Below is an overview of seven common and uncommon maxillary growth disorders including severe skeletal malocclusion, unilateral hyperplasia, condylar hypertrophy, condylar hypoplasia, condylar neoplasia, masticatory muscle hypertrophy, and muscular neoplasia.
1. Severe Skeletal Malocclusion
The clinical history and/or physical examination evidence needed for a diagnosis of a severe malocclusion includes an unstable occlusion. The exact type of malocclusion is variable as a patient may have a large cross-bite, an open-bite, or a severe skeletal discrepancy such as a large class II or III occlusion.
In many patients, the most severe malocclusions make the patient more likely to have an unstable TMJ with resulting derangement symptoms (clicking and locking). There are, however, many patients with a severe malocclusion who function normally.
The clinical history and evidence needed for this diagnosis includes substantially short maxilla or mandible with resulting malocclusion.
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2. Unilateral Hyperplasia of the Jaw
The evidence needed for a diagnosis of a unilateral mandibular hyperplasia is a dental midline and the chin being shifted to the contralateral side. This condition develops idiopathically, but imaging is needed to rule out localized condylar growth or tumors.
Evidence Need to Diagnose Unilateral Hyperplasia of the Jaw
- Chin is either off-center or the jaw is tipped down on one side
- The growth causes substantial alteration of the posterior occlusion (poor interdigitation of the teeth on the affected side)
- Panoramic film of the jaw confirms that the mandible, not the condyle, is dissimilar (one larger or longer than the other)
Related Reading: How to Perform a Jaw Bone Biopsy
3. Condylar Hypertrophy
This is an increased mandibular condyle growth that usually occurs unilateral and for unknown reasons. It is important to differentiate increased “normal “growth from benign osseous neoplasia (abnormal growth).
Condylar hypertrophy is characterized by a normal shape condyle which is either enlarged or exhibiting an elongated neck. It will often develop in the late teens or early twenties of age. It frequently does not progress after growth stops; however, continued growth is a concern.
Like condylar hypoplasia, condylar hypertrophy may also cause a facial asymmetry, a deviation in mandibular opening, or a change in the occlusion. This condition should also be confirmed with radiographs.
Evidence Need to Diagnose Condylar Hypertrophy
- Chin is either off-center or jaw/occlusal plane is tipped on one side
- If the growth causes substantial alteration of the posterior occlusion (poor interdigitation of the teeth on the affected side)
- Panoramic film of the jaw confirms that the condyles are dissimilar (one larger or longer than the other)
4. Masticatory Muscle Hypertrophy
Obvious jaw muscle enlargement (usually the masseters but sometimes also the temporalis muscles) is evidence for muscle hypertrophy. The tissue enlargement, when biopsied usually shows a non neoplastic enlargement of the normal muscle tissue.
If the muscles show a concomitant contracture along with the hypertrophy, then the biopsy usually shows excessive fibrous tissue deposits in the otherwise normal muscle.
An enlargement of the jaw closing muscles, commonly found in bilateral masseters, can also occur as a result of increased functional demand. It is not always possible to be sure which is the cause in an individual patient. There will usually be a bilateral enlargement of the masseter and sometimes the temporal muscles, with an increased density and growth of bone at the angle of the mandible where the masseter muscle attaches.
These changes are usually considered a functional accommodation due to increased usage. They are rarely tender or painful, although they may have a firm hard texture on palpation.
The clinical history and examination evidence needed for this diagnosis includes enlarged masseters and/or temporalis muscles.
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5. Condylar Hypoplasia
Condylar Hypoplasia is a decreased mandibular condyle growth and may develop idiopathically, but can also occur secondary to traumatic injury. Since the condyle contributes significantly to mandibular growth, if it is injured before reaching its final growth, hypoplasia producing facial asymmetry will result.
Suspected hypoplasia must be confirmed radiographically. If it is going to retard normal facial growth to such an extent that it is an esthetic problem, it should be treated as soon as possible. This treatment can involve any number of surgical procedures.
The clinical history and examination evidence needed for this diagnosis includes a very small condyle on a radiograph.
Related Reading: Mandibular Mobility Disorders
6. Muscle Neoplasia
Primary masticatory muscle neoplasms can be benign or malignant and are even rarer than TM joint neoplasms. The presence of a firm, slow-growing, well-circumscribed, elevated painless mass in one of the jaw muscles would indicate a rhabdomyoma. This lesion, appears more often in the palate, tongue, floor of the mouth, larynx, pharynx or uvula. It does not usually cause jaw dysfunction.
The malignant muscle neoplasms are, unfortunately, more common than benign cases. These lesions metastasize quickly and commonly interfere with jaw function.
The clinical history and examination evidence needed for this diagnosis includes a palpable mass within the muscle that has been found to be neoplastic on biopsy, or highly suggestive of a neoplasia on MRI.
7. Condylar Neoplasia
Tumors of the TMJ may also be benign or malignant. When neoplastic changes are present, they are usually involving the osseous or cartilaginous tumors and are more often benign.
Common benign tumors include osteoma, osteochondroma, chondroma, and chondroblastoma. The most common malignant tumor of the TMJ is a chondrosarcoma. Others include synovial sarcoma, fibrosarcoma, multiple myeloma and the metastatic carcinoma.
The clinical history and examination evidence needed for this diagnosis includes radiographic evidence of an erosive or proliferative progressive growth of the condyle.
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