X-ray signs of jaw and dental trauma

X-ray diagnostics of traumatic injuries of jaws and teeth

In case of traumatic injuries of the maxillofacial area, an X-ray examination is mandatory. In cases where the clinical diagnosis of the fracture is not in doubt, an X-ray is taken not only for documentation purposes, but also to obtain additional valuable information about the nature and location of the fracture, the number, position and displacement of fragments and chips, the condition of the roots of the teeth and sockets. Repeated X-rays taken after reposition are used to assess the correct alignment of the fragments and the dynamics of the fracture (photographs of the lower jaw are taken after 2 weeks and 2-3 months, and of the midface - after 3-4 weeks after reposition).

Jaw fractures account for approximately 2% of all skeletal bone fractures, with fractures of the lower jaw predominating and often associated with damage to other bones of the facial skull.

Radiographic signs of a fracture. Depending on the mechanism of action, a distinction is made between direct (occurring at the site of application of force) and indirect, or reflected (occurring at a distance from the site of action) fractures.

The fracture can be single or multiple (bone fracture in several places).

Taking into account the course of the fracture plane in relation to the long axis of the bone, transverse, longitudinal and oblique fractures are distinguished.

Depending on the relationship of the fracture line with the temporomandibular joint, extra- and intra-articular fractures are possible. Due to the variability of the level of attachment of the capsule, some fractures of the neck of the condylar process are intra-articular. Fractures of the condylar process are the worst to detect.

The main radiological signs of a fracture are damage to the integrity of the bone and displacement of fragments, indicating a complete fracture of the bone.

In case of subperiosteal incomplete fractures (cracks), there is no displacement of fragments. The displacement is caused by the acting force and contraction of the muscles attached to the fragments. Fractures with damage to the skin, rupture of the mucous membranes, passing through the cortical plate of the sockets, the maxillary sinus and the nasal cavity are classified as open. Inflammatory changes in the periodontium and periapical tissues of the teeth located on the fracture line can cause traumatic osteomyelitis.

Displacement of fragments detected on a radiograph is a pathognomonic sign of a fracture, eliminating the need for distinctive recognition. To detect displacement of fragments, it is necessary to perform radiographs in at least two mutually perpendicular projections.

In the case of a clinical picture suspicious for a fracture, if the fracture is not diagnosed on radiographs, repeat images are taken after 2-3 days. Due to osteoporosis and resorption of bone beams at the ends of the fragments, the fracture line becomes wider and is better defined on the radiograph.

Due to the violation of the integrity of the bone beams, the fracture line is determined as a strip of enlightenment with unclear contours. The fracture line is most clearly visible when the integrity of the cortical parts of the bone (cortical plates of the jaw or socket) is violated.

The image of the fracture line on the image changes depending on the projection conditions of the study. If the central beam passes parallel to the plane of the fracture, a strip or line of rarefaction of bone tissue is visible on the image. If the lingual and buccal cortical plates of the lower jaw are fractured at different levels, two fracture lines are visible on the image, forming an oval and simulating a comminuted fracture. In these cases, panoramic tomograms resolve diagnostic difficulties.

In case of longitudinal displacement with overlapping of fragments due to their superposition, the fracture zone looks like a strip-shaped compacted area. In complex cases of fracture diagnostics, computed tomography can be of significant help.

Fractures of the lower jaw

The anatomical features of the structure of the lower jaw predetermine the favorite localization of fractures: at the level of the canine, along the midline (corresponding to the intermaxillary suture), in the area of the angle and neck of the muscular process.

Among the factors influencing the displacement of fragments (the direction of the acting force, the mass of the fragment itself), the most important is the traction of the muscles attached to the fragment.

Displacement with overlapping of fragments occurs with transverse and oblique fractures in the area of the branch of the jaw, double fractures of the body of the jaw, fractures of the neck of the condylar process. In 40% of cases, double fractures are observed, in 4.5-6% - triple fractures.

In case of traumatic injuries of the lower jaw, the following approach to radiographic examination is recommended:

1. All patients undergo a direct frontal-nasal X-ray, which makes it possible to identify multiple fractures of other bones (zygomatic arches, integumentary bones of the skull), some of which are not clearly expressed clinically and are sometimes an accidental X-ray finding. Due to projection distortions, the size of the diastosis on these images is greater than in reality;
2. In order to obtain an idea of the condition of the alveolar part, cortical plates of the sockets and teeth in the fracture area, intraoral contact radiographs are taken. If this is not possible, extraoral radiographs are taken in oblique contact projections. In each specific case, the choice of technique is determined by the location of the fracture;
3. to examine the anterior parts of the jaw, direct panoramic radiography is performed;
4. in case of fractures of the body, angle and branch of the jaw, orthopantomograms or lateral radiographs are performed;
5. In case of fractures of the condylar process, orthopantomograms and lateral radiographs of the body and branch of the lower jaw are taken. In case of fractures of the head and high-lying fractures of the neck, tomograms or zonograms of the temporomandibular joint in the lateral projection with the mouth open are required.

In early childhood, subperiosteal greenstick fractures predominate, and fragment displacement is rare. In children aged 3 to 9 years, the weakest point in trauma is the neck of the condylar process. Neck fractures (trauma to the neck alone or in combination with damage to other parts) account for 30% of all mandibular fractures.

Fractures of the upper jaw

Fractures of the upper jaw are often combined with damage to other bones of the facial skull and sometimes the base of the skull. Taking into account the "lines of weakness" Lefort identified three types of fractures, which in their pure form are extremely rare. Upper fracture (Lefort type III): the fracture line passes through the nasal and lacrimal bones, the floor of the orbit in the direction of the pterygoid process of the sphenoid bone, a break in the zygomatic bone with the upper jaw and nasal bones from the base of the skull. Middle fracture (Lefort type II): the fracture plane passes through the nasal, lacrimal bones, the floor of the orbit, the maxillozygomatic suture, a break in the upper jaw from the base of the skull and the zygomatic bone is observed. In the case of a lower fracture (Lefort type I), the fracture plane passes through the alveolar processes (fracture of the alveolar process), maxillary tubercles and the lower parts of the pterygoid processes of the sphenoid bone. With these fractures, the alveolar process with teeth is displaced and the bite is disturbed. An indirect radiographic sign of a fracture is a decrease in pneumatization of the maxillary sinus due to hemorrhages and a violation of the integrity of one of its walls. Fractures of the midface can cause traumatic sinusitis. Hemorrhages and swelling of the soft tissues of the neck on a survey radiograph simulate a picture of darkening of the maxillary sinus. Orthopantomography, tomography and zonography, preferably with the patient in an upright position, help in differential diagnostics. If the integrity of the body of the jaw is violated and air gets into the soft tissues, emphysema with a typical radiographic picture occurs.

Due to the relatively rapid connective tissue fixation of fragments, even when they are displaced, pronounced deformations and functional disorders occur, the elimination of which requires complex reconstructive operations. This determines the need to recognize traumatic injuries in the shortest possible time to perform repositioning of fragments.

In case of traumatic injuries to the upper jaw, the following images are taken:

1. chin-nasal radiograph;
2. semi-axial or axial radiograph;
3. lateral panoramic skull radiograph;
4. orthopantomogram;
5. to examine the frontal parts of the jaw - a direct panoramic radiograph;
6. to assess the condition of the alveolar process and teeth in the fracture zone - intraoral contact radiographs, bitewing radiographs of the hard palate, extraoral contact radiographs in oblique projection.

Fracture of the zygomatic bone

The most common fractures are of the temporal process of the zygomatic bone, which is separated from both the temporal bone and the body of the zygomatic bone, with the fragment moving inward and downward.

When the zygomatic bone is injured, its body is often displaced inward, penetrates the upper jaw, and hemorrhages into the maxillary sinus.

To localize the fracture and determine the displacement of the fragments, an X-ray of the skull is taken in the axial projection. Aimed tangential X-ray of this area is quite informative: the film cassette is placed below the angle of the jaw, the central beam is directed from top to bottom along the tangent to the zygomatic arch perpendicular to the film.

Fracture healing

Fracture healing occurs as a result of metaplasia of blood clots in the perimaxillary soft tissues (parosteal callus), due to the reaction of the endosteum lining the bone marrow spaces (endosteal callus) and the reaction of the periosteum (periosteal callus).

Approximately 35 days after the injury, the osteoid tissue calcifies and turns into bone. On the radiograph, ossified periosteal layers are most often determined as a linear shadow along the edge of the mandible. Although the restoration of the bone structure in the fracture line area is completed in 3-4 months, the fracture line is visible on the images for 5-8 months. The orientation of the bone trabeculae in the fracture plane differs from the predominantly horizontal direction of the main bone trabeculae in the adjacent spongy bone substance.

Resorption of small fragments continues for 2-3 months. Fusion of the fracture in the area of the head and neck of the condylar process occurs faster (after 3-4 months the fracture line is no longer detectable).

Complications of fracture healing

One of the most common complications of jaw fractures is traumatic osteomyelitis. Complications also include the formation of a false joint (pseudoarthrosis) along the fracture line with a persistent disruption of bone continuity, which may result in mobility that is not typical for this section. The formation of a false joint may be due to improper alignment and fixation of fragments, interposition of soft tissues between them, the severity of the injury (loss of a significant portion of bone, crushing of soft tissues), or disruption of the blood supply to bone fragments.

Detection of pathological bone mobility during clinical examination makes it possible to diagnose pseudoarthrosis. However, pathological mobility may be absent due to fixation of fragments by fibrous tissue. In these cases, the most informative is X-ray examination in two mutually perpendicular projections, sometimes in combination with tomography.

On the radiograph of a pseudoarthrosis, there is no shadow of bone callus connecting the fragments, the ends of the fragments are rounded and smoothed, sometimes covered with a closing cortical plate. The space between the fragments, filled with connective tissue, is called the joint space. Depending on the severity of bone formation processes and the shape of the fragments, a distinction is made between atrophic and hypertrophic pseudoarthrosis.

Dislocation of the lower jaw

Due to the topographic and anatomical features of the temporomandibular joint structure, anterior dislocations occur most often. The cause of dislocation is trauma or excessively wide opening of the mouth, in particular when performing medical manipulations. Dislocations are classified as complete and incomplete (subluxation), unilateral and bilateral.

The purpose of the X-ray examination is to determine whether the dislocation is combined with a fracture of the condylar process. To diagnose dislocation, Parma X-rays or tomograms are performed. The tomogram in the lateral projection reveals the glenoid cavity, the head of the condylar process in case of dislocation is located anterior to the articular tubercle in the infratemporal fossa.

Dislocations in other directions (posteriorly, externally and internally) are rare and, as a rule, are accompanied by fractures of the condylar process and temporal bone.

Dislocations and fractures of teeth

Dislocations and fractures of teeth occur with acute trauma and removal of a tooth or root. Chronic trauma of teeth occurs with bite anomalies and after incorrectly performed orthopedic interventions.

In case of dislocation, periodontal tissues are torn and the tooth position in the socket changes (partial or complete dislocation). In case of tooth displacement from the socket, the radiograph shows widening of the periodontal space at the apex and deformation of the space. Tooth dislocations most often occur in the anterior part of the upper jaw. In case of impacted dislocation with destruction of the cortical plate of the socket, the periodontal space in the periapical region is absent. Impacted dislocations of primary teeth may be accompanied by damage to the corresponding rudiments of permanent teeth with disruption of their formation and death. In case of trauma to a temporary tooth without damage to the pulp, resorption of the root occurs within the usual time.

The fracture line can be located transversely or obliquely in any part of the root and neck, between the neck and the middle of the root; between the middle of the root and the apex; longitudinal fractures of the root and crown also occur.

In case of fractures and dislocations of teeth, an X-ray examination allows us to determine whether there is a fracture of the cortical plate and alveolar process.

Fracture healing is rare. In these cases, the radiograph shows a cuff-shaped thickening of the tooth, and the fracture line image disappears as a result of dentin formation.

When preserving the pulp, when analyzing repeated images, attention is paid to the presence or absence of replacement dentin in the tooth cavity and canals, the condition of root fragments, the periodontal gap and the cortical plate of the socket.

The pulp of a permanent tooth that has died due to trauma is removed and the canals of the fragments are sealed, which can be fastened with a pin. In case of a crown defect, inlays on a pin are used, the length and depth of insertion of which are determined taking into account the size of the root. Repeated radiographs assess the condition of the periodontal gap and the cortical plate of the socket.