Development of a Visualisation Approach for Analysing Incipient and Clinically Unrecorded Enamel Fissure Caries Using Laser-Induced Contrast Imaging, MicroRaman Spectroscopy and Biomimetic Composites: A Pilot Study

This pilot study presents a practical approach to detecting and visualising the initial forms of caries that are not clinically registered. The use of a laser-induced contrast visualisation (LICV) technique was shown to provide detection of the originating caries based on the separation of emissions from sound tissue, areas with destroyed tissue and regions of bacterial invasion. Adding microRaman spectroscopy to the measuring system enables reliable detection of the transformation of the organic–mineral component in the dental tissue and the spread of bacterial microflora in the affected region. Further laboratory and clinical studies of the comprehensive use of LICV and microRaman spectroscopy enable data extension on the application of this approach for accurate determination of the boundaries in the changed dental tissue as a result of initial caries. The obtained data has the potential to develop an effective preventive medical diagnostic approach and as a result, further personalised medical treatment can be specified. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 21-15-00026; Ministry of Science and Higher Education of the Russian Federation: N 075-15-2021-1351Funding: This work was funded by a grant from the Russian Science Foundation, grant number 21-15-00026. The access to scientific equipment and methodology was provided under support from the Ministry of Science and Higher Education of Russia, agreement N 075-15-2021-1351

Raman and XANES Spectroscopic Study of the Influence of Coordination Atomic and Molecular Environments in Biomimetic Composite Materials Integrated with Dental Tissue

In this work, for the first time, the influence of the coordination environment as well as Ca and P atomic states on biomimetic composites integrated with dental tissue was investigated. Bioinspired dental composites were synthesised based on nanocrystalline calcium carbonate-substituted hydroxyap-atite (Formula presented) (nano-cHAp) obtained from a biogenic source and a set of po-lar amino acids that modelled the organic matrix. Biomimetic composites, as well as natural dental tissue samples, were investigated using Raman spectromicroscopy and synchrotron X-ray absorption near edge structure (XANES) spectroscopy. Molecular structure and energy structure studies revealed several important features related to the different calcium atomic environments. It was shown that biomimetic composites created in order to reproduce the physicochemical properties of dental tissue provide good imitation of molecular and electron energetic properties, including the carbonate anion CO32− and the atomic Ca/P ratio in nanocrystals. The features of the molecular structure of biomimetic composites are inherited from the nano-cHAp (to a greater extent) and the amino acid cocktail used for their creation, and are caused by the ratio between the mineral and organic components, which is similar to the composition of natural enamel and dentine. In this case, violation of the nano-cHAp stoichiometry, which is the mineral basis of the natural and bioinspired composites, as well as the inclusion of different molecular groups in the nano-cHAp lattice, do not affect the coordination environment of phosphorus atoms. The differences observed in the molecular and electron energetic structures of the natural enamel and dentine and the imitation of their properties by biomimetic materials are caused by rearrangement in the local environment of the calcium atoms in the HAp crystal lattice. The surface of the nano-cHAp crystals in the natural enamel and dentine involved in the formation of bonds with the organic matrix is character-ised by the coordination environment of the calcium atom, corresponding to its location in the CaI posi-tion—that is, bound through common oxygen atoms with PO4 tetrahedrons. At the same time, on the surface of nano-cHAp crystals in bioinspired dental materials, the calcium atom is characteristically lo-cated in the CaII position, bound to the hydroxyl OH group. The features detected in the atomic and molecular coordination environment in nano-cHAp play a fundamental role in recreating a biomimetic dental composite of the natural organomineral interaction in mineralised tissue and will help to find an optimal way to integrate the dental biocomposite with natural tissue. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This work was supported by a grant from the Russian Science Foundation, grant number 21-75-10005; The access to scientific equipment and methodology was provided under support of the Ministry of Science and Higher Education of Russia, Agreement N 075-15-2021-1351

Engineering of biomimetic mineralized layer formed on the surface of natural dental enamel

The problem of engineering a biomimetic mineralized layer on the surface of native dental tissue (bio-template) was considered in our work. The formation of the mineralized layer on a biotemplate is achieved with the use of nanocrystalline carbonate-substituted calcium hydroxyapatite (HAp), calcium alkali, and a complex of polyfunctional organic and polar amino acids. By applying the set of structural and spectroscopic methods of analysis we have confirmed the formation of a mineralized biomimetic HAp layer on the surface of bio-template with properties resembling those of natural hard tissue. The thickness of the biomimetic mineralized layer varies from 300 to 500 nm, while the direction of some ncHAp nanocrystals coincides with that of the apatite crystals in the enamel. We also demonstrated that the engineered mineralized HAp layer was characterized by homogeneous micromorphology and enhanced nanohardness in the region of the enamel rods exceeding those of native enamel. The development of a strategy for biomimetic engineering and a technique for enamel surface pre-treatment to enable tissue mineralization has huge potential in dental applications. © 2022 The AuthorsRussian Science Foundation, RSF: 21-75-10005; Ministry of Science and Higher Education of the Russian Federation: N 075-15-2021-1351This work was funded by the Russian Science Foundation , grant number 21-75-10005 ;The access to scientific equipment and methodology was provided under support of the Ministry of Science and Higher Education of Russia, Agreement N 075-15-2021-1351

Thermal effects of carbonated hydroxyapatite modified by glycine and albumin

In this work calcium phosphate powders were obtained by precipitation method from simulated solutions of synovial fluid containing glycine and albumin. X-ray diffraction and IR spectroscopy determined that all samples are single-phase and are presented by carbonate containing hydroxyapatite (CHA). The thermograms of solid phases of CHA were obtained and analyzed; five stages of transformation in the temperature range of 25-1000°C were marked. It is shown that in this temperature range dehydration, decarboxylation and thermal degradation of amino acid and protein connected to the surface of solid phase occur. The tendency of temperature lowering of the decomposition of powders synthesized from a medium containing organic substances was determined. Results demonstrate a direct dependence between the concentration of the amino acid in a model solution and its content in the solid phase

Bound oxygen influence on the phase composition and electrical properties of semi-insulating silicon films

The purpose of this work is to establish of the bound oxygen effect on the phase composition of the Semi-Insulating Polycrystalline Oxygen-doped Silicon (SIPOS) films by means of three independent methods: X-ray diffraction (XRD), Ultrasoft X-ray Emission Spectroscopy (USXES) and Raman spectroscopy, also on their electrophysical properties, depending on the relative oxygen content in the gas mixture flow (γ=N2O/SiH4) of the plasma reactor during the chemical vapor deposition of submicron SIPOS layers on monocrystalline silicon wafers. The increase in the oxygen content in SIPOS layers from γ=0 to maximum at γ=0.15 leads to the reduction of Si nanocrystals size from ~75 nm to 2–5 nm, submerged in amorphous matrix. Oxygen is contained in the bound form of silicon-oxygen clusters SiOSi3 type in the amorphous silicon matrix without SiO2 formation. These nonlinear qualitative and quantitative changes in the atomic structure of the SIPOS layers under the influence of bound oxygen increase not only the resistivity of the films by two orders of magnitude but also the activation energy of conductivity in comparison with silicon at the temperatures above room temperature. © 2020 Elsevier LtdRussian Foundation for Basic Research, RFBR: 19-42-363013MD-42.2019.2Ministry of Science and Higher Education of the Russian FederationThe reported study was funded by RFBR and Government of Voronezh region according to the research project № 19-42-363013.The part of work was carried out with the support of the Ministry of Science and Higher Education of Russia Federation under the grand No. FZGU-2020-0036 .In part of diagnostics of the structures the work of P.V. Seredin was supported by the RF President's Grants Council (Grant MD-42.2019.2)