Diseases of bone and the maxillary sinus
This chapter covers the basic anatomy and diseases of the bones of the face and the maxillary sinus. Most diseases of the jaw are odontogenic in origin but the jaws can also be affected by systemic disease and by local non-odontogenic conditions. The clinical and radiological features, pathology and management of non-inflammatory/infective lesions are described. Chapter 4 deals with inflammations and infections of bone.
The mandible and maxillary bones form in membrane and are unusual in that they contain odontogenic epithelium and neurovascular bundles within their substance. Most diseases arising in the jaws are of odontogenic origin, but both non-odontogenic local and systemic disorders may affect the jaws.
The mandible is formed of a cortex and rather coarse trabecular medulla. A depression into the cortex may form around the submandibular salivary gland during development. It can give rise to a radiolucent area at the angle of the mandible, referred to as Stafne’s cavity (Fig. 7.1). It is important to be aware of this normal structure, which appears below the inferior alveolar nerve canal on radiographs, to avoid confusion with bone cysts. Another important normal structure is the torus mandibularis. Tori are smooth bone prominences found on the lingual aspect of the mandible, below the canine/premolar teeth (Fig. 7.2). They are often bilateral and may consist of single, double or triple prominences. The maxilla is often extensively pneumatised to form the maxillary sinus, described later in this chapter. The hard palate forms by elevation and fusion of embryonic shelves. A bony prominence may form in the midline, which is referred to as torus palatinus. Both the torus palatinus and pterygoid hamulus can be discovered by anxious patients and reassurance may be required.
At a histological level, bone is composed of mineralised collagenous matrix containing osteocytes. It is organised into an outer cortex and an inner cancellous (trabecular) structure, which is adaptive to stresses (Fig. 7.3). Endosteal surfaces are lined by bone lining cells; remodelling is achieved by the coordinated activity of osteoclasts (bone-resorbing cells) and osteoblasts (bone-forming cells) in bone metabolic units. Bone is surrounded by periosteum, which is continuous with oral mucosa in certain places in the jaws. The vascular supply to bone is via periosteal vessels and marrow spaces. Fatty and haemopoetic marrow may be present in the jaws.
Bone fractures and tooth extraction sockets heal by similar processes, which involve demolition of blood clot, formation of initial woven bone in a fibrous scaffold and subsequent remodelling to restore normal architecture. In tooth sockets, there is simultaneous epithelial healing. Alveolar remodelling occurs over a prolonged period, resulting eventually in a rounded ridge form. The lamina dura can be detected radiographically for up to 2 years after extraction.
Fibrous dysplasia is caused by mutation of the GNAS1 gene. Normal bone is replaced with fibrous tissue, which, in turn, undergoes gradual calcification. Monostotic (single bone) and polyostotic (more than one bone) types are seen. Around 30% of those affected have the polyostotic form of the disease.
An affected bone or area within a bone undergoes painless expansion. Other symptoms are few, but when the skull base is involved, neurological signs may occur, presumably owing to pressure on foramina. In the jaws, teeth are often affected, with effects upon eruption and developing malocclusion. The maxilla is affected twice as commonly as the mandible. The disease is most commonly unilateral but may involve multiple craniofacial bones and typically produces a visible facial asymmetry (Fig. 7.4). Fibrous dysplasia develops during childhood, usually before 10 years of age, with no sex predilection (except Albright’s syndrome). The disease becomes quiescent in early adult life, but the deformity persists.
The polyostotic form of fibrous dysplasia shares these general characteristics but has additional signs. There are two types: Jaffe’s type and Albright’s syndrome. In the first, multiple bones are affected and there are patches of skin pigmentation (café-au-lait spots). In Albright’s syndrome, which is almost always a disease found in females, there are usually various endocrine abnormalities, such as precocious puberty, hyperthyroidism and hyperparathyroidism.
The histopathological appearance is dependent on the stage of disease development. Initially, normal bone is replaced by cellular fibrous tissue within which, as the disease progresses, irregular islands and fine trabeculae of metaplastic woven bone develop. As the lesion matures, so too does the connective tissue, becoming more collagenous, while the bone is remodelled to a lamellar pattern. The lesional tissue merges with the adjacent normal tissue.
Initially an affected area appears radiolucent, reflecting the fibrous tissue content. As bone forms, the lesion becomes more radio-opaque. The alteration in trabecular pattern is particularly notable: the trabeculae are very small and fine, resulting in a picture that has been described as like ‘ground glass’, although coarser forms are often described as resembling a ‘fingerprint’ or ‘orange peel’ (Fig. 7.5). Where teeth are present, another commonly noted sign is loss of lamina dura. With age, there is a tendency for lesions to increase their radio-opacity. While lesions classically merge into surrounding normal bone, mandibular lesions sometimes have better defined margins.
There is no ideal treatment for fibrous dysplasia. Observation may be appropriate if the lesion is minor but development of any neurological signs or disfigurement would indicate a need for surgical or medical management. Surgery involves recontouring of the bony areas involved or resection and reconstruction. Medical management may involve the use of drugs that inactivate osteoclasts (bisphosphonates) and, therefore, limit invasion of lesions into normal bone. Medical management is undertaken by a physician, and consideration must be given to the unwanted effects of the drugs, particularly in children.
The cemento-ossifying fibroma shares much with fibrous dysplasia in its histopathology, but clinically and radiologically it is different. Its general behaviour is typical of a benign neoplasm in bone.
This fibroma typically affects young adult females, usually in the mandible. Its clinical presentation is that of any benign lesion, being that of a slowly growing swelling and developing asymmetry. The slow growth means cortices stay intact, so the swelling is firm to touch and painless.
The histopathological features of the ossifying fibroma are similar to those observed in fibrous dysplasia; however, in contrast to fibrous dysplasia, the lesional tissue of the ossifying fibroma is well demarcated from the surrounding normal bone.
In the early stages, the predominantly fibrous component means that it appears as a ‘cyst-like’ well-defined, corticated radiolucency. With time, radio-opaque foci appear and these increase in number and size until the lesion becomes predominantly radio-opaque. A thin radiolucent line often remains around the radio-opaque centre. Teeth in the path of the lesion may be displaced or resorbed (as is the case with any benign lesion).
In Paget’s disease, there is abnormal formation and resorption of bone. It is usually polyostotic, but invariably some bones in the skeleton will remain normal while others will be at different stages of the disease. Its aetiology may be viral.
Paget’s disease affects individuals in middle and old age. Males are more commonly afflicted than females. The clinical symptoms reflect the enlargement and weakening of bone that results from Paget’s disease. Slowly growing swelling of bones may lead to shape changes and enlargement of the skull and jaws (Fig. 7.6). Deformity of bones, typically of those bearing weight, may lead to bowing of legs and spinal curvature. Bone pain may occur and, if the skull base is affected, various neurological effects may develop.
In the jaws, the maxilla is affected more commonly than the mandible. In contrast to fibrous dysplasia, the disease is bilateral in the jaws. Spacing of teeth may develop and dentures may cease to fit. Extraction of teeth may be difficult, as a result of hypercementosis and ankylosis, and can be complicated by excessive bleeding, infection and slow healing. Other complications of Paget’s disease include high-output cardiac failure and an increased risk of sarcoma, in particular osteosarcoma.
Paget’s disease can be roughly divided into three overlapping phases. During the first of these, osteoclastic activity predominates, normal bone is resorbed and is replaced by well-vascularised cellular fibrous tissue. The surface of the bone is rimmed by giant osteoclasts resting in Howship’s lacunae. As the disease progresses, this osteolysis is accompanied by osteogenesis as new bone forms within the cellular fibrous tissue in the second phase of the disease. This combination of bone resorption and deposition gives rise to the classic mosaic appearance of bone in Paget’s disease (Fig. 7.7). The basophilic reversal lines that outline ‘the pieces of the mosaic’ mark switches in activity from bone resorption to bone deposition. Ultimately, in the third phase, osteoblastic activity predominates and the trabeculae of bone fuse together to give rise to masses of dense, sclerotic bone that is relatively avascular. Cementum is affected by Paget’s disease in a similar manner to bone, resulting in hypercementosis and, when bone and cementum fuse, ankylosis.
2. Mixed: the bony trabecular pattern is altered and often appears like ‘ground glass’ or may show a striking appearance of lines with few connections (Fig. 7.8); a few radio-opaque patches may appear in the bone.
Fig. 7.8 Intraoral radiograph of the mandible of an edentulous patient with Paget’s disease of bone.
There are two main features to note. There is an altered trabecular pattern with an impression of linearity/parallel lines. Mesially and distally there are densely radio-opaque areas (‘cotton wool’ radio-opacities).
If Paget’s disease is suspected, the serum alkaline phosphatase level should be measured. This is elevated while serum calcium and phosphate levels are normal. Observation may only be appropriate in an elderly patient with no symptoms. However, medical treatment is indicated in those with pain or neurological signs. This consists of calcitonin and bisphosphonates, which inhibit osteoclast activity and slow rather than stop the disease process. Oral surgery should be avoided if possible, and patients given antibiotic cover when it is necessary.
GCG occurs most commonly in younger age groups (first to third decades) and has a greater incidence in females. The mandible is more likely to be affected and the anterior parts of the jaws are favoured. Presentation is usually that of a painless swelling, which may be accompanied by displacement of teeth.
This lesion is identical histologically to the giant-cell epulis (peripheral giant-cell granuloma) and the brown tumours of hyperparathyroidism (see p. 156) and must be distinguished on clinical grounds. GCGs are characterised by the presence of multinucleate osteoclast-like giant cells lying in an extremely vascular stroma. The giant cells vary in size, shape, intensity of staining and the number of nuclei that they contain. The fibroblastic stroma is densely cellular and rich in capillaries, with which the giant cells are often intimately related. Extravasated red blood cells and deposits of haemosiderin may be present. Evidence of dystrophic calcification and metaplastic bone formation may also be seen. In some lesions, fibrous septa delineate foci of giant cells.
A round or ovoid radiolucency can be seen with a well-defined, non-corticated margin. Expansion is a common feature, with cortical thinning and sometimes perforation, producing a soft tissue mass. Occasionally there is wispy internal calcification. Displacement of teeth often occurs but resorption is less common (Fig. 7.10).
Fig. 7.10 Granuloma.
(A) A panoramic radiograph of a 20-year-old female who presented with a painless swelling of the anterior mandible with displacement of teeth. (B) True occlusal radiograph of the same patient, showing the marked buccal and lingual expansion. The expanded cortices are very thin, suggesting rapid growth.
It is important to distinguish the GCG from hyperparathyroidism. This is normally done by estimating serum calcium, which is raised in hyperparathyroidism. Patients with hyperparathyroidism are referred to a physician for further investigations and treatment. Surgical curettage of a GCG is usually adequate. This treatment may need to be repeated if there is recurrence; sometimes a wider resection may be indicated. Radiotherapy is contraindicated, as with any benign bone lesion.
Osteoporosis is a disease characterised by a microarchitectural deterioration of bone structure and a low bone mineral content, leading to increased bone fragility and an increase in fracture risk. It is a generalised disease, the effects of which are of greatest clinical importance in the hip, spine and forearm, but which will also occur in the jaws.
Osteoporosis may be primary, or may occur secondarily in association with other diseases or with drug therapy (e.g. corticosteroid use). There is a normal distribution of bone mineral density (BMD) in the population and osteoporosis in a particular bone is defined as a BMD lower than 2.5 standard deviations below the mean value for a young adult of the same sex. Women are more likely to suffer from the disease. Bone mineral loss is accelerated at the menopause or following hysterectomy. Patients may suffer from loss of height, a developing kyphosis and greater susceptibility to fractures. In the dental context, there is evidence that patients with osteoporosis may lose teeth earlier in periodontal disease and that modifications to implant treatment may be needed.
The trabeculae of cancellous bone are affected by a combination of thinning, reduction in number and discontinuities. Cortical bone undergoes endosteal and subperiosteal resorption and may ultimately resemble cancellous bone histologically.
There is greater radiolucency of bone and cortical thinning. The vertebrae undergo compression fractures. In the jaws, the cortex at the lower border of mandible becomes thinner (Fig. 7.11) and the trabecular pattern becomes sparse.
Hyperparathyroidism is an endocrine abnormality in which there is an excessive amount of parathyroid hormone (PTH). This causes bone resorption and hypercalcaemia. The disease may be primary, caused by excessive PTH formation by a parathyroid tumour (usually a functioning adenoma), or secondary to hypocalcaemia resulting from poor diet, vitamin D malabsorption, liver or kidney disease.
This disease usually affects the middle aged and is more often seen in women. Hypercalcaemia leads to clinical symptoms through renal calculi, peptic ulceration, bone pain and psychiatric problems. In the jaws, teeth may become loose or even be exfoliated.
Cortical bone is more severely affected than cancellous bone. The increase in osteoclastic activity results in thinning of the cortices with loss of lamina dura. Marrow is replaced by fibrovascular tissue; brown tumours of hyperparathyroidism may develop (Fig. 7.12).
There is increased radiolucency of bone, either generalised or localised. The earliest sign is subperiosteal resorption of the terminal phalanges. In the jaws, lamina dura of teeth is classically lost, along with the cortex of the inferior dental canal. There may be demineralisation of the cortex of the lower border of the mandible. Localised fairly well-defined radiolucencies (brown tumours) may be seen throughout the skeleton but are more common in facial bones than elsewhere (Fig. 7.13).
Fig. 7.13 Brown tumours of hyperparathyroidism.
There are two fairly well-defined radiolucencies in the symphysis and parasymphysial region of the mandible; these were brown tumours. Lamina dura is also difficult to identify on the teeth. The radiolucency in 12 region may be inflammatory rather than related to the systemic disease.
If hyperparathyroidism is suspected, assays of serum calcium, phosphate and alkaline phosphatase should be carried out by a physician. Both serum and urinary calcium levels and serum PTH levels are usually raised and serum phosphate levels decreased. Alkaline phosphatase levels are raised in severe disease. The most frequent cause of primary disease is an underlying parathyroid adenoma.
Numerous genetic disorders affect the jaws, and a good reference source for evaluation of individual cases is the Online Mendelian Disorders in Man (OMIM) database (www.ncbi.nlm.nih.gov/sites/entrez?db=omim). A number of disorders have effects in the jaw bones:
• Familial adenomatous polyposis (Gardner’s syndrome): multiple osteomas and odontomes, hazy sclerosis and hypodontia may be found in the jaws; numerous polyps develop in the large bowel and there is a very high risk of malignant change (adenocarcinoma of the bowel).
• Osteogenesis imperfecta: multiple bone fractures occur after minor trauma and soft tissues are typically lax, with hernia formation; the sclera may look blue and some patients develop dentinogenesis imperfecta; short stature is typical.
• Osteopetrosis: also known as marble bone disease, the medullary cavity infills with dense bone; the maxillary sinus may fail to pneumatise and bone appears dense and structureless on radiographs; there may be partial failure of tooth eruption.
A simple classification of bone swellings is given in Box 7.1. Osteomas occur most frequently in the paranasal sinuses and are dealt with in the section on maxillary sinus. Primary malignant bone tumours are rare and include osteosarcoma, chondrosarcoma and multiple myeloma. Direct invasion of bone by squamous-cell carcinoma arising in the oral mucosa is common in advanced oral cancers. Metastatic deposition of carcinoma from colon, lung, breast, kidney and other primary sites is more likely to be the cause of a destructive malignant lesion in bone than primary sarcoma.
The normal sinus in adults is pyramidal in shape. At birth, it is very small, growing laterally from its point of origin above the inferior turbinate bone until, by about the ninth year, it extends to the zygoma. Lateral growth ceases by 15 years of age. Radiologically, the sinus appears as a triangular-shaped air containing cavity on cone beam computed tomography (CBCT) and CT images (Fig. 7.14). On intraoral radiographs, the antrum is demarca/>