Permeability of enamel

permeability means ability of matters to penetrate, diffuse through anything. In the majority of cases this term is wider: the ability to exchange between the enamel and environment of oral cavity.

• Specific composition of enamel is supported due to the receiption of mineral components from saliva. (LESS FROM THE PULP TO THE INNER ENAMEL LAYER ACROSS THE DENTIN)

• The mechanism of permeability of enamel can be explained as follows: Every crystal of enamel has a hydrate membrane of the constrained ions of Ca10 (PO4)6 (OH)2. Due to this hydrate membrane an ionic exchange (an ion in a crystal is substituted by other ion ) is carried out.

• Sizes and volume of interprismes spices play a important role in permeability, (limit of entrance of large molecules).

• Enamel is characterized as the negatively charged membrane. Cations and water penetrate through an enamel more intensive compare to anions.

• Enamel permeability plays important role in the decision of caries problem.

D.O.Entin (1930) was the first to report that the tooth enamel is a semi-permeable membrane, The permeability depends on the physical-chemical peculiarities of the habitat.

The results of experimental research and clinical observations proved the fact of calcium penetration to dental tissues from the saliva.

The enamel composition can be maintained by years by salivary components.

The mechanism of enamel penetration was explained by Pakhomov G.M., in 1982 year.

Every enamel hydroxyapatite crystal is covered with the hydrate layer. Its width is 1nm, it provides the ion exchange process.

The distance between crystals is 2,5 nm. The enamel pores are 3-6% of its volume. The size and volume of microspaces play leading role in enamel permeability, as they restrict penetration of large molecules into it.

The fluoride ions with their little radius, may come through the microspaces of enamel, but they have high activity and can quickly bind to the enamel components and don’t penetrate into the deep layers. The Ca²⁺ ions are absorbed on the crystal surface or constitute the crystalline grid, that’s why Ca in large quantity is deposited on the external enamel surface and it slowly diffuses to the deep layers.

The enamel permeability isn’t a constant notion, its level depends on many factors: age, level of pH of the environment, properties of oral liquid, and enamel.

The enamel permeability changes with age, especially at the age of 20-30 years, it starts to reduce. The age-related reduction of enamel permeability is connected with the maintenance of mineral components in oral liquid. The complete enamel mineralization after dental eruption occurs as a result of mineral salivary components action. The primary level of hypomineralised enamel areas permeability is high and is greately reduced to the moment of hard dental structures maturation. So, as time goes by, dental enamel permeability depends on the time of dental contact with the medium, surrounding it,-oral liquid.

The permeability can change according to the level of pH. The experiments with rats indicated that radioactive calcium from the saliva with pH 4,5 penetrates to the enamel more intensively, on the greater depth than calcium from the neutral saliva.

Chemical and physical factors may greatly influence enamel permeability.

The experimental data prove that dental plaque may increase enamel permeability level. This happens under the influence of enzymes, i.e. hyaluronidase, kallikrein and others, which may change dental tissues permeability (enamel), and also in the presence of organic acids ( lactic, acetic acids), which are formed under the dental plaque and enhance the permeability because of demineralization.