STUDY OF NANOPHOTOCOMPOSITE MATERIAL MICROHARDNESS UNDER VARIOUS HARDENING CONDITIONS

Udod O. A., Bekuzarova Kh. I.

METHODS AND METHODOLOGIES

Scentific article

Considering all anatomical, functional and aesthetic characteristics, the nanofilled photocomposite materials, which have a number of undeniable advantages are commonly used while performing teeth restoration. Although, the certain disadvantages of mentioned materials can be observed, namely, volumetric shrinkage and incomplete conversion of double bonds of monomers. To reduce the negative effect of these factors, the lightpolymerization method of photocomposites called “soft start” is used, as well as the application of low viscosity photocomposites, so-called fluid-flow for basic restoring, with the optimal elastic modulus, reduced shrinkage, but little mechanical strength. The restoration technology is also promising, when the adhesive system is applied to the dentin of the prepared cavity, and the first layer of the photocomposite material on its bottom is polymerized by the luminous flux simultaneously. But the physical and mechanical properties of the material according to such technology have not been fully investigated. The aim of research was the experimental investigation of the nanophotocomposite material microhardness applying various approaches to light-induced polymerization of this material and adhesive system application. Object and methods of research. The microhardness of Filtek Ultimate, 3M ESPE, color A2 was studied on 40 samples in the form of cylinders 4.0 mm in diameter, 3.0 mm high, after 1 hour exposure to luminous flux of LED photopolymerizer with the intensity of 1500 mW/cm2. All samples were divided into four groups of 10 samples: samples of I and II groups were polymerized by luminous flux in the “soft start” mode and constant high intensity, correspondingly. Before III and IV groups sample manufacturing, the adhesive system was applied to the bottom of the split-type mould, samples were formed using material and polymerized by luminous flux, correspondingly, in the indicated modes. Microhardness was studied applying PMT-3 device at 5 points of each sample on the surface nearest to the luminous flux, then on the opposite surface, and also at a depth of 1.0 and 2.0 mm. Results of research and their discussion. The microhardness parameters of the sample surface of all groups closer to the photopolymerizer were almost the same (p> 0.05), according to the group order they amounted to 71.63 ± 1.21 kgf/mm2, 72.89 ± 0.94 kgf/mm2, 72.12 ± 1.17 kgf/mm2 and 73.25 ± 1.34 kgf/mm2. The indices were also not significantly different at a depth of 1.0 mm (p>0.05). The significant difference at a depth of 2.0 mm (p<0.05) was observed only between the II group microhardness parameters (69.18 ± 0.88 kgf/mm2) and III group (66.05 ± 1.12 kgf/mm2). The material microhardness of the III group samples was 46.36 ± 0.97 kgf/mm2 on the surface most remote from the light source (p<0.05). The IV group samples index was 52.78 ± 1.03 kgf/mm2 and also it was significantly different from all the others (p<0.05). Probably, the highest microhardness (p<0.05) was observed in the samples of I and II groups, which amounted to 60.27 ± 1.23 kgf/mm2 and 62.54 ± 1.12 kgf/mm2, correspondingly (the indices differed insignificantly p>0.05 in terms of I and II groups). Conclusion. The experimental research determined that the lowest microhardness was detected in the most remote from the luminous flux surface of the nanophotocomposite material samples, when adhesive system was applied to the bottom of the split-type mould before manufacturing and polymerization, even in case of “soft start” mode as well as luminous flux of high intensity application. Prospects for further research. The further experimental research should include the study of other physical and mechanical characteristics, which provide the durability and functionality of teeth restoration, and basis for possible implementation of certain improved approaches to clinical settings.

nanophotocomposite material, adhesive system, polymerization, microhardness

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«Bulletin of problems biology and medicine» Issue 4 Part 3 (141), 2017 year, 260-263 pages, index UDK 616.314 – 089.23

10.29254/2077–4214–2017–4–3–141–260-263