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Scaffold Materials and Structures

Scaffold Materials and Structures. M. Entezarian, Dick Smasal, Brad Heckendorf Phillips Plastics Corporation. Methods for making porous structures. Foaming Limited to polymeric materials Random pore structure weak Replication Copying geometry and features of precursor structure

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Scaffold Materials and Structures

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  1. Scaffold Materials and Structures M. Entezarian, Dick Smasal, Brad Heckendorf Phillips Plastics Corporation

  2. Methods for making porous structures • Foaming • Limited to polymeric materials • Random pore structure • weak • Replication • Copying geometry and features of precursor structure • Porous metallic and ceramic materials possible • Free-forming • Geometry not limited • Slow • Molding • Mass production

  3. A. Use reticulated foam of Polyurethane or Polyester, HA or TCP powder, water, and a binder B. Coat the foam with ceramic powder C. Fire B, burn the polymer scaffold and sinter the ceramic powders Macro reticulated porous ceramic process

  4. C. Dry and fire to produce the desired structure B. Construct the designed 3D structure A. Prepare formulation (Ceramic + binders) Solid-free forming

  5. C. use a pack of beads for cell growth A. Prepare formulation B. Make beads and fire to obtain porous structure Porous beads

  6. A. Mold porous structures with CIM feedstocks of HA or TCP B. Debind the molded structure C. Fire the structure and produce an ordered porous structure Macro reticulated porous ceramic process(Through injection molding)

  7. Replication Method Raw Material-Reticulated Foam Macrophotograph SEM micrograph

  8. Raw MaterialCeramic Powder • Materials — any sinterable ceramic: • Hydroxyapatite • Tri-Calcium Phosphate • Zirconia • Alumina Example Hydroxyapatite Powder

  9. Manufacturing Process • Preparation of ceramic slip (like paint) • disperse ceramic powder with: • water • polymeric binder • dispersant • additives

  10. Manufacturing Process • Coat reticulated polymeric foam • cell size of foam used to control ceramic foam cell size • Cut desired implant size • 3D geometric features possible • Sinter ceramic foam • burn out all organics — foam and slip additives

  11. “Green” coated foams ready for sintering Manufacturing Process

  12. Manufacturing Process • Sintering • Temperatures of 1000° C to 1600° C • Precursor foam and organics removed • Ceramic powder becomes dense

  13. Manufacturing Process Sintered foam parts

  14. Chemistry • Hydroxyapatite (Ca5(PO4)6OH) • Meets ASTM F1185 Standard Specification of Ceramic Hydroxyapatite for Surgical Implants • TriCalcium Phosphate (Ca3(PO4)2) • Meets ASTM F1088 Standard Specification for Beta-TriCalcium Phosphate for Surgical Implants

  15. Structure • Fully open and interconnected pores • Structure independent of material • Median pore size 264 µm • Narrow and controlled pore size distribution • 80% Porous (nominal) Scanning Electron Micrograph of Hydroxyapatite

  16. Physical • Hydroxyapatite • Bulk Density 0.57 g/cc (±0.03) • Porosity 81.1% (±1.01) • Sintered (strut) Density 95% • Crush Strength 1.89 MPa (±0.19) • Modulus 47.1 MPa

  17. Physical • TriCalcium Phosphate • Bulk Density 0.51 g/cc (±0.05) • Porosity 83.5% (±1.56) • Sintered (strut) Density 93% • Crush Strength 1.31 MPa (±0.25) • Modulus 39.9 MPa

  18. IN VIVO EVALUATION OF BONE SUBSTITUTES IN A RABBIT TIBIAL DEFECT MODEL

  19. Hydroxyapatite Start 6 Weeks 8 Weeks

  20. Tricalcium phosphate Start 6 Weeks 8 Weeks

  21. Alumina Start 6 Weeks 8 Weeks

  22. Sintered Dense/Macro Porous Ceramics • Biocompatible • Bioresorbable • Maintain structural strength • Elicit minimal foreign body reaction

  23. Study purpose: To compare two injection molded sintered dense ceramics, HAP and TCP,in a rabbit transcondylar femur model.

  24. Histologic Results • HAP – Well-defined smooth circumference with thin layer of biofilm. 12 weeks 24 weeks

  25. Histologic Results • TCP – Rough/irregular circumference with bone ingrowth into implant 12 weeks 24 weeks

  26. MOPS Introduction • Produce Porous Ordered Structures of polymers, metals, and ceramics through Injection Molding • 50% porosity • Pore size of 0.020” for polymeric materials • Pore size of 0.016” for metallic and ceramic materials

  27. Osteogenic Differentiations Dan Collins, BioE Inc.

  28. Chondrogenic Differentiation TCP 7 days TCP 14 days TCP 70 days Dan Collins, BioE Inc.

  29. Crush Strength Comparison

  30. Materials molded in these structures • Polyethylene • Polycarbonate • PEEK • PCL (bio-degradable) • PLA (bio-degradable) • Alumina • TCP • Stainless Steel (316L) • Titanium

  31. Potential Applications • Implants • Drug delivery • Cell growth • Catalyst support • Filtration • Electrodes

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