Chapter 28

THE JAWS, INCLUDING THE TEETH AND GUMS

TEETH: Dental caries--Impacted wisdom tooth. GUMS: Gingivitis; Pyorrhoea alveolaris; Hypertrophy; Epithelioma. JAWS: Pyogenic affections: _Periostitis_; _Osteomyelitis_; Tuberculosis; Syphilis; Actinomycosis--Tumours: _Of alveolar process_; _Of maxilla_; _Of mandible_--Fracture of maxilla--Fracture of mandible--Affections of the temporo-mandibular articulation: _Dislocation of the mandible_; _Acute arthritis_; _Tuberculous arthritis_; _Arthritis deformans_; _Closure of the jaws_.

#Dental caries# is a process of disintegration which begins in the enamel of a tooth--usually in the region of its neck--and gradually extends through the dentine till the pulp cavity is reached.

Infection of the exposed pulp cavity may set up an acute purulent _pulpitis_. This is associated with severe pain, which is not confined to the diseased tooth, but may spread to adjacent teeth, and sometimes to all the branches of the trigeminal nerve on the same side of the face.

The infection may spread from the tooth to the alveolo-dental periosteum, and set up a _periodontitis_. In the affected tooth there is at first a feeling of uneasiness, which is relieved by the patient biting against it. Later there is severe lancinating or throbbing pain. The affected tooth usually projects beyond its neighbours, and is excessively tender when the opposing tooth comes in contact with it in mastication. The gum becomes red and swollen, and the cheek is oedematous.

Periodontitis is usually followed by the formation of an _alveolar abscess_. The pus, which forms at the root of the tooth, in most cases works its way through the bone and into the gum, constituting a "gum-boil." The pus may then burst through the gum, or may spread underneath the external periosteum of the jaw and lead to necrosis.

In some cases the cheek becomes adherent to the gum and to the jaw before the abscess bursts, and the pus escapes through the skin, leaving a sinus which leads down to the defaulting tooth, and which is slow to heal, usually because there is a small sequestrum at the bottom of it. The opening of the sinus is most commonly situated at the under margin of the mandible a little in front of the masseter muscle. An alveolar abscess deeply seated in the maxilla may open into the maxillary antrum and set up suppuration in that cavity. To avoid a scar on the face, the abscess should be opened from the mouth. A periodontal abscess of one of the upper central incisors spreads backwards between the muco-periosteum and the bony palate, causing an elongated swelling in the roof of the mouth.

In all cases the extraction of the carious tooth is necessary before the abscess will cease discharging and the sinus heal. If a sequestrum is present it must be removed, and the bone scraped with a sharp spoon. Among the other effects of dental caries may be mentioned localised necrosis of the alveolar margin, cellulitis of the neck, and enlargement of the cervical lymph glands.

A _cyst_ is frequently found attached to the root of a decayed tooth. It is lined with epithelium, and is probably derived from a belated portion of the enamel organ which has been stimulated to active growth by infective processes in the pulp cavity. It is seldom larger than a pea, and contains a pultaceous mass like inspissated pus. It gives rise to no symptoms, and is only recognised after extraction of the root.

_Odontomas_ have already been described (Volume I., p. 192).

A localised swelling of the mandible, associated with pain referred to the ear and neck, and in some cases with spasmodic contraction of the muscles of mastication, may be due to _impaction of the wisdom tooth_ (lower third molar). If the tooth is merely embedded in the gum, incision may allow of its eruption; if the X-rays show that it is wedged under the second molar it must be extracted, and this may prove a difficult dental operation.

#Affections of the Gums.#--Inflammation of the gums--_gingivitis_--usually occurs in association with a general stomatitis. The gums are swollen and spongy, and may show superficial ulceration, associated with bleeding and extreme foetor of the breath. The teeth become loose, project from the alveoli, and sometimes fall out. These symptoms are prominent in cases of scurvy, and of chronic mercurial poisoning. In chronic lead-poisoning a characteristic blue line is seen on the gums near the dental margin. The _treatment_ consists in removing the cause, improving the hygienic and dietetic conditions of the patient, and administering lime-juice, iodide of potash, quinine, or cod-liver oil, according to the cause. Antiseptic mouth-washes and dentifrices are also indicated. Chlorate of potash, being excreted in the saliva, is particularly useful.

_Pyorrhoea alveolaris_ is a chronic form of gingivitis, met with after middle life, which begins in relation to the necks of the teeth and the alveolo-dental periosteum. It is due to bacterial infection, and is associated with an accumulation of tartar between the gums and the teeth. A muco-purulent discharge escapes from within the free edge of the gum and alveolus. The alveolar borders and the gum subsequently undergo atrophy, so that the roots are exposed, and the teeth are liable to become loose and eventually to fall out. The condition may only affect a few teeth, or it may spread to them all, in which case the patient may in the course of some years become edentulous. Gastro-intestinal disturbances, chronic joint affections of the nature of arthritis deformans, a form of pernicious anaemia, and other general conditions have been attributed to the absorption of toxic products. The _treatment_ consists in removing the tartar from the teeth, applying strong antiseptics to the groove between the teeth and the gums, and employing mouth-washes and dentifrices. Massage of the gums night and morning, and rubbing in a paste of chlorate of potash and menthol, is often of great value. Good results have followed the use of vaccines and improvement of the general health.

_Hypertrophy of the gums_ is occasionally met with in children and young adults who are mentally defective, and the teeth appear early and are abnormally large. The gum almost buries the teeth, and large polypoid masses form which tend to fungate. The treatment consists in removing not only the hypertrophied gums, but also the affected alveolus (Heath).

A localised hypertrophy--_polypus of the gum_--sometimes results from the irritation of a carious tooth, or from the pressure of an artificial denture, and may simulate an epulis (p. 513). The swelling is usually pedunculated, and if cut away close to the alveolar margin does not tend to recur.

_Epithelioma_ sometimes originates in the gum in relation to a carious tooth or to an artificial 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.

_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 ramus is involved, precautions must be taken to prevent fixation of the jaw taking place during the healing process. In the maxilla no new case is formed, and deformity results from sinking in of the cheek, unless this is prevented by wearing a plate made by the dentist.

#Tuberculous disease# is comparatively rare. It is occasionally met with on the orbital margin of the maxilla and in the region of the zygomatic (malar) bone. In the mandible it usually occurs near the angle. Stockman isolated the tubercle bacillus from a series of cases of "phosphorus necrosis" investigated by him. The sinuses that form when a cold abscess bursts on the surface are peculiarly intractable and only heal after the diseased bone has been removed, leaving a characteristically depressed scar, which is adherent to the bone.

#Syphilitic# affections are also rare. A localised gumma may develop in the neighbourhood of the angle of the mandible, or the whole of the body of that bone may be the seat of a diffuse gummatous infiltration (Fig. 248). In either case the clinical importance of the condition lies in the fact that it is liable to be mistaken for a new growth, such as an osteo-sarcoma, or for actinomycosis.

#Actinomycosis.#--This condition is met with in the jaws more frequently than in any other part, and the mandible is attacked oftener than the maxilla. The actinomyces gain access to the bone through a carious tooth or through the gum.

At the outset the patient complains of pain and tenderness referred to one or more carious teeth. Within a few weeks a swelling forms--in the mandible near the angle as a rule, and in the maxilla in some part of the cheek. The swelling, which varies in consistence, implicates the bone and cannot be moved apart from it. The skin over it becomes red, suppuration occurs, and sinuses form and give exit to a sero-purulent fluid in which the characteristic yellow "sulphur grains" may be detected. The surrounding soft tissues are infiltrated, and the part becomes riddled with sinuses, which lead down to bare bone. The disease usually runs a chronic course, lasting for one or two years, and, unless pyogenic infection is superadded, is not attended with fever.

In the absence of the characteristic yellow granules, actinomycosis may readily be mistaken for tuberculous or syphilitic disease, or for sarcoma.

The _treatment_ consists in removing the diseased tissue with the knife or sharp spoon, and in the administration of large doses of potassium iodide. The insertion of tubes of radium has a beneficial effect.

#Tumours of the Alveolar Process.--Epulis.#--The tumours that grow from the alveolar processes of the jaws appear at first sight to spring from the gums, hence the term _epulis_, generally applied to them. They really originate in the periosteum of the alveolus or in the periodontal membrane, and are essentially of the nature of fibro-sarcoma. In some, the fibrous element predominates, but the frequency with which they recur after removal, unless the segment of bone from which they spring is also excised, indicates their malignant tendency. In most cases the tumour is of the myeloid type--myeloma; in others new bone is formed in its substance--osteo-sarcoma.

An epulis usually begins in the gap between two teeth, and grows slowly, either towards the cavity of the mouth, or more frequently towards the lip or cheek, where it appears as a bright red, smooth, firm, rounded swelling, which is adherent to the jaw, and may be sessile or pedunculated (Fig. 249). It causes little pain, but is liable to interfere with mastication. As it increases in size it spreads over the alveoli of several teeth, becomes softer, and assumes a dark violet colour, and if subjected to pressure or irritation may ulcerate and bleed.

The true alveolar tumour is to be diagnosed from a mass of redundant granulations such as may form in relation to a carious tooth, from a polypus or an epithelioma of the gum, a tumour of the body of the jaw, or an angioma.

The _treatment_ consists in removing the tumour together with a wedge-shaped or quadrilateral portion of the alveolar process from which it grows. A dental plate should be fitted to fill up the gap in the alveolus. After such free removal these tumours show little tendency to recur and metastases are rare.

#Malignant Tumours of the Maxilla.#--All varieties of _sarcoma_ and _carcinoma_ are met with; of the former, the round and spindle-celled are the most common. Carcinoma occurs chiefly in two forms, less commonly a columnar epithelioma arising from glandular epithelium, much more commonly a squamous epithelioma either originating within the antrum and causing its expansion, or spreading to the maxilla from the mucous membrane of the nose or mouth. Clinically it is practically impossible to differentiate sarcoma from carcinoma; in the later stages the infection of the glands below the mandible is more marked in carcinoma. An important point to determine is whether the growth arises within the maxilla or has spread to it from adjacent parts, such as the base of the skull, the nose, or the palate. In this the X-rays are helpful. Their malignancy is evidenced by the rapidity of their growth, the manner in which they infiltrate adjacent parts, and the frequency with which they recur after removal. They occur at all ages, and have been met with even in children.

The _clinical features_ vary according to whether the tumour originates on the anterior aspect of the bone, in the maxillary antrum, or on the posterior aspect.

When the tumour originates in the periosteum covering the front of the bone, it forms a swelling under the cheek, usually in the vicinity of the zygomatic (malar) bone, and grows towards the mouth as well as towards the surface. The cheek is gradually invaded, and in some cases the growth extends into the maxillary sinus.

The typical malignant tumour of the upper jaw originates in the lining membrane of the antrum; it first fills the cavity and then bulges its walls in every direction, so that, on pressure being made over the swelling, the osseous shell of the sinus dimples and crackles under the finger. The sinus is dark on trans-illumination. The tumour may obstruct the nostril on the same side, and, by pressing on the tear duct, may cause the tears to flow over the cheek. It may be seen through the anterior nares, and may be attended with a sanious discharge from the nose. The eyeball is liable to be displaced upward, and if the ethmoid cells are invaded, it is also pushed outward; the palate may be depressed and the cheek projected (Figs. 250, 251).

When the tumour grows from the periosteum of the posterior aspect of the bone, and extends into the spheno-maxillary or pterygo-maxillary fossa, the eyeball is usually protruded by the invasion of the orbit from behind, and a swelling appears in the temporal region. If the sinus is invaded, the tumour spreads in the various directions already indicated. Not infrequently a tumour, which appears to have its seat in the maxilla, is really a downward prolongation of a growth originating in the base of the skull, a point on which the X-rays may yield valuable information.

In all cases the tumour tends to infiltrate the surrounding tissues indiscriminately. There is severe pain referred to the distribution of the maxillary division of the trigeminal nerve. Haemorrhage is liable to occur when exposed portions of the tumour ulcerate--for example in the nasal fossae. Sarcoma is to be distinguished from the solid and cystic forms of odontoma, which also may distend the bone, bulging the hard palate and projecting on the face.

_Treatment of Malignant Disease._--Without the help of radiation the results of operative treatment of malignant disease of the maxilla are far from encouraging. Probably the best line to follow is to embed several tubes of radium in different parts of the tumour for several days, and when the resulting shrinkage of the growth appears to have attained its limits, the maxilla should be excised. If on microscopic examination it is found to be a carcinoma, the glands on the same side of the neck should be removed at a second operation on lines similar to those in Butlin's operation in cancer of the tongue. The aid of the dentist is required to fit a denture which will at least restore the hard palate and alveolar margin. The operation of excising the upper jaw is not a dangerous one, especially if the risk of broncho-pneumonia is minimised by the intra-tracheal administration of ether. The final illness in cases of malignant disease of the upper jaw left to nature, or when it has recurred after operation, is a terrible one; the growth displaces and destroys the globe, blocks the nose and fungating on the face, causes hideous disfigurement.

#Simple tumours# are rare. _Fibroma_ may originate in the periosteum or in the lining membrane of the maxillary sinus. It usually tends to assume the characters of sarcoma. _Chondroma_ usually begins either on the nasal surface of the bone or in the maxillary sinus. _Osteoma_ occurs in two forms: the exostosis, which may be composed of cancellated or of compact tissue, and the diffuse osteoma or leontiasis ossea (Volume I., p. 485). All intermediate forms are met with, and when confined to the maxilla, the resulting disfigurement may be improved or remedied by operation; the cheek is raised or reflected and the bone shaved away with a strong knife or osteotome.

#Tumours of the Mandible.#--The same varieties are met with as in the maxilla. The non-malignant forms--osteoma, chondroma, and fibroma--are rare.

A _dentigerous cyst_ appears as a smooth, rounded, and painless swelling, usually in the region of the molar teeth. The bone gradually becomes expanded and crackles on pressure. The cyst is filled with a glairy mucoid fluid, and may contain one or more unerupted teeth (Fig. 252). The X-ray appearances are characteristic. The treatment consists in removing the anterior wall of the cyst, scraping the interior, and packing the cavity with iodoform or bismuth gauze.

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.

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.

When the frontal (nasal) portion of the maxilla is broken, the lachrymal sac and nasal duct may be damaged and the flow of the tears obstructed. In such cases emphysema is also liable to develop. Fractures of the facial portion are frequently complicated by haemorrhage from the infra-orbital vessels, and anaesthesia of the area supplied by the infra-orbital nerve. Suppuration may occur in the maxillary sinus. In some cases the maxilla is driven in as a whole, and in others the fracture radiates to the base of the skull and cerebral symptoms develop.

The _treatment_ consists in reducing any deformity that may be present, ensuring efficient drainage, and keeping the mouth as aseptic as possible. Union takes place rapidly, and owing to the vascularity of the parts necrosis is rare, even when suppuration ensues. When the alveolar portion is comminuted, the fragments may be kept in position by fixing the mandible against the maxilla by means of a four-tailed bandage (Fig. 255), or by adjusting a moulded lead or gutta-percha splint to the alveolus and palate.

The _zygomatic (malar) bone_ is sometimes fractured by direct violence, along with the adjacent portion of the maxilla. It may be possible to manipulate the displaced fragments into position with the fingers introduced between the cheek and the gum; if this fails, a small incision should be made in the mucous membrane anterior to the masseter, and the bone levered into position with an elevator.

The _zygomatic arch_ is occasionally fractured by a direct blow. As the depressed fragments are liable to interfere with the movement of the mandible, they should be elevated either by manipulation or through an incision.

#Fractures of the Mandible.#--The most common situation for fracture of the mandible is through the _body_ of the bone in the vicinity of the canine tooth (Fig. 254). The depth of the socket of this tooth, and the comparative narrowness of the jaw at this level, render it the weakest part of the arch. The fracture is usually due to direct violence, such as a blow with the fist, the kick of a horse, or a fall from a height. It is sometimes bilateral, the bone giving way at the canine fossa on one side and just in front of the masseter on the other; or both fractures may be at the canine fossae. The fracture is usually oblique from above downwards and outwards, and is nearly always rendered compound by tearing of the mucous membrane of the mouth.

When only one side is broken, the smaller fragment is usually displaced outwards and forwards by the masseter and temporal muscles, so that it overlaps the larger fragment. In bilateral fractures the central loose segment is driven downwards and backwards towards the hyoid bone by the force causing the fracture, and is held in this position by the muscles attached to the chin, while both lateral fragments are tilted outwards and forwards by the masseters and temporals. The amount of displacement is best recognised by observing the degree of irregularity in the line of the teeth. Abnormal mobility and crepitus are readily elicited, and there is severe pain, particularly if the inferior dental nerve is stretched or crushed. The patient's attitude is characteristic; he supports the broken jaw with his hands, and keeps it as steady as possible when he attempts to speak or swallow. Saliva dribbles from the open mouth, and the speech is indistinct.

In adults, the bone may be broken at the _symphysis_ as a result of lateral compression of the jaw--for example, pressing together of the angles. The general characters of the fracture are the same as those of fracture of the body, but the displacement is inconsiderable.

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.

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.

AFFECTIONS OF THE TEMPORO-MANDIBULAR ARTICULATION

#Dislocation of the Mandible.#--Dislocation of the lower jaw may be unilateral or bilateral. The bilateral form is the more common, and is met with most frequently in middle life, and in females. The liability to dislocation is greatest when the mouth is widely open--for example, in yawning, laughing, or vomiting--as under these conditions the condyle, accompanied by the meniscus, passes forwards out of the glenoid cavity and rests on the summit of the articular eminence. If, while the bone is in this position, the external pterygoid muscle is thrown into contraction, it pulls the condyle forward over the eminence into the hollow beneath the root of the zygoma, and the contraction of the masseter and temporal muscles retains it there. Muscular contraction is therefore an important factor in its production.

Dislocation may be produced also by a downward blow on the chin, by the unskilful introduction of a mouth gag, particularly while the patient is anaesthetised, or even in the attempt to take a big bite--say, of an apple. The dislocation that results from such causes is usually unilateral.

In some persons the ligaments of the joint are unnaturally lax, and dislocation is liable to occur repeatedly from comparatively slight causes--_recurrent dislocation_.

_Clinical Features._--The appearance of a patient suffering from _bilateral_ dislocation is characteristic. The mouth is open, the jaw fixed, and the chin protruded so that the lower teeth project beyond the upper. The patient has difficulty in swallowing, and the saliva dribbles from the mouth. As the lips cannot be approximated, the speech is indistinct and guttural. Just in front of the auditory meatus a deep hollow can be felt, and in front of this the condyle forms an undue projection. The coronoid process is displaced below and behind the zygomatic (malar) bone, and may be felt through the mouth. The contracted temporal muscle forms a prominence above the zygoma.

In _unilateral_ dislocation the deformity is the same in character, but is less marked, and in mild cases its cause is liable to be overlooked. In most cases the chin deviates towards the sound side.

_Treatment._--In recent cases, reduction is usually easily effected. The patient should be seated on a low chair or stool, an assistant supporting the head from behind. The surgeon, standing in front, places his thumbs, well protected by a roll of lint, far back on the molar teeth, and with his other fingers grasps the body of the jaw. Pressure is now made downwards and backwards to free the condyles from the articular eminence, and to overcome the tension of the temporal and masseter muscles, and as this is effected the tip of the chin is carried upward, while the whole jaw is pushed directly backward. The condyle slips into position, sometimes with a distinct snap. When difficulty is experienced in levering the condyle from its abnormal position, a cork may be placed between the molar teeth on each side to act as a fulcrum. After reduction the jaw is fixed by means of a four-tailed bandage for a few days. The patient is warned to avoid for some weeks opening the mouth widely.

_Old-standing Dislocation._--It sometimes happens that, from having been overlooked or neglected, the dislocation remains unreduced. In such cases the movement of the jaw is in time partly restored, and the patient acquires sufficient control of the lips to be able to articulate intelligibly and to prevent dribbling of saliva. The power of masticating the food, however, remains impaired. The hollow behind the condyle and the projection of the chin persist. Reduction by manipulation is seldom possible after the dislocation has existed for more than three months, but it has been effected as long as ten months after the accident. Several attempts at reduction should be made at intervals of two or three days, and if these fail recourse may be had to operation. As the masseter and internal pterygoid muscles have assumed a vertical position and become shortened, they form an obstacle to reduction, and to overcome their action it is necessary to separate them from their insertion to the ascending ramus of the bone through an incision carried round the angle. If the adhesions about the dislocated condyle are then separated, reduction can be effected (Samter). In some cases it is necessary to excise the condyle to restore movement.

_Internal Derangements of the Temporo-mandibular Joint._--The intra-articular cartilage is liable to be displaced by excessive traction exerted on it by the external pterygoid muscle during some sudden movement of the joint, particularly in closing the mouth. There is acute pain in the region of the joint, the teeth on the affected side cannot be brought into apposition, so that mastication is interfered with, and the patient is conscious of something locking inside the joint. The joint is tender to the touch, but there is no external swelling. Replacement is effected by keeping up firm pressure at the back of the condyle with the mouth open, and slowly closing the jaw. If recurrence takes place repeatedly, the disc may be sutured to the periosteum (Annandale), or excised (Hogarth Pringle).

#Arthritis# of the temporo-mandibular joint occurs in two forms, non-suppurative and suppurative.

The _non-suppurative_ form is usually due to gonorrhoeal infection, and as a rule is bilateral. The patient complains of neuralgic pains shooting towards the ears and temples, and of pain in the joint on movement. The jaw is therefore kept fixed, usually with the mouth slightly open and the chin protruded. Mastication is impossible, and the speech is indistinct. There is effusion into the joint, and a swelling may be detected in front of the ear. The inflammation may subside and movement restored, or fibrous ankylosis may ensue.

The _suppurative_ form may be due either to direct spread of infection from adjacent parts, as, for example, in middle ear disease, suppurative parotitis, or pyogenic affections of the mandible, or it may be part of a general pyaemic infection, as sometimes occurs after exanthematous fevers and in gonorrhoea. The clinical features are similar to those of the non-suppurative form, but the signs referable to the joint are often masked by those of the primary lesion. When the pus originates in the joint, it may point either towards the skin or into the external auditory meatus through the petro-tympanic (Glaserian) fissure. The joint is usually completely disorganised and ankylosis results.

#Tuberculous arthritis# is rare, and is usually secondary to disease of the mandible, the temporal bone, or the middle ear. It leads to destruction of the joint and ankylosis. It is treated by incision and scraping, or by excision of the condyle.

#Arthritis deformans# is a comparatively common affection, and is generally bilateral. In the earlier stages the condyle is usually hypertrophied and distorted, and the glenoid cavity is correspondingly broadened and flattened, and in time may be filled up by new bone. Osteophytic outgrowths form around the joint and lead to fixation or locking. The enlarged condyle may be felt in front of the ear, and there is pain and cracking on movement; the pain is worst at night and in wet weather. The jaw is usually depressed and the chin protruded. The disease runs a chronic course, with occasional acute exacerbations. Excision of the condyle may be advisable when non-operative measures have failed to give relief. In the later stages, the condyle, together with the meniscus, may be worn away and completely disappear.

#Closure or Fixation of the Mandible.#--_Temporary fixation_ is due to spasmodic contraction of the muscles of mastication, particularly the masseter. This may be symptomatic of some inflammatory condition in the vicinity, such as a pyogenic affection of the lower jaw--for example, that associated with a carious root or an unerupted wisdom tooth, or with parotitis or tonsillitis. In such cases the spasm passes off on the removal of the cause. It is occasionally a manifestation of hysteria. The administration of a general anaesthetic and the introduction of a wedge or separator is usually necessary to confirm the diagnosis and, it may be, to permit of operative measures, such as the extraction of a wisdom tooth.

Muscular fixation may be due to rheumatic or syphilitic myositis, and this is sometimes followed by fibroid degeneration of the muscles, rendering the fixation permanent.

_Permanent fixation_ may be due to a variety of causes. Fibroid degeneration of muscles following myositis has already been mentioned. Much more frequently it results from cicatricial contraction of the soft parts of the face or mouth following such conditions as cancrum oris, ulceration, or burns. Fixation following upon prolonged immobilisation after fracture or dislocation, or any of the forms of arthritis or suppurative or tuberculous disease of the adjacent portions of the mandible, is also met with. The ankylosis may be fibrous or osseous, and may be intra- or extra-articular.

The _clinical features_ vary with the degree of separation of the jaws. There is always some deformity, and more or less interference with mastication and speech. The patient usually feeds himself by pushing small portions of bread or meat with the fingers through some gap between the badly opposed and badly formed and preserved teeth. As the patient is unable to keep the mouth clean, particles of food lodge and decompose there, causing irritation of the mucous membrane, caries of the teeth, and foetor of the saliva and breath. When osseous ankylosis occurs in childhood, it leads to _arrest of development of the mandible_, which is small and markedly receding, so that the teeth do not oppose those of the maxilla (Fig. 256).

_Treatment._--When the cause of the fixation is in the joint itself, the best treatment is to resect one or both condyles.

When the fixation is due to cicatricial contraction of the soft parts, mobility is best restored by forming an artificial joint well in front of the cicatricial tissue, as suggested by Esmarch.