Fractures of the angle and through the ramus are less common, and are not attended with deformity, as the fragments are retained in position by the masseter and internal pterygoid muscles. Fracture of the coronoid process is rare.
The condyle is usually fractured just below the insertion of the external pterygoid muscle ([Fig. 254]) by a fall on the chin or by a severe blow on the side of the face. When the fracture is unilateral, the broken condyle is tilted inwards and forwards by the external pterygoid, and can be palpated from the mouth, while the rest of the jaw is displaced towards the affected side, and not away from it, as happens in unilateral dislocation. When the fracture is bilateral, the mandible falls backwards, so that the lower teeth lie behind those of the maxilla.
In a few cases the condyle has been driven through the floor of the glenoid cavity, causing fracture of the base of the skull. The diagnosis may be established by means of the X-rays.
Complications.—As the majority of these fractures are compound, suppuration is comparatively common during the process of repair, but if means are taken to keep the mouth clean it can usually be kept in check, and seldom leads to necrosis. The teeth adjacent to the fracture are liable to be loosened or displaced. If merely loosened they should be left in place, as they usually become firmly fixed in the course of a few days. Care must be taken that a displaced tooth does not pass between the fragments, as this has been the cause of difficulty in reducing a fracture and of its failure to unite. Irregular union, by destroying the alignment of the teeth, leads to interference with mastication. The bone usually unites in from four to six weeks. Want of union is a rare event.
Treatment.—In the majority of cases of unilateral fracture after reduction, the fragments can be kept in apposition by closing the mouth and keeping the lower jaw fixed against the upper by means of a four-tailed bandage ([Fig. 255]). Care must be taken that the posterior tails of the bandage do not pull the mandible backward. Additional security may be given by a light poroplastic or gutta-percha splint fitted to the chin, the vertical portion passing well up the ramus of the jaw. After a few days the apparatus is removed, the patient is encouraged to move the jaw, and massage is employed. The mouth must be regularly cleansed by an antiseptic mouth-wash, or by a spray of hydrogen peroxide.
Fig. 255.—Four-tailed Bandage applied for Fracture of Mandible.
In certain fractures implicating the body of the jaw, and particularly when bilateral, the co-operation of the dentist is necessary to obtain the best results. After the fragments have been coapted, a plaster impression is taken of the jaw and teeth, and from this a silver frame is cast which surrounds but does not envelop the teeth. This frame is then applied to the fractured jaw, and restrains movement of the fragments without interfering with the action of the jaw (W. Guy). The use of an intra-oral frame obviates the necessity of wiring the fragments.
Even in badly united fractures the original contour of the bone is eventually restored by the movements of the tongue moulding it into shape.