原文題目(出處)： Removal of ectopic mandibular third molar teeth: literature review and a report of three cases. Oral Surg 2012;5:39-44 原文作者姓名： Ahmed NM, Speculand B
通訊作者學校： Oral and Maxillofacial Surgery, University Hospital Birmingham NHS Trust, Birmingham,UK
報告者姓名(組別)： 萬信佑 intern I 組
報告日期： 101.5.11
內文：
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.
Introduction :
Unerupted impacted mandibular third molar teeth occur in 20–30% of the population, with a higher prevalence in women.
The majority of ectopic mandibular third molars are associated with cystic lesions. Others a lack of space between the second molar and ramus of the mandible, trauma and aberrant eruption
ectopic positions include: condyle, ramus, coronoid process, sigmoid notch and lower border of the angle ofthe mandible.
These teeth are often an incidental finding on a routine radiograph and no treatment is required.
Literature review :
We found 23 cases reported in 21 papers from 1976 to 2010
the mean age for presentation was 44.7years (range 23–70 years).
eight in the condyle
five 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
One bilateral case was described as being in the condyle and ramus.
The common approaches
conventional intra-oral approach(including one endoscopic)
an extra-oral approach(pre-auricular or submandibular)
sagittal split osteotomy.
CASE I
38-year-old female
recurrent pain, bad taste and left-sided facial swelling for which several courses of antibiotics
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.
The tooth was removed surgically under GA via an extra-oral approach (the Risdon neck approach) .
This approach involves incising 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 histological specimen sent was reported as a dentigerous cyst
CASE II
52-year-old female
presented with pain, trismus and a recurrent right-sided facial swelling which failed to resolve following five courses of antibiotics (suspect parotid infection)
Extra-oral examination revealed a discharging sinus at the right angle of mandible
The tooth was removed under GA also via an extra-oral Risdon neck approach.
Dissection through masseter muscle revealed a buccal perforation of the mandibular ramus .
The tooth was removed surgically and the associated cyst was enucleated. An extra-oral drain was placed.
Post OP : she had mild buccal branch weakness which recovered after a few weeks. The pathology was reported as a radicular cyst
CASE III
36-year-old female
mild asthma presented with pain and recurrent intra-oral infection (no antibiotics course)
Extra-oral examination was unremarkable.
The procedure was carried out under GA via an extended lower third molar intra-oral incision bilaterally, extending up the ramus of the mandible.
Both teeth were removed surgically and the associated cysts were enucleated.
Both inferior dental nerves (IDNs) were visualised and protected.
post-op : At the 1-month review the patient had moderate paraesthesia of both IDNs.
The histopathology was reported as dentigerous cyst for both.
Discussion :
Pathology in the mandibular ramus and condyle can lead to serious complications such as condylar resorption, osteolysis and even condylar fracture
An OPT or postero-anterior (PA) mandible radiograph sallow initial assessment but a more detailed investigation such as a CT scan
The anatomic position of the ectopic third molar may irritate the temporalis muscle fibres and cause pain during mastication
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 molar.
The treatment of choice is enucleation and removal of the impacted tooth
result in expansion of bone causing facial asymmetry, resorption of roots of adjacent teeth and loss of bone in the ramus, extending as far as the coronoid process and condyle.
Sagittal split osteotomy (one case)
This is useful where extensive removal of alveolar bone would be required.
This approach allows direct visualisation 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 months.
Intra-oral approach (eight cases)
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 mandible.
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 teeth.
In some cases, removal of the coronoid process may help.
Extra-oral approach (eight cases)
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.
allows good exposure of the surgical site, more control over the surgical plane, less bone removal and a lower chance of pathological fracture.
But a skin scar and a risk of damage to the marginal mandibular branch of the facial nerve.If the ectopic tooth is located below the level of the IDN then an extra-oral approach may be preferable
Endoscopic approach (one case)
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 .Be difficult to reach via an intra-oral approach, good illumination and magnification of the surgical area, a smaller scar and decreased risk of damage to the facial nerve.
This technique may not be indicated in all cases.
Conclusion : an extra-oral approach to the lower border, ramus or condylar regions of the mandible may be required.
題號 題目
1 下列哪一種囊腫最常見於顎骨
(A)Dentigerous cyst
(B)Radicular cyst (C)Odontogenic cyst
(D)Calcified odontogenic cyst 答案(B) 出處：oral & maxillaofacial pathology P.116~121
Radicular cyst > dentigerous cyst > residual cyst > OKC >…
題號 題目
2 下列哪些囊腫經過 enucleation 後復發率最高
(A)Periapical cyst (B)Dentigerous cyst (C)Odotogenic keratocyst (D)Solitary bone cyst
答案(C) 出處：contemporary oral and maxillofacial sugery 5th P.458 Odotogenic cyst was aggressive.
