The aim of the study was to assess the efficacy of three methods of enamel remineralization on initial approximal caries: (1) a nano-hydroxyapatite gel, (2) gaseous ozone therapy, (3) combination of a nano-hydroxyapatite gel and ozone. Patients (n = 92, age 20-30 years) with initial approximal enamel lesions on premolar and molar teeth (n = 546) were randomly allocated to three groups subjected to a 6-months treatment: Group I: domestic nano-hydroxyapatite remineralizing gel, group II: in-office ozone therapy, group III: both domestic remineralizing gel and ozone therapy. Caries lesions were assessed on bitewing radiographs at baseline, after 1 year and after 2 years. At one-year follow-up, the smallest rate of lesions with remineralisation (36.5%) was found in group I, and the highest (69.3%)-in group III. In group III a significant remineralisation was noticed in after 1 year and then a demineralisation after 2 years. Thus nano-hydroxyapatite gel and ozone therapy exert some capacities to remineralize approximal enamel and dentine subsurface lesions of premolar and molar teeth. Moreover, the combination of both methods produces the best effect compared to nanohydroxyapatite or ozone therapy applied alone. However, the treatment should be continued for a long time in order to achieve nonrestorative recovery of caries.

The aim of this study was to develop a polyethylene/polyamide (R-PE/R-PA) regranulated product made from post-consumer wastes grafted with polyethylene-graft-maleic anhydride (PE-g-MAH) by reactive extrusion in a twin-screw extruder equipped with an external mixing zone. The compatibility effect of PE-g-MAH used as a modifier in R-PE/R-PA blends was evaluated by means of differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), while the analysis of the chemical structure of this blend was carried out by Fourier transform infrared spectroscopy (FT-IR). The thermal properties, complex viscosity, and selected usage properties of R-PE/R-PA blends compatibilized with PE-g-MAH, i.e., density and water absorption, were evaluated. The morphology of the blends with and without the compatibilizer was observed by scanning electron microscopy. The R-PE/R-PA/MAH blend shows heterogenic structure, which is a result of the chemical reaction in reactive extrusion between functional groups of PE-g-MAH used as modifier and the end groups of R-PA6. The results show that the R-PE/R-PA blend with increased PE-g-MAH content showed increased hardness, stiffness, and ultimate tensile strength due to the increased degree of crystallinity. The increase in crystallinity is proportional to the improvement of the mechanical properties. Moreover, it is shown that 1 wt.% PE-g-MAH added to the R-PE/R-PA waste blend increases the interfacial interactions and compatibility between R-PE and R-PA, resulting in decreased polyamide particle size. Finally, the results show that it is possible to produce good quality regranulated products with advantageous properties and structure from immiscible polymer waste for industrial applications.

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The physicochemical properties of polyether ether ketone (PEEK) allow to use this material for prosthetic restorations applied in implant prosthetics. So far, such attempts have been made in the technology of milling rough material solids of this polymer, but the surface quality was unsatisfactory. Therefore, the production of these materials by additive manufacturing techniques was proposed and an attempt was made to shape their surface using a laser. The possibilities of the method are determined in the paper and preliminary works related to the product surface shaping are presented. The process of making individual prosthetic restorations from the PEEK material by the additive method together with the technology of laser modification of the geometric structure of the material surface for applications in implant prosthetic treatment of patients is innovative and has not been used so far.

calculating the reduced levels of the weight, the municipalities are obliged to limit the weight of municipal waste sent for landfill to 35% of the total mass of the biodegradable municipal waste. Therefore, the goal of numerous countries is to strive towards the utilization of the largest possible group of used products through biodegradation. Recyclable biocomposites based on degradable polymer matrices and natural fillers such as cellulose, starch, flaxen, hemp, and wood are desirable in a sustainable society due to their more favorable properties and shorter decomposition period.The fillers of natural origin also include halloysite [9], which is used as a raw material in the ceramic industry, for the production of mineral sorbents, as a feed additive, and as a catalyst for filter beds. Hence, the production of composites with biocompatible fillers is advantageous, mainly due to their easy biodegradation [10][11][12][13].In accordance with the ASTM D996 standard [14], the biodegradable polymers must "demonstrate the ability to biodegrade under certain assumptions in the composting environment so that the decomposed polymers are not visually distinguishable and decompose into carbon dioxide, water, inorganic compounds, and biomass, at a rate consistent with known compostable materials, e.g. cellulose. The first stages most often include abiotic processes such as temperature, light, atmospheric pressure, air and/or soil humidity, and biotic processes, i.e. bacteria, fungi, etc. Their purpose is to degrade the polymer to a low molecular weight form under favourable conditions. And the resulting fragments of polymer or polymer composite decay must be completely used up by microorganisms. Other-SPECIAL SECTION Machine modelling and simulations