In enamel hydroxyapatite crystals are present, carbonate, hlorapatita. fluorapatite, etc. Less than 2% of the weight of mature enamel are neapatitnye form. They represent the remnants of the minerals present during the development of forelock, and are the result of a breach of mineralization after its eruption.
The main mineral components of which are built apatite crystals are calcium (33-39%) and phosphates (16-18%), molar ratio in the enamel which averages 1.67. The concentration of these minerals is highest in the surface layer and decreased in the deeper layers.
The surface layer of enamel is different from the deep layers of greater salinity, density, microhardness, resistance to decay, a higher content of trace elements, including fluoride. The surface layer of enamel exposed to less acid than its internal parts.
Mineralization in some areas crowns Chub is different: the most mineralized chewing surfaces, the least cervical region, fissures and pits of teeth.
In the enamel is present about 40 trace elements, which can be subdivided into three groups.
The first group includes fluorine, zinc, lead, antimony, iron, whose concentration is higher in the surface layers of enamel
The second group includes sodium, magnesium, carbonates, the contents of which more in the inner layers of enamel
The third group includes strontium, copper, aluminum, potassium, which are evenly distributed throughout the thickness of enamel
The surface of the crystal gidroksiappatita has an electric charge which is balanced by ions of opposite sign, enamel behaves as a porous membrane, and in depth more easily pass small ions than large molecules that are adsorbed on the surface of the crystal and can be desorbed without changing its shape.
In the apatite exchanges to one third of the ions. So. calcium ions can be replaced with sodium ions, silicon, strontium, lead, cadmium, and other hydronium cations. Hydroxyl ions can be exchanged for nones fluorine, chlorine, and others.
The penetration of substances in the enamel and ion exchange taking place in several stages. On the surface enamel ions through mikroprostranstva penetrate the water layers surrounding the crystal surface, and then in different parts of the crystal lattice. If the first stage can last for several minutes, then the following days and weeks.
Important role in the mineralization of tooth eruption after the plug is a physiological property of the enamel, as permeability (p. capable of cells and tissues to pass gas, water and its dissolved substances).
Permeability of enamel for different substances varies. Monovalent ions and negatively charged particles penetrate better than the two-valent and positively charged. Adopted by a high penetration of organic matter and low calcium and phosphate.
Permeable in different anatomical parts of the tooth is not the same because of the inhomogeneity of its structure. Highest permeability was noted in cervical area, pits, fissure. The least permeable surface layers of enamel. With age, the speed and depth of penetration of substances in the enamel is reduced, probably due to compression of the crystal lattice.
