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Enamel of teeth in 4% of water
09-09-2009
Enamel is formed from the ameloblast. In the period of development is its cyclical mineralization. Crystallization of calcium phosphate compounds in the process of mineralization and the subsequent growth of crystals is defined as prederuptivnoe maturation of enamel. Whilst retaining growth lines formed due to irregular mineralization of enamel. Each crystal has a hydrated layer of enamel, which is carried out by ion exchange.
After teething porosity and heterogeneity leveled by maturing enamel. Formed tooth enamel - it no regenerating tissue, not containing cells, cellular elements.
Tooth enamel - the hard tissue in the human body. On average, its thickness varies between 2,8 and 3,0 mm, depending on the degree of maturity, chemical composition and topography. The hardness of enamel varies from 250 KHN (Knoop-hardness numbers) on the border of the enamel-dentin to 390 KHN at its surface.
The basic structural element of the tooth enamel - inorganic substances, with estimates of their number vary depending on the method of analysis and samples (93-98% wt). The second largest component of enamel is water: data on its amount varies between 1.5 and 4% mass. Enamel also contain ¬ inh organic compounds, in particular proteins and lipids.
The composition of enamel affected by nutrition, age and other factors. Its constituent parts - a few types of apatite, the principal of which is hydroxy-apatite. In addition, the tooth enamel showed more than 40 trace elements. Some of these trace elements fall into the oral cavity only as a result of surgical operations, others (eg, tin, and strontium) can be regarded as a consequence of environmental influences.
The composition of enamel varies depending on its topography, due to variations in the concentration of individual elements. Thus, the concentration of fluoride, iron, zinc, chlorine and calcium decreases from the surface of the enamel towards the enamel-dentin border. Fluoride concentration in this sector increases, while the concentration of water, carbonate, magnesium and sodium decreased from amelodentinal border to the surface of enamel.
Apparently, the content of magnesium carbonate and the effect on densities of enamel. In areas with high concentrations of magnesium, near the hillocks of dentin and directly under the central fissures of teeth, there is a lower density than, for example, mineralized areas and the lingual surfaces of the cheek. Calcium and phosphorus as apatite compound contained in the form of crystals in the ratio of 1:1,2 (Sa10-hRO6-x) * X2 * H2O. Internal replacement reactions can lead to the formation of fluoride-apatite or fluoride, hydroxy-apatite. Also allow the possibility of formation of carbonate minerals in the enamel. The resulting apatite is less resistant to decay than hydroxyapatite. Along with these compounds in the enamel in a small number identified a number of calcium-phosphate compounds, for example, oktakaltsiyfosfat.
The water contained in the tooth enamel in two forms. The first - bound water (hydrate crystals envelope), the second-free water, based in micro spaces.
Free water can evaporate when heated, but the enamel is able to absorb the water when you receive moisture. This property can be used as an explanation of certain physical phenomena associated with the occurrence of caries or its preuprezhdenii.
The enamel of the tooth is maintained as «molecular sieve», and the enamel fluid serves as carrier molecules and ions.
Smaller part of the organic substance of mature enamel is composed of protein (= 58%), lipids (= 48%) and small quantities of carbohydrates, citrate and lactate. Most of the organic matter is in the inner third of the enamel shell in the form of enamel tufts.
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