Silicon-hydroxyapatite‒glycerohydrogel as a promising biomaterial for dental applications.

Nanocomposite silicon-hydroxyapatite‒glycerohydrogel (Si-HA‒glycerohydrogel) with different hydroxyapatite (HA) contents of 0.75 and 1.75 wt.% and the same Si content (2.04 wt.%) was obtained by the sol‒gel method. Silicon tetraglycerolate in the form of glycerol solution was used as a biocompatible precursor and HА in the form of aqueous colloidal suspension - as a template and property modifier. Transmission electron microscopy was applied to demonstrate that there are nanoscale HA particles that are in the crystalline state. For the first time, using the atomic force microscopy method, the remineralizing properties of Si-HA‒glycerohydrogel were studied on human teeth extracted for orthodontic reasons. It was found that Si-HA‒glycerohydrogel containing 1.75 wt.% HA has a pronounced remineralizing effect. Immersion of tooth enamel samples in the gel for one month significantly reduces roughness and makes the enamel surface more uniform. Silicon contained in glycerolates in a biologically active and accessible form exerts an additional positive effect on the process of remineralization of tooth enamel. By the energy dispersive X-ray analysis, it was demonstrated that the tooth enamel had an increased silicon content; and the Vickers microhardness test showed greater microhardness values. The obtained data analysis allows the remineralizing Si-HA‒glycerohydrogel to be considered as a promising biomaterial for dental applications.

Features of silicon- and titanium-polyethylene glycol precursors in sol-gel synthesis of new hydrogels.

The formation of organic/inorganic hydrogels based on silicon and titanium polyethylene glycolates, new biocompatible water-soluble precursors in sol-gel processing, was investigated. The influence of different factors on the gelation process, such as excess of PEG, water molar content, pH of medium, electrolyte additives, was investigated in comparison with silicon- and titanium-glycerol precursors. The specific features of gelation for each type of precursor were revealed. It has been determined that titanium polyethylene glycolates synthesized and used in the excess of PEG formed transparent polymeric hydrogels resistant to syneresis under certain conditions. The titanium polyethylene glycolates synthesized without excess of PEG formed turbid heterogeneous colloidal gels. In the case of silicon polyethylene glycolates the hydrogels obtained were polymeric. Dynamic light scattering was used to confirm the polymeric or colloidal type of gelation. The solid and liquid phases of polymeric silicon- and titanium-polyethylene glycol hydrogels were separated by exhaustive extraction. The solid phase was characterized by combined thermal analysis with simultaneous quadruple mass spectrometry, XRD, IR spectroscopy, and liquid phase-atomic emission spectroscopy. The structural features of polymeric gels were investigated by SEM and TEM methods. The cross-linking density of polymeric hydrogels was evaluated using Flory-Rehner theory based on the mechanical properties of swollen networks of flexible polymeric chains.