Literaturereview Introduction Abstract Removalofectopicmandibularthirdmolarteeth:literaturereviewandareportofthreecases

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C A S E R E P O R T

Removal of ectopic mandibular third molar teeth: literature review and a report of three cases

N.M. Ahmed1& B. Speculand1

1Oral and Maxillofacial Surgery, University Hospital Birmingham NHS Trust, Birmingham, UK

Abstract

This article reviews 23 published cases of ectopic mandibular third molar teeth. We report three further cases and discuss the surgical approaches which can be used for their removal.

Key words:

extraction, mandible, surgery, third molar

Correspondence to:

Miss NM Ahmed STR Orthodontics Leeds Dental Institute Clarendon Way Leeds LS2 9LU UK

Tel.:+44 01133 431585 Fax:+44 01133 436282 email: nm.ahmed@yahoo.co.uk

Accepted: 21 October 2011

doi:10.1111/j.1752-248X.2011.01145.x

Introduction

Unerupted impacted mandibular third molar teeth occur in 20–30% of the population, with a higher prevalence in women1.

Mandibular third molars tend to occupy an abnormal position because of lack of space in the posterior mandible. The cause of their malposition is unclear although many theories have been put forward.

During mandibular development as the ramus elon- gates and grows upward, it may take the tooth germ with it. The development of an associated cyst or tumour may push the tooth into an abnormal position as the cyst grows2–7. When the tooth is grossly dis- placed, for example up into the ramus or down below the level of the mandibular nerve, it may be referred to as ectopic. The majority of ectopic mandibular

third molars are associated with cystic lesions. Other proposed causes include a lack of space between the second molar and ramus of the mandible8, trauma and aberrant eruption6.

Ectopic mandibular third molars are rare and the aetiology remains unclear. The normal position for a third molar is distal to the second molar, however ectopic positions include: condyle, ramus, coronoid process, sigmoid notch and lower border of the angle of the mandible.

These teeth are often an incidental finding on a routine radiograph and no treatment is required unless they are symptomatic or have associated pathology.

The purpose of this article is to review the literature on ectopic mandibular third molar teeth and to present three cases involving four ectopic lower third molars treated in our department which illustrate different surgical approaches for their removal.

Literature review

We searched Pubmed via Medline using the following key search terms: ‘ectopic third molar’ and most non- English language papers were excluded. This initial

Statement of clinical relevance: This article describes the techniques which can be used for removal of ectopic mandibular third molar teeth located low-down or high-up in the ramus of the mandible, including appropriate extra-oral approaches. We reviewed 23 cases from 21 papers and present an additional three patients with four ectopic lower third molars to illus- trate why and how such ectopic teeth may be removed.

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literature review yielded a review paper1which helped to identify some further papers.

We found 23 cases reported in 21 papers from 1976 to 2010, the majority of these were single (Table 1). Of the 23 cases, the mean age for presentation was 44.7 years (range 23–70 years).

With regard to site, eight of the ectopic mandibular third molars were located in the condyle, five were described as subcondylar, three in the angle, three in the ramus (one of which was bilateral) two in the coronoid process, one at the sigmoid notch, and one bilateral case was described as being in the condyle and ramus.

The common presentation was found to be that of pain and swelling, and others included in decreasing frequency trismus, a sinus, difficulty in mastication, discharge, fever, TMJ pain and a discharging fistula.

Of the 23 cases, 18 had removal of the ectopic mandibular third molars, two did not have any treatment, one did not specify the treatment, one was excised surgically and no further details were given, and one specified the tooth was left in the condyle and the parotid gland was dissected out.

The common approaches for removal in decreasing frequency were the conventional intra-oral approach (including one endoscopic) an extra-oral approach

Table 1 Published cases of ectopic mandibular third molar teeth in chronological order

Author Position tooth Signs and symptoms Management Age

patient Sex patient

Szerlip 19787 Subcondylar region Trismus, pain, swelling Intra-oral 50 F

Markowitz et al. 19799 Bilateral: ramus Facial pain right side Intra-oral 23 F

Burton and Scheffer 198010 Bilateral: Condyle and high ramus

Painful swelling left side Left side- extra-oral 57 F

Right side- intra-oral Srivastava and Singh 19825 Condylar neck Discharging sinus left

pre-auricular region

Sinus opened, ectopic tooth left in condyle, parotid gland dissected out

40 F

Muller 198311 Coronoid process Incidental finding Intra-oral 38 M

Chongruk 199112 Coronoid process No gross disease No treatment 27 F

Balan 199213 Sigmoid notch Pre-auricular pain Not specified 30 F

Toranzo Fernandez and Terrones Meraz 19926

Ramus Swelling, pain, trismus Not specified – ‘excised

surgically’

70 F

Bux and Lisco 19943 Subcondyle Painful swelling with draining sinus, trismus, fever, difficulty in mastication

Extra-oral submandibular access

66 F

Adams and Walton 19962 Angle/ posterior body Discomfort and unpleasant tasting discharge

Follow up long term 45 F

Medici et al. 20014 Condylar process Right TMJ pain, difficulty in mastication/ mouth opening, pre-auricular swelling

Intra-oral with removal coronoid process

41 F

Turner et al. 200214 Subcondyle Recurrent right-sided swelling Extra-oral pre-auricular 47 M

Suarez-Cunquiero et al. 200315 Condylar neck Pain, swelling Endoscopic intra-oral 45 M

Wassouf et al. 200316 Condylar neck Painful swelling left

massetricomandibular area, tenderness to palpation left angle of mandible

Extra-oral pre auricular 47 M

Jones et al. 200417 Angle? Chronic infection/ discharging sinus, facial swelling, trismus

SSO 48 M

Wang et al. 20081 Ascending ramus Right-sided facial swelling Intra-oral 31 F

Salmeron et al. 200818 Condylar neck Pre-auricular pain and swelling Endaural approach 53 F

Salmeron et al. 200818 Condylar neck Pre-auricular swelling Extra-oral (pre-auricular) 41 M

Naaj et al. 201019 Angle/ posterior body Pain, swelling, discharging fistula Extra-oral 43 M

Bortoluzzi and Manfro 201020 Subcondyle Pain, swelling, purulent discharge right side of face

Intra-oral 64 F

Gadre and Waknis 201021 Condyle Pre-auricular pain, swelling on right side

Intra-oral 30 F

Gadre and Waknis 201021 Condyle Left sided facial swelling, pain Intra-oral 40 M

Pace et al. 201022 Subcondylar region Erythematous skin swelling/

discharging sinus

Extra-oral (retromandibular) 53 M

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(pre-auricular or submandibular) and sagittal split osteotomy.

Cases

We present three cases seen in our department which illustrate different surgical approaches for the removal of these teeth.

Case 1

A 38-year-old female who was medically fit and well was referred from Birmingham Dental Hospital to the Oral and Maxillofacial Unit at Queen Elizabeth Hospital, Birmingham.

She presented with recurrent pain, bad taste and left-sided facial swelling for which several courses of antibiotics had been prescribed.

On extra-oral examination, a swelling was noted at the angle of the mandible with a discharging sinus adjacent to the lower third molar intra-orally.

An orthopantomogram (OPT) was taken which showed an ectopic mandibular third molar at the pos- terior border of the left angle of the mandible, with an associated coronal radiolucency (Fig. 1).

The tooth was removed surgically under general anaesthetic via an extra-oral approach (the Risdon neck approach) (Fig. 2). This approach involves incis- ing through skin and superficial fascia and platysma and exposing the superficial surface of the masseter muscle. After checking for the position of the branches of the facial nerve, the muscle is incised horizontally to expose the mandible. The ectopic tooth is exposed and removed and the wound is then closed in layers.

The histological specimen sent was reported as a dentigerous cyst. The patient was discharged from the clinic after a single post-operative visit.

Case 2

A 52-year-old female was also referred from Birming- ham Dental Hospital to the Oral and Maxillofacial Unit at Queen Elizabeth Hospital, Birmingham. She was medically fit and well.

She presented with pain, trismus and a recurrent right-sided facial swelling which failed to resolve following five courses of antibiotics. This was initially thought to be due to a parotid infection.

Extra-oral examination revealed a discharging sinus at the right angle of mandible and a radiograph (Fig. 3) revealed an impacted lower-right third molar in the sigmoid notch/high ramus region of the mandible.

Figure 1 Left side of orthopantomogram radiograph, case 1, showing ectopic mandibular third molar at the posterior border of the left angle of the mandible.

Figure 2 Extra-oral approach, case 1.

Figure 3 Right side of orthopantomogram radiograph, case 2, showing ectopic mandibular third molar at sigmoid notch/high ramus region of right mandible.

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The tooth was removed under a general anaesthetic also via an extra-oral Risdon neck approach. Dissection through masseter muscle revealed a buccal perfora- tion of the mandibular ramus (Fig. 4). The tooth was removed surgically and the associated cyst was enucleated. An extra-oral drain was placed.

The patient made good post-operative recovery although she had mild buccal branch weakness which recovered after a few weeks. Four-monthly review indicated good bony infill. Complete healing could be seen at 18 months on the OPT. The pathology was reported as a radicular cyst.

Case 3

A 36-year-old female with mild asthma presented with pain and recurrent intra-oral infection which had not resolved after several courses of oral broad spectrum antibiotics.

Extra-oral examination was unremarkable, although inflammation was noted in the retro-molar trigone area bilaterally. A computed tomography (CT) scan (Fig. 5) and OPT showed impacted lower third molars in the ramus of the mandible bilaterally.

The patient opted to have these teeth extracted and the procedure was carried out under a general anaes- thetic via an extended lower third molar intra-oral incision bilaterally, extending up the ramus of the mandible.

Both teeth were removed surgically and the associ- ated cysts were enucleated. Both inferior dental nerves (IDNs) were visualised and protected. The patient made a good post-operative recovery.

At the 1-month review the patient had moderate paraesthesia of both IDNs. The histopathology was reported as dentigerous cyst for both.

Discussion

Management of ectopic mandibular third molars is dependent on several key factors such as signs, symp- toms and associated pathology, which are listed as indications for extraction of third molars in the National Institute of Health and Clinical Excellence guidelines. Pathology in the mandibular ramus and condyle can lead to serious complications such as condylar resorption, osteolysis and even condylar frac- ture4,7. Once a decision has been made to extract the ectopic tooth, access can be achieved either intra- or extra-orally.

An OPT or postero-anterior (PA) mandible radio- graphs allow initial assessment but a more detailed investigation such as a CT scan is often carried out to determine the position of the ectopic tooth accurately, especially if it lies in the ramus of the mandible. This allows the clinician to assess the depth of the impac- tion, the relationship with the neurovascular bundle, and helps in surgical planning.

With increasing availability of small volume Cone Beam CT, this modality may be used more commonly in the future to locate the position of an ectopic lower third molar with better resolution and less radiation exposure than conventional CT scans.

The mean age of affected patients from our literature review was 44.7 years (range 23–70 years) compared with a mean age of 42 years in our reported cases (range 36–52 years).

Figure 4 Extra-oral approach, case 2.

Figure 5 Axial CT slice, case 3, showing bilateral ectopic third molar teeth in right and left ramus of the mandible.

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All but two of the reviewed cases of ectopic man- dibular third molars were symptomatic and presented with pain and repeated mandibular swelling, and several with a draining sinus extra-orally or intra- orally. The anatomic position of the ectopic third molar may irritate the temporalis muscle fibres and cause pain during mastication23. All three of our cases had repeated infections treated with several courses of antibiotics. One of our cases had an external sinus draining at the angle of the mandible.

All of our cases were associated with cyst formation.

In adults, a dentigerous cyst is the most common benign lesion associated with an impacted mandibular third molar2. The treatment of choice is enucleation and removal of the impacted tooth. Spontaneous reso- lution of the cyst is unlikely. In addition to displace- ment of the tooth, cystic involvement of an impacted or unerupted third molar may result in expansion of bone causing facial asymmetry, resorption of roots of adja- cent teeth and loss of bone in the ramus, extending as far as the coronoid process and condyle10.

Two of our reported cases were managed by extra- oral removal and one by intra-oral removal.

There are four surgical approaches which have been reported:

Sagittal split osteotomy (one case)17

This is useful where extensive removal of alveolar bone would be required17. This approach allows direct visu- alisation of the tooth and good exposure of the surgical site. There is a 22–78% incidence of post-operative immediate IDN damage, falling to 5–26% after 6 months24.

Intra-oral approach (eight cases)1,4,7,9–11,20,21

This is not possible if there is a limited surgical field or poor visualisation in an inaccessible region such as the lower border of the mandible19. The intra-oral approach is a more cosmetic approach with no skin scar. However there is a high risk of damage to the IDN significant alveolar bone loss and risk of damage to adjacent teeth19. In some cases, removal of the coronoid process may help4,16.

Extra-oral approach (eight cases)3,10,14,16,18,19,22

This is usually either submandibular or pre-auricular.

Teeth high in the ramus, condyle or at the lower border of the mandible may require an extra-oral approach.

Two of our three cases were removed extra-orally. This approach allows good exposure of the surgical site,

more control over the surgical plane, less bone removal and a lower chance of pathological fracture. However there will be a skin scar and there is a risk of damage to the marginal mandibular branch of the facial nerve19.

If the ectopic tooth is located below the level of the IDN then an extra-oral approach may be preferable.

Endoscopic approach (one case)15

The use of fibre optic technology and minimal access surgery has allowed some cases to be treated with endoscopy. The advantages of this more conservative approach are said to include access to a surgical site which would otherwise be difficult to reach via an intra-oral approach, good illumination and magnifica- tion of the surgical area, a smaller scar and decreased risk of damage to the facial nerve15. This technique may not be indicated in all cases.

Conclusion

Ectopic mandibular third molar teeth are uncommon and may not be detected unless symptoms occur.

Whilst some can be removed by an intra-oral approach, both the literature and our own experience have shown that an extra-oral approach to the lower border, ramus or condylar regions of the mandible may be required.

Acknowledgement

We would like to thank Mr Rhodri Williams, Con- sultant Oral and Maxillofacial Surgeon at University Hospitals Birmingham, for allowing us to include Case 3 in this article.

Conflict of interest

Funding: None.

Competing interests: None declared.

Ethical approval: None declared.

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