrine. A full- making a releasing incision distal to the second molar to
thickness mucoperiosteal incision is elevated with poste- facilitate closure. An immediate postoperative panoramic
rior buccal release. If necessary, a conservative buccal radiograph is obtained for a baseline assessment of the
trough is made using a #6 round carbide bur on a nitrogen- retained root fragment (Fig. 3AeF).
driven surgical hand piece, allowing access to the cemen- 5. Postoperatively, patients are placed on a 1-week course of
toenamel junction of the tooth. Care is exercised to antibiotic therapy. Typically penicillin VK, 500 mg by mouth
maintain as much crestal bone height as possible by mini- 4 times daily or clindamycin 300 mg by mouth 3 times daily
mizing the width of the buccal trough. After exposure is (in penicillin allergic patients) is used. Chlorhexidine glu-
obtained, a 701 fissure bur is used and a horizontal/ conate oral rinse 0.12% 3 times daily for 10 days is pre-
transverse cut is made through the tooth at the level of the scribed postoperatively. Analgesia is accomplished with
cementoenamel junction. Visualization is important to hydrocodone/acetaminophen and nonsteroidal anti-in-
ensure adequate sectioning of the crown without perfora- flammatories, as in patients who have had a third molar
tion through the lingual bone plate. The crown is delicately extracted. Patients are scheduled for a follow-up visit at
fractured and separated from the residual roots of the approximately 10 days after surgery, and are given an

Fig. 1 Patients noted to be at elevated risk for injury to the inferior alveolar nerve. (A) A 41-year-old woman presenting with peri-
coronitis, teeth #17 and #32. (B) A 69-year-old woman presenting with pericoronitis and caries, tooth #17. (C) A 41-year-old man presenting
with pericoronitis, tooth #17. (D) A 41-year-old woman presenting with pericoronitis and infection, tooth #32.
Coronectomy 223

Fig. 2 Photographic documentation of the coronectomy procedure using the author’s technique, involving 2 patients. Patient I.P. is a
41-year-old woman who presented with pericoronitis and infection associated with impacted tooth #32. Patient H.N. is a 41-year-old man
who presented with pericoronitis associated with tooth #17. (A) Patient I.P.: pretreatment panoramic radiograph (also seen in Fig. 1D). (B)
Patient I.P.: surgical exposure of tooth #32. (C) Patient I.P.: trough formation with #6 round bur. (D) Patient I.P.: horizontal cut made with
701 tapered fissure bur. (E) Patient I.P.: after removal of crown of tooth #32. (F) Patient H.N.: pretreatment panoramic radiograph (also
seen in Fig. 1C). (G) Patient H.N.: trough formation around tooth #17 with #6 round bur. (H) Patient H.N.: horizontal cut made with 701
tapered fissure bur. (I) Patient H.N.: after removal of crown, tooth #17. (J) Patient H.N.: residual roots smoothed with a 2.3-mm diameter
diamond round bur.

irrigation syringe for cleansing of the surgical site at that reduced incidence of permanent neurosensory disturbance
time. Patients are instructed to return for reevaluation at in these patients (Figs. 4e7).
6 months postoperatively. A periodontal assessment and
panoramic radiograph is obtained at the 6-month post-
treatment visit. In the author’s practice, an immediate Complications
posttreatment panoramic radiograph is obtained for base-
line assessment, and a subsequent panoramic radiograph or Complications after coronectomy are similar to those of
periapical radiograph is obtained at 6 months posttreat- traditional third-molar surgery, which are well known to oral
ment to assess for coronal migration of roots, potential and maxillofacial surgeons: bleeding, infection, pain, IAN
abscess formation, bone formation over the residual root damage, alveolar osteitis, and poor healing. Complications
fragments, and overall healing. It is the author’s opinion unique to coronectomy include mobilization of the roots during
that this radiographic protocol is warranted given the the procedure and postoperative migration of the roots.
224 Gady & Fletcher

Fig. 3 Completion of coronectomy procedures using the authors’ technique on patients I.P. and H.N. (A) Patient I.P.: doxycycline powder
is applied topically to residual root with #9 periosteal elevator. (B) Patient I.P.: doxycycline powder in surgical site. (C) Patient I.P.:
primary closure of surgical site with 3-0 chromic suture. (D) Patient H.N.: doxycycline powder applied topically to residual root with #9
periosteal elevator. (E) Patient H.N.: doxycycline powder in surgical site. (F) Patient H.N.: primary closure of surgical site with 3-0 chromic
suture.

Postoperative discomfort does not appear to be different fragment.7,11,12 Patients at higher risk are females and those
to that with traditional third-molar extraction, with some with teeth with conical root formation.12 Mobilization of the
investigators reporting less discomfort with coro- roots will also occur when significant force is applied when
nectomy.11e13 The incidence of alveolar osteitis is similar fracturing the crown of the tooth during the procedure. If
with coronectomy, reported in the range of 10% to 12%.13 inadvertent mobilization of the roots is noted perioperatively,
Delayed healing typically occurs for 1 of 2 reasons: mobili- the mobile root fragments must be removed to prevent a
zation of the root fragments during coronectomy or retention foreign-body reaction and poor healing. The most commonly
of enamel during the procedure.11 These patients require an reported long-term consequence of coronectomy is coronal
additional procedure to remove the root fragment or retained migration of the roots.7,11e13 Migration seems to always be in a
enamel. Infection rates are reported as between 1% and 5.2%, coronal direction, with 14% to 81% of roots migrating on
which is similar to the incidence after extraction of third average 2 to 4 mm.7,8,11e13 Although long-term follow-up
molars.11e13 studies are still needed, the coronal movement of roots seems
The most common perioperative complication when to occur predominantly during the first 6 months post-
performing coronectomy is mobilization of the root operatively and slows down thereafter.

Fig. 4 Patient W.B. is a 62-year-old man with a history of pain, pericoronitis, and caries associated with tooth #17. He was planned for
coronectomy on tooth #17. (A) Preoperative panoramic radiograph. (B) Immediate postoperative panoramic radiograph. (C) Panoramic
radiograph obtained 8 months postoperatively.
Coronectomy 225

Fig. 5 Patient K.N. is a 41-year-old woman who presented with pericoronitis associated with teeth #17 and #32. She was planned for
coronectomies on both teeth. (A) Preoperative panoramic radiograph (also seen in Fig. 1A). (B) Immediate postoperative panoramic
radiograph. (C) Panoramic radiograph obtained 6 months postoperatively. (D) Panoramic radiograph obtained 27 months postoperatively.
Note coronal migration of residual roots away from radiographic inferior alveolar nerve canals.

Fig. 6 Patient B.A. is a 69-year-old woman with caries and pericoronitis associated with tooth #17. She was planned for coronectomy. (A)
Preoperative panoramic radiograph. (B) Immediate postoperative panoramic radiograph. (C) Periapical radiograph obtained from restorative
dentist 7 months postoperatively. The patient refused to return for 6-month postoperative panoramic radiograph, stating “lack of symptoms.”

Fig. 7 Patient B.P. is a 58-year-old woman who presented with pericoronitis associated with tooth #17 and caries associated with tooth #32.
She was planned for coronectomy on tooth #17 and extraction of tooth #32. (A) Preoperative panoramic radiograph. (B) Immediate postoperative
panoramic radiograph. (C) Panoramic radiograph 6 months postoperatively. Note bone regeneration over the residual roots of tooth #17.
226 Gady & Fletcher

Outcomes 2. Smith A, Barry SE, Chiong AY, et al. Inferior alveolar nerve damage
following removal of mandibular third molar teeth. a prospective
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12-month postoperative follow-up data. However, few long- 3. Rood JP, Shehab BA. The radiological prediction of inferior alveolar
term studies exist. A 3-year follow-up study published in 2012 nerve injury during third molar surgery. Br J Oral Maxillofac Surg
by Leung and Cheung14 found no increase in the incidence of 1990;28:20e5.
infection, pain, development of abnormalities, and root 4. Sisk AL, Hammer WB, Shelton DW, et al. Complications following
eruption after 12 months. Moreover, 75% of roots stopped removal of impacted third molars: the role of the experience of
migrating 12 to 24 months postoperatively, and there was no the surgeon. J Oral Maxillofac Surg 1986;44:855e9.
migration of roots between 24 and 36 months. 5. Gulicher D, Gerlach KL. Sensory impairment of the lingual and
inferior alveolar nerves following removal of impacted mandibular
third molars. Int J Oral Maxillofac Surg 2001;30:306e12.
Summary 6. Sedaghatfar M, August MA, Dodson TB. Panoramic radiographic
findings as predictors of inferior alveolar nerve exposure following
It is the opinion of the authors that coronectomy is a reason- third molar extraction. J Oral Maxillofac Surg 2005;63:3e7.
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strate elevated risk for IAN injury with the removal of third the inferior alveolar nerve. J Oral Maxillofac Surg 2004;62:
molars. The procedure has been documented in the oral and 1447e52.
8. Leung YY, Cheung LK. Safety of coronectomy versus excision of
maxillofacial surgery literature as a treatment alternative to
wisdom teeth: a randomized controlled trial. Oral Surg Oral Med
third-molar extraction in patients considered at elevated risk Oral Pathol Oral Radiol Endod 2009;108:821e7.
for permanent nerve injury. Coronectomy is particularly 9. Gleeson CF, Patel V, Kwok J, et al. Coronectomy practice. Paper 1.
appropriate for patients older than 25 years, and who report Technique and trouble-shooting. Br J Oral Maxillofac Surg 2012;50:
low tolerance for the possibility of posttreatment neurosensory 739e44.
deficit at the consultation. The procedure is straightforward, 10. Sencimen M, Ortakoglu K, Aydin C, et al. Is endodontic treatment
and postoperative recovery is comparable with that of tradi- necessary during coronectomy procedure? J Oral Maxillofac Surg
tional third-molar extraction. Lastly, appropriate patient se- 2010;68:2385e90.
lection for coronectomy is paramount. Although not typical, 11. Patel V, Gleeson CF, Kwok J, et al. Coronectomy practice. Paper 2:
patients must have a realistic understanding that additional complications and long-term management. Br J Oral Maxillofac
Surg 2013;51(4):347e52.
surgery (eg, removal of residual roots or treatment of infec-
12. Renton T, Hankins M, Sproate C, et al. A randomized controlled
tion) may be necessary. Periodic follow-up assessments are clinical trial to compare the incidence of injury to the inferior
required and patient compliance is essential. In brief, coro- alveolar nerve as a result of coronectomy and removal of
nectomy is a reasonable treatment alternative for appropri- mandibular third molars. Br J Oral Maxillofac Surg 2005;43:
ately selected patients thought to be at elevated risk for IAN 7e12.
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nectomy (intentional partial odontecomy) for mandibular third
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