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European Journal of Radiology 66 (2008) 396–418

Current concepts in maxillofacial imaging

Rudolf Boeddinghaus ∗, Andy Whyte 1

Perth Radiological Clinic, 127 Hamersley Road, Subiaco, Western Australia 6008, Australia

Received 5 November 2007; accepted 7 November 2007

bstract

A review of state-of-the-art maxillofacial imaging is presented. Current imaging techniques include intra-oral radiographs, dental panoramic
omography, multidetector helical computed tomography, cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI).he commonest conditions encountered in clinical radiological practice are reviewed, including maxillofacial deformities, complicated dental
mpactions, maxillofacial trauma, jaw lesions (cysts, neoplasms, fibro-osseous lesions (FOLs) and infections), and temporomandibular jointathology. Pre-operative assessment for dental implant placement is also briefly reviewed.

2007 Elsevier Ireland Ltd. All rights reserved.

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eywords: Maxillofacial imaging; Odontogenic cysts; Odontogenic tumours; T

. Imaging techniques

Intra-oral radiographs, including periapical, bitewing andcclusal projections, are the basic and often the only imagingechnique required for much dental pathology. Usually, thesere performed and reviewed by the general dentist. The radiol-gist should be aware that intra-oral radiographs are performedithout intensifying screens, and therefore have higher spatial

esolution (of the order of 20 line pairs per millimetre (lp/mm))han panoramic radiographs (about 5 lp/mm). This also impliesrelatively high radiation dose for their small size. The higher

patial resolution allows detection of small carious lesions anderiapical lucencies which may not always be detectable withental panoramic tomography.

Dental panoramic tomography is a specialised tomographicechnique used to produce a flat representation of the curvedurfaces of the jaws. It is an excellent and widely performedechnique for providing an overview of the dentition, gener-lised pathology such as periodontitis, and odontogenic andon-odontogenic lesions of the jaws. It also gives a basic assess-
ent of the osseous status of the temporomandibular joints.owever, it is subject to considerable and unpredictable geomet-
ic distortion, and has relatively low spatial resolution compared

∗ Corresponding author. Tel.: +61 8 93804888; fax: +61 8 93804188.E-mail addresses: [email protected]

R. Boeddinghaus), [email protected] (A. Whyte).1 Tel.: +61 8 93804888; fax: +61 8 93804188.

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720-048X/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved.oi:10.1016/j.ejrad.2007.11.019

romandibular joints

ith intra-oral radiographs. Lateral and anteroposterior (AP)ephalograms (also known as cephalometric projections) aretandard extra-oral radiographs performed in a cephalostat usinglm-screen or digital techniques. They are used for orthodonticssessment and are of value in assessing the dental and skeletalelationships of the jaws, as well as asymmetric deformity.

Multidetector row computed tomography (MDCT), using6–64 detector rows, is the current state-of-the-art CT tech-ique, with many applications throughout the body. The multipleetector rows and very thin slice profiles result in the volu-etric acquisition of data, with isotropic voxels (i.e. as thin

n the craniocaudal plane as they are in the transverse andnteroposterior planes), so that data can be presented at equalesolution in any plane, including curved (panoramic) planes.hree-dimensional reconstructions and thick, slab-like multi-lanar reformats (MPRs) can also be derived from this volumeata set. This is the imaging technique of choice in evaluationf most maxillofacial pathology, giving excellent bone detail.hen a “soft-tissue” reconstruction algorithm is used, assess-ent of the maxillofacial soft tissues, including the articular

isc of the temporomandibular joint, is also possible. CT maye impaired by beam-hardening artefact from dental amalgam,nd it results in a relatively high radiation dose.

Cone-beam computed tomography (CBCT) uses a cone-haped X-ray beam (unlike the fan-shaped X-ray beam used
n conventional CT), to acquire projection data via a flat detec-or, during a single 360◦ rotation, from which a volumetric dataet is reconstructed using algorithms similar to those used inonventional CT. It results in a lower radiation dose than conven-
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dx.doi.org/10.1016/j.ejrad.2007.11.019

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Fig. 1. Acquired deformity, with neocondyle formation following a displacedcondylar fracture of the right mandibular condyle. Coronal CT reconstruction(a) shows a “double condyle” appearance; the plane of the oblique fracture isstill apparent (arrow). Volume-rendered three-dimensional CT reconstruction (b)sc

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R. Boeddinghaus, A. Whyte / Europea

ional CT (by one order of magnitude or more) [1], but thereforeuffers from significant image noise, and is not suitable for soft-issue assessment. CBCT is capable of higher spatial resolutionwith isotropic voxels as small as 0.125 mm3) than conventionalT. Scanning time is comparable to that of state-of-the-art con-entional CT (10–40 s). As with conventional CT, the volumeata set can be used to create multiplanar and three-dimensionaleconstructions. CBCT units are generally smaller and cheaperhan conventional CT scanners, and the patient sits upright, sim-lar to the positioning in a dental panoramic tomography unit.hick multiplanar reconstructions can be used to produce lat-ral and frontal cephalometric images (without distortion oragnification) for orthodontic assessment. Some current CBCT

nits are also capable of acquiring panoramic tomograms andephalometric projections directly.

Magnetic resonance imaging (MRI) is the technique of choicen the evaluation of temporomandibular joint pathology. Itsxcellent soft-tissue contrast resolution makes it ideal for theetection of internal derangement of the joint, and it can be usedo show joint effusions, synovitis, erosions and associated bone

arrow oedema. MRI also has a role in assessing the extent ofoft-tissue invasion by maxillofacial tumours. It provides greaterpecificity than CT in distinguishing between odontogenic cystswhich are commoner) and tumours (which are more prone toecurrence).

. Maxillofacial deformity

A full discussion of cranio-maxillofacial deformity is beyondhe scope of this review. The subject is complex and associatedith several syndromes with typical craniofacial deformities.his subject has been reviewed by Caruso et al. [2], whoescribed the role of CT in the diagnosis and presurgical evalu-tion of craniofacial malformations.

Less complex maxillofacial malformations may be acquiredr congenital. Acquired malformations are usually the resultf trauma (Fig. 1) or the sequelae of surgical resection ofumours with no or inadequate primary reconstruction (Fig. 2).ongenital or developmental malformations may be symmetricr asymmetric in nature. The standard method of analy-is of maxillofacial deformity employed by orthodontists orral and maxillofacial surgeons, is lateral and postero-anteriorephalostat radiographs combined with clinical photographs andcclusal analysis. The inter-relationships of the maxilla andandible to the fixed landmarks of the skull base as well as

he overlying soft-tissue silhouette are measured and traced onhe lateral cephalostat. This allows evaluation of the lateralental and skeletal relationship of the teeth and bones of theaxilla and mandible respectively. Based on this analysis, an

rthodontic treatment plan is formulated, occasionally supple-ented by orthognathic surgery when there is significant skeletal

iscrepancy between the jaws. Cone-beam CT combined withtate-of-the-art orthodontic software programmes allows more
ccurate and relatively low dose analysis of symmetric maxillo-acial skeletal and dental discrepancy [3]. Scan data is providedn a CD disc with midline lateral maximum intensity projectionMIP) reconstructions supplemented by 3D volume rendered
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hows a lateral view of the right mandibular ramus, with the deformed, flattenedondyle responsible for facial asymmetry.

econstructions of the maxillofacial region and conventional 2Dxial, coronal and sagittal reformations. The orthodontist thennalyses the data using proprietary software.

The lateral cephalostat is of limited value when the max-llofacial deformity is asymmetric as the abnormal side isuperimposed on the normal side of the face. CT (either CBCTr MDCT) is advisable in these cases for optimal evaluation of
he extent of deformity [4]. The commonest causes of asymmet-ic deformity are under or over-activity of one of the condylarrowth centres in the growing skeleton resulting in hypoplasia

398 R. Boeddinghaus, A. Whyte / European Journal of Radiology 66 (2008) 396–418

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Fig. 3. Panoramic MIP (a) and radial (b) reconstructions from a CT Dentascan oftow

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ig. 2. Sagittal oblique CT reconstruction of the right temporomandibular jointa) shows a prior costochondral graft. Sagittal oblique reconstruction of the leftemporomandibular joint (b) shows severe osteoarthritis.

r hyperplasia of the affected condyle. This results in classi-al patterns of deformity including mandibular asymmetry andometimes tilt of the occlusal plane and secondary deformity ofhe maxilla. When unilateral condylar hypoplasia is suspected,emifacial microsomia requires exclusion and this is normallyiagnosed clinically by concurrent developmental defects ofther first branchial arch structures such as the pinna, externaluditory canal or middle ear cleft.

Isotope bone scanning (Tc pertechnetate) is of value in deter-
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i. whether condylar hypoplasia or hyperplasia is present andwhich side is affected;

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he mandible, showing the inferior alveolar canal (arrows) perforating the rootsf the lower right second molar tooth (47), which is unerupted, and interlockedith the horizontally impacted lower right third molar (48).

i. determining whether condylar growth has ceased and cor-rective orthognathic surgery can be undertaken without riskof relapse. Condylar metabolic activity is compared betweenright and left condyles as well as with a baseline, either theclivus or the L4 vertebral body producing a ratio for eachside, which is then compared with the normal range.

. Complicated dental impactions

The commonest dental impactions involve third molar teeth.eeply impacted mandibular third molar teeth are often inti-ately related to the inferior alveolar canals, which may groove

r perforate the roots, and be displaced and narrowed by them.his may be suspected on dental panoramic tomography, but isore accurately assessed with CT (Fig. 3). Damage to the infe-

ior alveolar nerve during extraction of impacted third molars

R. Boeddinghaus, A. Whyte / European Journal of Radiology 66 (2008) 396–418 399

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Fig. 5. Zygomatic complex fracture. Axial CT image (a) shows a minimallydisplaced fracture of the zygomatic process of the temporal bone (large arrow).Note the normal zygomaticotemporal suture (arrowhead) and the air–fluid levelin the right maxillary antrum (small arrow). A three-dimensional volume ren-dered reconstruction (b, same case) is less sensitive for showing the actualfracture lines, but shows the displacements well. The comminuted orbital floorfracture (large arrow) and the mildly displaced fracture-diastasis of the zygomati-cts

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ig. 4. Radial reconstructions from a CT Dentascan of the maxilla, showingn inverted mesiodens (arrows), and its relationship to the nasopalatine canalarrowhead).

esults in permanent paraesthesia of the lower lip. Maxillaryanines are also frequently impacted, as are supernumeraryeeth, the commonest of which is the mesiodens, situated imme-iately adjacent to the midline nasopalatine canal, and frequentlynverted (Fig. 4).

. Maxillofacial trauma

Although plain radiographs are useful in the initial evaluationf suspected facial fractures, as is dental panoramic tomogra-hy for suspected mandibular fractures, CT is an excellent toolor detecting radiographically occult fractures, or fractures sus-ected on the basis of secondary signs, such as a sinus air–fluidevel, and for defining the displacements of fractures (Fig. 5)rior to surgical reduction and fixation.

Fractures of the nasal bone are the commonest fractures inhe maxillofacial region, and are generally adequately assessedlinically or by plain radiographs, taking care to recognise nor-al structures which can simulate fracture lines (Fig. 6). More

xtensive naso-orbito-ethmoidal fractures require CT for opti-al evaluation, particularly of the attachment of the medial

anthal ligament [5].Central midfacial fractures include naso-orbito-ethmoidal

ractures, isolated maxillary fractures and the Le Fort type frac-ures. The classic Le Fort fractures (type I, a “floating palate”;ype II a pyramidal fracture; and type III, complete craniofacialysjunction) are uncommonly seen in pure form. Le Fort typeractures are always bilateral, except when there is a paramedianracture of the palate. However, they are frequently asymmet-ic, for example with a Le Fort I pattern on one side and a Leort II pattern on the other. The fracture lines extend through

he pterygoid plates in all three types (Fig. 7).Lateral midfacial fractures include the common zygomatic

omplex fractures (see Fig. 5) and orbital blow-out fractures,s well as the less common isolated zygomatic arch fractures,

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ofrontal suture (arrowhead) are visible, but the minimally displaced fracture ofhe zygomatic arch is not. Small arrow shows the normal zygomaticotemporaluture.

ygomaticomaxillary fractures and zygomaticomandibular frac-
ures. Zygomatic complex fractures are the second commonestacial fractures (after nasal fractures), and are also known as tri-alar or tripod fractures, because there are three fracture lines,
nvolving the three “legs” of the malar eminence. The first of

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Fig. 8. Orbital blow-out fracture. Coronal T1W MRI shows herniation of a smallamount of extraconal fat into a defect in the lamina papyracea (arrow), withtdo

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ures which can simulate fractures are the nasofrontal suture (large arrowhead),he nasomaxillary suture (small arrows) and the grooves for the nasociliaryerves (small arrowheads).

hese involves the lateral orbital wall (usually diastasis of theygomaticofrontal and zygomaticosphenoid sutures); the sec-nd involves the orbital floor and zygomaticomaxillary suture,lose to the infra-orbital canal and foramen (accounting for theigh frequency of infra-orbital nerve damage complicating these
ractures); and the third is in the zyogmatic arch, usually inhe temporal bone, posterior to the zygomaticotemporal suture.ccasionally, the zygomatic arch is intact.
ig. 7. Line diagrams (a, frontal, and b, lateral) to show the three classic Le Fortractures. Note that all Le Fort fractures involve the pterygoid plates.

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ethering of the medial margin of the medial rectus. The patient presented withiplopia on leftward gaze following a remote left orbital injury. (Case courtesyf Dr. Michael Fallon, Perth Radiolgical Clinic, Western Australia.)

Orbital blow-out fractures result from a blunt blow to therbit with an object (frequently a ball or a fist) which is largerhan the orbital aperture: pressure is transmitted through thelobe and other intra-orbital structures, to the weakest pointsn the orbital walls, which are the lamina papyracea (medialrbital wall) and the orbital floor in the region of the infra-orbitalroove and canal. Important complications include damageo the infra-orbital nerve, with resultant loss of cheek sensa-ion, enophthalmos (a late manifestation following resolutionf oedema and haemorrhage) and entrapment or tethering ofhe extra-ocular muscles, resulting in diplopia (Fig. 8). Old,mall blow-out fractures are frequent incidental findings on CTerformed for paranasal sinus disease.

Frontal sinus fractures usually result from a direct blow,r are part of a larger calvarial fracture. The outer table isnvolved alone in about two thirds; in one third, the innerable is also involved (i.e. there is intracranial extension ofhe fracture line). The superomedial orbital rim is frequentlynvolved.

Mandibular fractures are common. They may be subtler inapparent on panoramic tomography, and full evaluationequires views at a right angle to the curved panoramic plane.his includes the mandibular condyle, which is not alwayslearly visualised, and CT may be necessary to demonstratendisplaced fractures (Fig. 9). Condylar fractures are frequentlyilateral or associated with a contralateral body fracture. Frac-ures of the condylar neck or head can result in a characteristicost-traumatic deformity, as the condyle is displaced antero-edially by the pull of the attached lateral pterygoid muscle

Fig. 10).

. Cysts of the mandible and maxilla

Most cystic lesions occurring in the jaws are related toeeth (odontogenic); some are non-odontogenic, and others


Fig. 9. Intra-articular condylar fracture of the left mandibular condyle. AxialCT image (a) and coronal reconstruction (b) show a mildly displaced obliquefa

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Fig. 10. Displaced fracture of the right mandibular condyle. Axial (a) and coro-nfc

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(luloss or removal of the tooth (Fig. 11). The radicular cyst is char-

racture (arrows) which extends to involve the lateral aspect of the condylarrticular surface. This was not definitely visible on panoramic tomography.

re not true cysts, but are conveniently considered withinhis category because of cyst-like radiographic appearances.ome neoplasms, notably ameloblastoma, can appear cystic,nd must be considered in the differential diagnosis of ayst. The entity traditionally known as an odontogenic ker-tocyst (OKC) has recently been reclassified as a neoplasm,he keratocystic odontogenic tumour (KCOT), to better reflect
ts potentially locally destructive behaviour and propensityor recurrence [6], but it will still be considered in this sec-ion.
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al oblique (b) CT bone-algorithm reconstructions show an oblique condylarracture (arrows), with typical anteromedial and inferior displacement of theondyle due to the pull of the lateral pterygoid muscle.

.1. Radicular (periapical or apical periodontal) cyst

Of the odontogenic cysts, the commonest is the radicular cystalso known as a periapical cyst), which is a post-inflammatoryesion related to the apex of a non-vital tooth root, and the resid-al cyst, which is the same entity remaining in the jaw following

cterised by its position adjacent to the apex of a carious oreavily restored non-vital tooth, often a maxillary incisor oranine. It can be difficult to distinguish from a periapical granu-

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Fig. 12. Dentigerous cyst (white arrows) related to an unerupted mandibu-lm(

rtprtoaomless likely to displace or resorb teeth than the dentigerous cyst.However, it may become large, and recurrence is relatively com-mon following removal. Multiple KCOTs occur in the basal cell

ig. 11. Radicular cyst. Cropped panoramic tomogram shows a well-definedyst (arrows) related to the upper right central incisor. The root canal of thisooth is widened (arrowhead).

oma, but is generally larger (often greater than 20 mm), with aounder contour, and a well-defined border. A residual cyst, theyst remaining after extraction of the associated tooth, has a non-pecific appearance, but its nature can usually be appreciatedith the relevant history and prior radiographs.

.2. Dentigerous (follicular) cyst

The second commonest odontogenic cyst is the dentigerousfollicular) cyst, characterised by its pericoronal position, aroundhe crown of an unerupted tooth. The commonest teeth affectedre the third molars (Fig. 12) and the maxillary canines, butentigerous cysts may also be associated with the crown ofn unerupted supernumerary tooth, most commonly a mesio-ens. It can be difficult to distinguish a dentigerous cyst fromhyperplastic follicle; the follicular space should be less than

–3 mm, and a hyperplastic follicle should not displace the toothr cause cortical expansion. The pericoronal (dentigerous) posi-ion is not specific, and the keratocystic odontogenic tumour andther benign tumours may be pericoronal in position.

.3. Keratocystic odontogenic tumour (KCOT, formerlyKC)

The keratocystic odontogenic tumour (formerly odontogeniceratocyst) arises from the dental lamina, and has a thin lining of
eratinized epithelium, and can have thick cheesy contents dueo desquamated keratinizing squamous cells. These contents canccasionally increase the radiographic attenuation of the lesiont CT (Fig. 13), but this is not appreciable on panoramic tomog-
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ar third molar, shown on a panoramic MIP reconstruction from a CT of theandible. Note the mild inferior displacement of the inferior alveolar canal

black arrowheads) by the cyst.

aphy. The KCOT has a wide age range but is commonest inhe second and third decades. It most commonly occurs in theosterior mandible (90% posterior to the canines, 50% in theamus). Like all odontogenic lesions, its epicentre is superior tohe inferior alveolar canal. In 40% of cases it has a dentiger-us relationship with an unerupted tooth, and should thereforelways be considered in the differential diagnosis of a dentiger-us cyst. It usually has a well-defined corticated margin, whichay be scalloped. It causes relatively slight expansion, and is

ig. 13. Odontogenic keratocyst (KCOT) in the maxilla. Axial CT section showsell-defined cyst centred in posterior right maxilla (white arrowheads), with

morphous hyperattenuating central contents (black arrow).


Fig. 14. Gorlin-Goltz syndrome. Cropped panoramic tomogram showing twokeratocystic odontogenic tumours (arrows) in the right mandibular body. A kera-tmv

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ocystic odontogenic tumour has been previously resected from the left posteriorandible (arrowhead). Dense falx calcification was visible on a frontal scout

iew for a CT scan (not shown).

evus syndrome (Gorlin-Goltz syndrome), which is also char-cterised by vertebral and rib anomalies and heavy calcificationf the falx cerebri (Fig. 14).

.4. Uncommon odontogenic cysts

Lateral peridontal cysts are small, and occur lateral to theooth root, often in the mandibular canine and premolar region.he buccal bifurcation cyst (also known as mandibular infecteduccal cyst or paradental cyst) is centred buccal to the root bifur-ation of the first or second mandibular molar, often presentingith delayed eruption. The buccal position may be inferred from

ilting of the tooth, such that the occlusal surface of the toothecomes visible, and is confirmed with occlusal films or CTFig. 15). The calcifying odontogenic cyst is uncommon, occur-ing anteriorly in either jaw (most commonly in the maxillaryanine region), and internal calcification may be apparent.

.5. Non-odontogenic cysts

Non-odontogenic cysts specific to the jaws include the
asopalatine duct cyst in the maxillary midline, which has a char-cteristic heart shape, and may have scalloped margins (Fig. 16).
The simple bone cyst, which does not have an epithelial lin-ng, and is therefore not considered a true cyst, can occur in the

ig. 15. Mandibular infected buccal cyst (buccal bifurcation cyst). Coronaleformatted CT image shows a cyst (arrow) buccal to the roots of the loweright second molar tooth, resulting in characteristic tilting of this tooth.

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ig. 16. Nasopalatine duct cyst (arrow) on an axial CT image. Note the scal-oped margins and the position palatal to the maxillary incisors. This was ansymptomatic incidental finding on a CT performed for suspected sinusitis.

andible, where it is sometimes known as a traumatic bone cystthough no connection to trauma has been shown). As elsewheren the skeleton, it occurs in the first two decades of life and isommoner in males. Its superior margin often scallops betweenhe roots of the teeth, but it usually has no effect on the teethhemselves.

The so-called Stafne cyst, better termed a lingual mandibularone depression, is a focal concavity in the lingual aspect of theandible, classically in the submandibular fossa, close to the

nferior margin of the mandible, and usually below the inferiorlveolar canal. This is also described further mesially, in theremolar region, and rarely as far distal as the medial surfacef the ramus. Although this may have the appearance of a cystadiographically, the nature of this incidental finding is clear onT, which also shows that the defect is not necessarily filledith salivary gland tissue (Fig. 17).

. Odontogenic tumours

Odontogenic tumours comprise 9% of all tumours of the oralavity. These arise from ectoderm, mesenchyme or a combina-ion of these two tissues (ectomesenchyme) that are involved inhe formation of the tooth germ. The recent revised histopatho-ogical classification of odontogenic tumours by the Worldealth Organization (WHO) [6] classified benign odontogenic

umours into four categories according to the tissue of origin.

Category 1: Tumours arising from odontogenic epithelium,
e.g. ameloblastoma, keratocystic odontogenic tumour (previ-ously known as an odontogenic keratocyst or OKC), calcifyingepithelial odontogenic tumour and adenomatoid odontogenictumour.

404 R. Boeddinghaus, A. Whyte / European Jou

Fig. 17. Stafne cyst (lingual mandibular bone depression). Panoramic recon-struction (a) from a CT shows the well-defined lucent lesion (arrows) in a typicalposition in the posterior mandible, inferior to the inferior alveolar canal (arrow-hasl

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ead). Rarely, these lesions occur superior to the inferior alveolar canal, ornteriorly, in the premolar or canine region. Axial CT with soft-tissue recon-truction algorithm (b) shows that the lesion is not a cyst, but a depression in theingual aspect of the mandible, containing fat (arrow).

Category 2: Tumours arising from odontogenic epitheliumand mesenchyme with/without hard tissue formation, e.g.ameloblastoma variants (such as an ameloblastic fibroma),odontoma, calcifying cystic odontogenic tumour (previouslyknown as a calcifying odontogenic cyst).Category 3: Tumours arising from mesenchyme and/orectomesenchyme with/without odontogenic epithelium, e.g.odontogenic fibroma, odontogenic myxoma and cementoblas-toma.Category 4: Bone-related lesions, e.g. ossifying fibroma,fibrous dysplasia (FD), osseous dysplasia, central giant cell
lesion, cherubism, aneurysmal bone cyst and simple bone cyst.
Malignant tumours are generally considered as the malignantounterpart of these benign categories and are very uncom-

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on. Neoplastic lesions and cysts that arise embryologicallyrom epithelium (ectoderm) appear as pericoronal lesions beinglosely related to the crown of an unerupted tooth (Category 1).n contrast, Category 3 tumours arising from ectomesenchymere related to the tooth root apex (periapical lesions).

.1. Imaging of odontogenic tumours

Most odontogenic tumours are cysts which are discoveredn intra-oral radiographs or dental panoramic tomography.ntra-oral radiographs have extremely high spatial resolution,ptimally demonstrating the relationship of a lesion to the toothrown or apex but due to their small size can only show smallesions less than 20 mm in size. Dental panoramic tomographyiven a very good overview of medium to large-sized lesions andultiple lesions and bone-related lesions can also be demon-

trated.Multidetector or cone-beam CT has excellent spatial and high

ontrast resolution. Application of ‘Dentascan’ software allowshe production of panoramic, radial and axial 2D reconstruc-ions. Additional software allows the production of maximumntensity projections and 3D volume rendered images. MDCTas the advantage over CBCT of demonstrating soft-tissue detailnd allowing accurate measurement of attenuation. Soft-tissueisualisation allows detection of dense keratin debris in kerato-ystic odontogenic tumours (see Fig. 13) and allows distinctionetween cysts and solid tumours. The extent of a lesion’s rela-ionship to teeth, root resorption, internal structure, corticalxpansion and erosion, the boundary of a lesion and the presencef multiple lesions can all be evaluated. Lesions are commonlylassified according to the type of matrix into: radiolucent, radio-paque or mixed radiolucent–radio-opaque.

MRI can add specificity in diagnosis allowing accurateistinction of solid and cystic lesions on the basis of signal char-cteristics and enhancement patterns. Application of specificriteria for diagnosis allows accurate distinction between the ker-tocystic odontogenic tumour and other odontogenic lesions [7].he keratin-rich debris in a KCOT shows characteristic centralrop in signal on T2-weighted images.

.2. Radiolucent lesions

Well-defined radiolucent lesions are the commonest radio-raphic appearance of benign odontogenic cysts and tumours.hey are sub-classified as unilocular, lobulated or multilocu-

ar depending on their margin and peripheral internal structure.sually well defined with a corticated margin, this may be lost

f secondary infection occurs.

.3. Ameloblastoma

Ameloblastomas account for 11% of all tumours in the
axillofacial region and are the most common and clinically
ignificant odontogenic tumours. They arise from odontogenicpithelium, cyst formation is common and there are several his-ological patterns which cannot be differentiated radiologically.

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Fig. 18. Maxillary ameloblastoma. Initial imaging for a cheek lump was per-formed with ultrasound (a), which showed a complex mass (arrows) breaching


Ameloblastomas predominate in the molar region andscending ramus of the mandible. They may be unilocularFig. 18), multilobular or multilocular (Fig. 19). Unilocularesions in young people have the best prognosis but solid lesionshow high recurrence rates (50–90%). Differentiation from aCOT and other odontogenic lesions is very difficult by plain

adiography and CT, and usually a differential diagnosis is given.he ameloblastoma usually replaces a tooth (especially whenultilocular) and produces more marked buccolingual expan-

ion and root resorption than a KCOT.MRI features of ameloblastomas provide a more specific

iagnosis: multilocularity, mixed solid and cystic components,ural and septal enhancement, irregular thickened walls and

apillary projections [7] (see Fig. 18).

.4. Radio-opaque lesions

There is a wide differential diagnosis of sclerotic lesions inhe maxilla and mandible. A representative radio-opaque odon-ogenic tumour is the odontome.

.5. Odontome (compound and complex)

The odontome is characterised by the proliferation of hardental tissues and can be classified into two types:

. Compound—coalescent mass of multiple, deformed tooth-like structures (denticles) and is most common in the anteriormaxilla.

. Complex—is found in older individuals and is most com-mon in the mandibular molar and premolar region. It appearsradiographically as a conglomerate mass of densely calcifiedand ossified tissues.

.6. Mixed radiolucent and radio-opaque

Lesions of this category include fibro-osseous lesionsFOLs), inflammatory processes (e.g. osteomyelitis, osteonecro-is) and less commonly, odontogenic tumours. Typical tumoursn this category include the adenomatoid odontogenic tumournd the calcifying epithelial odontogenic tumour. They will note discussed further.

. Non-odontogenic neoplasms of the jaws

A wide variety of non-odontogenic neoplasms can involvehe jaws and maxillofacial region. Invasion by squamous cellarcionoma is common (Fig. 20). Lymphoma is relatively com-on in the head and neck region (Fig. 21). Discussion of the

arious non-odontogenic tumours is beyond the scope of thiseview.

. Maxillofacial infection

Caries (decay of the tooth crown), periodontitis (infectionf the supporting structures of the tooth root) or pericoroni-is (infection of the gum flap or operculum around a partially

the antral cortex. Coronal bone-algorithm CT reconstruction (b) shows a well-defined opacity in the inferior aspect of the left antrum. This could be mistakenfor a retention cyst, but thinning and focal defects (arrowheads) in the antral wallare evident. Coronal gadolinium-enhanced T1W fat-saturated MRI (c) shows acomplex lesion with nodular mural enhancement (arrow).


Fig. 19. Recurrent mandibular ameloblastoma. This patient presented with amass in the right temporal fossa after resection of ameloblastoma in the rightmandibular ramus. Axial bone-algorithm CT (a) demonstrates expansion of theright mandibular body by a multilocular lucent lesion. Coronal soft-tissue algo-rithm CT reconstruction (b) shows a large soft-tissue cystic component of tumourec

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Fig. 20. Stage T4 squamous cell carcinoma involving the right side of themandible. Bone-algorithm axial CT (a) shows extensive poorly defined lyticdestruction of the right mandibular body. Soft-tissue algorithm post-contrastae

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xtending deep to the zygomatic arch into the right temporal fossa (arrow). Theostochondral graft reconstruction of the ramus (arrowheads) is visible.

rupted tooth, most commonly a third molar) are the commonauses of pyogenic infection in the oral cavity. Depending on theacterial load and host immunity, this may lead to the formationf pus and acute maxillofacial infection.

.1. Acute infection

The infection and pus may remain localised and drainntra-orally or extra-orally (i.e. drainage occurring either spon-aneously or surgically). Infection may also spread either

xial CT demonstrates an enhancing mass (arrows) involving the mandible andxtending into the buccal soft tissues.

aematogenously, via the lymphatics or directly, via the deepascial spaces.

i. Haematogenous: There is an extensive interconnectingvascular network in the maxillofacial region with communi-cation between the extra- and intra-cranial vessels. Veins act
as valveless, low velocity conduits which may lead to cav-ernous sinus thrombophlebitis, orbital cellulitis or a cerebralabscess.

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ig. 21. Lymphoma: contrast-enhanced axial CT image shows soft-tissueasses (arrows) in the medial aspect of the right masticator space. There was

lso expansion of the right inferior alveolar canal (not shown).

ii. Lymphatic: There is a complex and rich lymphatic systemin the maxillofacial region and infection may cause eitherlymphadenitis or a lymph node abscess.

ii. Direct extension: This is the most common cause. Spread isby pre-determined routes dependant on local anatomy andfascial attachments. The deep fascial spaces of the maxillo-facial region communicate freely. A single space or multiplespaces are involved with the same frequency. The buccalspace is the most commonly infected space when a singlesite is involved and the submandibular space, when mul-tiple sites are infected. The predilection for these spaces isbecause of the proximity of the mandibular molars, the teethmost commonly affected by periapical or pericoronal sepsis.

Most acute maxillofacial infections are minor, localised andespond rapidly to correct medical and surgical management.owever, if treatment is delayed and there is significant bacte-

ial load or virulence, then infection may spread along fasciallanes to become severe and life-threatening [8], especiallyhen host resistance is impaired. Significant morbidity includes

irway obstruction, retropharyngeal abscess, orbital cellulitis,ecrotising fasciitis, carotid sheath suppuration, mediastinitisnd pulmonary, pleural or pericardial sepsis.

Acute maxillofacial infection is odontogenic in origin in5% of cases and non-odontogenic in 25%. Odontogenic infec-ions are polymicrobial in nature with anaerobes more commonhan aerobes (reflecting the oral flora) and streptococci are pre-minent. In children, infection of the palatine (faucial) tonsil ishe most common cause of maxillofacial infection [9]. Strepto-
occi are the most common causative organisms and the majoromplication is peritonsillar abscess (quinsy). Infection maypread to the lateral pharyngeal or parapharyngeal spaces andubsequently to the retropharyngeal space.
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nal of Radiology 66 (2008) 396–418 407

.2. Imaging of acute maxillofacial infection

Intra-oral or dental panoramic tomograms provide excellentvaluation of the dentition, periodontium and supporting alveo-ar bone and should exclude an odontogenic cause for infectionn most cases. However, this does depend on radiographic qual-ty and correct evaluation, supplemented by adequate clinicaletails (Fig. 22).

Cross-sectional imaging (optimally post-contrast MDCT)s required for optimal evaluation of suspected serious oromplicated maxillofacial infection. Information is providedoncerning:

(a) Source of infection: CT supplements standard radiographicexamination. Application of applied anatomy may deter-mine the likely source of sepsis when this is not apparentclinically or radiographically. Sublingual sepsis (abovemylohyoid) is caused by sepsis related to tooth roots/apicesthat lie above the mylohyoid line, i.e. incisors, canines,premolars and first molars.

The apices of third (and usually second) molars lie belowthe mylohyoid line. Periapical infection therefore passesdirectly to the submandibular space. The submandibu-lar and sublingual spaces communicate via the posterior,unattached margin of mylohyoid.

b) Extent of disease: Understanding of fascial boundaries andcommon patterns of spread of maxillofacial infection arenecessary to correctly interpret cross-sectional imaging.From the commonly affected sublingual, submandibular andbuccal spaces infection may spread postero-superiorly to themasticator space and from there to other critical, deep fascialspaces.

(c) Presence of an abscess: If pus is present it should besurgically drained unless spontaneous drainage occurs.Cross-sectional imaging demonstrates a defined fluidcollection with an enhancing margin. This must be dis-tinguished from a phlegmon (Fig. 23), which is managedmedically.

d) Complications: Ludwig’s angina is a diffuse infection ofthe submandibular spaces and the midline submental spacewithout large pockets of pus. Seventy percent of cases resultfrom odontogenic infection. Cellulitis results in rapid airwaycompromise and is a medical and surgical emergency. Vas-cular complications and osteomyelitis significantly affectmanagement.

.3. Osteomyelitis

In the maxillofacial region this is defined as an inflamma-ory process that involves the marrow and cortex of the maxilland mandible. Osteomyelitis affects the mandible much moreommonly than the maxilla.

Acute osteomyelitis lasts up to 1 month. Subacute osteomyeli-
is refers to a transitional stage of osteomyelitis including thehird and fourth weeks within the initial one month of acutenfection. This may heal with appropriate treatment or progresso chronic osteomyelitis, defined as osteomyelitis persisting


Fig. 22. Periapical sepsis presenting with a fistula. Cropped panoramic tomogram (a) shows irregular periapical lucency (arrowheads) associated with the heavilyrestored lower right first molar tooth, and very subtle periosteal new bone formation (arrow). Panoramic reconstruction from a CT Dentascan (b) shows similarfi ccal ca m the

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ndings. Radial reconstructions from a CT Dentascan (c) show a defect in the bulgorithm CT reconstruction (d) demonstrates the fistula (arrows) extending fro

eyond one month. If preceded by an acute episode it is knowns secondary chronic osteomyelitis. Primary chronic osteomyeli-is is an insidious disease not preceded by an acute phase. It issually confined to a hemimandible and includes entities such as
iffuse sclerosing osteomyelitis, chronic osteomyelitis with pro-iferative periostitis (Garre’s osteomyelitis) and non-suppurativesteomyelitis. Rarely, primary chronic osteomyelitis may be aanifestation of systemic disease including chronic recurrent
cmoS

ortex (arrow) and extensive periosteal new bone formation. Coronal soft-tissuebuccal mandibular defect to the skin.

ultifocal osteomyelitis (CRMO) and synovitis, acne, pustulo-is, hyperostosis and osteitis (SAPHO).

Acute osteomyelitis of the jaws usually results from peri-pical infection at the apex of a tooth rendered non-vital by
arious involvement of the pulp, most commonly a mandibularolar. Non-odontogenic causes are uncommon; haematogenous
steomyelitis most commonly affects the maxilla in children.econdary chronic osteomyelitis results from persistence of


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ig. 23. Periapical sepsis and osteomyelitis. Axial CT (a) shows a small periapiT image further inferiorly (b) shows breach of the cortex and well-defined pesmall phlegmon straddling the thickened platysma muscle (arrowhead), lymp

acteria in necrotic bone or within tooth fragments despite treat-ent.

.4. Imaging of acute osteomyelitis

The acute inflammatory infiltrate of osteomyelitis results inysis of cancellous bone by osteoclasts. Bone density has to
e reduced by 30–50% to be visible on plain radiography andhis usually takes 2–3 weeks. Computed tomography (either
DCT or CBCT) depicts the osteopaenia and better demon-trates cortical lysis (including the inferior alveolar canal and

cima

ency (arrow) related to the root of the lower right second molar tooth. An axialal new bone formation (arrowheads). Axial soft-tissue algorithm CT (c) showsitis (thick arrow) and mild submandibular sialadenitis (thin arrow).

ental foramen), sequestra and periosteal new bone formation.his periosteal reaction most commonly affects the buccal platef the mandibular angle or body. Both CT and MRI show adja-ent soft-tissue inflammation especially within the masticatornd submandibular spaces. MRI shows soft-tissue involvementn 12% of cases, most commonly in masseter. Multiple studiesave demonstrated the high sensitivity of MRI in detecting can-
ellous marrow abnormality in acute osteomyelitis. This resultsn reduced T1 signal, increased T2 signal and contrast enhance-
ent of bone and the adjacent inflamed soft tissues. In contrast,bnormalities of cortical bone (e.g. sequestra) are more clearly

4 n Journal of Radiology 66 (2008) 396–418

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hown by CT. Scintigraphy is highly sensitive (up to 100%) inhe detection of acute osteomyelitis but requires anatomic cor-elation. Technetium-labelled compounds depict bone turnovernd labelled white cell scans confirm this is due to infection.

.5. Imaging of chronic osteomyelitis

Plain radiographs, and more accurately CT, demonstrateedullary sclerosis, periosteal reaction and sequestration for-ation. In secondary chronic osteomyelitis, sequestra occur

ig. 24. Osteoradionecrosis: bone-algorithm (a) and soft-tissue algorithm (b)xial CT images of the mandible in a patient with a history of prior segmen-al resection and radiotherapy for squamous cell carcinoma which involved the

andible. Bone sclerosis (arrowheads), a large lucency and a small sequestrumlong arrow) are demonstrated, as is significant soft-tissue swelling in the sub-andibular space (short arrows). A miniplate and surgical clips are also visible.

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ig. 25. Fibrous dysplasia: cropped orthopantomogram shows a poorly definedesion centred in the posterior body and angle of the right side of the mandible.ote the superior displacement of the inferior alveolar canal (arrows).

n approximately 90% of cases (as depicted by CT) and most
ommonly on the buccal aspect. Periosteal new bone apposi-ion results in cortical thickening and mandibular enlargement,his is more marked in young patients. Swelling of the adja-
ig. 26. Fibrous dysplasia: axial CT of the skull base showing ground-glasspacification and expansion in the left sphenoid bone (between arrowheads),urrounding and mildly narrowing the left Vidian canal (white arrows). A secondmall focus of fibrous dysplasia was also present in the right mandibular condyleblack arrow) and extending into the condylar neck, and this was thereforeolyostotic disease.

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rbtbe more advanced and extensive than is visible on radiographs.In addition to cortical fragmentation and adjacent soft-tissueswelling, MRI shows diffuse marrow signal alteration withintense enhancement following contrast.


ent masseter and medial pterygoid muscles is common. Postadolinium-enhanced T1-weighted MRI distinguishes seques-

ra from normal cortical bone and demonstrates periostealnflammation, important in planning decortication surgery.

In secondary chronic osteomyelitis, sclerosis is com-only mixed with lysis and foci of mixed density giving a

eterogeneous appearance. Primary chronic osteomyelitis isharacterised by more extensive and diffuse sclerosis sometimesccompanied by expansion. Scintigraphy can be used to monitorisease activity.

.6. Osteonecrosis

Osteoradionecrosis (ORN) is an uncommon complicationf radiation therapy of head and neck tumours, the reportedncidence varies from 0 to 37.5%. If radiation induced mucosi-is persists after a few weeks following treatment, soft-tissuelceration, bone exposure and eventually bone necrosis occurecondary to impaired vascular and lymphatic flow because ofndothelial damage and fibrosis. Because irradiated tissue has aeduced capacity for repair, local trauma is associated with theevelopment of ORN with an initial peak at 3 months followingompletion of radiotherapy and a second, delayed peak from 2o 5 years. The mandible and particularly the buccal cortex of the
ody, are vulnerable to ORN because radiation-induced fibro-is occludes the inferior alveolar artery. Vitality of bone thenepends on transcortical vascularisation by the periosteum anduscular insertions.
ig. 27. Cemento-ossifying fibroma. Cropped panoramic tomogram showing aell-defined ovoid mixed radiolucent and radio-opaque lesion (arrows) related

o the roots of the lower right first and second molar teeth. Note the apicalesorption of the distal root of the 47 tooth (arrowhead).

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nal of Radiology 66 (2008) 396–418 411

Typical imaging appearances of established ORN on plainadiography and CT are mixed sclerosis and lysis, sequestra,one fragmentation, pathological fracture, gas bubbles and soft-issue swelling [10] (Fig. 24). CT shows radiological changes to

ig. 28. Compound odontome. Cropped panoramic tomogram (a) shows a well-efined sclerotic lesion preventing the eruption of the upper right third molarooth (18), the crown of which is directed distally. There is a thin radiolucent

argin around this lesion (arrows), and there is very dense material withint, consistent with enamel. Axial CT (b) confirms the presence of denticlestooth-like structures) (arrows), pathognomonic of compound odontome.

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Increasing therapeutic use of bisphosphonates to decreaseone turnover by inhibiting osteoclast activity is associatedith osteonecrosis of the jaws. These drugs have a role in the

reatment of osteoporosis, Paget’s disease, pain from osseous
etastases and malignancy-related hypercalcaemia. Patientsith this condition present with non-healing extraction sock-
ts and painful bone exposure. The most common findings onental panoramic tomography and CT scans are osseous sclero-

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ig. 29. MRI of non-reducing anterolateral disc displacement and associated erosat-saturated image (a) shows anteriorly displaced mildly deformed disc (betweenompartment synovitis (small white arrows), as well as condylar marrow oedema (blsubtle superior condylar cortical erosion (arrow). Coronal oblique PDW image (c)2W image in the open-mouth position (d) shows that the disc (between arrowheads) r


is commonly affecting the alveolar margin, thickening of theamina dura and poor-healing or non-healing extraction sockets11].

. Fibro-osseous lesions of the jaws

The term “fibro-osseous lesion” is applied to bone dys-lasias and benign bone neoplasms characterised by replacement

ive arthropathy in the right temporomandibular joint. Sagittal oblique T2Warrowheads), superior compartment effusion (large white arrow) and inferiorack arrow). Sagittal oblique PDW image (b) shows similar findings, as well asshows the lateral component of the disc displacement (arrow). Sagittal-obliqueemains displaced. There is only mild restriction of anterior condylar translation.

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f normal bone by a fibrous stroma within which vary-ng amounts of woven bone and cementum-like material areound [12]. This term encompasses three main entities: (1)brous dysplasia (which affects extra-gnathic sites as wells the jaws, and is therefore familiar to general radiolo-ists), (2) cemento-osseous dysplasias (COD) (which includeseriapical cemental dysplasia (PCD), florid COD and focalOD); and (3) cemento-ossifying fibroma (COF), a benignone neoplasm which encompasses the previously separate
ntities of ossifying fibroma and cementifying fibroma, nowonsidered to be parts of the spectrum of a single dis-ase.
ig. 30. CT of reducing anterior disc displacement with hypermobility. (a) Sagit-al oblique soft-tissue reconstruction shows marked anterior displacement ofhe disc (between arrowheads). (b) With mouth opening, the disc is recapturedarrowheads) and there is evidence of hypermobility, with excessive anteriorranslation of the condyle, which lies anterior to the summit of the articularminence.

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nal of Radiology 66 (2008) 396–418 413

Fibrous dysplasia (FD) may be monostotic (about 70%) orolyostotic. Rarely, almost exclusively in girls, the polyostoticorm may be accompanied by multiple smoothly marginatedafe-au-lait spots and endocrine hyperfunction (classicallyausing precocious puberty), when it is known as the McCune-lbright syndrome. FD of the maxillofacial region is usuallynifocal (i.e. monostotic), although frequently affecting morehan one adjacent bone within the facial skeleton, extendingn a flowing manner across sutures, but not usually crossinghe midline. Radiographically, lesions vary from radiolucent to
adio-opaque, frequently with a ground-glass texture, dependingn the degree of mineralisation. The margins of the lesion arerequently ill defined in the jaws (although usually well defined
ig. 31. CT of internal disc derangement and associated arthropathy of the tem-oromandibular joint. Sagittal oblique soft-tissue algorithm reconstruction (a)hows marked anterior displacement of the disc (between arrowheads), a largeuperior compartment effusion (large arrow) and evidence of inferior compart-ent synovitis (small arrow). Sagittal oblique bone-algorithm reconstruction indifferent patient (b) shows a small superior condylar cortical erosion (arrow).

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Internal disc derangement (IDD) is common, and may beseen in asymptomatic temporomandibular joints. The disc is usu-ally displaced anteriorly or anterolaterally, and less frequently


lsewhere in the skeleton), and this feature is helpful in distin-uishing FD from other radio-opaque lesions. Expansion occurs,sually fusiform in the mandible, and more complex in the max-lla, reflecting the more complex anatomy of the latter; in bothases the underlying morphology of the bone is largely pre-erved, and this is useful to distinguish FD from a neoplasmuch as COF. Because FD has no dental relationship, it is notonfined to the alveolar processes; and may superiorly displacehe inferior alveolar canal [13] (Fig. 25). CT is useful to assesshe precise extent of the lesion in the complex facial skeleton,specially when there is orbital involvement, or involvement ofhe neurovascular foramina of the skull base (Fig. 26).

Periapical cemental dysplasia is the commonest subtype ofemento-osseous dysplasia. Well-defined lesions typically occurn a periapical relationship to several anterior mandibular teeth,sually in women (90%), especially Asian and black women,ver the age of 30. The lesions are asymptomatic, being discov-red incidentally on radiographs, and the related teeth are vital.n the early stages, the lesions are radiolucent. With abnormalone and cementum formation within the fibrous tissue, centraladio-opacity appears, and mature lesions are almost completelyadio-opaque, although a thin radiolucent margin is usually vis-ble: the latter is helpful in distinguishing the lesion from annostosis (also known in the jaws as idiopathic osteosclerosisIOS)). PCD usually affects two or more anterior mandibulareeth. When a single site is involved, the lesion is sometimesnown as focal COD. Florid COD is probably the widespreadorm of PCD, occurring in the same demographic population,ut usually affecting three or more quadrants in both jaws. Bonexpansion may occur, and the lesions may present with pain,lthough frequently asymptomatic. Bone cysts may develop, andhere is a propensity for osteomyelitis to develop in the poorlyascularised lesions.

Although cemento-ossifying fibroma is classified as a benigneoplasm, it has the same pathology as the other fibro-osseousesions. It is focal, round or oval, and often causes resorptionf tooth roots, as well as displacement (Fig. 27). Although thenternal structure can be similar to that of FD, it has well-defined

argins and a thin radiolucent line, separating the lesion fromurrounding bone. The concentric growth pattern also distin-uishes it from FD, the latter tending to expand bone whileargely preserving its morphology. A subtype of COF in youngatients (under 20), known as juvenile ossifying fibroma (JOF),s a more aggressive, rapidly growing lesion.

Other radio-opaque lesions of the jaws may need to be con-idered in the differential diagnosis of fibro-osseous lesions.diopathic osteosclerosis (i.e. enostosis) and periapical condens-ng osteitis (CO) lack a radiolucent margin; CO is related to thepex of a carious or heavily restored tooth, while IOS may haveperiapical relationship to a vital tooth, or may be unrelated to

eeth. Benign cementoblastoma is usually fused to a root, typi-ally that of a mandibular premolar or first molar tooth, and mayause pain which responds to non-steroidal anti-inflammatory
rugs. It is well defined and has a radiolucent margin. Hyper-ementosis is smooth, less nodular, and has a thin radiolucentargin which is continuous with the periodontal ligament space.ompound odontomes are usually easily diagnosed because of
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he presence of tooth-like structures (denticles) (Fig. 28), butcomplex odontome may be harder to distinguish from COD,

lthough the latter tends to have a less well-defined and morerregular radiolucent margin. A flow-chart may be helpful in theiagnosis of radio-opacities within the jaws [12].

0. Temporomandibular joint pathology

ig. 32. TMJ osteoarthritis. CT sagittal oblique bone-algorithm reconstructiona) shows marked condylar flattening, irregularity and sclerosis and anteriorondylar osteophyte (arrow). CT coronal oblique bone-algorithm reconstructionb): joint space narrowing is typically most severe superolaterally (arrow).

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nteromedially. Pure medial and pure lateral displacement arencommon, and posterior disc displacement is rare [14]. Withouth opening, the disc may be reduced (recaptured) or remain

isplaced. There may be an associated arthropathy. Joint effu-ions, synovitis, erosions (usually condylar), and subchondralarrow oedema are all well demonstrated with MRI, performedith dedicated surface coils in the closed- and open-mouth
ositions (Fig. 29). Multidetector CT, also performed in thelosed- and open-mouth positions, with sagittal oblique andoronal oblique reconstructions using both bone and soft-tissue
ig. 33. TMJ ankylosis. CT coronal oblique bone-algorithm reconstruction ofhe right temporomandibular joint (a) shows marked joint space narrowing, andelatively congruent irregularity of the condylar and temporal articular surfaces,onsistent with fibrous ankylosis. Axial CT of the left temporomandibular jointn a different patient (b) shows early bony ankylosis, with bridging of bonearrow) in the anterolateral aspect of the joint.

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nal of Radiology 66 (2008) 396–418 415

econstruction algorithms, and with careful attention to opti-al windowing, can also show disc displacement (Fig. 30)

s well as synovitis, effusions and erosions (Fig. 31). Long-tanding IDD and the associated arthropathy may progress tosteoarthritis (OA), which is usually apparent on panoramicomography and MRI, but is optimally visualised with CTFig. 32). Fibrous and bony ankylosis are also well seen with CTFig. 33). Tumours and tumour-like conditions in the region ofhe TMJ include osteochondromas (Fig. 34) and synovial chon-
romatosis (Fig. 35). Ultrasound has been described in imaginghe TMJ, but its role is doubtful. Fluoroscopy is useful in guid-ng joint injections of corticosteroids and local anaesthetic forymptomatic relief; these injections are usually made into the
ig. 34. Osteochondroma. Axial CT (a) and T1W MRI (b) show a large cartilage-apped exostosis (osteochondoma, arrows) projecting anterolaterally from theeft mandibular coronoid process (arrowhead), and forming a pseudoarthrosisith the remodelled anterior aspect of the left zygomatic arch. The patient was

eferred for MRI evaluation of the temporomandibular joints because of severerismus.

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nferior compartment, where the synovitis usually appears moreevere.

1. Pre-operative assessment for dental implant
lacement
Osseo-integrated, root-form implants are the treatment ofhoice for edentulism, but these require sufficient residual alve-

ig. 35. Synovial chondromatosis. T2W sagittal oblique MRI (a) demonstrates aarge superior compartment effusion (arrows) containing small bodies of approx-mately uniform size. A reformatted sagittal oblique CT image in the same patientb) shows the effusion (arrow) and the bodies, some of which are faintly calcified.

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lar bone for placement of the titanium implant fixture. Alveolarone is resorbed in edentulous segments, sometimes quite dra-atically, and imaging is required to assess residual bone height,idth and quality. Dental panoramic tomography is sometimessed in the initial assessment, but suffers from unpredictableagnification, and does not render an assessment of alveolar

one width in the buccolingual plane. Conventional tomogramsay overcome the latter shortcoming and are sometimes useful

f a short edentulous segment is being assessed. However, themaging technique of choice is CT (either multidetector CT orone-beam CT), with curved (panoramic) and radial reconstruc-ions [15]. Bone height, width and quality are easily assessedn the radial reconstructions. Unerupted teeth and retained rootragments within proposed implant sites are also important find-ngs (Fig. 36).

Within the mandible, the critical structure is the inferior alve-lar canal: if this is breached at implant placement, permanentaraesthesia of the lower lip may result. The inferior alveolaranal is usually visible, or its position can be inferred from a

ig. 36. Retained root fragment on a CT maxilla performed for pre-implantssessment. Axial (a) and sagittal (b) reconstructions show a non-healing extrac-ion socket (arrowhead) in the proposed 12 implant site, with a filled rootragment (arrow) protruding through the buccal cortex.


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iche in the lingual cortex. The depth of the submandibular fossaan be assessed. If insufficient bone remains in the mandible,
nterior implants can be placed mesial to the mental foramina,nd these can be used to support an overdenture. The canal forhe incisive artery, mesial to the mental foramina, must not be
istaken for the inferior alveolar canal (Fig. 37).

ig. 37. Pre-implant assessment in edentulous mandible. Radial (a) andanoramic (b) reconstructions from a CT Dentascan of the mandible. The radialeconstructions show the right mental foramen (MF). Distal to this, there is insuf-cient bone height for implant placement: the superior margin of the inferiorlveolar canal (horizontal white line) is close to the crest of the partially resorbedlveolar ridge. However, implants can be placed in the anterior mandible, mesialo the mental foramina, where the thin canal for the incisive artery (arrow) shouldot be mistaken for the inferior alveolar canal. Panoramic reconstructions showhe inferior alveolar canals (arrowheads). The numbers at the bottom of eachmage show the site of the corresponding radial reconstructions.

Fig. 38. Buccal bone augmentation graft. Axial image (a) and radial reconstruc-twG

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ions (b) from a CT Dentascan of the maxilla show an onlay bone graft, fixedith a screw, in the anterior left maxilla at the site of planned implant placement.raft union is not complete.

Within the anterior maxilla, the degree of proclination of thelveolar ridge can be assessed, and the size of the nasopalatineanal and its relationship to the proposed implant site noted.esio-distal width is frequently narrow: this is best assessed in

he axial plane. If the labiopalatal width is narrow, a buccal boneraft may be placed prior to the first stage of implant placementFig. 38). Within the posterior maxilla, alveolar bone width issually adequate, but bone height is often markedly reduced. Aaxillary sinus lift procedure, with placement of bone graft in a

ubperiostial position in the sinus floor, may be used to supple-ent bone height prior to implant placement. Therefore, antral

isease and inferior antral septations should always be noted.nteractive software allows simulated placement of implants ofarying size with appropriate angulation avoiding the inferior
lveolar canal, nasopalatine canal and maxillary antrum. Theseeconstructions can be used to make a stent which is worn at theime of surgery and acts as a drill guide for complication-freemplant placement, avoiding critical neurovascular structures.

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2. Conclusion

We have presented a short review of the commonest prob-ems encountered in maxillofacial imaging, a discipline whichtraddles the areas of expertise of the head and neck radiologistnd the dental radiologist.

eferences

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[3] Farman AG, Scarfe WC. Development of imaging selection criteria andprocedures should precede cephalometric assessment with cone-beam com-puted tomography. Am J Orthod Dentofacial Orthop 2006;130:257–65.

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[7] Janse van Rensburg L, Paquette M, Morkel JA, Nortje CJ. Correlative MRIand CT imaging of the odontogenic keratocyst: a review of 21 cases. OralMaxillofac Surg Clin N Am 2003;15:363–82.

[8] Bridgeman A, Wiesenfeld D, Hellyar A, Sheldon W. Major maxillo-facial infections. an evaluation of 107 cases. Austral Dent J 1995;40:281–8.

[9] Branstetter BF, Weissman JL. Infection of the facial area, oral cav-ity, oropharynx and retropharynx. Neuroimaging Clin N Am 2003;13:393–410.

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