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BACKGROUND: The article presents a review of the chemical aspects of the reaction of light polymerization of composites in dental practice. This reaction refers to free radical polymerization reactions, with photons as activators. In dentistry, composites are classified as chemically cured, light cured, doubly cured, and thermally cured. This depends on the origin of the activation energy of free radical polymerization of methacrylates. Chemically, dental composites are usually a mixture of four main components: an organic polymer matrix, an inorganic filler, an appret compound, a binder matrix and filler, and an initiatoraccelerator system. The radical polymerization process includes four main stages. The first stage is activation; in the case of light cured dental composites, it is photoactivation. In this case, a photoinitiator molecule is excited, for example, camphorquinone, which is widely used in the production of dental composite materials. If a free radical is formed, the polymerization process is similar for all composite materials based on a methacrylate organic matrix. The only difference is exactly how free radicals are formed and the rate of their formation. Under the influence of light quanta, the carbon atom of the ketone group of camphorquinone passes into an excited state, which allows the excited photoinitiator molecule to interact with two methacrylate molecules by a double bond. The double bond gives one electron to the excited camphorquinone molecule, and the second electron acts as a free radical agent; in other words, a macroradical is formeda monomer molecule that can attach other monomer molecules to itself.

BACKGROUND: Тhe article presents a review of adhesive systems in terms of their component chemical composition. Seven generations of adhesive systems have been studied. The first generation of adhesive systems emerged in the 1970s. The result of the action was the bond reaction of the adhesive with calcium enamel and dentin. Glycerophosphoric acid dimethacrylate was used. The use of methacrylates in adhesive systems was widespread because polymers with high biological indifference to biological objects are formed when they are polymerized in combination with acrylic resin. The second generation used a lubricated layer to obtain higher adhesion rates. Chloro-substituted phosphate esters of various monomers were used as active groups. The main compound mechanism remained the ionic binding of calcium dentine by chlorophosphate groups. The third generation used a lubricated layer to attach the composite to the dentin in the same way as the second generation. In the chemical composition, aluminosilicates, aluminitrates, hydroxyethylmethacrylate (HEMA), 4-methacryloxyethyltrimethyl anhydride (4-META), and other substances were most often used as active groups. The fourth generation is a multicomponent system that provides a three- and four-step application technique. These systems contain three to four components (conditioner, primer, and adhesive). The technique of their use includes three stages, namely, etching with 37% orthophosphoric acid, priming, and bonding. Adhesive systems of the fifth generation are two-component systems that provide a two-step technique of application. First, acid (etching) is applied to the tooth tissue, and second, the adhesive itself. Adhesive systems of the sixth and seventh generations are one-component self-etching since the adhesive contains acid. From a chemical point of view, these adhesive systems are a mixture of phosphoric esters and adhesive substances. Therefore, analyzing the adhesive composition of seven generations in such way, the mechanism of chemical interaction of adhesive components with hydroxyapatite and dentin has not significantly changed; however, the number of hydrophobic fragments has increased, which significantly increases dentin contact.

In the article stated mechanism of formation organic and inorganic pigmentary complexes which changes color of teeth. Chemical aspects of dentistry procedure of whitening teeth are consider, original author's schemes of ion-changes and oxidative process are given, which happen with it. Knowledge of intermolecular interaction, which leads to the appearance of coloration and proceeding in process of his removal, will allow to develop new treatment methods and to improve existing, which apply in an esthetic dentistry.

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