Dental anomalies

X-ray examination of congenital and acquired deformities of the maxillofacial region

Deformations of the maxillofacial region occur when the shape, size and relationship of individual bone components change. They can be congenital (chromosomal diseases, the effect of teratogenic factors on the fetus) and acquired (after childhood illnesses, injuries, radiation therapy, endocrine and metabolic disorders, etc.).

According to the WHO classification (IX revision), the following are distinguished:

• enlargement of the entire or individual parts of the jaw (upper or lower) - macrognathia;
• reduction of the entire or individual sections of the jaw (upper or lower) - micrognathia;
• incorrect positioning of the jaws in relation to the base of the skull - displacement in the sagittal, vertical or transverse direction;
• deformations, including those listed above.

Anomalies of teeth and jaws occur in 30% of school-age children. Anomalies of jaws are usually accompanied by malocclusion.

Anomalies in dental development

Common anomalies of permanent teeth manifest themselves in changes in their number, position, size, shape and structure.

The number of teeth may be reduced (edentia) or increased (hyperdentia) compared to the norm. The reasons for this are the same as those causing deformations of the maxillofacial region. X-ray examination is indicated in all cases of missing teeth in the dental row in order to establish the presence of rudiments of milk and permanent teeth. X-rays can also help to determine the reasons for the delay in their eruption.

Adentia is more often observed in the permanent bite, less often in the temporary bite. The most common congenital absence is of the lateral incisors of the upper jaw and wisdom teeth, lower and upper second premolars.

Partial or complete adentia occurs with ectodermal dysplasia - a hereditary disease associated with a developmental disorder of the ectoderm. The remaining individual teeth have conical crowns. Patients have smooth, atrophic skin, no sweat and sebaceous glands, impaired nail development, a prominent forehead, saddle nose, thick lips, and xerostomia due to aplasia of the parenchyma of the salivary glands.

In case of congenital increase in the number of teeth, the supernumerary tooth may be normally developed or rudimentary, located in the dental row or outside it. Milk supernumerary teeth have the same shape as the complete teeth, and permanent teeth are usually atypical. Sometimes supernumerary teeth do not erupt and are discovered accidentally on radiographs taken for another reason. Supernumerary teeth are most often found in the area of the lower incisors, and fourth molars are often observed.

Incorrect position of a tooth in the dental row (from the buccal or lingual side), rotation of a tooth around the axis, location of the tooth crown below the chewing surface of adjacent teeth are determined during a clinical examination. X-ray examination is indispensable for assessing the position of a tooth in the jaw. The gap between adjacent teeth is called a trema. The absence of tremas in children aged 5 years indicates a delay in jaw growth. Tremas 0.5-0.7 mm wide are considered a normal variant. A gap between the central incisors 0.6-7 mm wide is called a "diastema".

The size of teeth can be reduced (microdontia) or increased (macrodontia). This concerns one, several or all teeth. Incisors are most often affected. Macrodontia of all teeth is one of the symptoms of pituitary diseases.

The most common anomalies in the development of the roots of permanent teeth are curvature, shortening or lengthening, increase or decrease in their number, divergence and convergence, bifurcation. The most variable are the shape and number of roots of the lower molars, especially the third ones.

The shape of all teeth changes with cretinism and ectodermal dysplasia. The barrel-shaped central incisors with a crescent-shaped notch along the cutting edge observed in congenital syphilis are called Hutchinson's teeth (named after the English doctor J. Hutchinson).

Intrauterine teething is observed in only one in 2000 newborns. In 85% of cases, the central lower incisors erupt in utero,

Ankylosis - the fusion of root cement with the alveolar bone tissue - develops after the use of the formalin-resorcinol method, trauma, and rarely in second primary molars. Due to the absence of a periodontal gap occupied by bone tissue, a duller sound is noted upon percussion of an ankylosed tooth. Significant difficulties arise when removing such teeth.

Tooth in a tooth (dens in dente): in the cavity of the tooth and the wide root canal there is a tooth-like formation, surrounded on the periphery by a strip of enlightenment.

One of the types of anomalies is the fusion of adjacent teeth - fused teeth. Most often, the fusion of the central incisor with the lateral one or one of them with a supernumerary tooth is observed. When the enamel organ splits, two crowns with one root are formed. Fusion of teeth in the root area can only be determined radiologically. When the crowns merge, they have one large dental cavity and two canals. If only the roots merge, then there are two tooth cavities and two root canals. In the presence of enlarged teeth, there is a lack of space in the dental row: the teeth located next to it erupt later and, as a rule, from the lingual or buccal side.

If a tooth is missing in the dental row by the time of its eruption (fluctuations in the range from 4 to 8 months from the average period are acceptable), it is necessary to take radiographs in order to determine whether there is a tooth rudiment. When analyzing the radiograph, it is also possible to establish the cause of the delay in eruption (retention): incorrect position of the tooth due to the displacement of the rudiment (dystopia), the presence of a pathological process (fracture, osteomyelitis, cyst, neoplasm). The most common cause of retention is a lack of space in the dental row. Tooth rudiments may be located far from their usual location (in the branch or at the base of the lower jaw, in the walls of the maxillary sinus), and their eruption becomes impossible. A retained tooth can cause displacement and resorption of the roots of adjacent teeth.

The most common types of impacted teeth are wisdom teeth (mainly lower), canines (mainly upper), and premolars (upper) less often. When planning the removal of an impacted or displaced tooth, it is necessary to determine its position and relationship with the nasal cavity, maxillary sinus, mandibular canal, and roots of adjacent teeth. To solve this problem, it is necessary to take X-rays in at least two mutually perpendicular projections.

When examining the teeth of the lower jaw, intraoral radiographs and extraoral radiographs in axial projection are taken. To determine the position of retained teeth of the upper jaw, along with intraoral radiographs (contact or axial), images in tangential projections are the most informative.

Dentinogenesis imperfecta is a congenital disease (Stainton-Capdepont syndrome); it occurs as a result of connective tissue dysplasia, sometimes combined with osteogenesis imperfecta. In sick children, the facial part of the skull is significantly smaller than the brain, the fontanelles and sutures remain unclosed for a long time, the bones of the skull are thinned. With normally formed enamel, the structure of dentin is disrupted (less mineral salts, fewer tubules and they are wider, their direction is changed). Such teeth are rarely affected by caries. At the same time, early progressive abrasion of teeth down to the gum occurs. An X-ray shows a decrease in the size or complete obliteration of the tooth cavity and root canals due to the formation of replacement dentin. Root canals are not determined or are visible only at the apex of the root. Due to the fact that the roots are usually thinner, there is a higher risk of their fractures due to injury. The color of the teeth is blue-brown, purple or amber.

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