MAXILLA AND MANDIBLE – BENIGN & MALIGNANT

TUMOURS

By Navdeep Singh

Dentition

In the primary dentition, there are normally 20 teeth; in adult dentition there are 32.

Using one of two systems - Zsigmondy system, which uses single digits for the permanent dentition and letters for the primary (deciduous) dentition,

Federation Dentaire International (FDI) notation, which assigns double digits for each tooth

Part of a panoramic radiograph showing the permanent dentition of a normal 18-year-old. The teeth in the upper left quadrant have been numbered 1–8. The third molars are unerupted, incompletely formed and impacted.

HE ZIGMONDY (SINGLE DIGIT) AND FDI (DOUBLE DIGIT) SYSTEMS OF TOOTH

                       

Part of a panoramic radiograph showing the dentition in a 6-year-old child. The deciduous teeth in the upper left quadrant have been labelled A–E. The first permanent molars (labelled 6) and the lower central incisors have erupted. All four primary first molars and the primary lower second molars are carious.

All teeth consist of a crown and a root. The crown is covered with a layer of enamel with a

composition of 97 per cent mineral, thus being the most radio-opaque tissue in the body.

The bulk of the tooth consists of dentine, which is 70 per cent mineralized.

The root is covered by a thin layer of cementum, which has a similar radiodensity to dentine and so is indistinguishable from it.

Lying within the centre of the tooth is the radiolucent soft tissue of the pulp, which runs from the pulp chamber in the crown along each root canal to the root apex, through which enter the neurovascular bundles.

The tooth is supported in the jaws by the periodontal ligament, as a narrow radiolucent line. These fibres are inserted into a thin layer of dense bone lining the tooth socket (lamina dura), which appears as a linear radio-opaque structure, and is continuous with the cortical bone of the alveolar crest.

Disorders of tooth eruption The commonest cause for failure of full

eruption is insufficient room in the dental arch to accommodate the erupting tooth.

Alternatively a tooth may be prevented from erupting by, for example, a tumour, cyst or supernumerary tooth.

Delayed eruption occurs in certain endocrine disorders, e.g. hypothyroidism and some genetic abnormalities, e.g. Down's syndrome. Multiple failure of eruption of the permanent dentition is found in cleidocranial dysplasia

Panoramic radiograph of cleidocranial dysplasia in an adult. There are numerous unerupted teeth including several supernumeraries.

Hypodontia (oligodontia) Anodontia It is seen in association with cleft lip and

palate, Ellis-van Creveld (chrondo-ectodermal dysplasia) and facial-digital syndromes. Marked absence of teeth is seen in hydrotic ectodermal dysplasia.

Hyperdontia - presents as either supplemental or supernumerary teeth.

Amelogenesis imperfecta is a developmental disorder of enamel formation affecting all or most of the teeth.

Varying degrees of hypoplasia from being pitted to almost complete absence of enamel when the crown appears angular. Alternatively, the enamel may be of normal thickness but be hypomineralized such that its radiographic density is similar to that of dentine.

Intra-oral (bitewing) radiographs showing marked hypoplasia and pitting of the enamel, whilst the dentine appears normal. Several of the teeth are carious.

Dentinogenesis imperfecta is a developmental anomaly of collagen formation.

The teeth are discoloured, having a brown or purple hue. The enamel chips away and the teeth rapidly wear down.

The initial radiographic appearance shows bulbous crowns and large pulp chambers, which soon calcify with abnormal dentine so that little or none of the root canal is visible.

Although the teeth may appear sound, they are prone to infection resulting in pulpal necrosis and periapical radiolucencies.

associated with osteogensis imperfecta.

A panoramic radiograph of a young adult with dentinogenesis imperfecta. The teeth have bulbous crowns, short stumpy roots and sclerosis of the root canals.

DENTAL CARIES Dental caries is caused by microbial action on sugar

with the formation of acid, which causes progressive demineralization of the teeth, initially of the enamel, and then the dentine with destruction of their organic components.

Radiographic detection of dental decay requires images with good contrast and resolution. Despite its limitations, intra-oral radiographs are valuable in the detection and monitoring.

A carious lesion appears as a radiolucent zone, which represents an area of demineralization. An approximal lesion develops in the enamel just below the contact point with an adjacent tooth and has a triangular shape with the apex pointing towards the dentine.

If left untreated, the caries reaches the pulp chamber and the weakened crown eventually crumbles away.

Periapical granuloma at the apex of the grossly decayed upper right lateral incisor. Although well defined, its margins are not corticated. Note the loss of the lamina dura at the tooth apex. There is a similar but smaller lesion at the apex of the exfoliating upper right first premolar root and the upper right central incisor is markedly carious.

CYSTS OF THE JAWS

Odontogenic and non-odontogenic cysts Common findings - slow-growing lesions,

i.e. they are radiolucent, well defined and often have a cortical margin.

they have raised intracystic pressure and expand by tissue fluid transudation, and so appear as circular or oval in shape.

Jaw cysts tend to displace structures

Radicular cysts are the most common of the odontogenic cysts.

They are derived from the cell rests of Malassez. develop at the apex of a nonvital tooth Any tooth can be affected but the majority are

found on the permanent anterior teeth or first molars.

When small (less than 15 mm in diameter) they resemble periapical granulomas but, unlike granulomas, can enlarge well beyond this size.

In many cases extraction of the causative tooth brings about resolution, but when this does not happen, the cyst is then termed a ‘residual cyst’. Thus a residual cyst found in an edentulous part of the jaw, has a well-defined, circular radiolucency usually with a cortical margin.

Part of a panoramic radiograph showing a corticated radiolucent lesion associated with the carious root of the upper left second premolar, extending into the maxillary antrum above the hard palate, consistent with a radicular cyst. Note the periapical radiolucency (granuloma/abscess) on the upper left second molar.

Dentigerous cyst (follicular cyst) - arises from the reduced enamel epithelium, the tissue which surrounds the crown of an unerupted tooth.

It is thus found only on teeth that are buried, particularly mandibular third molars and maxillary canines.

Cystic enlargement of the tooth follicle produces a pericoronal radiolucency, which is attached to the tooth at its neck, with the crown appearing to lie within the cyst lumen; however with large cysts this relationship may not be apparent.

Part of a panoramic radiograph of a dentigerous cyst arising on a lower left wisdom tooth, which is unerupted and lying horizontally. It appears as a well-defined, circular radiolucency attached to the tooth at its neck. The inferior alveolar canal has been displaced inferiorly.

Odontogenic keratocysts arise from remnants of the dental lamina, the precursor of the tooth germ.

The cyst lining has a higher mitotic activity and is thought to enlarge by mural growth and so behaves more like a benign neoplasm and is now classified as such.

It appears as a unilocular or multiloculated, elongated, irregularly shaped radiolucency with a scalloped, well-defined margin.

It lacks the more ballooning characteristics of the other odontogenic cysts, which is an important diagnostic feature.

Keratocysts occur most often in the lower third molar/ramus region, where they may displace, or occasionally replace an unerupted wisdom tooth.

Recurrence is common (15–20 per cent) so radiographic follow-up is necessary for several years.

On CT, attenuation values of cyst fluid are higher than most other jaws cysts due to its high protein (keratin) content, ranging from 30–200 Hounsfield Units, with longstanding, multilocular cysts having the higher value.

Part of a panoramic radiograph of an odontogenic keratocyst which appears as a loculated radiolucency extending from the condylar neck to the lower first molar region. There is thinning of the bony cortices but no jaw expansion, a feature associated with odontogenic keratocysts. Note the displaced lower right third molar.

Odontogenic keratocyst in a 13-year-old boy. An abnormality was seen incidentally on conventional radiographs obtained for planning of orthodontic treatment

Multiple odontogenic keratocysts are a feature of Gorlin-Goltz syndrome which also includes multiple basal cell naevi, calcification of the falx, bifid ribs, synostosis of the ribs, kyphoscoliosis, temporal and parietal bossing, hyperptelorism, and shortening of the metacarpals.

Part of a panoramic radiograph showing multiple odontogenic keratocysts consistent withGorlin-Goltz syndrome. All four third molars have been extensively displaced and a lateral facial view showed the upper right one to lie posteriorly close to the orbit.

OKC in a 41-year-old man with basal cell nevus syndrome (Gorlin-Goltz syndrome). Contrast material–enhanced CT scan shows multiple cysts (arrows) in the mandible. Cystic lesions (arrowheads) are also identified within the maxilla. CT also demonstrated a calcified falx and large frontal sinuses, findings that helped establish the diagnosis.

Non odontogenic cyst

The nasopalatine cyst is probably the commonest non-odon-togenic cyst.

believed to arise from epithelial residues in the nasopalatine canal.

It appears as a round, well-defined, midline radiolucency between, but not associated with, the upper central incisor teeth.

Three lesions that may resemble jaw cysts but have no epithelial lining are sometimes considered with jaw cysts.

Solitary bone cyst occurs during the first 2 decades of life, mainly in the premolar/molar regions of the mandible.

Its margin is less well defined than those of odontogenic cysts and its superior border arches up between the roots of the adjacent teeth.

Tooth displacement and root resorption is uncommon. At surgery an empty cavity is found, which subsequently heals after bleeding has been induced.

Part of a panoramic radiograph showing a partially corticated radiolucency in the right mandible involving the apices of the second premolar and first and second molars diagnosed as a solitary bone cyst. Note the characteristic scalloping between the roots of the first and second molars.

Aneurysmal bone cyst is considered to be a reactive lesion of bone and is characterized by a fibrous connective tissue stroma containing many cavernous blood-filled spaces.

It is rare and occurs mainly in the young, with over 90 per cent occurring before 30 years of age.

It is typically found in the posterior region of the mandible as a well-defined, multilocular, often septated, circular radiolucency. It has a tendency to produce marked cortical expansion.

Computed tomography (CT) or magnetic resonance imaging (MRI) shows the presence of fluid levels due to the presence of blood-filled cavities.

Stafne's bone cavity is asymptomatic and typically found in men over the age of 35 years.

It forms a depression in the lingual cortex of the mandible just in front of the angle and below the inferior dental canal.

Its origin is controversial and it has been postulated that it arises from pressure from the submandibular salivary gland, however whilst some may contain salivary gland tissue a number develop anterior to the gland.

On plain radiographs, it appears as a well defined, punched out, dense radiolucency, which rarely exceeds 2 cm in diameter. Its appearance is characteristic and so does not require further imaging or biopsy. However, if CT or MRI is performed, the cavity is often found to contain fat.

Part of a panoramic radiograph showing a corticated radiolucency between the inferior alveolar canal and the lower border of the mandible due to the presence of a Stafne bone cavity. The 3D CT (B) shows the depression on the lingual aspect of the mandible.

Static bone cavity (Stafne cyst) in a 35-year-old man. CT scan reveals a cortical defect (arrow) in the lingual surface of the right mandibular angle, a finding that does not represent a true cyst.

ODONTOMES AND ODONTOGENIC TUMOURS

Odontomes are developmental malformations or hamartomas consisting of dental hard tissues or tooth-like structures.

Most are diagnosed in the second decade of life and frequently impede tooth eruption.

There are two main types. The compound odontome consists of a collection of small discrete teeth called denticles and is found typically in the anterior region of the maxilla,

Complex odontome consists of a randomly arranged mass of enamel, dentine and cementum found predominantly in the lower premolar/molar region.

Both types are densely radiopaque due to the presence of tooth enamel and are surrounded by a thin radiolucent capsular space and radio-opaque cortical margin.

Cystic odontoma in a 17-year-old boy with painful third molars

Odontogenic tumours are uncommon, mostly benign and arise from either the odontogenic epithelium, odontogenic epithelium and ectomesenchyme, or primarily ectomesenchyme.

The commonest is the ameloblastoma, which accounts for 11%.

It occurs mainly in patients between 30–50 years of age with most (80 per cent) forming in the molar/ramus region of the mandible.

When the maxilla is involved, it has the potential to spread insidiously to involve the infratemporal fossa, orbit and skull base, thus a thorough assessment is essential.

Part of a panoramic radiograph showing an ameloblastoma, which appears as an expansile, multilocularradiolucency involving the left body of the mandible.

Unilocular or multilocular radiolucency, but typically contains septa or locules of variable size to produce a honeycombed appearance.

The margin is well defined, often corticated but when large, produces jaw expansion with perforation of the bony cortex.

A useful diagnostic feature is knife-edge resorption of the tooth roots by the tumour, which can be quite marked.

The lesion is locally aggressive and requires a wide excision margin.

Multislice CT can be used to differentiate ameloblastoma from odontogenic keratocysts because of higher density increase during the arterial phase.

On T1-W images with gadolinium enhancement and T2-W images, there is good conspicuity of the tumour margin with the soft tissues, the lesion having a moderate to high signal.

Very rarely undergoes malignant transformation with metastases occurring in the lungs.

An axial CT on bone window settings of a large cystic ameloblastoma of the right side of the mandible showing marked thinning and expansion of the bone. Note the presence of root resorption.

CHAPTER 63 -Dental and Maxillofacial Radiology from Adam: Grainger & Allison's ...

Odontogenic myxoma is a benign but locally aggressive tumour of odontogenic mesenchyme occurring mainly in those younger than 45 years of age.

Most occur in the mandible in the premolar molar region.

The lesion is usually well defined, unilocular and contains a variable number of internal coarse trabeculations to produce a reticular pattern.

Panoramic radiograph shows an expan-sile, ellipsoid, partially corticated, lucent lesion with heterogeneous internal mineralization in the right posterior aspect of the mandibular body and extending into the lower ascending ramus (arrows).

Calcifying epithelial odontogenic tumour - well defined and contain variable amounts of focal mineral deposits.

more common in men, occurs in middle life and is found mainly in the premolar/molar region of the mandible.

Adenomatoid odontogenic tumour - affects females in the second decade of life and typically occurs anteriorly, especially in the maxilla and is associated with an unerupted tooth.

well defined and contain variable amounts of focal mineral deposits.

Developmental disorders

Fibrous dysplasia is a localized abnormality in which cancellous bone is replaced by fibrous tissue containing varying amounts of calcified tissue.

When the jaws are affected, the maxilla is involved twice as frequently as the mandible.

An immature lesion is largely radiolucent and may mimic a dental cyst, typically having an orange peel or ground-glass texture.

On radiographs the margins are usually indistinct, blending in with the normal adjacent bone.

It may displace teeth or prevent their eruption.

Large lesions produce jaw expansion, with thinning of the bony cortices and displacement of the antral floor.

It can resemble both a cemento-ossifying fibroma, which is better defined, and an osteosarcoma, which produces destructive changes.

Axial CT on bone window setting of fibrous dysplasia of the anterior aspect of the mandible. There is thinning and expansion of the bony cortical plates. The lesion shows areas of low attenuation, lingual to the teeth, due to the presence of fibrous tissue.

CHAPTER 63 -Dental and Maxillofacial Radiology from Adam: Grainger & Allison's ...

Figure 63.22 Axial CT on bone window setting of fibrous dysplasia of the anterior aspect of the mandible. Ther

Cherubism is a rare dysplasia of bone that develops during the first decade of life.

It occurs bilaterally in both jaws, but more commonly affects just the mandible.

It develops in the posterior aspects of the jaws as a multilocular, honeycombed, expansile radiolucency.

Tooth displacement is common. It regresses spontaneously after skeletal growth ceases.

Periapical cemento-osseous dysplasia and florid cemento-osseous dysplasia are similar conditions, with the latter being a more extravagant version of the former.

Women, particularly of Afro-Caribbean origin, after 25 years of age.

Characterized by the formation of multiple deposits around the tooth roots and the mandible is more frequently involved than the maxilla.

Teeth are clinically sound, radiolucent lesions form at the apices of the teeth, which resemble periapical granulomas.

Gradually cemental-like tissue is deposited within so that it become increasingly radiopaque but is surrounded by a thin, peripheral radiolucent zone, which helps distinguish it from sclerosing osteitis.

The appearance of florid cemento-osseous dysplasia is similar to periapical cemental dysplasia but the lesions are larger, may produce jaw expansion, are more numerous, and often in both the maxilla and mandible. May resemble Paget's disease of bone.

Inflammatory disorders

Osteomyelitis of the jaws is uncommon. It may develop from a dental abscess or

complicate tooth extraction. In acute osteomyelitis, there is thinning and

discontinuity of the bony trabeculae to produce ill-defined, patchy areas of radiolucency within the cancellous and cortical bone.

With time bony sequestrae form and are recognized as irregularly shaped islands of bone set against a region of radiolucency.

The features of osteomyelitis are more readily visualized on CT, which also is useful to show periosteal bone formation.

On MRI, the marrow usually shows a low signal intensity on T1 and a high signal on T2 weighted images.

If the disease becomes chronic, the bone becomes diffusely affected and extensively involved with sclerosis of the marrow spaces. CT will demonstrate the internal structure and the presence of sequestration.

Part of a panoramic radiograph of the right mandible of a patient who developed acute osteomyelitis following the extraction of a premolar root 3 weeks previously. There are three sequestra in the alveolar portion of the mandible.

Hyperparathyroidism of the jaws results in a general demineralization of the bone, creating a ‘ground glass’appearance, loss of the lamina dura, formation of brown tumours, and subperiosteal erosions at the angle.

Haematological replacement disorders may affect the jaws. In moderate to severe thalassaemia, the jaws become radio-lucent with the presence of coarse trabeculations due to marrow hyperplasia and the maxillary antrum is reduced in size. The skull takes on a granular appearance, with thickening of the diploic spaces and occasionally a ‘hair on end’appearance.

Panoramic radiograph of a case of thalassaemia. There is marked increase in the height of the mandible, which is composed of coarse trabeculae enclosing large marrow spaces and the small maxillary sinuses. Note the generalized loss of the lamina dura and the periodontal abscess on the distal root of the lower right first molar.

TUMOURS OF BONE

Cemento-ossifying fibroma - Its behaviour varies from those showing slow growth to others being quite aggressive.

Occurs mainly in young adults, mostly in the body of the mandible.

The radiographic appearance depends on its degree of mineralization, and typically contains a wispy or tufted bony trabecular pattern. The lesion is encapsulated and so appears well defined, helping to distinguish it from fibrous dysplasia.

Bone window setting of an axial CT of a cemento-ossifying fibroma of the mandible showing mainly buccal expansion and thinning of both cortical plates, which remain intact. The lesion is of mixed attenuation as it contains areas of fibrosis, mineralization, and coarse bony trabeculations.

Osteomas of the maxillofacial bones and jaws are usually slow-growing, painless and thus discovered by chance.

In the jaws, osteomas more commonly affect the mandible than the maxilla and, whilst any site can be involved, they tend to be found posteriorly on its medial aspect.

CT assists in showing the site of origin and provides three-dimensional (3D) topographic detail.

Multiple osteomas are a feature of Gardner's syndrome (familial adenomatous polyposis) and precede the formation of intestinal colonic polyposis.

Bone window setting of an axial CT showing a dense (compact) osteoma arising from the medial aspect of the ramus of the right mandible.

Osteosarcoma is uncommon in the jaws(7 %) It tends to be slower growing and occurs about 10

years later than osteosarcoma of the long bones. The mandible is more commonly affected than the

maxilla. Maxillary lesions tend to arise from the alveolar ridge, and mandibular ones in the body.

It has a destructive appearance and its density varies from being radiolucent, to patchily radio-opaque or predominantly sclerotic.

An important early dental radiographic sign is widening of the periodontal ligament space due to tumour spread along the periodontal ligament, however this feature is also seen in other sarcomas (e.g. fibrosarcoma Ewing's sarcoma).

When the periosteum is elevated a ‘hair-on-end’, sunray or onion skin appearance may be visible. CT is required to demonstrate accurately tumour calcification, bone destruction, and bone reaction ( Fig. 63.28 ), whilst MRI (T1- and T2-weighted images) will provide better information on the intramedullary and extraosseous components of the tumour.

Bone window setting of an axial CT of osteogenic sarcoma of the left mandibular ramus. There is bone destruction in the region of the sigmoid notch. The lesion contains areas of neoplastic bone formation and extends medially towards the lateral pterygoid plate, posteriorly to the styloid process, and laterally resulting in facial swelling

Pag

Extranodal lymphoma of the maxilla shown on a bone window setting axial CT at the level of the alveolus. Although a few areas of the lesion are well defined, the overall appearance is destructive with loss of much of the buccal alveolar plate.