The parameters of abrasive blasting process directly affect the condition of the metal surface, changing the degree of surface roughness and wettability, depending on the size of the used particle, the pressure or type of abrasive. The aim of this study was to analyze the condition of Ni-Cr alloy surface after abrasive blasting using various process variants. The samples were blasted by Al 2 O 3 abrasive using various particle sizes and pressures of the process. Basic and specific roughness parameters were investigated, and a surface wettability test was performed, and the percentage share of abrasive particles penetrated in the surface after abrasive blasting was also examined. The most considerable differences in the condition of the surface were observed with the change in the particle size of Al 2 O 3. Statistical analysis confirmed the statistical significance of all these relationships.

Purpose: A review regarding the mechanisms of metal-ceramic join is presented. Design/methodology/approach: The impact of the air-abrasion parameters on the mechanical bond strength of the ceramic crowns was discussed. The presence of opaque on the chemical bond was analysed. Research of the influence of the difference in the coefficient of thermal expansion values on the metal-ceramic bond was included. The methods of testing the bond strength were analysed. Findings: The metal substructure-dental ceramic bond strength is affected by all types of bond. In bond strength, 3-point bending test and shear test are mainly used. Created samples simulate the ceramic crowns veneered on one side. The role of physical bond on ceramic crowns veneered around metal substructure is unknown. Research limitations/implications: The prosthetic restorations with the ceramic surrounding whole the metal substructure are commonly used. The impact of shrinkage in the cylindrical deposition of the ceramic on metal substructure should be analysed. Practical implications: Numerical analysis and FEM simulation can be helpful in the analysis of the physical bond between the metal substructure and the dental ceramic around it. Originality/value: The impact of the type of the bond to metal-ceramic bond strength is presented, taking into account the cognitive gap in the influence of the coefficient of thermal expansion on the cylindrical placement of ceramic on the substructure.

Purpose: Many printers are tempting at low prices, but later their accuracy turns out to be insufficient. The study has included checking the accuracy of printing and reproducing details of 3D printers used in dental technology and dentistry such as MultiJet Printing (ProJet MP3000, 3D Systems) and Fused Deposition Modelling (Inspire S2000, Tiertime). Design/methodology/approach: The 3D prints were created from scans of the maxillary gypsum model with the loss of left premolar. In the test, objects were set to the X and Y-axis. In order to check the dimensional differences after printing, scans of the printed models were superimposed on scans of the plaster model in the GOM Inspect V8 SR1 (Braunschweig, Germany). The focus was on the distance of scans from each other and a deviation map was created for each object. Findings: The average absolute value of deviations for each of models were equalled: FDMfor X-axis 0.06 ± 0.04 mm, for Y-axis 0.07 ± 0.04 mm; MJP- for X-axis- 0.04 ± 0.02 mm, for Y-axis- 0.06 ± 0.02 mm. A chart of arithmetic averages calculated for each tooth for the best printouts in each series show that higher deviation values exist in case of FDM printout. The models printed in the X-axis have smaller values of deviations from those printed in the Y-axis. Practical implications: MultiJet Printing technology can be used to create more precise models than the FDM, but these printouts meet the requirements of dimensional accuracy too. Originality/value: CAD / CAM technology in the future will exist in every dental technology laboratory so it is important to be aware of the way the 3D printers works. By paying attention to the quality of detail reproduction, a Dental Technician is able to choose the best 3D printer for them.

Fixed prosthetic restorations in the form of ceramic crowns or bridges are characterized by good aesthetics and durability. The most important turn out to be the mechanical attachment of the ceramic material in the unevenness of the metal, formed after abrasive blasting. The aim of this research is to investigate the impact of abrasive blasting of a nickel-chromium alloy on the covering the unevenness with ceramics. In the research was used a Ni-Cr alloy (Heraenium® NA, Hera). The metal surface was blasted with alumina of variable size (50, 110 and 250 µm) and pressure (0.4 and 0.6 MPa), which was then fired with ceramics in the form of 2 layers of IPS Classic Opaque (Ivoclar Vivadent). Samples were hot mounting and cut to obtain a cross-section of the connection. The samples was examined under a Scanning Electron Microscope. The results show the presence of air bubbles at the metal-ceramic interface and in the layers of ceramic material. The photographs show a difference in the appearance of the unevenness of the metal surface by comparing samples after blasting with an abrasive of different sizes. No significant differences in the appearance of metal roughness are observed when comparing samples after treatment with the same grain size and different pressures.

Purpose: A review of the literature regarding the occurrence of fretting wear in orthodontics and its test methods have been presented. Design/methodology/approach: The influence of micro-movements occurring in the oral cavity on the occurrence of fretting wear in a fixed orthodontic appliance is discussed. The fretting test methods were analysed, taking into account the shape of the samples and the amplitude of the movements, calculated according to the Hertz contact problem. Fretting-corrosion tests on the wear of materials are included. Findings: Fretting occurs between the bracket and the orthodontic archwire in a fixed appliance. The test of the amount of wear material mainly uses samples created for the needs of the device. The test of ready-made components of a fixed appliance usually relate to the value of the coefficient of friction. The use of coatings increases the coefficient with the simultaneous reduction of the amount of wear material. Fretting-corrosion occurring in the oral environment has a negative impact on the wear of materials. The value of the total area of abraded material after fretting is unknown. Research limitations/implications: Particles of fretting wear get through to the organism from the elements of a fixed orthodontic appliance and they may cause hypersensitivity of surrounding tissues. The amount of wear material and its total area should be tested. Originality/value: Presented are the methods of fretting wear testing in a fixed orthodontic appliance, taking into account the cognitive gap in the knowledge of the amount of abraded material from ready-made components and the value of their total area.