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British Journal of Oral and Maxillofacial Surgery 52 (2014) 415–419
Histological evaluation of mandibular third molar roots retrieved after coronectomy Vinod Patel a , Chris Sproat a , Jerry Kwok a , Kiran Beneng a , Selvam Thavaraj b , Mark McGurk c,∗ a b c
Oral Surgery Department, Floor 23, Guys Dental Hospital, London Bridge, London SE1 9RT, United Kingdom Oral and Head & Neck Pathology, King’s College London, 4th Floor Tower Wing, Guy’s Hospital, London SE1 9RT United Kingdom Department of Oral and Maxillofacial Surgery, Atrium 3, 3rd Floor, Bermondsey Wing, Guy’s Hospital, London SE1 9RT, United Kingdom
Accepted 20 February 2014 Available online 29 March 2014
Abstract There is a resurgence of interest in coronectomy for the management of mandibular third molars because it has a low risk of injury to the inferior dental nerve. However, there is concern that the root that is left in place will eventually become a source of infection. We describe the histological evaluation of 26 consecutive symptomatic coronectomy roots in 21 patients. All roots had vital tissue in the pulp chamber and there was no evidence of periradicular inflammation. Persistent postoperative symptoms related predominantly to inflammation of the soft tissue, 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.
Keywords: Coronectomy; Root retrieval; Mandibular third molars
Introduction Coronectomy or partial odontectomy involves the deliberate retention of a portion of a mandibular third molar root. The technique was reported in 1984 by Ecuyer and Debien1 but did not gain universal acceptance because there was a perceived risk of late complications associated with the retained root. There is no scientific evidence to confirm or refute this risk so the technique has now been acknowledged with reservations. Renewed interest in coronectomy has developed because it seems to almost remove the risk of injury to the inferior dental nerve (IDN).2 However, this advantage is countered by the perceived threat of possible ∗
Corresponding author. E-mail addresses: [email protected]
(V. Patel), [email protected]
(C. Sproat), [email protected]
(J. Kwok), [email protected]
(K. Beneng), [email protected]
(S. Thavaraj), [email protected]
late infection caused by loss of pulpal vitality in the retained root. To find out the pulpal and periradicular status of the retained root of mandibular third molars, we histologically evaluated coronectomy roots that were removed because of persistent symptoms, which we presumed had been caused by an infected root. This study provides insight into the possible causes of symptoms and late complications following coronectomy.
Method Approximately 840 coronectomies were carried out in the Oral Surgery department at Guy’s Dental Hospital from September 2011 to May 2013 (21 consecutive months). A total of 21 consecutive patients (26 teeth) had persistent symptoms after the procedure and had the residual root retrieved. All except one had had their original operation at
http://dx.doi.org/10.1016/j.bjoms.2014.02.016 0266-4356/© 2014 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
V. Patel et al. / British Journal of Oral and Maxillofacial Surgery 52 (2014) 415–419
Guy’s Hospital. Information was recorded on the persistent symptoms, and the clinical signs and radiographic appearance of the retained roots including their migratory status. All patients had the roots removed surgically (16 unilateral, 5 bilateral). Function of the IDN was assessed before and at 2 weeks after retrieval. The roots were extracted under local anaesthesia with or without sedation, or under general anaesthesia using a traditional buccal approach and rotary instruments. A 3sided buccal mucoperiosteal flap was raised, buccal bone was removed to expose the roots, and they were sectioned if required or simply elevated. The site was curetted superficially, irrigated with saline, and closed primarily with resorbable sutures. All patients were reviewed at 2 weeks to check healing. Nerve function was also assessed, primarily by verbal enquiry and if necessary by clinical examination. The retrieved roots were fixed in 10% (v/v) buffered formal saline for 48 h then longitudinally hemisected using a diamond band saw, and decalcified in 10% (v/v) buffered formic acid. Blocks of decalcified tissue were processed and embedded in paraffin wax. Sections of 5 m were cut and mounted on slides coated with poly-l-lysine. They were deparaffinised in xylene, dehydrated in 100% (v/v) industrial methylated spirit, and rinsed in running tap water. All sections were routinely stained with haematoxylin and eosin and submitted for routine microscopy.
Results In the study group, the mean age of patients was 31.6 years (range 22–70) with a female dominance of 17:4. The ratio of left:right molars was 1.4:1. The causes of the persistent symptoms are shown in Fig. 1. A total of 21 patients had persistent symptoms involving 26 sockets. Each socket contained 2 roots, which provided 52 individual root canals for analysis. Of the 26 symptomatic teeth, radiographic assessment showed that coronectomy had been adequate in 20, but a shard of enamel had been retained on the root fragment in 6. The mean time to the second operation was 15 months (range 2–54) in the 20 patients who had had an adequate coronectomy. Of these, healing was uncomplicated in 15 apart from root migration, which eventually resulted in the fragments erupting through the mucosa where they developed localised soft tissue inflammation. In this group the time to second operation was 19 months (range 6–54) compared with 3.3 months (range 3–6) in those who had an enamel shard attached to the root. At the time of retrieval, 11 of 26 cases were radiographically clear of the inferior dental nerve canal on two-dimensional imaging. All roots were retrieved with no complications apart from one patient who had transient dysfunction of the nerve. In this case, the panoramic radiograph before retrieval suggested that there was risk of injury to the
nerve so cone beam computed tomography (CBCT) was used to aid the operation. All 52 roots contained vital pulp (Fig. 2). In 3 there was partial necrosis but it was limited to the coronal portion of the root canal; the apical portion contained vital pulp that was not inflamed (Fig. 3). In all cases, including those presenting with acute symptoms, the periradicular soft tissues showed no evidence of an acute or chronic inflammatory cell infiltrate (Fig. 4). There was variable hypercementosis in all cases.
Discussion The most appropriate technique that will allow extraction of an impacted mandibular third molar with minimal risk of injury to the IDN is debatable. The resurgence of interest in coronectomy has occurred because it is reported almost to eliminate the risk of injury to the nerve. However, the retained root is a possible source of late symptoms, and the aetiopathogenesis of persistent symptoms is poorly understood. The principles underpinning coronectomy are not new. Dentists worldwide have inadvertently left vital root apices in situ with minimal complications,3–5 and elective root retention has been used by restorative dentists for many years as a basis for overdenture abutments. More recently, where no active caries is present in the retained roots, the abutments are left untreated and do not even require root canal treatment because of pulpal sclerosis. The roots tend to remain asymptomatic despite being exposed to the oral cavity. In theory, a root that is vital after coronectomy is in an environment more conducive to healing as it is sealed within the mandible and isolated from the oral cavity. To reduce the risk of a root becoming infected, teeth selected for coronectomy should be sound and have no clinicoradiological evidence of caries, or pulpal, periodontal, or apical disease. To preserve the vitality of the root the crown must be separated from the root without mobilising the root within its socket. Coronectomy seems to decompress the pulp chamber and provides adequate space to accommodate the pulpal oedema.2 Interestingly, therapeutic interventions such as root canal treatment of the retained root have previously been shown to result in a high rate of infection and the subsequent need for removal.6 Fig. 1 shows the indication for the retrieval of roots in this study. Patients were subdivided into successful and unsuccessful (retained enamel) coronectomy groups. In general, symptoms were modest in their extent. In the successful group, the symptoms were related to breach of the mucosa by a root, which is similar to that of pericoronitis. There were 4 non-healing sockets in the successful group and each had had alveolar osteitis (dry socket). Retained shards of enamel attached to the root caused the symptoms after unsuccessful coronectomy; enamel is inert and soft tissues cannot attach to its surface so the socket does not heal. The symptoms in 15 of our 26 patients were caused by continued eruption of the root fragment. Other symptoms
V. Patel et al. / British Journal of Oral and Maxillofacial Surgery 52 (2014) 415–419
Fig. 1. Indications for retrieval of coronectomy roots in our group.
were failure of the socket to heal (n = 9) and acute inflammation with facial swelling (n = 2). Interestingly, in most cases (n = 23), the pulpal tissues were vital and not inflamed. In 3 there was pulpal necrosis of the coronal portion of the root canal, but the apical region remained vital and was not inflamed. This report is seminal as it shows that all the roots retrieved had a vital vascularised pulp, and in all cases the periradicular soft tissues were not inflamed. The data therefore suggest that symptoms after coronectomy do not result from loss of pulpal vitality or subsequent periradicular inflammation. The histopathological finding of vital pulpal tissue in all the roots supports the argument against the risk of late infective complications. In relation to minimising injury to the IDN, as most roots recommenced their eruptive process away from the nerve canal they could be removed without injuring the nerve. Of the 3 cases with partial necrosis of the pulp, 2 had a partially erupted root and there was a direct communication between the root canal and the mouth. The patients had been asymptomatic until the root had erupted into the oral cavity, which suggests that this might have caused the necrosis. In the remaining case, the tooth socket had been dressed on multiple occasions with AlveogylTM (Septodont, Maidstone, UK) and it is likely that this caused the exposed portion of the pulp to become necrotic. On histological examination, a degree of hypercementosis (mild to moderate) was evident on the surface of all the roots, and trauma is known to be a cause. Coronectomy may stimulate the periodontium, which may explain the late reactivation of migration. Interestingly, the eruption of teeth is predominantly driven by the development of roots, but in
many patients who have coronectomy this is complete, so other factors must be at play. As the socket lays down new bone, migration tends to stop. The role of hypercementosis requires further investigation to see whether a gradual accumulation over the root contributes to the slowing or stopping of root migration over time. Our findings are supported by animal studies, which showed that root fragments with vital pulps were maintained in the alveolus without any inflammatory reaction.7–11 Furthermore, removal of asymptomatic retained root tips in humans histologically confirmed the lack of any inflammatory infiltrate.12,13 In a primate model, pulpal tissues blended with the overlying connective tissues when the mucosa healed successfully14 and the opening of the canal was sealed with osteocementum.15 Subsequent findings in animals and humans have shown that in vital roots, calcific spurs attempted to bridge the pulp canal. We observed a similar finding in one case where enamel had been left and reactionary dentine was formed at the interface between the contents of the vital pulp and pericoronal soft tissues. Removal of a coronectomy root should be considered when it has erupted and is symptomatic or if there is radiological evidence of apical disease, which to date and to our knowledge has not been reported. Lleung and Cheung16 reviewed coronectomy roots 3 years postoperatively and did not identify associated disease. To avoid unnecessary treatment, clinicians should be aware of 2 common situations that can follow coronectomy. Firstly, if patients remain symptomatic, but clinical and radiographic examinations show that the sites have healed satisfactorily, then the original diagnosis (third molar origin) should be revisited. Second, the presence of a radiolucent area
V. Patel et al. / British Journal of Oral and Maxillofacial Surgery 52 (2014) 415–419
Fig. 4. High-power view of the periapical soft tissue of a root retrieved from a patient who presented with acute symptoms. There is lack of appreciable acute or chronic inflammatory cell infiltrate (haematoxylin and eosin, original magnification x100).
Fig. 2. Representative whole-mount vertical section of a retrieved root showing vital uninflamed pulp (haematoxylin and eosin, original magnification x20).
below the root initially indicates apical disease, but radiographs taken before and after operation should be examined closely for root migration. The radiolucent area delineates the original outline of the root; it indicates delayed regeneration of bone behind the moving root and is not infection2 (‘migration-lucency zone’).17 In this consecutive series of patients, no case of persistent symptoms could be attributed to an apically infected root. On the contrary, all the pulp chambers retained a viable blood supply. This undermines the argument that the coronectomy root is a potential infective risk and supports the drive towards a more minimally invasive procedure.
Conﬂict of interest There are no known conflicts of interests for the authors to declare.
Ethics statement/conﬁrmation of patient permission No clinical pictures or identifying information has been used in this manuscript. Ethical approval was not required. This study was retrospective analyses of interventions were carried out as part of routine clinical practice.
Fig. 3. Retrieved root showing partial necrosis of the root canal (A); whole mount (B); and pulpal necrosis of the coronal portion (C). The apical portion was vital (haematoxylin and eosin, original magnification A x20, B & C x40).
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