Browsing by Author "Khandaker, M."
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Publication Effect of micro-grooving on the stress shielding of titanium: Experimental and numerical investigations(Amer, 2018-01-01) Jamadagni, Harsha G.; Karaman, Hasan; Karpat, Fatih; Williams, Wendy; Dhanasekaran, Lokesh; Khandaker, M.; ASME; Karaman, Hasan; KARPAT, FATİH; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü; 0000-0001-8474-7328; A-5259-2018; HJS-9729-2023Micron sizes grooves can control the cell settlement on the implant surface or be used to direct tissue generation at the implant/bone interface. The effect of shape, size and the type of material of the microgrooves on the mechanical stimulus transfer from the implant to bone at physiological loading is not known yet. Therefore, this study evaluated both experimentally and numerically the effect of surface modification on a titanium implant to the load transfer characteristics from implant to bone for examining stress shielding parameters. This study measured the effect of micron grooves on titanium to the mechanical stability of titanium using a rabbit model. This study also developed a finite element model based on the in vivo test model to examine the stress shielding parameters. The results showed that the mean values of fracture strength were significantly higher for grooved titanium samples (1.32 +/- 0.45 MPa, n = 3) compared to control samples (without any groove) (0.22 +/- 0.16 MPa, n=6) (P < 0.05). The load-displacement graph from the pull out tension tests was used to measure the frictional coefficient between Ti and bone from the FEA model. It was found from the FEA model that the average co-efficient of friction between titanium and bone was 0.50. Maximum equivalent stress along the interface of microgrooves on titanium was higher from groove area in compare to the non-groove area because of the change of the geometry along the groove. The microgrooves in the model have a significant effect on the stress transfer parameter between implant and adjoining bone. The unequal load sharing due to micro-grooving causes an increase in stiffness of the adjacent bone to the implant.Publication Evaluation of biomechanical performances of electrospun fiber anchored silicone disc as an intervertebral disc implant(Amer Soc Mechanical Engineers, 2018-01-01) Tummala, Subhakar; Doğan, Oğuz; Karpat, Fatih; Riahinezhad, Shahram; Khandaker, M.; ASME; DOĞAN, OĞUZ; KARPAT, FATİH; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü; 0000-0003-4203-8237; 0000-0001-8474-7328; AAV-7897-2020; A-5259-2018; GXH-1702-2022A tissue engineered intervertebral disc (IVD) anchor the circumference and top/bottom sides of nucleus pulposus (NP) implants with annulus fibrosus and endplates. The proper anchorage of a NP implant to annulus fibrosus and endplates is possible by enclosing the NP by electrospun fiber mesh that mimics the surrounding structures. The biomechanical performance of silicone based NP can be improved if electrospun fiber mesh can secure all sides of silicone NP. However, it is unknown whether silicone surrounded by an electrospun nanofiber matrix can better restore the biomechanical functions of the disc in compare to intact, IVD made with silicone only, and, IVD made with silicone anchored all sides by nanofiber. This study compared the compressive and viscoelastic properties of a silicone and electrospun nanofiber anchored silicone discs (ENAS) under compression and shear with the same properties of human NP. This study developed a nonlinear finite element model (FEM) for the intact and ENAS implanted human lumbar vertebra segments. The compression test results show that ENAS disc compressive modulus (87.47 +/- 7.56 kPa, n = 3) is significantly higher in compare to silicone gel (38.75 +/- 2.15 kPa, n = 3) and the value is within the range of the compressive modulus of human NP (64.9 +/- 44.1 kPa). The rheological test results show that ENAS disc compressive modulus (16 similar to 40 kPa) is significantly higher in compare to silicone gel (0.10 similar to 0.16 kPa) and the value is within the range of the compressive modulus of human NP (7 similar to 20 kPa). These results confirm the suitability of ENAS disc over silicone as NP implant. A finite element model has been developed based on the ENAS properties. The FEA results showed that ENAS can restore better the biomechanical motions of a lumbar vertebra segments in compare to silicone NP.