::Meso-electro-mechanical devices - bioimplants::Meso-electro-mechanical devices - bioimplants
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Biocompatible implants and tissue-cellular scaffolds:
Biocompatible material – NiTi (named as “nitinol”) has a high specific strength, corrosion resistance, property of damping, and at last, unique property of shape memory effect (SME), including a porous condition. At our researches in SB of Lebedev Physics Institute of RAS (1997) firstly there was shown a possibility of a laser control overlapping of SLS and SHS processes in Ni-Ti = 1:1 powder composition for the intermetallics synthesis, including Hydroxyapatite additive possibility.
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Cranioplasticity Plate(pure Ti) |
Layer-by-layer 3D cladding of Ti powder on the stomatological dowel. |
SLS of Tooth /di-molar, NiTi/. |
The FE model was constructed, allowing analyze an influence of meso porosity, sizes /up to some mk/ and forms /sphere or cylinder/ of laser sintered particles, external implant shape /complex and cylinder/ on the results of redistributions of stresses, strains and displacements in the bone-implant complex under external normal or tangential chewing loads. Comparative calculations are shown, that maximum values of all studied parameters (ui, eij, sij) for the Ti alloy are different from nitinol. Behavior of nitinol structure is more latent than titanium structure as a factor of durability biointegration and osteogenous.
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Design of implant model in Solid Works |
Model import and finite element meshing in ANSYS© |
Stress-strain diagram for dowel implant in the bone tissue. |
It has been shown through a number of studies that application of a rough or porous surface at the bone/implant interface makes adhesion between bone tissue and implant substantially higher. This results in a more effective, stronger biomechanical connection between the implant and bone. The topography of the contact surface should also match the bone structure. Bone shape and size in the human body differ from person to person, and it is it is difficult to achieve a durable, solid fixation when relying only upon biological fixation with non-customized geometries. Hence, development of a method that allows for alternative types of fixation to the bone surface which can be customized to individual structural peculiarities of different persons would be highly advantageous.
Intrinsic implant porosity appear the positive factor, as will ensure a germination of soft tissue in implant, will allow to infiltrate the interstice by sterilizing preparations, at last to promote an increase of biological compatibility and to actuate the process of healing. Moreover, porous biocompatible structure could be excellence repository for stem cells.
Ingrowth of organic structures in SL- Synthesized implant (after 3 months) |
Ogranotypic structures near porous SLS implant |
Ingrowth of stem cells in SLS implant (4 days) |
Ti |
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NiTi |
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Pre-clinical histological probes on biocompatibility and biointegration of porous nitinol in comparison with porous and molten titanium were conducted on rats within 3 months. All porous items were manufactured by direct SLS method.
Also, morphological study was conducted on the primary cultures of dermal fibroblasts and mesenchymal stromal human cells of the 4-18 passages. Dermal fibroblast culture was received from musculocutaneous tissue with 6-10 week period by the method of primary explants.
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SLS of reaction-capable powder compositions is a promising direction for fabrication of ordering arrays of nanostructures.Geometric similarity of the synthesized structures indicates their fractal nature. Summarizing the above arguments it is possible to conclude that the developed micro- and nano structured nitinol surface promotes biointegration as well as overall mechanical integrity of the implant to the live organism.
