Wojciech Ryniewicz

Microstructural and micromechanical tests of titanium biomaterials intended for prosthetic reconstructions.

PURPOSE The aim of the present paper was a question of structural identification and evaluation of strength parameters of Titanium (Ticp - grade 2) and its alloy (Ti6Al4V) which are used to serve as a base for those permanent prosthetic supplements which are later manufactured employing CAD/CAM systems. METHODS Microstructural tests of Ticp and Ti6Al4V were conducted using an optical microscope as well as a scanning microscope. Hardness was measured with the Vickers method. Micromechanical properties of samples: microhardness and Youngs modulus value, were measured with the Oliver and Pharr method. RESULTS Based on studies using optical microscopy it was observed that the Ticp from the milling technology had a single phase, granular microstructure. The Ti64 alloy had a two-phase, fine-grained microstructure with an acicular-lamellar character. The results of scanning tests show that titanium Ticp had a single phase structure. On its grain there was visible acicular martensite. The structure of the two phase Ti64 alloy consists of a β matrix as well as released α phase deposits in the shape of extended needles. Micromechanical tests demonstrated that the alloy of Ti64 in both methods showed twice as high the microhardness as Ticp. In studies of Youngs modulus of Ti64 alloy DMLS technology have lower value than titanium milling technology. CONCLUSIONS According to the results obtained, the following conclusion has been drawn: when strength aspect is discussed, the DMLS method is a preferred one in manufacturing load structures in dentistry and may be an alternate way for the CAD/CAM system used in decrement processing.

The evaluation of the accuracy of shape imaging of prosthetic abutment

PURPOSE The aim of the study was the in vitro evaluation of the accuracy of shape imaging of abutment teeth using different impression compounds. METHODS To compare the accuracy of the shape of the numerically imaged real prosthetic abutments with the tested models of abutments obtained with the replica technique, the Geomagic Qualify program was applied. Making use of the licensed program Statistica, statistical analysis of the results obtained was conducted. RESULTS In the research procedures, analyses were conducted for 10 abutment premolars and 10 abutment molars. The tests allowed us to state that the dimensional accuracy of the models of prosthetic abutments obtained with the application of elastic compounds tested ensures comparable shape imaging. CONCLUSIONS The objective method developed and applied here is suitable for controlling the imaging of the abutment teeth. The Geomagic Qualify program that was used during the research is a reliable tool of 3D analysis for the estimation of procedure of abutment tooth preparation and indication of an error of shape of prepared occlusal surface, lateral surface of abutment and errors of shaping the chamfer zone.

Identification of the Cause of the Stem Neck Fracture in the Hip Joint Endoprosthesis

Abstract Endoprosthesis stem fractures are among the rarest complications that occur after hip joint arthroplasty. The aim of this paper is to evaluate the causes of the fractures of the Aura II stem neck, which is an element of an endoprosthesis implanted in a patient. In order to achieve it, a radiogram was evaluated, the FEM analysis was carried out for the hip joint replaced using the Aura II prosthesis and scanning tests as well as a chemical analysis were performed for the focus of fatigue. The tests performed indicate that the most probable causes leading to the fatigue fracture of the Aura II stem under examination were material defects in the process of casting and forging (forging the material with delamination and the presence of brittle oxides and carbides) that resulted in a significant reduction of strength and resistance to corrosion. In the light of an unprecedented stem neck fracture, this information should be an indication for non-destructive tests of ready-made stems aiming to discover the material and technological defects that may arise in the process of casting and drop forging.

Experimental research and modeling of selected layers of the trachea based on EBUS

Abstract This study presents the use of endobronchial ultrasound (EBUS) for imaging and dimensional measurements of a trachea. An assessment of shape reproduction accuracy was based on a comparative method using one- and two-later models. It was found that dimensions determined from EBUS scans of digital models are overstated by 1.2–2.9 mm on average. Developed 2-D and 3-D models of tracheal structures facilitate the evaluation of dimensions and thickness distribution for tissue layers.

The application of spherical standards for the evaluation of the accuracy of mapping shape in computed tomography

Abstract Anatomical structures are characterized by free surfaces, and most are in lobed and pseudo-spherical shapes. The aim of this article is to analyze selected procedures for accuracy assessment of the shape and dimensions of these structures using certified sphere and Ball Bar standards and to propose metrology parameters facilitating comparison of diagnostic devices. The spherical standard of various materials and Ball Bar standards with various distances between spheres centers can be a tool for evaluation of computed tomography metrology applications. Errors in geometry mapping can be identified on the basis of standardized control systems used in coordinate measuring techniques.