The effect of porous compliance bushings in a dental implant on the distribution of occlusal loads.

Porous dental implants are clinically used, but the mechanism of load distribution for stepped implant shaft surrounded by compliance bushings is still not known, especially for different bone conditions. The aim of the study was to assess the impact of the design of a dental implant with compliance bushings (CBs) on the occlusal load distribution during primary and secondary stability using finite element simulation (FEA), with a distinction between low and high quality cervical support under primary stability. The FEA of the oblique occlusal load transfer (250 N; 45°) was carried out for implants under variable bone conditions. The stepped shaft in the intermediate part of the dental implant was surrounded by CBs with an increasing modulus of elasticity of 2, 10 and 50 GPa. With a smaller Young's modulus of the bushings the increase of stress in the trabecular bone indicated that more bone tissue can be protected against disuse. The beneficial effect for the trabecular bone derived from the reduction of the stiffness of the bushings in relation to the loss of the implant's load bearing ability can be assessed using the FEM method.

Structural characterization of newly-developed Al79Ni5Fe5Y11 and Al79Ni11Fe5Y5 alloys with amorphous matrixes.

The low glass-forming ability of aluminium-based metallic glasses significantly limits their development and preparation. This paper updates the current state of knowledge by presenting the results of structural studies of two newly-developed Al79Ni5Fe5Y11 and Al79Ni11Fe5Y5 alloys with a reduced aluminium content (< 80 at.%). The alloys were produced by conventional casting (ingots) and melt-spinning (ribbons). Structural characterization was carried out for bulk ingots first, and then for the melt-spun ribbons. The ingots possessed a multiphase crystalline structure, as confirmed by X-ray diffraction and scanning electron microscopy observations. The amorphous structure of the melt-spun ribbons was determined by X-ray diffraction and transmission electron microscopy. SEM observations and EDX element maps of the cross-section of melt-spun ribbons indicated a homogeneous elemental composition. Neutron diffraction revealed the presence of nanocrystals in the amorphous matrix of the melt-spun ribbons. DSC data of the melt-spun ribbons showed exothermic events corresponding to the first crystallization at temperatures of 408 °C and 387 °C for Al79Ni5Fe5Y11 and Al79Ni11Fe5Y5, respectively.

Evaluation of the biocompability and corrosion activity of resorbable CaMgZnYbBAu alloys.

Calcium-based alloys can be promising candidates for use as biodegradable implants because of attractive properties as mechanical, corrosive, and biocompatible. In the work, the biocompatibility authors discussed the results of the Ca32Mg12Zn38Yb18-xBx (x = 0, 1, 2, 3 at.%) and Ca32Mg12Zn38Yb18-2xBxAux (x = 1, 2 at.%) alloys. The tests were performed using a MTT assay. The corrosion behavior of such Ca-based alloys in PWE fluid at 37 °C was studied and compared with the results in Ringer's solution from previous works. Electrochemical tests were presented by open circuit potential and potentiodynamic curves. Different concentrations of boron and gold in the alloys caused changes in the corrosion results. The best corrosion resistance in PWE solution was observed for the Ca-based alloy with 2 at.% Au due to the lowest value of the corrosion current density (jcorr), equal to 10.6 µA·cm-2. A slightly higher value of jcorr was obtained for the Ca32Mg12Zn38Yb15B3 alloy with the lowest roughness values. The results of the cytotoxicity tests also showed that the alloy with 3 at.% boron was characterized by the highest cell viability. The investigation results discussed in the work allow us to suggest that the presented calcium alloys with 3 at.% of B, and 2 at.% of Au addition may be promising materials for the use in implantology.

Study of crystallization mechanism of Al-based amorphous alloys by in-situ high temperature X-ray diffraction method.

The role of transition metals (TMs) addition on the formation and crystallization of amorphous Al85TMs10Y5 alloys was described using in-situ high-temperature X-ray diffraction. The structural results were compared with differential scanning calorimetry and dynamical mechanical analysis to obtain detailed information about the nucleation and growth of crystalline phases. The performed analysis confirmed that Fe and Cu addition drastically changes the crystallization temperature and the phase composition of the fully crystallized alloys. While for Al85Ni10Y5 alloy, the second crystallization step is related to the formation of Al19Ni5Y3 phase, for Al85(Ni, Fe)10Y5 and Al85(Ni, Fe, Cu)10Y5 alloys crystallization of Al15Fe9Y2 phase was observed. Interestingly, the performed analysis showed that forming a homogenous amorphous phase is not necessary to obtain the best corrosion resistance. It was noted that the precipitation of the YCr2Al20 phase in the Cu-rich amorphous matrix should be a much more interesting approach.

The Influence of Rapid Solidification on Corrosion Behavior of Mg60Zn20Yb15.7Ca2.6Sr1.7 Alloy for Medical Applications.

Biodegradable magnesium alloys with Zn, Yb, Ca and Sr additions are potential materials with increased corrosion resistance in physiological fluids that ensure a controlled resorption process in the human body. This article presents the influence of the use of a high cooling rate on the corrosion behavior of Mg60Zn20Yb15.7Ca2.6Sr1.7 alloy proposed for medical applications. The microstructure of the alloy in a form of high-pressure die-casted plates was presented using scanning electron microscopy in the backscattered electrons (BSEs) mode with energy-dispersive X-ray spectrometer (EDX) qualitative analysis of chemical composition. The crystallization mechanism and thermal properties were described on the basis of differential scanning calorimetry (DSC) results. The corrosion behavior of Mg60Zn20Yb15.7Ca2.6Sr1.7 alloy was analyzed by electrochemical studies with open circuit potential (EOCP) measurements and polarization tests. Moreover, light microscopy and X-ray photoelectron spectroscopy were used to characterize the corrosion products formed on the surface of studied samples. On the basis of the results, the influence of the cooling rate on the improvement in the corrosion resistance was proved. The presented studies are novel and important from the point of view of the impact of the technology of biodegradable materials on corrosion products that come into direct contact with the tissue environment.