Effect of Micro-Grooving on the Stress Shielding of Titanium: Experimental and Numerical Investigations

2017 ◽  
Author(s):  
Harsha G. Jamadagni ◽  
Hasan Karaman ◽  
Fatih Karpat ◽  
Wendy Williams ◽  
Lokesh Dhanasekaran ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
Equivalent Stress ◽  
Rabbit Model ◽  
Frictional Coefficient ◽  
Stress Shielding ◽  
Test Model ◽  
Implant Surface ◽  
Fea Model ◽  
Pull Out ◽  
Micro Grooving

Micron 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.

Effect of Bioactive Grade Surface on In Vivo Behavior and Mechanical Stability in Titanium Based Implant Surface-Modified by Plasma Spray Coating and Chemical Treatments

2004 ◽  
Vol 449-452 ◽  
pp. 1221-1224
Author(s):  
Baek Hee Lee ◽  
Young Do Kim ◽  
Kyu Hwan Lee
Keyword(s):  
Mechanical Stability ◽  
Testing Machine ◽  
Spray Coating ◽  
Implant Surface ◽  
Chemical Treatments ◽  
Pull Out ◽  
Living Bone ◽  
Surface Modified ◽  
Pull Out Strength

Geometrical and chemical designs of an implant surface affected the stabilization of implant and the healing of tissue. In this study, effects of surface designs in implants on in vivo behavior and mechanical stability were compared by histological and mechanical analyses. The implants were transversely grafted on dog thighbone and healed for 4 and 8 weeks. The pull-out strength between living bone and implant was evaluated by universal testing machine (UTM).

scholarly journals Optimizing Manufacturing and Osseointegration of Ti6Al4V Implants through Precision Casting and Calcium and Phosphorus Ion Implantation? In Vivo Results of a Large-Scale Animal Trial

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1670 ◽  
Author(s):  
Wölfle-Roos JV ◽  
Katmer Amet B ◽  
Fiedler J ◽  
Michels H ◽  
Kappelt G ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Large Scale ◽  
In Vivo Studies ◽  
Control Group ◽  
Implant Surface ◽  
Precision Casting ◽  
Pull Out ◽  
Significant Difference ◽  
Calcium And Phosphorus

Background: Uncemented implants are still associated with several major challenges, especially with regard to their manufacturing and their osseointegration. In this study, a novel manufacturing technique—an optimized form of precision casting—and a novel surface modification to promote osseointegration—calcium and phosphorus ion implantation into the implant surface—were tested in vivo. Methods: Cylindrical Ti6Al4V implants were inserted bilaterally into the tibia of 110 rats. We compared two generations of cast Ti6Al4V implants (CAST 1st GEN, n = 22, and CAST 2nd GEN, n = 22) as well as cast 2nd GEN Ti6Al4V implants with calcium (CAST + CA, n = 22) and phosphorus (CAST + P, n = 22) ion implantation to standard machined Ti6Al4V implants (control, n = 22). After 4 and 12 weeks, maximal pull-out force and bone-to-implant contact rate (BIC) were measured and compared between all five groups. Results: There was no significant difference between all five groups after 4 weeks or 12 weeks with regard to pull-out force (p > 0.05, Kruskal Wallis test). Histomorphometric analysis showed no significant difference of BIC after 4 weeks (p > 0.05, Kruskal–Wallis test), whereas there was a trend towards a higher BIC in the CAST + P group (54.8% ± 15.2%), especially compared to the control group (38.6% ± 12.8%) after 12 weeks (p = 0.053, Kruskal–Wallis test). Conclusion: In this study, we found no indication of inferiority of Ti6Al4V implants cast with the optimized centrifugal precision casting technique of the second generation compared to standard Ti6Al4V implants. As the employed manufacturing process holds considerable economic potential, mainly due to a significantly decreased material demand per implant by casting near net-shape instead of milling away most of the starting ingot, its application in manufacturing uncemented implants seems promising. However, no significant advantages of calcium or phosphorus ion implantation could be observed in this study. Due to the promising results of ion implantation in previous in vitro and in vivo studies, further in vivo studies with different ion implantation conditions should be considered.

scholarly journals The Effect of Ti-6Al-4V Alloy Surface Structure on the Adhesion and Morphology of Unidirectional Freeze-Coated Gelatin

Coatings ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 434
Author(s):  
Snehashis Pal ◽  
Zdenka Peršin ◽  
Tomaž Vuherer ◽  
Igor Drstvenšek ◽  
Vanja Kokol
Keyword(s):  
Bone Ingrowth ◽  
Dip Coating ◽  
Freezing Process ◽  
Implant Surface ◽  
Adhesion Properties ◽  
Wetting Properties ◽  
Pull Out ◽  
Biomimetic Coating ◽  
Substrate Surfaces ◽  
Surrounding Bone

The modification of a metal implant surface with a biomimetic coating of bone-like anisotropic and graded porosity structures to improve its biological anchorage with the surrounding bone tissue at implanting, is still a high challenge. In this paper, we present an innovative way of a gelatin (GEL) dip-coating on Ti-6Al-4V substrates of different square-net surface textures by the unidirectional deep-freezing process at simultaneous cross-linking using carbodiimide chemistry. Different concentrations of GEL solution were used to study the changes in morphology, density, and mechanical properties of the coatings. In addition, the surface free energy and polarity of Ti-6Al-4V substrate surfaces and GEL solutions have been evaluated to assess the wetting properties at the substrate interfaces, and to describe the adhesion of GEL macromolecules with their surfaces, being supported by mechanical pull-out testing. The results indicate that the coating’s morphology depends primarily on the Ti-6Al-4V substrate’s surface texture and second, on the concentration of GEL, which further influences their adhesion properties, orientation, morphological arrangement, as well as compression strength. The substrate with a 300 × 300 μm2 texture resulted in a highly adhered GEL coating with ≥80% porosity, interconnected and well-aligned pores of 75–200 μm, required to stimulate the bone ingrowth, mechanically and histologically.

Impact of Grooves in Hydraulically Expanded Tube-to-Tubesheet Joints

2020 ◽  
Author(s):  
Dinu Thomas Thekkuden ◽  
Abdel-Hamid I. Mourad ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Contact Pressure ◽  
Equivalent Stress ◽  
Pull Out ◽  
Expansion Pressure ◽  
Loading And Unloading ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Maximum Contact ◽  
Pull Out Strength

Abstract The stress corrosion cracking of tube-to-tubesheet joints is one of the major faults causing heat exchanger failure. After the expansion process, the stresses are developed in a plastically deformed tube around the tube-to-tubesheet joint. These residual stressed joints, exposed to tube and shell side fluids, are the main crack initiation sites. Adequate contact pressure at the tube-to-tubesheet interface is required to produce a quality joint. Insufficient tube-to-tubesheet contact pressure leads to insufficient joint strength. Therefore, a study on the residual stress and contact pressure that have a great significance on the quality of the tube-to-tubesheet joint is highly demanded. In this research, a 2D axisymmetric numerical analysis is performed to study the effect of the presence of grooves in the tubesheet and the expansion pressure length on the distribution of contact pressure and stress during loading and unloading of 400 MPa expansion pressure. The results show that the maximum contact pressure is independent of the expansion pressure length. However, the presence of grooves significantly increased the maximum contact pressure. It is proven that the presence of grooves in the tubesheet is distinguishable from the maximum contact pressure and residual von mises equivalent stress. The tube pull-out strength increases with the expansion pressure and the number of grooves. In conclusion, the presence of the grooves affects the tube-to-tubesheet joints.

scholarly journals UV Light Assisted Coating Method of Polyphenol Caffeic Acid and Mediated Immobilization of Metallic Silver Particles for Antibacterial Implant Surface Modification

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1200 ◽  
Author(s):  
Ji Yeon Lee ◽  
Ludwig Erik Aguilar ◽  
Chan Hee Park ◽  
Cheol Sang Kim
Keyword(s):  
Caffeic Acid ◽  
Mechanical Stability ◽  
Uv Light ◽  
Oxidative Polymerization ◽  
Titanium Implants ◽  
Metallic Silver ◽  
Functional Coatings ◽  
Implant Surface ◽  
Coating Application

Titanium implants are extensively used in biomedical applications due to their excellent biocompatibility, corrosion resistance, and superb mechanical stability. In this work, we present the use of polycaffeic acid (PCA) to immobilize metallic silver on the surface of titanium materials to prevent implant bacterial infection. Caffeic acid is a plant-derived phenolic compound, rich in catechol moieties and it can form functional coatings using alkaline buffers and with UV irradiation. This combination can trigger oxidative polymerization and deposition on the surface of metallic substrates. Using PCA can also give advantages in bone implants in decreasing inflammation by decelerating macrophage and osteoclast activity. Here, chemical and physical properties were investigated using FE-SEM, EDS, XPS, AFM, and contact angle. The in vitro biocompatibility and antibacterial studies show that PCA with metallic silver can inhibit bacterial growth, and proliferation of MC-3T3 cells was observed. Therefore, our results suggest that the introduced approach can be considered as a potential method for functional implant coating application in the orthopedic field.

scholarly journals Three-Dimensional Printed Porous Titanium Screw with Bioactive Surface Modification for Bone–Tendon Healing: A Rabbit Animal Model

2020 ◽  
Vol 21 (10) ◽  
pp. 3628
Author(s):  
Yu-Min Huang ◽  
Chih-Chieh Huang ◽  
Pei-I Tsai ◽  
Kuo-Yi Yang ◽  
Shin-I Huang ◽  
...  
Keyword(s):  
Surface Modification ◽  
Tibial Tunnel ◽  
Rabbit Model ◽  
Interference Screw ◽  
Fixation Method ◽  
Titanium Screw ◽  
Pull Out ◽  
Screw Breakage ◽  
Bioactive Surface Modification ◽  
Screw Group

The interference screw fixation method is used to secure a graft in the tibial tunnel during anterior cruciate ligament reconstruction surgery. However, several complications have been reported, such as biodegradable screw breakage, inflammatory or foreign body reaction, tunnel enlargement, and delayed graft healing. Using additive manufacturing (AM) technology, we developed a titanium alloy (Ti6Al4V) interference screw with chemically calcium phosphate surface modification technology to improve bone integration in the tibial tunnel. After chemical and heat treatment, the titanium screw formed a dense apatite layer on the metal surface in simulated body fluid. Twenty-seven New Zealand white rabbits were randomly divided into control and additive manufactured (AMD) screw groups. The long digital extensor tendon was detached and translated into a tibial plateau tunnel (diameter: 2.0 mm) and transfixed with an interference screw while the paw was in dorsiflexion. Biomechanical analyses, histological analyses, and an imaging study were performed at 1, 3, and 6 months. The biomechanical test showed that the ultimate pull-out load failure was significantly higher in the AMD screw group in all tested periods. Micro-computed tomography analyses revealed early woven bone formation in the AMD screw group at 1 and 3 months. In conclusion, AMD screws with bioactive surface modification improved bone ingrowth and enhanced biomechanical performance in a rabbit model.

ACETABULAR LOAD-TRANSFER AND MECHANICAL STABILITY: A FINITE ELEMENT ANALYSIS COMPARING DIFFERENT CEMENTLESS SOCKETS

2014 ◽  
Vol 14 (05) ◽  
pp. 1450063 ◽  
Author(s):  
D. F. M. PAKVIS ◽  
D. JANSSEN ◽  
B. W. SCHREURS ◽  
N. VERDONSCHOT
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Load Transfer ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Stress Shielding ◽  
Physiological Strain ◽  
Element Analysis ◽  
Strain Pattern ◽  
Component Interface

Acetabular stress shielding may be a failure mechanism of acetabular constructs promoting osteolysis, aseptic loosening and failure. We used three-dimensional finite element analysis (FEA) to evaluate the effect of flexible sockets on acetabular stress shielding. The sockets were made of (1) full polyethylene (PE), (2) PE with a metal bearing and (3) a PE insert with a metal backing was used as a traditional stiff implant. We compared the strain energy density and interfacial micro-motions between bone and cementless sockets during walking. In our FEA model, the most elastic socket (case 1) showed the highest levels of micro-motion during walking (400 μm). The most rigid socket (case 3) showed smaller areas of high micro-motions. Assuming a threshold for ingrowth of 50 microns, the flexible cup showed an ingrowth area of almost 40%, whereas the other two cases showed stable areas covering 60% of the total bone–component interface. Furthermore, we found that the introduction of an implant generates a very different strain pattern directly around the implant as compared with the intact case, which has a horse-shoe shaped cartilage layer in the acetabulum. This difference was not affected much by the stiffness of the implant; a more flexible implant resulted in only slightly higher strain levels. Bone strains over 1.5 mm from the cup showed physiological values and were not affected by the stiffness of the implant. Hence, this study shows that the physiological strain patterns are not obtained in the direct periprosthetic bone, regardless of the stiffness of the material.

scholarly journals Influence of pedicle screw thread width and recovery time after surgery on fixation strength

2021 ◽  
Vol 7 (2) ◽  
pp. 751-754
Author(s):  
Harikrishna Makaram ◽  
Ramakrishnan Swaminathan
Keyword(s):  
Cortical Bone ◽  
Pedicle Screw ◽  
Stress Shielding ◽  
Stress Transfer ◽  
Fixation Strength ◽  
Screw Thread ◽  
Fe Model ◽  
Contact Conditions ◽  
Transfer Parameter ◽  
Pull Out

Abstract Introduction: Pedicle screw fixation systems are widely used for treatment of various spinal pathologies, including spinal stenosis, scoliosis, spinal deformities and fractures. Stress shielding is considered to be a major factor contributing to insufficient fixation strength, leading to screw loosening. In this study, the influence of pedicle screw thread width on the displacement of pedicle screw and stress transfer is analyzed using 2-Dimensional axisymmetric finite element (FE) model. Methods: FE model consisting of cancellous and cortical bone, along with pedicle screw is developed for this study. The pedicle screw thread width is varied between 0.1 mm and 0.6 mm in steps of 0.1 mm, while the other geometric parameters, including screw half-angle, pitch, diameter, and length are kept constant. Three different contact conditions between screw and bone, such as frictionless, frictional, and bonded are considered to simulate hours, days, and months after surgery, respectively. The material properties and boundary conditions are applied based on previous studies. An axial force of 80 N is applied on the screw head to simulate axial pull-out test. Results: Similar patterns of stress distribution are observed for all screw models, with high stress concentration above the first thread. The highest displacement in screw is observed shortly after surgery, while the highest displacement in cancellous and cortical bone is observed few days and months after the surgery, respectively. The average von Mises stress in screw decreases with increase in thread width for all contact conditions. In few hours/days after the surgery, stress transfer parameter increases with increase in thread width, up to a thread width of 0.5 mm and then decreases. The changes in stress transfer parameter are negligible few months after the surgery. Conclusion: This study highlights the influence of thread width on displacement and stress transferred to the bone, at different durations after the surgery. It is observed that a thread width of 0.5 mm exhibits the highest stress transfer, leading to reduced stress shielding and improved bone remodeling. It appears that this study might aid in developing better pedicle screws for the treatment of various spinal pathologies.

scholarly journals Thermosensitive Chitosan–Gelatin–Glycerol Phosphate Hydrogels as Collagenase Carrier for Tendon–Bone Healing in a Rabbit Model

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 436 ◽  
Author(s):  
Yu-Min Huang ◽  
Yi-Cheng Lin ◽  
Chih-Yu Chen ◽  
Yueh-Ying Hsieh ◽  
Chen-Kun Liaw ◽  
...  
Keyword(s):  
Bone Healing ◽  
Healing Process ◽  
Rabbit Model ◽  
Bone Volume ◽  
Control Group ◽  
Glycerol Phosphate ◽  
Bone Interface ◽  
Anterior Cruciate Ligament Graft ◽  
Pull Out ◽  
Collagenase Treatment

Healing of an anterior cruciate ligament graft in bone tunnel yields weaker fibrous scar tissue, which may prolong an already prolonged healing process within the tendon–bone interface. In this study, gelatin molecules were added to thermosensitive chitosan/β-glycerol phosphate disodium salt hydrogels to form chitosan/gelatin/β-glycerol phosphate (C/G/GP) hydrogels, which were applied to 0.1 mg/mL collagenase carrier in the tendon–bone junction. New Zealand white rabbit’s long digital extensor tendon was detached and translated into a 2.5-mm diameter tibial plateau tunnel. Thirty-six rabbits underwent bilateral surgery and hydrogel injection treatment with and without collagenase. Histological analyses revealed early healing and more bone formation at the tendon–bone interface after collagenase partial digestion. The area of metachromasia significantly increased in both 4-week and 8-week groups after collagenase treatment (p < 0.01). Micro computed tomography showed a significant increase in total bone volume and bone volume/tissue volume in the 8 weeks after collagenase treatment, compared with the control group. Load-to-failure was significantly higher in the treated group at 8 weeks (23.8 ± 8.13 N vs 14.3 ± 3.9 N; p = 0.008). Treatment with collagenase digestion resulted in a 66% increase in pull-out strength. In conclusion, injection of C/G/GP hydrogel with collagenase improves tendon-to-bone healing in a rabbit model.

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