For many patients, their first full jaw imagining will be requested and reported by an orthodontist. This may lead to the discovery of unexpected pathology in the jaws. In this review article, we discuss the clinical and radiological appearance as well as the pathologic features and treatment of the more common entities of the jaws. In addition, we will discuss the less common lesions which carry important consequences for the patient. Through the identification of these lesions, appropriate referral and management can be pursued.
Highlights
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A clinical and radiological description of the most common pathology of the jaws is provided.
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Uncommon but important pathology of the jaws is discussed.
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Example images are provided for several diseases of the jaw bones.
Many children and young adults will receive their first full jaw imagining from an orthodontist. Approximately 6% of radiographs for orthodontic treatment planning will reveal other abnormalities, some of which may require surgical management or have implications for a patient’s general health. Though many patients treated by orthodontists in the United Kingdom are children, an increasing number of adults are also having orthodontic treatment. In either case, there is significant scope for an orthodontist to be the first clinician to encounter disease of the jaws and other bones of the head and neck. This review aims to describe common hard tissue pathology an orthodontist may encounter as well as less common but important diseases that present in children, young adults, and adults ( Table I ). The first publication of this series, published in this issue, described the pathology of soft tissues.
| Reactive/inflammatory | Developmental/hamartomas | Benign neoplasms | Malignant neoplasms |
|---|---|---|---|
| Periapical granuloma | Dentigerous cyst | Ameloblastoma | Langerhans cell histiocytosis |
| Radicular cyst | Odontoma | Adenomatoid odontogenic tumor | Osteosarcoma |
| Giant cell granuloma | Odontogenic keratocyst | Ameloblastic fibroma | Ewing sarcoma |
| Inflammatory collateral cyst | Exostoses | Cemento-ossifying fibroma | |
| MRONJ | Nasopalatine cyst | ||
| Fibrous dysplasia |
Common entities
Odontogenic cysts are the most commonly encountered pathology of the jaws in children and adults. In addition, pathology related to the teeth is also very common (eg, periapical granulomas , and other odontogenic lesions such as odontomas ). In descending frequency, we will discuss periapical granuloma, radicular cysts, dentigerous cysts, odontomas, odontogenic keratocysts, bone exostoses, peripheral/central giant cell granulomas, inflammatory collateral cysts and nasopalatine cysts.
Periapical granuloma
Of all specimens originating in the jaws submitted to oral pathology laboratories, periapical granulomas are the most frequently encountered. , They are commonly asymptomatic but may present with pain. The lesions will be associated with a nonvital tooth and appear as a well-defined radiolucency associated with the apex of a tooth. The lamina dura of the associated tooth will be disrupted. Distinguishing a radicular cyst from a periapical granuloma is difficult radiologically, though larger lesions are more likely to be cysts, so histologic assessment is valuable. A periapical granuloma, when assessed microscopically, comprises granulation tissue with an associated inflammatory infiltrate that may include variable lymphocytes, macrophages, polymorphonuclear leukocytes, and plasma cells. Removal of the nonvital tooth or successful endodontic treatment will typically resolve the lesion.
Radicular cyst
Radicular cysts are the most common odontogenic cysts in both children and adults, , accounting for 52% of odontogenic cysts. These cysts are caused by chronic inflammation from the apex of a nonvital tooth, which can be a primary or secondary tooth. Most are asymptomatic but may cause pain where infection has occurred, and occasionally, cysts can grow large enough to cause expansion of the jaws. They appear as well-defined, often corticated round radiolucencies on radiographs, with continuation between the lamina dura of the affected tooth and the cyst. They may cause root resorption. Microscopic examination shows an inflamed fibrous cyst wall lined by a nonkeratinized stratified squamous epithelium. Cholesterol clefts may also be seen. Treatment is through a combination of enucleating the cyst and treating the tooth causing the inflammation, whether through root canal treatment, if possible, or extraction.
Dentigerous cyst
Dentigerous cysts are developmental cysts that surround the crown of an unerupted tooth, with a lining derived from the reduced enamel epithelium, and have an uncertain pathogenesis. They are the most common developmental cyst of the jaws in all age groups. , , The mandibular third molars are the most commonly affected tooth, followed by the maxillary third molars. This is followed by the canines and then the second premolars in a distribution that matches the general pattern for unerupted teeth. Often, these lesions are asymptomatic, but they may present with swelling, pain, or infection when large. On radiological examination, they appear as well-defined, corticated, unilocular radiolucencies associated with the crown of an unerupted tooth. , They may cause both displacements of teeth or root resorption. Histologic examination of the cyst will show a thin, nonkeratinized epithelial lining and fibrous cyst wall, though these cysts may become inflamed, giving the lining similar qualities to a radicular cyst. As such, either radiographically or at the macroscopic pathologic examination, a relationship between the cyst and tooth crown must be established to make a diagnosis of a dentigerous cyst. Treatment is by enucleation of the cyst with removal of the associated tooth in most cases. However, marsupialization may be used if keeping the associated tooth is important for orthodontic treatment. ,
Odontomas
Odontomas are hamartomas that comprise all forms of dental tissue, including enamel, dentine, cementum, and dental pulp. They come in 2 forms: compound and complex. In compound lesions, the dental tissues are organized into structures similar to teeth, whereas a complex odontoma comprises dental tissues in a haphazard arrangement. Odontomas are the most common solid odontogenic lesion in children, , though less common in adults. The majority occur in patients aged <20 years. Usually, these lesions are incidental findings, but they may also be present because of delayed eruption of the permanent teeth, a common reason for referral to an orthodontist. , On radiological examination, they appear as well-defined radiopacities, sometimes in close association with the crown of an erupting tooth ( Fig 1 ). Complex odontomas have a haphazard pattern of calcification on radiographs, with compound odontomas forming abnormal but tooth-like structures. Both may rarely cause root resorption. Histologically, both complex and compound odontomas have similar features. Both usually have a fibrous capsule surrounding various amounts of partially mineralized enamel, dentine, cementum, pulp, and odontogenic epithelium. After local excision, recurrence is rare.
Odontogenic Keratocyst
Odontogenic keratocysts are developmental cysts with a broad age range of presentation, , although they are the third most common cyst of the jaws in children. They are most frequently identified in the second and third decades. Many patients present asymptomatically, and the cyst is discovered during radiographic examination. However, patients may present with jaw swelling, pain, or sinus formation. These cysts are more common in the mandible than the maxilla and tend to be located more posteriorly. They appear radiologically as well-defined, corticated radiolucencies, which may be unilocular ( Fig 2 , A ) or multilocular. , They are often described as having scalloped margins and may cause root displacement or resorption. , Often, the differential diagnosis of these cysts is an ameloblastoma, making biopsy for histologic assessment a valuable tool before committing to enucleation of these lesions. The histology of these lesions comprises an uninflamed fibrous cyst wall lined by thin parakeratinized stratified squamous epithelium with palisading of the basal cells. Although, as with any odontogenic cyst, if the lesion becomes inflamed, characteristic histologic features may be lost. Treatment of these cysts is by enucleation ( Figs 2 , B and C ), marsupialization, or, in rare circumstances, resection with the treatment often dictated by the size of the cyst, age of the patient and its association with adjacent structures. , There is ongoing debate about the most appropriate management of these lesions. The recurrence rate is up to 30%, with higher rates after enucleation compared with marsupialization or resection.
Exostoses
Bony exostoses of the jaws are very common, though the reported prevalence is highly variable. They are most commonly observed in the 35-65-year age group, but they also present in children and are the most frequently observed bone pathology in this group. They appear clinically as protuberances of the hard tissue of the jaws and palate and are classified as torus mandibularis ( Fig 3 , B ), torus palatinus, or buccal exostoses ( Fig 3 , A ) depending on the location. , They are rarely sent for histologic examination but will appear as normal cortical or cancellous bone when they are. , They are only removed when they are causing issues, such as with the fitting of a removable appliance or denture. Bony exostoses may ulcerate when traumatized, exposing the underlying bone. Often, these ulcers have a protracted course and may be slow to resolve. Care should be taken not to traumatize exostoses when taking intraoral radiographs or impressions. Occasional patients with spontaneous necrosis of bony exostoses have been reported.
Giant cell granulomas
Both peripheral and central giant cell granulomas are reactive lesions with the same histologic features, the distinguishing feature being the involvement of bone. Central giant cell granulomas are uncommon but tend to present in children and young adults as opposed to older adults. The peripheral form is more common overall and has an older mean age of presentation. , , The central giant cell granulomas usually present as a painless swelling of the jaws, possibly with a blue to purple soft-tissue extension, and may cause displacement of teeth. Alternatively, peripheral types occur outside of the bone and present as soft red, blue, or purple polypoid lesions, often on the gingivae with a predilection for the mandibular gingivae. The radiological features of central giant cell granulomas are variable, but they are usually radiolucencies, which may be either unilocular or multilocular. Displacement of teeth and root resorption is common. The histologic features of these lesions are identical, comprising osteoclast-like multinucleated giant cells in a background of spindled to polygonal cells in a highly vascular stroma. Treatment is by excision with curettage of the bone involved. Recurrence occurs in up to 49% of central cases and approximately 10% of peripheral lesions. Giant cell granulomas need to be distinguished from other lesions with giant cells that may present in the jaws. For example, blood tests for parathyroid hormone can help rule out brown tumors of hyperparathyroidism.
Inflammatory collateral cysts
Inflammatory collateral cysts are uncommon inflammatory odontogenic cysts accounting for approximately 5% of all odontogenic cysts in adults , and 3% in children. They have been given various names over time but are generally separated into paradental cysts or buccal bifurcation cysts, depending on where the cyst is located. , , Paradental cysts are associated with the distobuccal aspect of the third molars, whereas buccal bifurcation cysts are present on the buccal aspect of the first or second molars. They usually occur in younger patients with a mean age of presentation of 26 years for paradental cysts and 17 years for buccal bifurcation cysts. Paradental cysts may present with symptoms of pericoronitis, but buccal bifurcation cysts are often asymptomatic. , Though the radiographic appearance is variable, if identifiable on a radiograph, they appear as a well-defined and sometimes corticated radiolucency adjacent to the crown of a tooth. , The histologic appearance of an inflammatory collateral cyst is essentially the same as a radicular cyst, which is described above, and therefore clinic-pathologic correlation is required. Treatment for paradental cysts associated with third molars is often enucleation with extraction of the associated tooth, whereas enucleation with preservation of the tooth is likely when the cyst is associated with other teeth.
Nasopalatine cyst
Nonodontogenic cysts can also occur in the jaws, such as the nasopalatine duct cyst. These cysts are more frequent in adults but also present in children. , , Although many are asymptomatic, some patients present with swelling, drainage of fluid, or pain. They are localized to the midline of the anterior maxilla, in which the remnants of the nasopalatine duct lie. Radiologically, they are symmetrical, well-defined radiolucencies in the anterior palate and may cause displacement of the teeth. They have a mean diameter of 17 mm but can be as large as 60 mm and the lamina dura of adjacent teeth is retained. It is useful to confirm the vitality of the teeth adjacent to the cyst; vitality will be retained in a nasopalatine duct cyst. On microscopic examination, these cysts will have a fibrous wall and a lining consisting of a mixture of stratified squamous and respiratory epithelium. , Enucleation is curative, and recurrence is rare.
Less common entities
The following lesions of the jaw are less common than those discussed so far but often have more significant implications for the patient. They require more extensive treatment, often come with a risk of recurrence, or have a greater impact on a patient’s function and appearance. We will discuss the 3 most common odontogenic tumors in children and young adults, as well as the fibro-osseous lesions that occur in young adults and children.
Ameloblastoma
Ameloblastoma is the most common odontogenic tumor in adults and the second most common in children, , with approximately 15% of ameloblastomas seen in patients aged <20 years. There are 2 forms: conventional ameloblastoma, which is a solid tumor, and unicystic ameloblastoma, which forms a single cyst. Unicystic ameloblastomas tend to present in younger patients, with 50% arising in the second decade. This is especially the case when the cyst is associated with an unerupted tooth. Alternatively, conventional ameloblastomas have a peak incidence in the fourth and fifth decades. Conventional ameloblastomas are often locally aggressive tumors. Ameloblastomas are most often present in the posterior mandible, though they may occur anywhere in the jaws. , The most common symptom is painless swelling of the jaw, with tooth mobility and pain being less common. The conventional type of ameloblastoma appears as a well-defined and corticated multilocular or unilocular radiolucency, , whereas unicystic ameloblastoma is unilocular. They may also cause expansion of the jaws and root resorption. , , The histologic appearance of conventional ameloblastoma comprises islands of central stellate reticulum-like cells surrounded by a peripheral layer of ameloblast-like cells, and there are many histologic variants ( Fig 4 ). , The unicystic form comprises a fibrous cyst wall, a lining of palisading basal cells, and a stellate reticulum-like appearance to the upper epithelial layers. Treatment of conventional ameloblastoma is by excision or resection, depending on the extent of the tumor. For larger tumors, reconstruction of the surgical defect is required. Recurrence is common for these tumors, especially when more conservative management is employed. , Unicystic ameloblastomas are less aggressive and can usually be enucleated.
Adenomatoid odontogenic tumor
An adenomatoid odontogenic tumor (AOT) is the most common odontogenic tumor in children and young adults, with 80% presenting before 30 years old and half before 20 years old. Although these lesions may manifest with other presentations, including as an extraosseous peripheral variant, 70% of patients have cystic lesions associated with an unerupted canine tooth. An adenomatoid odontogenic tumor is more common in female patients, and two-thirds occur in the maxilla, particularly the anterior maxilla. , , Most lesions are asymptomatic and may be identified after delayed eruption of a tooth or as an incidental finding. The radiographic appearance is of a well-defined and often corticated unilocular radiolucency ( Fig 5 , A ), usually associated with the crown of an unerupted tooth. , Calcifications may be seen within the radiolucency. Root resorption occurs in 17% of patients. These lesions are formed from sheets of odontogenic epithelium, which appear to form ducts alongside variable amounts of dentine-like material, surrounded by a fibrous capsule ( Fig 5 , B ). , Treatment is by enucleation, and recurrence is rare.
