Comparative characteristics of the chemical structure of ormokers and traditional composites

Abstract

The article presents a review of the of the advantages of using ormokers in comparison with composite filling materials from a chemical point of view. Ormokers are a modified type of hybrid organo-inorganic dental materials. They were developed in order to reduce polymerization shrinkage of filling materials, improve edge adaptation, abrasion resistance and increase biocompatibility (compared to composites). The new matrix was obtained on the basis of inorganic polymers, which are polycondensed siloxanes (triblock copolymers). The formation of an inorganic chain of molecules occurs by hydrolysis and polycondensation of Si(OR) groups. Unstable organosilanols are formed from chlorine-containing silanes, since at least two hydroxyl groups are associated with one carbon atom. Such compounds do not exist, as they are rapidly isomerized to form carbonyl compounds (aldehydes, ketones). The resulting organosilanols are then oligomerized to form polysiloxanes with polymerized groups. The basis for the production of ormokers is the sol-gel process. The classical approach involves the formation of an inorganic grid by hydrolysis and condensation of a monomeric organic alkoxy compound followed by crosslinking of the introduced reactive groups, for example by ultraviolet polymerization. The traditional synthesis of ormokers begins with the fact that alkoxysilanes are functionalized by metal alkoxides to form Si-O-Si nanostructures. One of the metals that functionalize alkoxysilanes is titanium. In addition to titanium alkoxide, zirconium- or aluminum-alkoxides can also be used. These oligomers replace traditional methacrylic monomers in composites. Composite filling materials available on the market today, based on the technology of ormokers, are not purely ormoker systems. To regulate the viscosity of the condensate, traditional methacrylate monomers-diluents are used, which does not contribute to improving biocompatibility. In our opinion, it is the presence of an amide group in the structure of ormokers that causes an increase in their biocompatibility with protein compounds of dental tissues.