X-ray signs of cysts of the jaws

X-ray diagnosis of cysts of the jaws

According to the International Histological Classification of Odontogenic Tumors, Jaw Cysts and Related Diseases (WHO, 1971), jaw cysts formed as a result of their developmental disability, and cysts of inflammatory nature (radicular) are distinguished.

In the group of cysts associated with developmental disorders, odontogenic (primary cyst-keratokist, tooth-containing - follicular cyst, gingival cyst and eruption cyst) and non-dodontic (cyst of nosonephal canal and globose-maxillary) fissural cysts and nasolabial cyst are included.

Among the cysts, follicular and radicular predominate. They are 3 times more likely to form on the upper jaw.

Zubosoderzhaschaya (follicular) cyst is a malformation of the dental epithelium, occurs mainly in the second-third decade of life. On the roentgenogram, a single tissue destruction center of a round or oval shape with a diameter of 2 cm or more is defined with clearly defined, sometimes wavy contours. The entire rudiment, crown or part of it, sometimes two rudiments are immersed in the cavity of the cyst. The roots of the teeth at different stages of formation may be outside the cyst. There is no tooth in the dentition, but the follicular cyst can develop from the rudiment of the superfine tooth. Expansively growing cyst causes displacement of the rudiments by a number of located teeth. Thus, the displacement of the rudiment of the third lower molar upward can serve as an indirect sign of the presence of the follicular cyst. Cysts cause pronounced deformation of the face due to swelling of the jaw, cortical plates are displaced, thinned, however, their destruction is rarely observed.

Pain sensations in the follicular cyst, as a rule, are absent, and its detection on the roentgenogram can be an accidental finding. Delay of teething is sometimes the only clinical sign that allows one to suspect a pathology. The pain occurs when the cyst is infected and pressure is applied to the sensitive nerve endings. The exception is follicular cysts located in the area of milk molars, sometimes accompanied by pain, possibly due to the pressure of the cyst on the unprotected pulp of the resorbed root of the milk tooth.

Significant difficulties arising in the diagnosis of follicular cysts of the upper jaw in children are due to the fact that the interpretation of the radiographic picture is made difficult by the rudiments of permanent teeth located above the milk teeth.

The radical cyst, which is the final stage of development of the cystogranuloma, is formed due to the proliferation of metaplastic epithelium and the transformation of granulomatous tissue into a mucin-like substance. It can also form as a complication of endodontic measures by pushing the necrotic pulp into the periodontium periapically, especially when manipulated under anesthesia.

In children aged 7-12 years, radicular cysts develop more often in the region of the lower molars (2-3 times more often than in the upper jaw), in adults, mainly the upper jaw in the frontal region is affected.

The growth of the cyst occurs not so much due to the growth of the epithelium, but as a result of an increase in intracavitary pressure. There is an increase in the cyst in the volume with resorption and restructuring of surrounding bone tissue. The pressure inside the cyst varies from 30 to 95 cm of water. Art. For several years the diameter of the cyst reaches 3-4 cm.

Radicular cyst is a cavity lined with a shell and containing a cholesterol-rich liquid. The outer layer of the membrane is represented by a dense fibrous connective tissue, the inner layer is a multilayer, planar, nonkeratinized epithelium.

On the roentgenogram of the cyst is defined as a focus of destruction of bone tissue of round or oval shape with clear, even, sometimes sclerotized contours. In contrast to the granuloma for the radicular cyst, a sclerotic rim along the contour is characteristic.

However, it is impossible to reliably distinguish the radicular cyst from the granuloma according to roentgenological data. When the secondary inflammatory process (festering cyst) is attached, the sharpness of the contours is disturbed, fistulous movements may appear.

The tip of the root of the tooth, usually affected by caries or treated for pulpitis or periodontitis, is immersed in the cavity of the cyst. As expansive growth, the cyst causes displacement of cortical plates; on the lower jaw predominantly in the cheek-lingual direction, on the upper - in the nebula-vestibular. Sometimes the cyst grows along the spongy layer of the lower jaw, without causing its deformation.

The direction of growth of the cyst is to a certain extent due to the peculiarities of the anatomical structure of the lower jaw. In cysts located up to the third lower molars, deformation occurs mainly in the buccal direction, since the cortical plate on this side is thinner than with the lingual. With the spread of the cyst for the third molar swelling occurs more often in the lingual side, where the plate is thinner.

As a result of bloating, asymmetry of the face occurs. Depending on the condition of the displaced cortical plate, palpation of this region shows a symptom of parchment crunch (with a sharp thinning of the plate) or fluctuation (when its plate is interrupted). The cyst causes displacement and spreading of the roots of a number of located teeth (divergence of the roots and convergence of the crowns). The position of the causative tooth usually does not change. In the case of a defect in the dentition in this region, the crowns flexibly bend to each other.

Patients with granulomas left after removal of the causative tooth may develop a residual (resundial) cyst. The cyst located at the socket of the removed tooth, usually has an ellipsoidal shape, its diameter does not exceed 0.5 cm. Subsequently, the cyst causes deformity of the jaw and asymmetry of the face. Residual cysts are formed more often on the upper jaw of men.

In connection with the presence of signs of chronic inflammation in the walls of cysts located at the roots of the upper premolars and molars, they can cause a nonspecific reaction of the closely adjacent mucous membrane of the maxillary sinus. The degree of severity of the reaction of the mucous membrane depends on the thickness of the bone layer between it and the pathological focus near the top of the root.

Depending on the relationship between the cyst and the maxillary sinus, the adjacent, displacing and penetrating cysts are distinguished.

With adjacent cysts between the mucous membrane and the cyst, the unchanged cortical plate of the alveolar bay and the bony structure of the alveolar process are visible. With crowding cysts, the cortical plate of the alveolar sinus bay is shifted upward, but its integrity is not disturbed. On the roentgenogram, the penetrating cysts have the form of a hemispherical shadow with a clear upper contour against the background of the air of the maxillary sinus, the cortical plate of the alveolar bay is sometimes interrupted or absent. Significant help in determining the relationship between the cyst and the maxillary sinus is provided by orthopantomograms, lateral panoramic radiographs and contact extraoral images in an oblique projection.

A distinctive recognition of the radicular cysts of the upper jaw and retention of the mucous membrane of the maxillary sinus is associated with certain difficulties. On zonograms and tomograms in the frontal-nasal projection, the cyst has the appearance of a shadow of an oval, spherical shape, sometimes tapering to the base, with a clear outline against the background of the air sinus. Retention cysts can increase, remain unchanged, or undergo regression.

To identify the relationship of radicular cysts with the bottom of the nasal cavity, it is expedient to perform direct panoramic radiographs.

With large cysts of the upper jaw, sprouting into the soft tissues of the cheek, the most informative are the radiographs in oblique tangential projections.

The keratokist appears as a malformation of the formation of the tooth rudiment and is characterized by keratinization of the lining of the multilayered corneal flat epithelium. It is more often localized behind the third lower molars in the region of the angle and branch and has a tendency to spread along the body and into the interalveolar septa, displacing the roots of the teeth, but not causing their resorption. Contours of the cavity are even, clear, sclerosed.

Developing sometimes near the emerging follicle, the cyst is separated from it only by a connective tissue capsule and resembles a follicular cyst by a formal x-ray picture. The final diagnosis is established only after a histological examination. Relapses after surgery occur in 13-45% of cases.

The cyst of the nosonebus canal refers to fissural non-dental cysts. The cyst develops from embryonic remains of proliferating epithelium, sometimes retained in the incisive canal. Radiographically, the cyst is manifested in the form of a focus of rarefaction of bone tissue of round or oval shape with even, clear contours. The cyst is located along the midline in the anterior sections of the hard palate above the roots of the central incisors. The closing cortical plates of the wells and periodontal cracks are traced against the background of the cyst.