Teeth and jaws in X-ray image

In the dental formula used to shorten the record, the temporary teeth (20) are denoted by Roman numerals, the constants (32) are Arabic. The right or left half of the upper and lower jaws is designated by the sign of the angle, open respectively to the left, right, up or down.

The main mass of the tooth is dentin. In the area of the crown, dentin is covered with enamel, and the root - with cement. On the roentgenogram, the enamel is represented by an intense linear shadow that fringes the dentin of the crown; it is better visible on the contact surfaces of the tooth. Dentin and cement on the roentgenogram do not differ.

Between the root of the tooth and the cortical plate of the alveolus of the jaw is a narrow slit-shaped space - a periodontal gap (width 0.15-0.25 mm), which is occupied by periodontium (dental ligament). It consists of a dense connective tissue (bundles of fibrous fibers, interlayers of loose connective tissue, blood and lymphatic vessels, nerves) fixed to the cement and cortical plate of the socket. Periodont provides fixation of the tooth and participates in supplying it with blood.

On the X-ray, the milk teeth differ from the permanent ones: the crown and roots of smaller teeth, the root canals and the tooth cavity are wider. The roots of the molars move away from each other at a large angle.

The cavity of the tooth on radiographs is defined as a source of rarefaction with clear contours in the background of the tooth crown, root canals - in the form of linear foci of rarefaction with smooth and clear closing contours.

In the alveolar bone, the teeth are separated from each other by an interdental septum covered with a gum. The vertices of the interdental septa in children are located at the level of the enamel-cement border, in adults at a distance of 1.5-2 mm from it. The septa constructed from the spongy bone on the periphery are bordered by a clearly expressed closing cortical plate, which is a continuation of the cortical plate of the socket. The tops of the interdental partitions are pointed in the region of the front teeth and have the shape of a truncated pyramid in the zone of premolars and molars. After removal of the teeth, the interdental septa atrophy, the alveolar margin flattening.

Upper jaw

Upper jaw is a pair of bones consisting of a body and four processes (frontal, malar, palatine and alveolar). On the body of the upper jaw, four surfaces are distinguished (anterior, nasal, ophthalmic and transverse).

The front surface is located between the lower edge of the orbit and the alveolar process. At 0.5-1 cm below the edge of the orbit, the lower nostril canal opens, in which the maxillary nerve (the second branch of the trigeminal nerve) and the corresponding artery and vein pass. Below the hole on the front wall there is an impression (canine, or canine, fossa), where the sinus is usually opened during surgery.

The upper (ophthalmic) surface forming the sinus roof passes the infraorbital canal with the maxillary nerve and vessels. The upper wall of the sinus is very thin and easily disintegrates with inflammatory and neoplastic diseases of the upper jaw with involvement of the orbit in the process.

The nasal surface of the inner wall of the sinus forms the outer wall of the nasal cavity. In the anterior part of her there is a tear duct, which opens into the lower nasal passage. The opening of the sinus, located above its bottom, opens into the middle nasal passage. This explains the fact that outflow from the sinus is better in the prone position.

The podznosochnaya surface nadnenaruzhnoy wall facing the wing-palatine fossa - the place of introduction of anesthetic drugs with "tuberal" anesthesia.

In the jaw body there is an air maxillary (maxillary) sinus, resembling a pyramid in shape.

The maxillary sinuses appear on the 5th month of intrauterine development in the form of small pits on the nasal surface of the body of the upper jaw. Already in the seven-month-old fetuses, the bone walls of the sinus are visible on the roentgenogram of the skull.

In children aged 2.5-3 years, the sinuses are occupied by the rudiments of the teeth and are defined as triangular enlightenments in the upper and outer regions. At the bottom of the sinus, there are rudiments of the teeth; in children up to 8-9 years of age they are located at the level of the bottom of the nasal cavity. In children and adolescents molar roots are sometimes in direct contact with the mucosa of the maxillary sinus.

The volume of the sinus increases as the teeth erupt, forming it ends with the completion of the eruption of permanent teeth (by 13-15 years). After 50-60 years, the sinus volume (15-20 cm ³ ) begins to decrease. In adults, the sinus is located between the first premolar (sometimes canine) and the second-third molar. An increase in sinus pneumonitis can be observed after removal of the teeth. Sometimes the sinus extends also into the septa between the premolars and molars, to the area of the maxillary hillock.

The left and right sinuses can be of different sizes, they contain bone septa.

On the X-ray, the lower border of the sinus is represented as a thin, nowhere-broken linear shadow. Depending on the pneumatization and peculiarities of the sinus (high or low) between the roots of the teeth and the compact plate of the sinus bottom, layers of spongy substance of different thickness are determined. Sometimes the roots of the teeth are near the maxillary sinus or in it itself, which facilitates the spread of infection from the periapical tissues to the mucosa (odontogenic sinusitis). Above the lower border of the sinus is a thin linear shadow - a reflection of the bottom of the nasal cavity.

The cortical layer of the base of the zygomatic process is visible on the intraoral radiographs above the region of the first molar in the form of an inverted loop. When the shadow of the body of the malar bone is placed on molar roots, it becomes difficult or impossible to assess the condition of the periapical tissues. Overlays can be avoided by changing the direction of the central beam of X-rays.

The lower sections of the maxillary hill are visible on the intraoral radiographs of the upper molars. The hook of the pterygoid process, projecting from a different length and width, is projected behind it. The relationship between the tuberosus and pterygoids of the main bone is clearly seen on orthopantomograms, along which it is possible to evaluate the condition of the pterygoid fossa.

The crown of the coronoid process on some intraoral contact radiographs is determined behind the upper molars.

In the posterior sections of the hard palate, the focus at the level of the first or second molars can be seen on the shots of a rounded shape with clear outlines, a projection of the lacrimal nasal canal located at the junction of the maxillary sinus and the nasal cavity.

The structure of the bone tissue of the alveolar process is fine-meshed, predominantly with the vertical course of the ossicles.

On intraoral radiographs between the central incisors through the interdental septum passes a band of enlightenment - intermaxillary (incisal) suture. At the level of the tips of the roots of the central incisors, sometimes projecting onto them, there is an incisal hole in the form of an oval or rounded clearly defined focus of enlightenment of different sizes. On the midline of the hard palate at the level of premolars, a smooth or tuberous bone formation of different sizes - torus palatinum is sometimes seen.

Lower jaw

The lower jaw is an unpaired flat bone of the horseshoe shaped spongy structure, consisting of a body and two branches extending at an angle of 102-150 ° (angle of the lower jaw). In the body of the jaw distinguish the base and the alveolar part, containing 8 teeth alveoli on each side.

Variants of the structure of the jaw bones are most clearly revealed on direct panoramic radiographs and orthopantomograms. X-ray anatomical details are presented on the charts from orthopantomograms and panoramic X-rays of the upper and lower jaws. On the lower edge of the jaw with the transition to the branch is the cortical layer, thicker in the central regions (0.3-0.6 cm) and attenuated to the corners of the jaw.

The bony structure of the lower jaw is represented by a loopy pattern with more clearly contoured horizontally extending (functional) beams. The structure of the bone structure is determined by the functional load: the pressure on the teeth is transmitted through the periodontium and the cortical plate of the hole to the spongy bone. This is the reason for the pronounced pettiness of the bone tissue in the alveolar processes on the periphery of the dentition. The size of the bone cells is not the same: smaller ones are in the anterior part, larger ones are in the zone of premolars and molars.

In the newborn, the lower jaw consists of two halves, between which a connective tissue is located along the median line. In the first months after birth ossification occurs and merges them into one bone.

On the extraoral X-rays in the lateral projection, the hyoid bone is projected onto the angle or roots of the molars, and on the branch back to the molars - the air column of the pharynx, which extends downwards almost vertically beyond the jaw.

Below the roots of the molars, the focus of rarefaction of bone tissue with fuzzy contours is sometimes determined - the reflection of the submandibular fossa (the location of the submandibular salivary gland).

The external oblique line extends to the front edge of the branch, projecting onto molars in the form of a band of sclerosis of different shapes and densities. After removal of molars and atrophy of the alveolar part, it may prove to be marginal.

The internal oblique line, passing below the outer oblique line (the attachment site of the maxillofacial muscle), is located on the inner surface and can be projected onto molar roots.

The upper branch of the branch ends in front of the coronoid process, behind the condylar process, separated by a notch of the lower jaw.

On the inner surface in the middle of the branch there is an opening of the mandibular canal (the focus of rarefaction of bone tissue is triangular or round in shape, rarely 1 cm in diameter).

The position of the mandibular canal, represented in the form of a band of rarefaction of bone tissue, is variable: it passes at the top of the roots of the molars, rarely - just above the lower edge of the jaw.

Throughout the lower jaw canal is visible on panoramic radiographs, its clearance 0.4-0.6 cm. The canal begins with a mandibular opening, located in the branch at different heights. Cortical plates of the canal, especially the upper one, are clearly visible. In children the canal is located closer to the lower edge, in young people, as well as with loss of teeth and atrophy of the alveolar part, it is displaced cranially. This fact should be taken into account when planning surgical interventions.

Intraoral roentgenograms do not allow establishing the relationship between the roots of the teeth and the canal. On orthopantomograms between the upper wall of the canal and the tips of the teeth, a layer of a spongy bone 0.4-0.6 cm thick is usually determined.

At the level of the tips of the premolar roots in adults and canines in children, the canal ends with a round or oval chin opening (diameter 5-7 mm), sometimes spreading anterior to it. When the hole is projected onto the tip of the premolar, it becomes necessary to differentiate it from the pathological process (granuloma).

The chin on the images of the frontal part of the lower jaw is determined in the form of protruding bone formation on the lingual surface of the jaw.

On the lingual surface of the lower jaw, respectively, the roots of the canine and premolars are sometimes determined by smooth or hilly bone formation of different sizes - torus mandibulars.

In the absence of the cortical plate of the lower jaw from the lingual side (anomaly of development), a bony defect of 1 x 2 cm in size, round, oval or ellipsoidal in shape with distinct contours is determined on the roentgenogram in the lateral projection, which is localized between the angle of the jaw and the mandibular canal, not reaching the apex of the roots teeth.

Vessels passing through the bone are sometimes reflected in the form of a strip or section of dilated bone tissue of round or oval shape, located between the roots. They are better visible after losing teeth. The posterior upper alveolar artery passes through the lateral wall of the maxillary sinus.

Sometimes, above or between the tips of the roots of the second and third molars, one can see a large palatal hole in the form of an indistinctly delineated focus of rarefaction.

Involutive changes in the teeth consist in the gradual erasure of enamel and dentin, the deposition of replacement dentin, sclerotic changes and petrification of the pulp. As a result of deposition of replacement dentin on radiographs, a decrease in the size of the tooth cavities is determined, the root canals are narrowed, poorly contoured, and with complete obliteration are not visible. Involutive changes in the teeth, especially the lower jaw, are noted during X-ray examination at the age of 40-50 years in the form of focal osteoporosis. At the age of 50-60 years on diffractograms diffuse osteoporosis, atrophy and a decrease in the height of the interlittent septa, narrowing the periodontal cracks. As a result of a decrease in the height of the alveolar margin, the neck of the teeth is exposed. Along with the thinning of the bony beams and a decrease in their number in a unit of volume, the cortical layer is thinning, which is especially well detected radiographically along the lower and posterior margins of the mandibular branch. The structure of the body of the lower jaw acquires a large-bladed character, the horizontal trabeculae trajectory can not be traced in accordance with force trajectories.

Involutive changes are more pronounced in people with complete loss of teeth, if they do not use removable dentures.

After the removal of the teeth, the lunettes gradually disappear, the height of the alveolar margin decreases. Sometimes the holes after tooth extraction are determined on radiographs in the form of a rarefy focus for several years (more often after removal of the lower molars and incisors).