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British Journal of Oral and Maxillofacial Surgery 52 (2014) 415–419

Available online at www.sciencedirect.com

istological evaluation of mandibular third molar rootsetrieved after coronectomyinod Patel a, Chris Sproat a, Jerry Kwok a, Kiran Beneng a,elvam Thavaraj b, Mark McGurk c,∗

Oral Surgery Department, Floor 23, Guys Dental Hospital, London Bridge, London SE1 9RT, United KingdomOral and Head & Neck Pathology, King’s College London, 4th Floor Tower Wing, Guy’s Hospital, London SE1 9RT United KingdomDepartment of Oral and Maxillofacial Surgery, Atrium 3, 3rd Floor, Bermondsey Wing, Guy’s Hospital, London SE1 9RT, United Kingdom

ccepted 20 February 2014vailable online 29 March 2014

bstract

here is a resurgence of interest in coronectomy for the management of mandibular third molars because it has a low risk of injury to thenferior dental nerve. However, there is concern that the root that is left in place will eventually become a source of infection. We describe theistological evaluation of 26 consecutive symptomatic coronectomy roots in 21 patients. All roots had vital tissue in the pulp chamber andhere was no evidence of periradicular inflammation. Persistent postoperative symptoms related predominantly to inflammation of the soft

issue, which was caused by partially erupted roots or failure of the socket to heal.

2014 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

eywords: Coronectomy; Root retrieval; Mandibular third molars

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oronectomy or partial odontectomy involves the deliber-te retention of a portion of a mandibular third molar root.he technique was reported in 1984 by Ecuyer and Debien1

ut did not gain universal acceptance because there was perceived risk of late complications associated with theetained root. There is no scientific evidence to confirm orefute this risk so the technique has now been acknowl-dged with reservations. Renewed interest in coronectomy

as developed because it seems to almost remove the riskf injury to the inferior dental nerve (IDN).2 However, thisdvantage is countered by the perceived threat of possible

∗ Corresponding author.E-mail addresses: vinod.patel@hotmail.co.uk (V. Patel),

hris.sproat@gstt.nhs.uk (C. Sproat), jerry.kwok@gstt.nhs.uk (J. Kwok),iran.beneng@kcl.ac.uk (K. Beneng), selvam.thavaraj@kcl.ac.ukS. Thavaraj), mark.mcgurk@kcl.ac.uk (M. McGurk).

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ttp://dx.doi.org/10.1016/j.bjoms.2014.02.016266-4356/© 2014 The British Association of Oral and Maxillofacial Surgeons. Pu

ate infection caused by loss of pulpal vitality in the retainedoot.

To find out the pulpal and periradicular status of theetained root of mandibular third molars, we histologicallyvaluated coronectomy roots that were removed because ofersistent symptoms, which we presumed had been causedy an infected root. This study provides insight into the pos-ible causes of symptoms and late complications followingoronectomy.

ethod

pproximately 840 coronectomies were carried out in theral Surgery department at Guy’s Dental Hospital from

eptember 2011 to May 2013 (21 consecutive months). A

otal of 21 consecutive patients (26 teeth) had persistentymptoms after the procedure and had the residual rootetrieved. All except one had had their original operation at

blished by Elsevier Ltd. All rights reserved.

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16 V. Patel et al. / British Journal of Oral

uy’s Hospital. Information was recorded on the persistentymptoms, and the clinical signs and radiographic appear-nce of the retained roots including their migratory status.ll patients had the roots removed surgically (16 unilateral,

bilateral). Function of the IDN was assessed before and at weeks after retrieval.

The roots were extracted under local anaesthesia withr without sedation, or under general anaesthesia using araditional buccal approach and rotary instruments. A 3-ided buccal mucoperiosteal flap was raised, buccal boneas removed to expose the roots, and they were sectioned

f required or simply elevated. The site was curetted super-cially, irrigated with saline, and closed primarily withesorbable sutures. All patients were reviewed at 2 weeks toheck healing. Nerve function was also assessed, primarilyy verbal enquiry and if necessary by clinical examination.

The retrieved roots were fixed in 10% (v/v) buffered for-al saline for 48 h then longitudinally hemisected using a

iamond band saw, and decalcified in 10% (v/v) bufferedormic acid. Blocks of decalcified tissue were processed andmbedded in paraffin wax. Sections of 5 �m were cut andounted on slides coated with poly-l-lysine. They were

eparaffinised in xylene, dehydrated in 100% (v/v) indus-rial methylated spirit, and rinsed in running tap water. Allections were routinely stained with haematoxylin and eosinnd submitted for routine microscopy.

esults

n the study group, the mean age of patients was 31.6 yearsrange 22–70) with a female dominance of 17:4. The ratio ofeft:right molars was 1.4:1.

The causes of the persistent symptoms are shown in Fig. 1. total of 21 patients had persistent symptoms involving 26

ockets. Each socket contained 2 roots, which provided 52ndividual root canals for analysis.

Of the 26 symptomatic teeth, radiographic assessmenthowed that coronectomy had been adequate in 20, but ahard of enamel had been retained on the root fragment in.

The mean time to the second operation was 15 monthsrange 2–54) in the 20 patients who had had an adequate coro-ectomy. Of these, healing was uncomplicated in 15 apartrom root migration, which eventually resulted in the frag-ents erupting through the mucosa where they developed

ocalised soft tissue inflammation. In this group the time toecond operation was 19 months (range 6–54) compared with.3 months (range 3–6) in those who had an enamel shardttached to the root.

At the time of retrieval, 11 of 26 cases were radio-raphically clear of the inferior dental nerve canal on

wo-dimensional imaging. All roots were retrieved with noomplications apart from one patient who had transient dys-unction of the nerve. In this case, the panoramic radiographefore retrieval suggested that there was risk of injury to the

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xillofacial Surgery 52 (2014) 415–419

erve so cone beam computed tomography (CBCT) was usedo aid the operation.

All 52 roots contained vital pulp (Fig. 2). In 3 there wasartial necrosis but it was limited to the coronal portion ofhe root canal; the apical portion contained vital pulp that wasot inflamed (Fig. 3). In all cases, including those presentingith acute symptoms, the periradicular soft tissues showedo evidence of an acute or chronic inflammatory cell infiltrateFig. 4). There was variable hypercementosis in all cases.

iscussion

he most appropriate technique that will allow extraction ofn impacted mandibular third molar with minimal risk ofnjury to the IDN is debatable. The resurgence of interestn coronectomy has occurred because it is reported almost toliminate the risk of injury to the nerve. However, the retainedoot is a possible source of late symptoms, and the aetiopatho-enesis of persistent symptoms is poorly understood.

The principles underpinning coronectomy are not new.entists worldwide have inadvertently left vital root apices

n situ with minimal complications,3–5 and elective root reten-ion has been used by restorative dentists for many years as

basis for overdenture abutments. More recently, where noctive caries is present in the retained roots, the abutmentsre left untreated and do not even require root canal treat-ent because of pulpal sclerosis. The roots tend to remain

symptomatic despite being exposed to the oral cavity. Inheory, a root that is vital after coronectomy is in an envi-onment more conducive to healing as it is sealed within theandible and isolated from the oral cavity.To reduce the risk of a root becoming infected, teeth

elected for coronectomy should be sound and have no clin-coradiological evidence of caries, or pulpal, periodontal, orpical disease. To preserve the vitality of the root the crownust be separated from the root without mobilising the rootithin its socket. Coronectomy seems to decompress theulp chamber and provides adequate space to accommodatehe pulpal oedema.2 Interestingly, therapeutic interventionsuch as root canal treatment of the retained root have previ-usly been shown to result in a high rate of infection and theubsequent need for removal.6

Fig. 1 shows the indication for the retrieval of roots in thistudy. Patients were subdivided into successful and unsuc-essful (retained enamel) coronectomy groups. In general,ymptoms were modest in their extent. In the successfulroup, the symptoms were related to breach of the mucosay a root, which is similar to that of pericoronitis. There were

non-healing sockets in the successful group and each hadad alveolar osteitis (dry socket). Retained shards of enamelttached to the root caused the symptoms after unsuccessful

oronectomy; enamel is inert and soft tissues cannot attacho its surface so the socket does not heal.

The symptoms in 15 of our 26 patients were caused byontinued eruption of the root fragment. Other symptoms

V. Patel et al. / British Journal of Oral and Maxillofacial Surgery 52 (2014) 415–419 417

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ere failure of the socket to heal (n = 9) and acute inflamma-ion with facial swelling (n = 2). Interestingly, in most casesn = 23), the pulpal tissues were vital and not inflamed. In

there was pulpal necrosis of the coronal portion of theoot canal, but the apical region remained vital and was notnflamed.

This report is seminal as it shows that all the roots retrievedad a vital vascularised pulp, and in all cases the periradicu-ar soft tissues were not inflamed. The data therefore suggesthat symptoms after coronectomy do not result from lossf pulpal vitality or subsequent periradicular inflammation.he histopathological finding of vital pulpal tissue in all the

oots supports the argument against the risk of late infectiveomplications.

In relation to minimising injury to the IDN, as most rootsecommenced their eruptive process away from the nerveanal they could be removed without injuring the nerve. Ofhe 3 cases with partial necrosis of the pulp, 2 had a par-ially erupted root and there was a direct communicationetween the root canal and the mouth. The patients had beensymptomatic until the root had erupted into the oral cav-ty, which suggests that this might have caused the necrosis.n the remaining case, the tooth socket had been dressed onultiple occasions with AlveogylTM (Septodont, Maidstone,K) and it is likely that this caused the exposed portion of

he pulp to become necrotic.On histological examination, a degree of hypercemen-

osis (mild to moderate) was evident on the surface of allhe roots, and trauma is known to be a cause. Coronectomy

ay stimulate the periodontium, which may explain the late

eactivation of migration. Interestingly, the eruption of teeths predominantly driven by the development of roots, but in

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onectomy roots in our group.

any patients who have coronectomy this is complete, sother factors must be at play. As the socket lays down newone, migration tends to stop. The role of hypercementosisequires further investigation to see whether a gradual accu-ulation over the root contributes to the slowing or stopping

f root migration over time.Our findings are supported by animal studies, which

howed that root fragments with vital pulps were main-ained in the alveolus without any inflammatory reaction.7–11

urthermore, removal of asymptomatic retained root tipsn humans histologically confirmed the lack of any inflam-

atory infiltrate.12,13 In a primate model, pulpal tissueslended with the overlying connective tissues when theucosa healed successfully14 and the opening of the canalas sealed with osteocementum.15 Subsequent findings in

nimals and humans have shown that in vital roots, calcificpurs attempted to bridge the pulp canal. We observed aimilar finding in one case where enamel had been left andeactionary dentine was formed at the interface between theontents of the vital pulp and pericoronal soft tissues.

Removal of a coronectomy root should be consideredhen it has erupted and is symptomatic or if there is radio-

ogical evidence of apical disease, which to date and tour knowledge has not been reported. Lleung and Cheung16

eviewed coronectomy roots 3 years postoperatively and didot identify associated disease.

To avoid unnecessary treatment, clinicians should beware of 2 common situations that can follow coronec-omy. Firstly, if patients remain symptomatic, but clinical and

adiographic examinations show that the sites have healedatisfactorily, then the original diagnosis (third molar origin)hould be revisited. Second, the presence of a radiolucent area

418 V. Patel et al. / British Journal of Oral and Maxillofacial Surgery 52 (2014) 415–419

Fig. 2. Representative whole-mount vertical section of a retrieved root show-ing vital uninflamed pulp (haematoxylin and eosin, original magnificationx20).

Fig. 3. Retrieved root showing partial necrosis of the root canal (A); wholemount (B); and pulpal necrosis of the coronal portion (C). The apical portionwas vital (haematoxylin and eosin, original magnification A x20, B & C x40).

Fig. 4. High-power view of the periapical soft tissue of a root retrieved froma patient who presented with acute symptoms. There is lack of apprecia-ble acute or chronic inflammatory cell infiltrate (haematoxylin and eosin,o

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elow the root initially indicates apical disease, but radio-raphs taken before and after operation should be examinedlosely for root migration. The radiolucent area delineateshe original outline of the root; it indicates delayed regener-tion of bone behind the moving root and is not infection2

‘migration-lucency zone’).17

In this consecutive series of patients, no case of persistentymptoms could be attributed to an apically infected root. Onhe contrary, all the pulp chambers retained a viable bloodupply. This undermines the argument that the coronectomyoot is a potential infective risk and supports the drive towards

more minimally invasive procedure.

onflict of interest

here are no known conflicts of interests for the authors toeclare.

thics statement/confirmation of patient permission

o clinical pictures or identifying information has been usedn this manuscript. Ethical approval was not required. Thistudy was retrospective analyses of interventions were carriedut as part of routine clinical practice.

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