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Howard A. Kuhn - Additive Manufacturing in the Biomedical Space

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Howard A. Kuhn - Additive Manufacturing in the Biomedical Space

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Howard A. Kuhn - Additive Manufacturing in the Biomedical Space

  1. 1. Additive Manufacturing Of Bioresorbable Scaffolds R3D@TRI-C September 9, 2016 Howard A. Kuhn PhD FASM Adjunct Professor, University of Pittsburgh Technical Advisor, America Makes
  2. 2. Selective transformation of material having primitive form (liquid, powder, wire, sheet) Additive Manufacturing Additive Manufacturing Machine solid 3D form prescribed by a CAD solid model into a 0 CAD solid model
  3. 3. Major Applications of Additive Manufacturing Aerospace Tooling Biomedical
  4. 4. Biomedical Applications Surgery Planning Models Splints Exoskeleton Components Prostheses Limbs Hearing Aids Dental Aligners Implants (Replacement Therapy) Bioresorbable implants (Regenerative Therapy) Functional Tissue Generation (Organ Replacement) Taking advantage of additive manufacturing/3DPrinting capabilities for production of patient specific parts:
  5. 5. Windpipe Splint produced by Selective Laser Sintering of a Bioresorbable Polymer Polycaprolactone Splints degrade after they’ve done their job
  6. 6. How about bioresorbable materials for bone repair? Windpipe Splint produced by Selective Laser Sintering of a Bioresorbable Polymer Polycaprolactone Splints degrade after they’ve done their job
  7. 7. Bioresorbable Materials for Bone Tissue Repair • Bioresorbable polymer and ceramic alternatives to permanent metal implants or bone grafts • Advantages – No side effect from long term use – No secondary surgery – Potential for multi-functional treatments • Limitations – Low mechanical properties [1] – Acidic degradation products (polymers) [1] – Slow degradation (biocomposites, ceramics, and some polymers) [1,2] 1. J.C. Middleton, A.J. Tipton / Biomaterials 21 (2000) 2335}2346 2. Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 22, No 9 (September), 2006: pp 993-999
  8. 8. Bioresorbable Materials for Bone Tissue Repair • Bioresorbable polymer and ceramic alternatives to permanent metal implants or bone grafts • Advantages – No side effect from long term use – No secondary surgery – Potential for multi-functional treatments • Limitations – Low mechanical properties [1] – Acidic degradation products (polymers) [1] – Slow degradation (biocomposites, ceramics, and some polymers) [1,2] How about Bioresorbable Metals ?
  9. 9. Bioresorbable Magnesium alloys Properties Natural Bone Magnesium alloys Titanium alloys Stainless steel PLGA/PLLA Density (g/cm3) 1.8–2.1 1.74–2.0 4.4–4.5 7.9–8.1 ~1.3 Elastic modulus (GPa) 14 - 17 41–45 110–117 189–205 7-0.2 Comp, yield strength (MPa) 130–180 250-1000 758–1117 170–310 NA Tensile yield strength (MPa) 104-120 100-300 700-900 221-1213 27-1 But, pure Mg resorbs too quickly Through Density Functional Modeling, alloy additions to extend resorption of pure Mg were developed and patented Properties of Mg alloys closer to those of bone than other implant materials
  10. 10. Bioresorbable Mg Alloy Examples Bone plates and screws ACL screw AV fistula stent 1mm 1mm Nerve guide Craniofacial (TMJ) screw Tracheal stent
  11. 11. Mg Ti Mg degradation does not inhibit fracture healing In vivo Tests Mg enhances bone growth
  12. 12. ERC-RMB Devices Implanted in Animal Models Orthopedic plates and screws AV fistula Stents Trachea stent Kirschner wire Just after implantation 14 weeks after implantation
  13. 13. ERC-RMB Devices Implanted in Animal Models What about Additive Manufacturing of Bioresorbable Metals?
  14. 14. Conforming bone plates could be produced by additive manufacturing with properties matched to localized stresses
  15. 15. Image acquisition of bone defect site Image post- processing and analysis 3D CAD model of bone graft generated Implant 3D printed from biodegradable metal Customized biodegradable bone graft substitute by 3DPrinting Sterilized bone graft substitute is implanted into defect site Image credit: Synthes CMF Patient Specific Implants Benefits: • Avoids need for bone grafting • Matching complex 3D anatomical defects reduces operating room time ($56 per minute) • Eliminates secondary surgery ($58,000 per operation) : Biodegradable Metallic Bone Scaffolds
  16. 16. Binder-jet 3D printed prototype scaffolds using pure Mg powder (particle size < 50 μm) But sintering the scaffolds proved to be difficult
  17. 17. Additive Manufacturing of Mg BJ 3DP • Pros: Easily printed • Cons: Difficult to sinter SLM/EBM • Pros: No sintering • Cons: Low vapor pressure, melting point Further research is necessary to achieve 3D printing of stable Mg-based alloys
  18. 18. Bioresorbable Fe-Mn alloys Material Yield strength (MPa) Ultimate strength (MPa) Elongation (%) Young’s modulus (GPa) Fe-30Mn 3DP 106 ± 8 115 ± 1 0.73 ± 0.15 32 ± 5 Natural bone 104-121 86-151 1-3 14-17
  19. 19. Bioresorbable Fe-Mn alloys Material Yield strength (MPa) Ultimate strength (MPa) Elongation (%) Young’s modulus (GPa) Fe-30Mn 3DP 106 ± 8 115 ± 1 0.73 ± 0.15 32 ± 5 Natural bone 104-121 86-151 1-3 14-17 But Fe-Mn alloys take too long to resorb
  20. 20. ThermoCalc determination of suitable alloying elements to accelerate resorption of Fe-Mn
  21. 21. Material Corrosion potential, Ecorr [V) Corrosion current density, icorr [µA cm-2] Fe-Mn -0.72±0.04 1.00±0.06 Fe-Mn-1Ca -0.71±0.02 2.12±0.92 Fe-Mn-2Ca -0.66±0.02 6.36±1.75 Fe-Mn-1Mg -0.65±0.02 5.89±0.80 Fe-Mn-2Mg -0.64±0.03 9.16±1.25 ~10-fold increase in corrosion rate of 3DP Fe-Mn compared to pure iron (0.73 to 0.065 mmpy)
  22. 22. Cytotoxicity testing of 3DP Fe-Mn alloys • Live/dead cell viability assay of the cytotoxicity of 3DP Fe-based alloys • Pure Fe exhibited no live cells on the surface • Fe-Mn-1Ca exhibited most live cells (green)
  23. 23. Fe-Mn 3DPrinting of Fe-Mn alloys Fe-Mn-1Ca 3D printing & Sintering 20µm20µm • ExOne’s RX1 BJ printer was used for this study • Sintered at 1200 ºC, 3 hours 20µm20µm
  24. 24. Fe-30Mn 3DPrinted/Sintered parts Bone cells seeded onto scaffolds In Vitro results prototype scaffolds with 1 mm and 500 µm square pores miniature femur before and after tumble finishing
  25. 25. •High cell attachment •Cells infiltrated into pores Chou et al., Acta Biomater. 2013 In-vitro testing of 3DPrinted Fe-30Mn alloys
  26. 26. Technical feasibility Goat mandible model 2. CT Scan Goat mandible CT Scan STL file 3DP mandible BJ/Sintering SLM - Renishaw
  27. 27. Next Steps In-Vivo Testing Innovative Design (for 3DPrinting) of Bone Implants
  28. 28. To Your Good Health Acknowledgements: Drs. Daeho Hong, Da-Tren Chou, Abhijit Roy, Prashant Kumta

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