Amelogenesis imperfecta is a genetically determined violation of the structure of tooth enamel. The main complaints are reduced to a change in the color of teeth, an increase in their sensitivity, the appearance of depressions, furrows, and pits on the enamel surface. The diagnosis is based on the collected anamnesis, physical examination data, and X-ray results. Treatment is aimed at eliminating aesthetic and functional defects. In case of disease, remineralizing preparation, restoration of the shape and color of teeth with the help of restorations or by prosthetics are shown.
Amelogenesis imperfecta (brown enamel dystrophy) is a hereditary disease that occurs due to a violation of the laying and formation of ectodermal sheets, manifested by defects in the enamel of temporary and permanent teeth. There are 3 types of inheritance of amelogenesis imperfecta: autosomal dominant, autosomal recessive and X-linked. The population frequency is 1:7000-1:14000. Of all the hereditary enamel lesions, hypocalcification with an autosomal dominant type of inheritance is the most common, the frequency of diagnosis of which reaches 1:20,000. Female and male representatives suffer equally. Amelogenesis imperfecta can be not only an isolated pathology, but also combined with other systemic disorders. Often there are combinations of amelogenesis imperfecta with a narrowed arch of the upper jaw, an inverse curve of the Spee, a vertical type of growth, an open skeletal bite.
Amelogenesis imperfecta is a hereditary malformation of enamel. The transfer of mutant genetic material is carried out both through the sexual X chromosome and through autosomes. With an autosomal dominant type of inheritance, the probability of the disease in the offspring is 50%, with an autosomal recessive – 25%. The main cause of amelogenesis imperfecta is mutations of the amelogenin gene, which is associated with the X chromosome. In total, up to 14 such mutations are distinguished.
The KLK4 gene (belongs to the kallikrein gene family) is located in the telomere region of chromosome 19. With the pathological activity of KLK4, enamel crystals of a smaller thickness are formed. The MMP-20 gene encodes the formation of an enzyme – calcium-dependent proteinase, affects the formation of an organic enamel matrix. The DLX3 gene regulates the processes of osteogenesis, is associated with the development of amelogenesis imperfecta, and is also directly related to the occurrence of tricho-dentoossal syndrome, taurodontism. The role of genes localized in chromosome 4 (enamelin, ameloblastin, amelotin) in the origin of amelogenesis imperfecta remains insufficiently studied.
In dentistry , there are four main forms of amelogenesis imperfecta:
- Hypoplastic type. Occurs when there is a violation of tissue differentiation. With the development of the hypoplastic form, the secretory activity of ameloblasts is disrupted.
- Hypomaturation. It develops in case of failure at the stages of formation and primary mineralization of the enamel matrix. The thickness of the enamel is within the normal range, but the mineral content is reduced. During hypomaturation, the following changes are observed: pathological cleavage of enamel matrix proteins, abnormal proteinase activity.
- Hypocalcification form. Occurs when the mineralization phase is disrupted. It is accompanied by an abnormal growth of crystallites and a decrease in the mineral component of enamel.
- Hypomaturation with hypoplasia and taurodontism. The failure occurs at the stages of tissue differentiation and layering of the enamel matrix.
The severity of the clinical picture depends on the form of amelogenesis imperfecta. All four types are characterized by the following manifestations: thinning of the enamel, a change in its color, a violation of transparency, the appearance of depressions on the cheek surfaces, partial or complete absence of enamel, the presence of pathological tooth erasability.
With hypoplastic type of amelogenesis imperfecta, the teeth are of normal shape. There is a decrease in the thickness of the enamel, as a result of which dysocclusion develops. Point defects are located longitudinally on the cheek walls. Cup-shaped depressions are often found on the chewing surfaces of molars, which subsequently leads to chipping of the tubercles, a decrease in the height of the bite, displacement of the articular head of the temporomandibular joint. The color of the teeth varies from light yellow to dark brown. In the hypoplastic form of amelogenesis imperfecta, there is a delay in teething with resorption of their roots.
The hypomaturation type is characterized by a normal enamel thickness with a reduced mineral content. This leads to a low X-ray density of the enamel. The color changes from milky, matte white (with a “snow cap”) to amber. The vestibular surface of the teeth is covered with small dots, vertical stripes. The hypocalcification form characterized by the following signs: color change, loss of luster, violation of the structure, the appearance of frequent chips. The enamel becomes soft, as a result of which it gradually separates from the dentin.
With this disease, a sufficient thickness of the enamel layer is preserved, as a rule, only in the cervical region, which is explained by a higher level of calcification. Also, resorption of uncut teeth is often observed. In hypomaturation with hypoplasia and taurodontism, the enamel of temporary and permanent teeth has a diverse color, covered with opaque specks. Due to chipping, teeth acquire a different shape: cone-shaped, rounded, cylindrical with pitted cutting edges.
Significant importance in the diagnosis of amelogenesis imperfecta is given to the collection of anamnesis and the identification of genetically determined factors of the disease. During a clinical examination, a dentist determines a violation of the enamel structure in the form of furrows, pits, specks. There is no natural shine, the teeth look “plaster”. With the localization of lesions in the area of the chewing surface, a decrease in the height of the bite is diagnosed. Due to the thinning of the enamel, dentin is exposed, the staining of which leads to a change in the color of the teeth from yellow to dark brown. Dentists often identify a combination of amelogenesis imperfecta with an open bite.
During radiography, a smaller thickness of the enamel is determined, areas of different shapes and different densities are projected on the crowns of the teeth. In most cases, with the hypoplastic form of amelogenesis imperfecta, hypomaturation and hypocalcification, the pulp chamber, root canals, the shape of the roots without pathological changes. Occasionally there is obliteration of channels due to dystrophic calcification of the pulp. Hypomaturation with hypoplasia and taurodontism has characteristic radiographic signs: an expanded pulp chamber, a shortened root, an increased distance from the occlusal plane to the bifurcation site.
Pathology must be differentiated with manifestations of imperfect dentinogenesis, as well as with such non-carious lesions of the teeth as enamel hypoplasia, fluorosis, erosion, enamel necrosis. To determine the hereditary nature of amelogenesis imperfecta and to identify a combined systemic pathology, a medical and genetic consultation is indicated.
The basis for the treatment of amelogenesis imperfecta is symptomatic therapy. At the first stage, remineralizing preparation is carried out. For this purpose, applications of fluorine- and calcium-containing preparations are used. The procedures are carried out every 3 months. Dentists also recommend covering the affected areas of enamel with fluorides at home. A good effect can be achieved when using a drug containing casein phosphopeptide and amorphous calcium phosphate as the active substance. For preventive purposes, the fissures of the lateral teeth are sealed with glass ionomer materials that emit fluorine.
The elimination of an aesthetic defect with amelogenesis imperfecta can be carried out both with the help of restorations and by prosthetics. Since acid etching aggressively affects the hard tissues of the teeth, composite materials are recommended to be used later. At the initial stage, glass ionomer cements are used to restore the chewing surfaces of the lateral teeth. This is due to their biocompatibility, good adhesion to enamel and dentin, and acceptable aesthetics.
Dentists consider the use of hybrid composite materials to be a temporary measure. With the thinning of enamel, compensatory processes occur in the dentin, as a result of which its structure becomes hypermineralized. This significantly reduces the strength of chemical adhesion, since the dentine tubules remain closed during etching. The optimal method of restoring aesthetics and function is orthodontic preparation followed by prosthetics.
When using direct restoration with composite materials as the main method of treating amelogenesis imperfecta, the prognosis is unfavorable, since the teeth continue to deteriorate further. Good long-lasting results can be achieved when the occlusal curves are aligned with removable orthodontic equipment, followed by covering the teeth with crowns.