ificial tooth-plate. The growth tends to invade the
bone and to spread to the cheek or buccal mucous membrane, or to the
maxillary antrum, and its malignant nature is suggested by its
persisting after the removal of the irritation. The only treatment is
early and complete removal of the growth and the adjacent segment of
bone.

Other tumours of the gums, such as angioma and papilloma, are rare.

THE JAWS

#Pyogenic Infections.#--The jaws may be infected in fractures
communicating with the mouth or as a result of the unskilful
extraction of teeth, but the majority of pyogenic infections originate
in relation to carious teeth, beginning as a periodontitis which is
followed by diffuse periostitis that may lead to necrosis of
considerable portions of bone. In workers exposed to the fumes of
yellow phosphorus, the bone may be so devitalised that it readily
becomes infected with pyogenic organisms and undergoes a process of
cario-necrosis--the _phosphorus necrosis_ of the older writers.

[Illustration: FIG. 247.--Cario-necrosis of Mandible.]

_Acute osteomyelitis_ occasionally attacks the mandible, less
frequently the maxilla. Pus rapidly forms under the periosteum, and a
considerable area of bone may undergo necrosis.

In _cancrum oris_, also, the bones are frequently attacked and may
undergo necrosis.

The _treatment_ is to let out the pus, and, whenever possible, this
should be done from the mouth to avoid a cicatrix on the face. When
the angle or the ascending ramus of the mandible or the facial portion
of the maxilla is involved, it is not possible to avoid making an
external opening. Drainage is secured, and the mouth kept sweet by the
frequent use of antiseptic washes. When the condition is due to a
carious stump or to an unerupted tooth, this should be extracted at
the same time as the abscess is opened.

The separation of a sequestrum is usually slow, taking from two to
four months according to the acuteness of the infection and the extent
of the necrosis. In the mandible the sequestrum becomes surrounded by
a sheath of new periosteal bone, so that, even if the greater part of
the jaw undergoes necrosis, the arch is reproduced, and after removal
of the sequestrum little or no deformity results. The sequestrum can
usually be removed after dividing the mucous membrane and gouging away
a portion of the outer aspect of the new sheath. The cavity is packed
with iodoform or bismuth gauze. When the ascending ram