Fig. 252.—Dentigerous Cyst of Mandible containing rudimentary tooth.
(From Sir Patrick Heron Watson's collection.)
The myeloid tumour or myeloma is comparatively common. It develops in the interior of the bone and expands the affected segment ([Fig. 253]). It grows slowly, is more or less encapsulated, and therefore does not infiltrate the surrounding tissues. Sometimes it so weakens the bone that pathological fracture occurs. There is no glandular involvement, and the tumour shows little evidence of malignancy.
Fig. 253.—Osseous Shell of Myeloma of Mandible.
(From Professor Annandale's collection.)
The periosteal sarcoma is the most malignant form. It grows rapidly, and infiltrates the surrounding tissues. The submaxillary salivary glands and the cervical lymph glands are usually implicated, and the disease tends to spread by metastasis to distant parts.
Epithelioma is the commonest new growth affecting the mandible; it usually involves the central portion of the bone, being a direct spread from the lower lip, tongue, or floor of the mouth. When it originates in the pillars of the fauces it implicates the ascending ramus. In all cases the infection of the cervical lymph glands is a serious factor both in prognosis and treatment.
Treatment.—Partial removal of the mandible may be undertaken for myeloma, and in cases of sarcoma and epithelioma in which the tumour is limited to a small area of the bone—for example, to the alveolar process, the angle, the horizontal ramus, or the symphysis; in other cases, the whole bone must be removed.
Injuries of the Jaws
Fracture of the Maxilla.—Fractures of the maxilla are nearly always due to direct violence, such as a blow on the face, a stab, or a gun-shot wound. They are often rendered compound by opening into the mouth, into the maxillary sinus, or on to the skin of the cheek. The alveolar process, in whole or in part, may be separated from the body of the bone by a severe blow, such as the kick of a horse, and when the whole alveolus is detached, it may carry with it the hard palate. Limited portions of the alveolus are frequently broken in the extraction of teeth. The main trouble after severe alveolar fractures is that the upper teeth do not accurately oppose the lower ones, and mastication is thereby interfered with.