Łukasz Bojko

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

PURPOSEnThe 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.nnnMETHODSnMicrostructural 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.nnnRESULTSnBased 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.nnnCONCLUSIONSnAccording 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.

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.

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.