RESUMO
The issue of bone volume loss is playing an increasing role in bone tissue engineering. Research has focused on studying the preparation and use of different types of human or xenogenic materials and their osteogenic properties. An alternative source for this purpose could be autologous extracted teeth. The simple preparation protocol, minimal immune response, and rapid organizing of the newly formed bone with optimal mechanical properties predispose autologous hard teeth tissues (HTTs) as a promising material suitable in the indication of augmentation of maxillary and mandible defects, comparable to other high-end augmentation materials. The aim of this study was to experimentally evaluate the osteogenic potential of ground native autologous HTTs prepared by different demineralization procedures, aimed at potentiating the osteoinductive and osteoconductive properties of their organic components. The results indicate that the most effective preparation process for HTT stimulation is the application of Cleanser for 10 min followed by exposure to 0.6 N HCl for 5 min with a wash in phosphate-buffered saline solution.
RESUMO
High entropy metal sub-lattice stabilized nitride coatings based on multicomponent refractory transition metals (TM = Ti, Nb, V, Ta, Zr, Hf) are promising candidates for extreme conditions due to their high thermal, mechanical, and corrosion properties. The aims of the current work included the investigations of the possibilities of the novel High Target Utilization Sputtering (HiTUS) technique applied to reactive sputtering of TiNbVTaZrHf-xN coatings from the viewpoints of hysteresis behavior during reactive sputtering as well as the structure, composition, stoichiometry, and mechanical properties of the resulting coatings. With increasing nitrogen content, coating structures varied from amorphous in metallic alloy coatings to textured nano-columnar fcc structures. Despite certain deviations of TM from equiatomic concentrations, homogeneous solid solutions corresponding to single-phase multicomponent nitride analogous to high entropy stabilized compounds were obtained. Mechanical properties were found to be proportional to nitrogen content. The highest hardness HIT ~ 33 GPa and indentation modulus EIT ~ 400 GPa were found in a slightly sub-stoichiometric (~42 at% nitrogen) composition. HIT/EIT and limited pillar split measurements suggested that these coatings exhibit low fracture toughness (around 1 MPa.m1/2). The work confirmed that reactive HiTUS is suitable for the preparation of multicomponent nitrides with the control of their stoichiometry and mechanical properties only via nitrogen additions.
RESUMO
PURPOSE: The aim of this work was a finite element analysis of the effect of a sloped platform in tilted implants in the All-on-4 treatment concept on the level of maximum stresses in compact bone. MATERIALS AND METHODS: Finite element modeling of the stresses at tilted microthread implants with standard and sloped abutment platform under four loading conditions and two levels of osseointegration was performed. RESULTS: The sloped abutment platform in tilted implants positioned at rim bone level resulted in a two to four times reduction of the maximum von Mises stresses in the adjacent cortical bone compared with the standard platform. These stresses were well below the yield stress of the cortical bone. The main importance of the proposed sloped platform in tilted implants is substantial stress reduction in the case of immediate loading. The stress reduction also results in the reduction of the deformation of the framework of the All-on-4 concept. CONCLUSION: The suggested modification of the slope of the abutment platform on tilted implants is recommended as a technically simple and highly effective solution for significant reduction of maximum stresses in the cortical bone around the implant.
