DISLOCATION OF THE LOWER JAW.
The movements of the lower jaw in chewing, yawning, and laughing cause its articulating processes to move forwards in the socket of the joint, and it is by spasm of certain muscles during these movements that the bone may be jerked so far forwards as to be forced out of joint. Immediately in front of the socket is a small bony knob, which the bone slides over in the act of dis location, and which bars time return of the bone to its socket. Fig.
52 represents this disloca tion, * being opposite the socket, r be ing time articulating process of the lower jaw, and k the bony knob referred to. A blow on the chin, when time mouth is open, may also produce the dislocation, but it occurs most frequently in the act of yawning. It may be on one side only, or on both sides.
Signs.--When both sides are dislocated the mouth is fixed widely open ; saliva dribbles from the mouth ; the patient cannot speak nor swal low ; and there is a hollow in front of the ear on each side, and above in front of this the promi nence of the head of the bone. When the dislo cation is on one side the chin is twisted towards the sound side. If the jaw is left alone, partial recovery takes place in course of time. The power of speech and of swallowing is gradually restored ; the jaws come together to a consider able extent; and the saliva ceases to flow ; but for a very long period great discomfort re mains. .
Treatment.—Let the operator stand in front of the patient and insert the thumb of each hand into the mouth, resting them on the teeth of the lower jaw. The thumbs must be well protected by lint or by a napkin wrapped round them. They should reach back to the last grinding tooth. The fingers are at the same time placed under the chin and base of the jaw. The patient's
head being fixed against a wall or the back of a high chair, the operator presses the grinding teeth downwards with his thumbs, while raising the chin with his fingers. As soon as the bone becomes disengaged from its unnatural position the muscles pull it backwards into the joint. The return is effected suddenly, and the opera tor's thumbs are liable to be caught by the quick snapping closure of the mouth and seriously bruised, unless they have been properly pro-. tected. If the person is quick enough he may succeed in avoiding the snap by slipping his thumbs to the side between the gums and cheek. If this method of reduction fails greater power may be exerted by placing a piece of soft wood between the upper and lower grinding teeth on each side, the piece being thick enough to fill the space between them. The chin is then steadily pulled upwards, but not forwards. The pieces of wood act as a fulcrum for depressing the hack teeth. A spoon or handle of a fork laid along the teeth would fulfil the same purpose.
After the reduction the chin ought to be con fined for a time, a week or two, by a bandage, to prevent renewed dislocation ; and the person ought always afterwards to guard against opening the mouth too widely, as this is a dislocation which, once effected, is easily re produced.
Partial dislocation of the jaw may occur, espe cially in people of relaxed habit of body. The symptoms are not so marked, but the mouth is fixed, and cannot be shut. A smart push may be sufficient to return the bone, and the person must exercise care in opening the mouth.