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The purpose of this study is (1) to introduce a new approach for edge detection in orthopantograms (OPGs) and an improved automatic parameter selector for common edge detectors, (2) to present a comparison between our novel approach with common edge detectors and (3) to provide faster outputs without compromising quality. A new approach for edge detection based on statistical measures was introduced: (1) a set of N edge detection results is calculated from a given input image and a selected type of edge detector, (2) N correspondence maps are constructed from N edge detection results, (3) probabilities and average probabilities are computed, (4) an overall correspondence is evaluated for each correspondence map and (5) the correspondence map providing the best overall correspondence is taken as the result of edge detection procedure. A comparison with common edge detectors (the Roberts, Prewitt, Sobel, Laplacian of the Gaussian and Canny methods) with various parameter settings (304 combinations for each test image) was carried out. The methods were assessed objectively [edge mismatch error (EME), modified Hausdorff distance (MHD) and principal component analysis] and subjectively by experts in dentistry and based on time demands. The suitability of the new approach for edge detection in OPGs was confirmed by experts. The current conventional methods in edge detection in OPGs are inadequate (none of the tested methods reach an EME value or MHD value below 0.1). Our proposed approach for edge detection shows promising potential for its implementation in clinical dentistry. It enhances the accuracy of OPG interpretation and advances diagnosis and treatment planning.

The work deals with the evaluation of strength characteristics of thermally sprayed coatings. The main aim was concentrated on the tensile and shear loading of HVOF (Stellite Alloy 6, Tribaloy 400) and arc sprayed (13%Cr, CuAl8) coatings. The investigation of the coatings behaviour on the coating-substrate interface is important for the evaluation of one of significant coating mechanical properties that influence properties of the whole coating-substrate system. The magnitude of the coating bond strength during tensile and shear stresses predicates the coating stability, reliability, impact resistance, resistance against failure and mostly operating lifetime. The determination adhesive-cohesive strength was performed according to EN 582 and EN 15340 Standards.

The HVOF sprayed wear resistant hardmetal coatings with favourable sliding properties are suitable for increasing the lifetime of sliding applications, such as pistons of combustion engines, pumps and other hydraulic devices. In practice, the coatings face the problem of their interaction with other media, in the case of sliding wear usually lubricants. In the paper, the friction properties of five different HVOF sprayed coatings are evaluated by pin-on-disk test according to ASTM G-99 under dry and lubricated conditions and lubricated block-of-ring test according to ASTM G77. Several types of lubricants designed for combustion engines were used to compare their influence on coatings sliding wear behavior. Based on the results, the suitability of coatings for the application on the engines parts is discussed and the effect of counterpart material and different types of lubricants on the coefficient of friction and coatings wear rate is analyzed. It was confirmed, that the CrC-based coating are more suitable for the application under the condition corresponding to combustion engines, e.g. elevated temperature and steel counterpart, than the WC-based coatings. From the group of CrC-based coatings, the superior behavior was observed at the CrC-CoNiCrAlY coating, the matrix material of which offers further enhancement of the sliding wear behavior.

In this paper, one of the tribological tests for the evaluation of friction properties is introduced. The test, named “Block-on-Ring”, (in accordance with the standard ASTM G77) was carried out by the SKODA VÝZKUM Ltd. company and realized on renovated apparatus. The brief description of the measurement is as follows: the flat surface of the sample is pressed against the cylindrical surface of the rotating wheel. Arbitrary oil is fed to the materials’ contact surface and the increasing temperature can be detected using the thermocouple that is placed in close proximity of the contact materials. Using the strain-gauge dynamometer, the friction force is recorded. The test is run on a number of periods and, including after the first expiration time, the wear track formed in the sample is measured and evaluated. The final results are the summary of partial results of the long-standing tests, which serve for the preliminary detection of the friction behaviour of the materials. The friction properties of the thermally sprayed coatings were investigated. The Cr3C2-NiCr, 13% Cr and Cr2O3 coatings were tested. The thin-base babbit was selected as the counter-part. The main interest was in the characterization of the friction properties in the dependence on the amount of added lubricant and on the normal load of sliding couples.

The friction between a piston, piston rings and a cylinder is responsible for almost 55% of total power loss in engines. The decrease of friction in the piston area leads to a significant fuel saving and also to emission reduction. Application of a surface treatment, such as PEO, PVD, HVOF, plasma sprayed coatings, surface texturing, etc. on engine components is a way to reduce corrosion, friction, wear and weight of engines. In the paper, the potential of the application of HVOF sprayed coatings on the engine components is discussed with respect to their sliding friction properties. The technology of thermal spraying enables one to create the surface coating approximately 50 µm thick, which provides functional surface protection of the coated parts. HVOF technology offers the possibility of creating the coatings of materials based on the principle of hardmetals with high wear resistance and favourable sliding properties. Such a combination predestinates HVOF sprayed coatings for sliding applications, such as pistons of combustion engines, pumps and other hydraulic devices. In this application area they are used on a regular basis. In practice, the producers and users of thermally sprayed coatings face the problem of the interaction of the coatings and their counterparts with the presence of other media, fuels, or, in the case of sliding wear more often, lubricants. The paper describes the methodology of measurement suitable for lubricated HVOF coatings using the pin-on-disc test according to ASTM G-99 and on the evaluation of the influence of lubricants on the friction properties, wear rate and mechanism of HVOF sprayed coatings. The pin-on-disc test according to ASTM G-99 was performed on the thermally sprayed Cr3C2-25%NiCr coating to determine and describe their sliding wear behaviour under different test conditions. The influence of various test parameters (load, wear track diameter, temperature, lubrication, counterpart

The recent progress in understanding the biomedical basis for temporomandibular joint. (TMJ) therapy as well as in computer and imaging technologies is beginning to provide novel insights into TMJ reconstruction, rational diagnostic and therapeutic strategies. Several methods are available for imaging the TMJ. These include basic radiography (such as panorexes and corrected tomograms), ultrasonography, magnetic resonance imaging, and spiral or conebeam computed tomography. The latter technologies allow the joint to be visualized as sections in different planes and can also be rendered as 3 D volumetric reconstructions to enhance diagnostic capabilities. The aim of the study is demonstrate patient's therapy including 1 year recall. This contribution deals with 3D analysis of the mathematical and computer modeling of biomechanics of the jaw. Case report monitors step by step treatment plan, preprosthetic surgery, mandibular reconstruction and process of healing. 3D- CT was used to monitor the patient with dental cysts. The mathematical and computer TMJ models analysis using overlapping of 3D CT before and after 1 year therapy shows the stability of TMJ partial prosthesis reconstruction. Mathematical modeling and mathematical simulation of the reconstruction of patient jaw and/or patient TMJ may predict the joint loading of the reconstructed condyle. Our study demonstrated practical use of 3D images during TMJ therapy. Although many of the disorders involving the temporomandibular joint and associated structures can be diagnosed clinically on the basis of the history and physical findings, there are others that require the use of various imaging techniques to make an accurate diagnosis or to determine the extent of involvement. Imaging the hard and soft tissues of the temporomandibular joint can be used not only for treatment planning but also long-term treatment evaluation.

The tribological properties of the surfaces of parts, namely their wear resistance and friction properties, are in many cases decisive for their proper function. To improve surface properties, it is possible to create hard, wear resistant coatings by thermal spray technologies. Using these versatile coatings it is possible to increase the lifetime, reliability and safety of parts. For proper function of the surface treatment it is necessary to find and keep the optimal condition and parameters during preparation, deposition and further processing of the sprayed part. The spraying angle is one of the deposition parameters that influence the quality of thermally sprayed coatings. According to the theory, with decreasing spraying angle the process deposition efficiency decreases, whereas the porosity of coatings increases, being a cause of aggravated microstructure and mechanical properties. In this paper, the microstructure together with the basic mechanical properties and wear of WC-Co and Cr3C2-NiCr HVOF sprayed coatings were investigated in dependence of the spraying angle. For each coating, the marginal spraying angle that can be used without a significant decrease of the coating’s quality was identified. With respect to the change in coating properties as well as to process deposition efficiency, the maximum 30° diversion from a normal spray direction is recommended in the case of WC-Co and 15° diversion in the case of Cr3C2-NiCr.

One of the tribological tests for the evaluation of friction properties is introduced in this paper. The test, named “Block-on-Ring”, is in accordance with the standard ASTM G-77 and in SKODA VÝZKUM Ltd. is realized on the VRS-3 renovated apparatus. The measurement is as follows: the flat surface of the sample is pressed against the cylindrical surface of a rotating wheel of the rotor material. Arbitrary oil is fed to the material contact surface and the increasing temperature is detected using a thermocouple. The friction force is recorded using the strain-gauge dynamometer. The test is performed in a number of periods and always after one expiration time the wear track formed in the sample is measured and evaluated. The final results are the summary of the partial results of the long-standing tests and are used for the preliminary detection of the friction behavior of individual material couples.

Hardmetal coatings prepared by high-velocity oxy-fuel (HVOF) spraying represent an advanced solution for surface protection against wear. The work presented in this paper focussed on the comparison of the tribological behaviour of WC-Co, Cr3C2-NiCr and (Ti,Mo)(C,N)-NiCo hardmetal coatings under dry sliding wear conditions at room and elevated temperatures (at 500°C and 700°C). The friction properties of these HVOF-sprayed coatings were studied in detail. The progression of the coefficient of friction (CoF) was measured during the pin-on-disc tests at the different temperatures. The mechanisms of wear and the heat-related changes in surface roughness and microhardness of the coatings were studied.