Factors influencing the formation of teeth. Factors in the formation of groundwater composition. Oral fluid, as the main source of calcium, phosphorus and other mineral elements into tooth enamel, affects the physical and chemical properties of tooth enamel, while

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Timing of formation and mineralization of temporary teeth. Factors that interfere with tooth formation

Bookmark of the primordium

Beginning of mineralization

End of mineralization

7-13 week

47-20weeks

4-5 months

" 7*13 week

17-20 weeks

4-5 months

7-13 week

10-12 months

7-13 ;^|dividing

10-12 months

7-13th?

10-12 months

The formation and mineralization of tooth buds are influenced by: 1) In the prenatal period:

I. Health status of the expectant mother

1. Gynecological pathology of the expectant mother: fibroids, chronic adnexitis, short intervals between births, polyhydramnios, toxicosis of the first trimester, as well as repeated threat of miscarriage.

2. Acute respiratory infection and other viral diseases suffered in the first 12 weeks.

3. Nephropathy, rheumatism, bronchopulmonary pathology, purulent diseases (erysipelas, furunculosis)

II. The effect of unfavorable factors during pregnancy:

1. Taking antibiotics, salicylates, sulfonamides.

2. Malnutrition of a pregnant woman, unbalanced diet - deficiency of protein, mineral salts, microelements, vitamins.

3. Alcoholism and smoking

4. Stressful situations for the mother in the first trimester

5. X-ray exposure, occupational hazards (working with varnishes, paints, chemicals)

2) After the birth of the child

1. Malnutrition of the child

3. Ectodermal anhydrotic dysplasid.

4. Endocrine pathology with disorders of phosphorus-calcium metabolism

5. Frequent infectious diseases

6. Taking antibiotics

7. Lack of fluoride in drinking water

8. Excess fluoride in drinking water (fluorosis

Of these factors, nutrition, health status, etc. are constantly in play), some

Some (inferior

occasionally (infectious diseases, taking medications, etc.)

The effect of unfavorable factors can affect the formation, formation and mineralization of teeth.

Mineralization of teeth begins from the cutting edge or cusps and spreads along the lateral edges to the neck of the tooth.

Thus, if unfavorable factors act at the beginning of mineralization, then disturbances in the structure of hard dental tissues (usually enamel hypoplasia) are localized closer to the cutting edge and cusps; if closer to the end of mineralization, then the changes are localized closer to the neck.

Knowing the timing of the formation and mineralization of tooth buds (both temporary and permanent), it is possible to judge by the localization of tooth enamel hypoplasia when the influence of unfavorable factors occurred. And vice versa, knowing when such an effect was observed, it is possible to predict disturbances in the mineralization of some teeth.

All factors in the formation of the composition of groundwater can be divided into physical-geographical, geological, physical-chemical, physical, biological and artificial.

Physiographic factors include topography, hydrology, climate and weathering.

Relief influences water exchange, which determines the mineralization and composition of groundwater. All other things being equal, the more dissected the relief is, the more favorable the opportunities for the appearance of fresh groundwater. In the elevated areas of the basins, where the rocks are well washed, the groundwater has a relatively low mineralization and mainly a hydrocarbonate composition: in the lower parts, where the flow of salts from the elevations is directed, the mineralization increases, and the concentration of sulfates and chlorides in the waters increases. There is a fairly stable dependence of the concentration of iron in shallow groundwater in Belarus on the relief. This issue was studied due to the fact that in Belarus, groundwater from Quaternary sediments very often contains iron, much more than its maximum permissible concentration, and the task was to outline the location of wells for water supply, from which it would be possible to obtain water with a minimum iron content . It turned out that in elevated areas there is less iron in the waters than in low relief areas.

The hydrological factor (hydrology) affects groundwater primarily through the hydrographic network, which affects water exchange. A dense hydrographic network with a deep erosional incision promotes water exchange in aquifers, the removal of salts and the formation of fresh groundwater. With a sparse hydrographic network and its shallow incision, underground flow is difficult, which causes an increase in the mineralization of groundwater. This is an indirect influence of the hydrographic network on the composition of groundwater. In those cases when aquifers are fed from the waters of rivers and lakes, the influence of the hydrological factor is direct and decisive. In the middle zone, this is especially pronounced during floods, and in deserts, rivers (for example, Amu Darya, Syr Darya) can feed groundwater throughout the year. Oceans and seas act as a leading factor during transgressions. At the same time, mineralized waters are buried in the accumulating sediments, i.e. the seas transfer salts to groundwater in “ready” form.

Climate can be considered one of the most important direct factors in the formation of groundwater composition. Among the many climatic elements, the primary ones include precipitation, temperature and evaporation. Atmospheric precipitation forms groundwater resources and transfers salts to them (albeit a very small amount, but in a “ready-made form”). The total amount of meteoric moisture arriving annually on the land surface is more than 110 km 3 . This water is capable of covering the globe with a layer 834 mm thick. Of course, not all atmospheric precipitation participates in the recharge of groundwater, but only a tenth of it. Precipitation that falls in temperate latitudes in spring, summer or autumn penetrates into the bowels of the earth. In dry climates, precipitation may evaporate quickly and not reach the groundwater surface. The penetration of atmospheric water into the subsoil is also difficult under conditions of seasonal or permafrost.

Evaporation, which depends on air temperature, is most effective in areas of insufficient moisture. Here it causes concentrated salts in the waters. Evaporation does not only occur on the surface of the earth. The change in the composition of groundwater is strongly affected by the so-called intra-rock evaporation, during which water vapor molecules are separated from the groundwater table.

The leading physical and geographical factors in the formation of the composition of groundwater include weathering, a phenomenon that occurs on/and near the surface and is directly related to climate (in English weathering from weather). The combination of processes of physical, chemical and biochemical destruction of minerals and rocks, called weathering, leads to the enrichment of groundwater with various compounds. Weathering acts primarily as a process of transferring a substance into solution. As a result of weathering, the most soluble compounds are removed from the rocks and enter the groundwater first. It is interesting that if we take a large number of analyzes of the chemical composition of fresh groundwater in the sandy-clayey Quaternary strata of Belarus and calculate the average mineralization of these waters for the northern and southern parts of the republic, we will get a greater value for the northern regions. This is due to the fact that in the north the Quaternary deposits are younger than in the south. In the north, they were formed as a result of the activity of the last (Valdai) glaciation, which did not spread to the southern part of Belarus. In younger, less weathered rocks, more unstable components (feldspars, dark-colored minerals) have been preserved, which are currently being destroyed and, thereby, enrich the water with various compounds. In older rocks, the bulk of the unstable components have already been destroyed and removed during repeated water exchange. Thus, the role of weathering in the formation of groundwater composition is revealed even for very young and poorly soluble aluminosilicate sediments.

Geological factors. These factors include geological structure, tectonic movements, material composition of rocks, magmatism and gas factor.

The geological structure determines the dynamism, and with it the mineralization and composition of groundwater. The importance of geological and structural forms in the distribution of groundwater in terms of mineralization and composition is clearly manifested when comparing structural elements in terms of openness, flow, permeability or intensity of water exchange. Groundwater of closed structural elements is the most mineralized, and its composition is predominantly sodium or calcium chloride. In exposed structural elements, groundwater is the least mineralized and usually has a calcium bicarbonate composition.

Tectonic movements are usually divided into oscillatory, folded (or plicative) and discontinuous (or disjunctive). Oscillatory movements of a positive sign can cause desalination of groundwater in elevated areas of land, since these areas can be brought into the sphere of action of atmospheric waters. As a result of negative movements, the zone of fresh groundwater sinks and salinization becomes possible in it due to the fact that negative movements are accompanied by marine transgressions and the involvement of sea waters into the subsoil.

Fold and fault tectonic movements sharply disrupt the established hydrogeochemical conditions. Mountainous countries that have undergone active folding and rupture movements find themselves deeply washed by fresh waters. Disruptive faults, i.e. tectonic faults serve as pathways for unloading groundwater, channels for hydraulic communication between aquifers, facilitating the mixing of groundwater of different compositions, zones where, as a result of a sharp pressure drop, mineral deposition from groundwater and, as a result, a change in the composition of the latter is possible.

Material composition of rocks. If the geological structure and tectonic movements are among the indirect factors in the formation of the composition of groundwater, then rocks and minerals directly form the substance of the underground hydrosphere. The material composition of rocks is a direct factor of paramount importance, as was pointed out by Aristotle and Pliny the Elder, who said that water is the same as the rocks through which it flows. It should, of course, be noted that this connection between the composition of waters and rocks is not as simple as it seemed to the ancients. The influence of rock composition on the composition of groundwater is especially noticeable when fresh water interacts with easily soluble minerals and rocks: halite, gypsum, dolomite, limestone. Halite produces sodium chloride waters, gypsum produces calcium sulfate waters, dolomite produces magnesium-calcium hydrocarbonate waters, and limestone produces calcium bicarbonate waters. However, the same hydrocarbonate waters as in limestones can and very often occur in quartz-feldspathic sands. In this case, Ca 2+ and HCO 3 - ions appear in waters due to carbon dioxide weathering of feldspars, while in limestones - due to the dissolution of calcite (CaCO 3).

The material composition always affects the composition of groundwater. You just need to be able to see this influence. In the so-called Devonian intersalt deposits of the Pripyat trough, the same type of chloride calcium and sodium brines occur throughout its entire territory. However, the brines in the southern part of the trough contain significantly less potassium than the brines in the northern part. This is due to the fact that the intersalt strata of the southern part has a terrigenous (sandy-clayey) composition, while the northern part has a carbonate composition. In terrigenous rocks at depths starting from 2-3 km, the process of new formation of the clay mineral - hydromica - is actively occurring, for the construction of the crystal lattice of which the necessary potassium is extracted from underground brines.

There are other forms of manifestation of the influence of rock composition on the composition and mineralization of groundwater. Thus, the most mineralized brines (320-600 g/l) are found only in those strata above which rock and potassium salt formations lie. When gypsum and anhydrite are present in place of these chloride salts, the mineralization of the brines beneath them usually does not exceed 260 g/l. This is due to the fact that sedimentary complexes underlying salt rocks, gypsum and anhydrites (generally called evaporites) contain subsurface brines, which are transformed parent brines (brine) of the overlying salt (or evaporite) basins. These parent brines penetrate the underlying sediments by gravitational drainage or pressing from evaporitic sediments. But since evaporite minerals, during the thickening of sea water in a salt basin, are precipitated at a certain mineralization of the brine (for example, gypsum (CaSO 4 2H 2 O), starting from 140 g/l, halite (NaCl) - from 260-280 g/l, sylvite (KCl) - with 350-360 g/l), then depending on what minerals (rocks) the evaporite strata is represented by, there will be mineralization of underground brines under this strata. Here we have touched in passing on one of the grandest processes taking place on Earth—the evaporitic process or halogenesis. It is usually not identified as a factor in the formation of groundwater composition, because it can be represented by simpler physical and geographical factors: hydrology, climate, relief. However, it must be borne in mind that the area of ​​distribution of only salt (without taking into account gypsum-anhydrite) deposits reaches 34% of the territory of the continental block of the Earth. Evaporites are found in all geological systems from the Precambrian to the Anthropocene. Therefore, halogenesis plays a huge role in the formation of the composition of groundwater: both through the dissolution of evaporite rocks by water, and through the involvement into the depths of huge quantities of brines formed on the Earth’s surface during evaporative concentration.

Speaking about the material composition of rocks as a factor in the formation of groundwater, it is important to emphasize what is meant by this term “material composition of rocks”. Until now, speaking about the material composition of rocks, we have focused on the mineralogical composition of rocks, i.e. on the set of main minerals that make up the rock. However, when rock interacts with water, for example, during dissolution, not only chemical elements from rock-forming and minor (accessory) minerals will enter the liquid phase, but also adsorbed ions located in the absorbed rock complex, as well as so-called pore solutions contained in breed. All this together - solid minerals, adsorbed ions and pore solutions - is called the ion-salt complex of rocks. We will get acquainted with the complex of concepts associated with the phenomenon of sorption further - when considering the processes of formation of groundwater, and we will analyze the concept of “pore solutions” when we discuss the issue of paleohydrogeochemical reconstructions,

Let's return to the factors of groundwater formation. Of the geological factors, we only have to consider magmatism and the gas factor.

Magmatism. The role of this factor in the formation of groundwater composition is still problematic. Some researchers consider this factor to be the leading factor in some cases, while others completely reject it. This is explained by poor knowledge of volatile substances released during magma differentiation. The complexity of the issue lies in the fact that elements characteristic of magmatic exhalations can enter groundwater in other ways.

The gas factor has a great influence on the basic salt composition of groundwater. Suffice it to say that an increase in the content of gases dissolved in water affects the dissolving ability of water. Thus, an increase in the concentration of dissolved CO 2 in water leads to an increase in the solubility of calcite and quartz, which, naturally, can lead to a change in the composition of water.

Physico-chemical factors. These factors include the chemical properties of the elements, the solubility of chemical compounds, acid-base and redox conditions.

Chemical properties of elements. They determine the ability to form natural compounds. The most important physicochemical properties include the ionic radius and valence of the ion. The ionic radius largely characterizes the mobility of a chemical element. In principle, the smaller it is, the more mobile the hydrated ions.

The migration ability is also determined by the valency of the ion. For metals, with increasing valency, the formation of less soluble compounds is observed. Monivalent metals usually give easily soluble compounds (NaCl, Na 2 SO 4, K 2 CO 3). Compounds of divalent metals (CaSO 4, CaCO 3, MdSO 3) and even less soluble are compounds of trivalent metals (F e 3+ and Al 3+). There are, of course, exceptions to these patterns.

The solubility of chemical compounds is a direct factor in the formation of the composition of groundwater. There is no need to substantiate this thesis at length. Fresh waters are characterized by a predominance of bicarbonate, since it is this anion that forms a slightly soluble salt with calcium. As mineralization increases, a sulfate ion appears, characteristic of salt waters. However, due to its relatively low solubility, calcium sulfate quickly gives way to sodium or magnesium sulfate, and more often to chlorides, which form easily soluble salts with all the main cations. The most highly concentrated brines, in terms of the composition of the predominant salts, are magnesium or calcium chloride, since CaCl 2 and Mg Cl 2 are extremely easily soluble.

Acid-base and redox conditions, which we have already considered earlier, regulate the migration of chemical elements in groundwater, since the solubility of minerals and the form of occurrence of elements in solution (in the form of ions, certain complex compounds) depend on pH and Eh.

Physical factors. The range of physical factors in the formation of the composition of groundwater includes temperature, pressure and time.

Temperature is the leading factor on which the equilibrium in the water-rock-gas system depends. Temperature greatly influences the solubility of groundwater and the rate of chemical reactions. The solubility of most salts increases as the temperature rises, less often (for example, CaCO 3) it decreases.

Within the studied depths of the earth's crust, the temperature of groundwater varies from -16 °C (concentrated brines of permafrost rocks) to +400 °C (steam-hydrotherms of the centers of modern volcanism). Temperature determines the phase transitions of water into solid and vapor states. At temperatures above 75 °C, the activity of microorganisms stops. Temperature changes affect the viscosity of water. All these changes that occur in water and with water affect the formation of its chemical composition.

Pressure is a factor in the formation of water composition of paramount importance. This factor has a number of manifestations. Hydrostatic pressure determines the rate of water exchange, the speed of water movement, and therefore the composition. Geostatic pressure determines a complex set of processes associated with the extraction of solutions from the pores of clayey rocks into reservoirs, and thus also affects the composition through the dynamics of solutions. Finally, pressure affects the solubility of rocks and minerals. This issue has not been sufficiently studied, however, for a number of minerals (gypsum, anhydrite, silica minerals), pressure increases solubility.

An integral factor in the formation of the composition of groundwater is time. Time is the speed of chemical reactions, it is the duration of interaction in the water-rock-gas system, it is the age of the sediments containing groundwater, it is the age of the groundwater itself, and finally, it is geological history.

Biological factors. From the point of view of the influence of these factors on the composition of groundwater, the entire set of living organisms is important, which V.I. Vernadsky called it a living substance. The space where the activity of living matter manifests itself is a kind of shell of the Earth - the biosphere. The biosphere covers the terrestrial hydrosphere, the upper part of the lithosphere and the lower part of the atmosphere. In the earth's crust, the lower boundary of the biosphere corresponds to a temperature of 75-100 ° C - critical for the development of bacteria. Bacteria are distributed to a depth of 4 km and tolerate pressures of up to 3-4 thousand atm.

Animals and plants influence the composition of groundwater, mainly through microorganisms. As animals and especially plants die, they release minerals to the soil, which then enter the groundwater. The influence of plant activity on the composition of groundwater is also manifested in the fact that plants accumulate huge amounts of moisture and selectively absorb chemical components from groundwater.

Artificial factors. The essence of artificial factors in the formation of the composition of groundwater lies in human production activities. Here is a far from complete list of artificial factors. This is a violation of the natural regime of groundwater caused by the development of mineral resources, hydraulic engineering construction, land reclamation, exploitation of aquifers for water supply purposes, as well as the discharge of contaminated wastewater into the subsoil, the entry into aquifers of products of atomic explosions and sprayed toxic chemicals. As examples, let's look at the action of some artificial factors in more detail.

A lot of chemical compounds (NaCl, CaSO 4, CaCO 3, metals, oil, etc.) are extracted from the depths of the Earth every year. In addition to disturbing the natural balance in the rock-water system, this leads to the penetration of a large amount of air oxygen into the depths, i.e. to oxidation processes, which causes the inevitable transfer of additional substances into groundwater. The depth of the oxidizing effect sometimes reaches several kilometers (for example, in oil and gas fields, where entire rivers of water are pumped into deep horizons to maintain pressure during hydrocarbon production).

Hydraulic construction causes redistribution of underground flow and changes in the geochemical regime of groundwater. During the creation of the reservoir of the Bratsk hydroelectric power station in the coastal carbonate massifs, groundwater was desalinated, which sharply intensified the processes of karst formation.

On the territory of Belarus, during reclamation work in a number of areas, undesirable salinization of groundwater was noted. A significant environmental problem for the territory of our republic is the pollution of shallow groundwater with nitrates, which is associated with the low standard of using fertilizers and keeping livestock. Significant contamination of groundwater occurs under the influence of salt dumps of the Soligorsk potash plant and phosphogypsum dumps of the Gomel Chemical Plant. In the latter case, the waters become polluted with sulfur, phosphorus, and fluorine.

A lot can be said about artificial factors in the formation of the composition of groundwater. But what has been said is apparently enough to make it clear how acute the problem of clean water is in our time.

In connection with the above, it is advisable to distinguish two periods of mineralization of temporary teeth that occurs in utero: 1 - mineralization of incisors and initial signs of mineralization of molars; 2 - mineralization of all surfaces of the incisors, except the cervical part, and mineralization of the molars.

Using these data, it is possible to calculate the formation time of other tooth surfaces.

Based on the data obtained, it can be argued that the defects of hard fabrics temporary teeth, localized in the cervical region of the incisors, in the area of ​​the cutting surfaces of the canines and the vestibular surface of the molars, arise under the influence of extreme situations in the development of a newborn child in the first months of life.

Pathology of temporary incisors, isolated from the pathology of molars, occurs in cases of pathological influence on the developing rudiment before 17 weeks of pregnancy.

Pathological conditions affecting the formation of temporary teeth in the period after 17 weeks of pregnancy can cause the development of defects only in temporary molars.

Temporary central incisors, in which by this time their cutting part and adjacent tissues have been calcified, may not be affected by this pathological process

Pathological conditions affecting the calcification of primary teeth during pregnancy after 24 weeks disrupt the process of formation of both incisors and molars, however, the localization of these defects will correspond to the middle third of the vestibular surface of the incisors and the cutting surface of the canines.

The above indicates that antenatal pathology of primary molars is localized on the cusps and the adjacent vestibular surface of the crown.

Dental malformations in children born prematurely from mothers with extragenital diseases, toxicosis of pregnancy, etc. Literature data convincingly prove that many maternal diseases, both acute and chronic, leading to chronic fetal hypoxia, toxicosis of pregnancy, antigenic incompatibility blood mother and fetus lead to serious changes that can cause fetal death, premature birth of a child, as well as deviations in the development and function of organs and systems in the child after birth.

Such profound changes in body mother and fetus have a negative effect on the formation of organs cavities mouth and teeth of the fetus.

Thus, G.S. Chuchmai (1965) showed that during the physiological and pathological course of pregnancy, different degrees of maturity of the rudiments of temporary teeth are recorded. In healthy pregnant women, under optimal conditions for fetal development, tooth formation occurs faster and calcification of the dental tissues of the temporary incisors is better, while in women with toxicosis and concomitant extragenital diseases the development of primary teeth in the fetus is somewhat delayed, and the mineralization of the tissues of these teeth lags significantly behind.

Disruption of the process of embryogenesis in the rudiments of teeth manifests itself in the form of various forms of hypoplasia of hard teeth. fabrics teeth. In this case, degeneration or destruction of adamantoblasts occurs, the insufficient, slow, and often perverted function of which causes a disruption in the process of formation of protein structures and mineralization of temporary teeth.

Many researchers have scientifically proven that the resistance of primary teeth to caries is seriously influenced by carbohydrate metabolism disorders that developed in the mother during pregnancy, caused by thyroid diseases, mental trauma, viral diseases, chronic hypoxia, etc.

O. A. Prokusheva showed that the degree of mineralization of the enamel of primary teeth and the saturation of the mineral components of this substrate in premature children is significantly lower than in children born at term, and depends on the health status of the child born prematurely. The enamel of temporary teeth of premature children who have suffered various diseases during the neonatal period and infancy is hypomineralized compared to the enamel of the teeth of healthy full-term children.

Malformations of temporary teeth, complicated by caries and combined with caries, are found in children born with the first degree of prematurity in 59.0%, in children with the second degree of prematurity in 72.5% of cases, in children who suffered more than 3^4 diseases during the neonatal period and infancy , the frequency of the described pathology is 72.5% of all children [Prokusheva O. A., 1980; Belova N.A., 1981).

Having compared the data from a clinical examination of children born prematurely and an X-ray study of the jaw blocks of fetuses of different ages (from 16 to 38 weeks), N. A. Belova (1981) found that calcification of the incisors is ahead of the calcification of the molars. The cutting surfaces of the incisors become calcified in the first half of pregnancy (1st critical period of antenatal tooth formation), molars are formed in the second half of pregnancy. That is why, when examining children in the first year of life, a doctor may not register pathologies, but when examining a child at 3 years old, he may find malformations of his primary molars.

The impact of factors that disrupt antenatal odontogenesis throughout pregnancy and continuing during the period of intramaxillary odontogenesis causes the formation of malformed teeth of all groups of incisors, canines and molars.

If the frequency of registered malformations of primary teeth during examination of a child at 1 and 3 years of age can “increase,” then this frequency cannot decrease.

Misconception about reducing the incidence of malformations fabrics temporary teeth can be created in cases where the defects are complicated by caries; the carious process spreads to the entire area of ​​​​malformed tissues and clinically, as it were, replaces them. However, this does not exclude the correct diagnosis of the combined pathological process in the tooth. To correctly diagnose and differentiate this process, it is recommended to use the method of examining tooth tissue under ultraviolet light. Healthy tissue tooth glows in ultraviolet light - luminesces, appearing as a light green glow; with hypoplasia textile acquires a gray-green glow; with caries, the lesion darkens (extinguishes). Differential accounting of changes in the luminescence of tooth tissues in ultraviolet lighting allows, using this method, to differentiate malformations of dental tissue, caries and defects complicated by caries.

In the last decade, the study of the eruption of permanent teeth has acquired particular importance due to the impact on the growing organism of an increasing number of unfavorable environmental factors. Moreover, in the literature there is data on the eruption of permanent teeth in various regions of Russia, characterized by different climates and ecology, as well as in groups of children with different living and nutritional conditions. Many authors draw attention to the relevance of studying the processes of variability of the dental system depending on gender, ethnicity, region of residence and anthropometric characteristics of a person, since these processes reveal the direction of evolution in the ontogenesis of modern humans.

Teething is influenced by various external and internal factors: heredity, characteristics of individual development, general somatic pathology, social factors, local factors.
Thus, the genes responsible for the process of teething can be different - some, through the endocrine system, determine the growth rate of the entire organism, others determine localized growth gradients that establish the order of teething and the appearance of ossification centers in the wrists. In terms of skeletal maturity, as well as in terms of the criteria for the process of eruption, girls are on average ahead of boys throughout the entire period of growth, from birth to adulthood. The lag of boys is primarily associated with the action of Y-chromosome genes, since all known specific male hormones have an accelerating, rather than inhibiting, effect on bone maturation. Various authors indicate that environmental factors play a decisive role in the process of teething.

Features of individual development are also associated with the process of teething. Physical development is the state of the morphological and functional properties and qualities of a growing organism, as well as the level of its biological development. In view of significant individual differences, a time characteristic was introduced that reflects the rate of individual growth, development, maturation and aging of the organism: biological age. Indicators such as the degree of puberty, body size, number of permanent teeth, age-related changes in physiological and biochemical parameters, “bone age” are interrelated, as they reflect a single and multifaceted process of growth and somatic development. Due to the fact that the formation of teeth occurs in the prenatal period, the criteria for assessing dental age are less dependent on environmental influences than bone age indicators, and therefore more clearly characterize biological age. The greatest information content for determining the latter belongs to the first molars and central incisors. The human constitution reflects not only the morphological characteristics of the body, but also its functional state. Thus, a relationship was identified between the type of hemodynamics and the constitutional type, as well as the nature of the response of the cardiovascular system to aerobic physical activity and the connection with the physiological indicators of the external respiratory system. In addition to the parameters of the physical development and constitution of the child, the relationship between teething and other anthropometric parameters, in particular, the size of the facial skeleton, was traced. It has been shown that facial changes are closely related to the appearance of teeth.

The formation of the lower jaw and an increase in its size occurs up to 25 years in parallel with the development and eruption of teeth. The angular width, projection length, height of the body and branches of the lower jaw increase especially intensively during the eruption of primary teeth, change of bite and during the eruption of third permanent molars.

For the normal formation of the dental system, past and concomitant diseases during mineralization, formation and eruption of teeth are important. A special role belongs to the endocrine system and primarily to the activity of the thyroid gland. For example, in children with hypofunction of the gland, teething is delayed, while in children with hyperfunction it is accelerated. In cases of cerebral-pituitary dwarfism, Itsenko-Cushing's disease and tumors of the adrenal cortex, the sequence and pairing of teeth eruption may change, the resorption of the roots of milk teeth may be delayed, and the timing of the formation of the roots of permanent teeth may change. The etiology of delayed eruption also includes rickets, especially its severe forms, which is manifested by long breaks between the appearance of teeth of different classes, a violation of the sequence and symmetry of teeth eruption. Clinical studies indicate a significant impact of health status and previous diseases on the process of teething. Thus, there is a corresponding connection with vitamin deficiency, tuberculosis intoxication, exudative diathesis, diseases of the large intestine and stomach.

The process of teething may depend on a number of local factors, for example, on the depth of the tooth germs in the bone, on the presence of various types of dentoalveolar anomalies. It has been observed that incisors and first molars erupt earlier in children with malocclusions, and canines, premolars and second molars erupt earlier in children without dental anomalies. The relationship between teething and the depth of the vestibule of the oral cavity is shown: in children with a shallow vestibule, the average number of erupted permanent lower incisors is higher than in children with a vestibule of physiological depth. The influence of caries of primary teeth and its complications on the rudiments of permanent teeth is important. These pathological factors are especially relevant in relation to the change of temporary molars to premolars, since they are more often than other temporary teeth affected by caries, remain longer in the jaw, and their roots are topographically closer to the rudiments of permanent premolars. According to some authors, the eruption of permanent teeth occurs in place of untreated and pulpless primary teeth, which is explained by the accelerated resorption of roots with necrotic pulp and the facilitating effect of destructive changes in the periapical structures on the advancement of tooth germs to the alveolar edge. According to other researchers, intact teeth are replaced earlier due to the vigorous participation of living pulp and root resorption.

The importance of regional factors, or rather climatic-geographical, ethnic, nutritional and environmental factors, is also emphasized by many researchers. Thus, fluctuations in the timing of the eruption of permanent teeth have been noted in various climatic and geographical regions of the countries of the former USSR.

A significant correlation between growth and average annual temperature has been established for various regions of the globe. On the other hand, significant intergroup differences have also been identified in teething depending on ethnic characteristics. For example, the timing of teething is different among Russian and Kyrgyz children, among Russians and Kazakhs, white Americans and Europeans, children of Ghana and white Europeans. Negative factors of the environmental situation that change teething include the proximity of a nuclear test site and fluoride pollution.

The role of a balanced diet, in particular its effect on protein and mineral metabolism, also plays a role in the development of the dentofacial apparatus. With poor nutrition, teething is delayed and the order of their eruption is disrupted.
Among the group of external factors, the social environment has a significant influence on the rate of growth and development, outstripping geographic factors. In this case, the profession or income of the father, the size of the family, the type of settlement, the standard of living of the population, living conditions, and the share of expenses for the child in the family budget are taken into account. Children from socially prosperous families develop faster in all respects; Accordingly, teeth change earlier than in children from middle-income or low-income strata. Differences in the dynamics and other indicators of teething have also been proven depending on the type of settlement
— children living in cities are ahead of their rural peers in terms of teething.
Thus, the multifactorial nature of the teething process shows the need to pay closer attention to studying the influence of many factors on this process, which may be of interest not only for researchers, but also for practicing pediatric dentists and orthodontists.

Lecture No. 3

1. Anatomy - physiological characteristics of the child’s body. Periods of childhood.

2. Development of teeth.

3. Primary mineralization of hard dental tissues.

4. Mechanism of teething. The timing of the eruption of temporary and

Permanent teeth.

5. Growth, development and formation of the tooth root and periodontal tissue.

6. Secondary mineralization of hard dental tissues.

Anatomical and physiological features of the child’s body

The development of tissues and the improvement of the functions of individual organs and the entire organism as a whole are processes that fundamentally distinguish a child’s body from an adult.

According to the nature and intensity of changes occurring in the body, it is customary to distinguish the following periods of child development:

1) intrauterine (antenatal) development - 280 days (10 lunar

months);

2) newborns - about 3-3.5 weeks;

3) infant - up to 1 year;

4) nursery - from 1 to 3 years;

5) preschool - from 3 to 6 years;

6) school - from 6 to 17 years old, in this period there are:

Junior school - from 6 to 12 years;

Senior school age - from 12 to 17 years old.

Prenatal period of development. Maxillofacial development

The period of intrauterine development is the most important, responsible and most vulnerable phase of fetal development.

All anomalies, in general, are characterized by deviations from the normal development of the face, jaws and teeth during embryogenesis, begin mainly in the early stages and are of an initial nature. Violation of the structure, shape and size that occurs with further growth and development of the dental system are derivative, secondary in nature.

Dental development

The development of teeth lasts two main periods - intramaxillary (before tooth eruption) and intraoral (after eruption). The main stages of development of human teeth are identified, which smoothly transition into each other and cannot be clearly demarcated:

1) the laying of the dental plate with the subsequent formation of tooth germs occurs during the period of intrauterine development. The formation of tooth germs can occur both in the antenatal and postnatal periods of human development. always intramaxillary.

2) tissue differentiation;

3) histogenesis;

4) primary (intramaxillary) mineralization.

5) tooth eruption;

6) growth, development and formation of roots and periodontal tissues, with which the processes of secondary mineralization of hard dental tissues are simultaneously activated. 7) stabilization (of functioning). The duration of this period for each group of both temporary and permanent teeth is individual.

8) resorption (resorption) of roots.

Formation and formation of a tooth germ

At the 7th week of intrauterine development, along the upper and lower edges of the primary oral cavity (in the area of ​​the future dental arches of the upper and lower jaws), a thickening of stratified squamous epithelium occurs, which grows into the underlying mesenchyme, creating a dental plate.

The dental plate grows in depth, takes a vertical position and is divided into vestibular and lingual. The epithelium of the syncinal part of the dental plate first actively grows, thickens, and later, part of its cells degenerates, forming a gap - the vestibule of the oral cavity, which separates the lips and cheeks from the gingival arch. The epithelium of the lingual part of the dental plate, plunging into the mesenchyme, gives rise to all temporary and permanent teeth (Fig. 2).

Fig. 2 Early stage of tooth development: 1 - epithelium of the oral mucosa, 2 - neck of the enamel organ; 3 - outer enamel epithelium; 4-pulp of the enamel organ; 5 - internal enamel epithelium; 6 - dental papilla; 7 - dental sac; 8 - trabeculae of newly formed bone; 9 - mesenchyme.

First, the epithelium proliferates in the form of buds, which transform into flask-shaped growths, which later take on the appearance of caps, forming an enamel organ. In the enamel organ of the tooth germ, formed by two thickened layers of stratified epithelium, a protein liquid is produced between the cells in the central part of the enamel organ, which gradually separates these layers into outer and inner, between which the pulp of the enamel organ is formed.

As a result of differentiation, the cells of the enamel organ, which were initially identical in morphology, acquire different shapes, functions and purposes. The epithelium adjacent to the mesenchyme of the dental papilla is tall cells of a cylindrical or prismatic shape, in the cytoplasm of which an increased content of glycogen accumulates. Subsequently, these cells form enameloblasts (ameloblasts, adamantoblasts) - cells that produce the organic matrix of tooth enamel.

Thus, the enamel organ gives rise to tooth enamel and cuticle, which is directly involved in the formation of the dentogingival attachment. The function of the enamel organ is also that it gives the crown part of the tooth a certain shape and induces the processes of dentinogenesis.

At the same time, under the concave part of the enamel organ, under the inner layer of its epithelium, the mesenchymal cells that make up the dental papilla intensively aggregate. It gives rise to the formation of dentin and dental pulp. The mesenchyme surrounding each enamel organ and dental papilla compacts and forms the dental sac, from which the cementum and psriodont are formed.

Thus, as a result of the transformation of epithelial and mesenchymal tissue, which most intensively occurs during the periods of anlage, differentiation, and histogenesis, a tooth germ is formed (Fig. 3).

Fig.3. Early stage of tooth development (tooth germ): 1 - epithelium of the oral mucosa; 2-nameloblasts; 3-enamel; 4-dentin, 5 - predentin; 6 - dentinoblasts; 7 - dental plate and permanent tooth anlage; 8 - dental pulp, 9 - remnant of the enamel organ, 10 - bone trabeculae; 11 - mesenchyme.

The formation of the rudiments of all temporary teeth occurs in the antenatal period of development, starting from 6-7 weeks of embryogenesis. The formation of the rudiments of permanent teeth occurs in the following sequence: the dental rudiments of the first permanent molars and central incisors begin to form at 5 and, respectively, 8 months of the prenatal period of development. In the first six months of a child’s life, the development of the dental buds of the permanent lateral incisors occurs. In the second half of the 1st year of life and in the first half of the 2nd year of the child’s life, the development of the dental buds of the first premolars occurs. At the end of the 2nd year of a child’s life, the dental buds of the second premolars are formed, and at the 3rd year, the second permanent molars and canines form. The formation of dental buds of the third permanent molars ("Wisdom" teeth) occurs before the age of 5 years. By this period of child development, the bone tissue of the jaws still contains remnants of embryonic tissues - epithelial and mesenchymal, which are capable of differentiation and initiate histogenesis.

Primary mineralization of hard dental tissues

The synthesis of the organic matrix of hard dental tissues initiates their primary mineralization. The timing of the onset of primary mineralization of primary teeth is shown in Table. 1.

Primary mineralization of hard tooth tissues occurs very intensively during the intramaxillary period of its development. It always starts from the cutting edge of the incisors and canines, as well as from the tubercles of the chewing teeth and continues along the entire length of the tooth crown. Dentin located under the enamel is first structured by organic substances and later acquires signs of mineralization. The period of primary mineralization of hard dental tissues lasts for different times. Primary mineralization is more active in primary teeth, namely, in the central and lateral incisors of both jaws (6-8 months).

Rice. 4. Structure of the enameloblast (A Ham, D. Cormack, 1983): 1 - enamel matrix, 2 - Tom's process 3 - secretory granules; 4-apical locking plates; 5-Golgi complex; 6 - granular endoplasmic reticulum, 7 - nucleus, 8 - mitochondria; 9-basal locking plate

Rice. 5. Structure of dentinoblast (A Ham, D. Cormack, 1983): 1-dentin; 2-zones of mineralization; 3 - Toms' process, 4 - predentin; 5-zamikasigshastinka; 6-granular endoplasmic reticulum, 7 - Golgi complex; 8-core.

The young enamel of a tooth that has not yet erupted is similar in chemical composition to mature enamel. It consists of 65% water, the content of organic substances is 20%, and mineral substances - less than 15% (the so-called soft enamel). The quality of the processes of primary and secondary mineralization of hard tissues of the tooth shapes its caries resistance in the future. After intramaxillary mineralization of the coronal part of the tooth germ, it erupts.