Metallic scaffolds for bone tissue engineering (Titanium/Nickel-Titanium/Tantalum/Cobalt chromium and stainless steel ). We will discuss metallic scaffolds requirements,disadvantages,types and the pros and cons of each type.

1. Metallic scaffolds for
bone tissue engineering
Mohamed Mahmoud Abdul-Monem
09-708
Spring 2019
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2. Content
• Introduction
• Requirements of metallic scaffolds for bone
tissue engineering
• Types of metallic scaffolds for bone tissue
engineering .
• Fabrication techniques of metallic scaffolds for
bone tissue engineering
• References
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3. Introduction
• Bone tissue engineering is an emerging
interdisciplinary field in science, combining
expertise in medicine, material science and
biomechanics.
• Porous scaffolds are essential to hard tissue
engineering strategies because they provide a 3D
framework for delivering cells or regenerative
factors in an organized manner to repair or
regenerate damaged tissues.
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5. 5
Scaffolds for bone
tissue engineering
Polymeric Ceramic Metallic Composites

6. 6
Metallic
scaffolds
Biodegredable
For small-sized
defects
Non-
Biodegredable
For Large-sized
defects
•Mg
•Fe
•Zn
•Ti
•Ni-Ti
•Ta
•St.St
•Co-Cr

7. Requirements of metallic scaffolds
for bone tissue engineering
• Total porosity
Parameter
• Percentage of
total void
space
Definition
• Affects
mechanical
strength of
the scaffold
Biological
response
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8. 8

9. Requirements of metallic scaffolds
for bone tissue engineering
9
• Open
porosity
Parameter
• Percentage of
pores that are
interconnected
Definition
• Affects cell
permeability and
vascularization,
as well as growth
factor diffusion
Biological
response

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11. Requirements of metallic scaffolds
for bone tissue engineering
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• Surface area
to volume
ratio
Parameter
• Ratio of total
scaffold surface
area to total
scaffold volume
Definition
• Cell seeding
density and
concentration
of growth
factors
Biological
response

12. Requirements of metallic scaffolds
for bone tissue engineering
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• Pore Diameter
Parameter
• Diameter of
largest sphere
that fits within
pore channel
Definition
• Cell
infiltration
and bone
ingrowth
Biological
response

13. 13

14. Requirements of metallic scaffolds
for bone tissue engineering
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• Stiffness
Parameter
• Mechanical
property
Definition
• Affects cell
attachment
Biological
response

15. Metallic scaffolds
Disadvantage How to overcome ?
1. Lack of biological recognition
on the material surface
(Bioninert)
•Surface coating or surface
modification
•Integrate cell-recognizable
ligands and signaling growth
factors on the surface of the
scaffolds
2.Release of toxic metallic ions
and/or particles through
corrosion
Surface modification
3.High elastic modulus which
leads to stress shielding
Use of composite scaffolds
4. Difficult in processing and
porosity control
Rapid prototyping
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16. 16
Non –Biodegredable
Metallic scaffolds for bone
tissue engineering
Titanium
alloys
Nickel
Titanium
Tantalum
Stainless
steel
Cobalt
Chromium

17. I.Titanium alloys scaffolds
Advantages Disadvantages
•Osseointegration •Toxicity from Aluminum and
vanadium
•High Mechanical properties •Susceptible to crack
propagation
•Biocompatible
(Passive oxide layer)
•Low wear resistance compared
to Co-Cr
•Low Density
•Not ferromagnetic
(MRI Compatible)
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18. Surface modification of Titanium
scaffolds
• Ti alloys are classified as biocompatible
materials; however, being bioinert materials,
they do not possess the required bioactivity to
bond to bone directly, resulting in a longer
recovery time for bone regeneration.
• Without surface modification ,Ti alloys are
generally encapsulated by soft-fibrous
connective tissue.
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19. Surface modification of Ti scaffolds
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Mechanical
Machining
Grinding
Sandblasting
Physical
Thermal
sprayed
coatings
e.g Plasma arc
spray of
Hydroxyapatite
or Titanium
oxide
Chemical
Acidic
treatment
Alkaline
treatment
Hydrogen
peroxide
Sol-Gel
Anodic
oxidation

20. Mechanical modification of titanium
scaffolds
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21. Physical modification of titanium
scaffolds
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22. Chemical modification of titanium
scaffolds
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23. II.Nickel Titanium alloys scaffolds
Advantages Disadvantages
•Shape memory •Allergy and Toxicity from
Ni
In order to overcome this
problem:
1. surface modifications
such as oxidation
treatment of NiTi to
obtain a Ni-free surface
2. Ni-free shape memory
alloys, mainly niobium
based, are currently
under development.
•Superelasticity
•Elastic modulus close to
bone
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24. III.Tantalum scaffolds
Advantages Disadvantages
•High volume porosity (80%) •Higher coefficient of friction
than bone
•Interconnected pores •High production cost
•Modulus of elasticity similar
to bone
•Difficult processing due to
high melting point (3017˚C)
compared to Ti (1668˚C)
and high oxygen affinity
•Biocompatible due to self-
passivating oxide layer
•High density (16.65 g/cm3 )
compared to Ti(4.5 g/cm3 )
•Corrosion resistant
•Osseointegration
•Excellent cell attachment
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25. IV.Stainless steel scaffolds
Advantages Disadvantages
•Corrosion resistance due to
high chromium content (12%)
•Lower Biocompatibility than
Ti alloys due to chromium
and Nickel content in some
alloys .
•Low cost •No osseointegration
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26. V.Cobalt Chromium scaffolds
Advantages Disadvantages
•Higher wear resistance
compared to Ti alloys
•Higher modulus of elasticity
than bone which leads to
great stress shielding
•High strength •Low biocompatibility
•High ductility •No osseointegration
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27. Comparison between different
metallic scaffolds
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28. Elastic modulus of different metallic
scaffolds compared to bone
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UHMW PE : ultra high molecular weight polyethylene

29. Fabrication techniques of metallic
scaffolds
I.Conventional techniques
II.Rapid prototyping
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30. I.Conventional techniques
1. Sintered metal powder
2. Sintered metal fibers
3. Space-holder method
4. Gas injection into the metal melt
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31. However, there are inherent limitations in
these processing methods, which offer little
capability to control precisely pore size, pore
geometry, pore interconnectivity and
spatial distribution of pores.
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32. 1.Sintered metal powder
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Sintering
Metal powder Porous metallic
scaffold

33. 2.Sintered metal fiber
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Sintereing
Metal fibers
Porous metallic
scaffold

34. Sintering vs melting
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35. 3.Space holder method
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36. 4.Gas injection into metal melt
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37. II.Rapid prototyping
Rapid prototyping allows fully interconnected
porous network and highly controllable
porosity and pore size.
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38. Rapid prototyping includes:
1. Selective laser sintering (SLS)
2. 3D fiber deposition
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39. 1.Selective laser sintering
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40. 2.3D fiber deposition
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42. Porous Tantalum scaffold
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43. Defect Ta scaffold in place
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44. Push-out test
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45. 45
a Ta+BMP
b Ta
c Blank

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48. References
1. Matassi et al.Porous metal for orthopedics implants
Clinical Cases in Mineral and Bone Metabolism 2013;
10(2): 111-115
2. Nouri et al.Biomimetic Porous Titanium Scaffolds for
Orthopedic and Dental Applications.Biomemtics
learning from nature .2010 :416-450
3. Alvarez et al.Metallic scaffolds for bone regeneration.
Materials 2009, 2, 790-832
4. Glenske et al.Applications of Metals for Bone
Regeneration. Int. J. Mol. Sci. 2018:1-32
5. Ahmadi Set al. Mechanical behavior of regular open-cell
porous biomaterials made of diamond lattice unit cells.
Journal of the mechanical behavior of biomedical
materials 2014; 34:106-15.
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49. References
6. Hazlehurst Ket al.An investigation into the flexural
characteristics of functionally graded cobalt chrome femoral
stems manufactured using selective laser melting. Materials &
Design 2014; 60:177-83.
7. Wang et al.Application of combined porous tantalum
scaffolds loaded with bone morphogenetic protein 7 to repair
of osteochondral defect in rabbits.Int Orthoped.2018 :1-12
8. Cheng et al.Advances in Porous Scaffold Design for Bone and
Cartilage TissueEngineering and Regeneration.
9. Prasad et al.Metallic Biomaterials: Current Challenges and
Opportunities. Materials 2017:1-33
10. Chen et al.Biocompatible porous titanium scaffolds produced
using a novel spaceholder technique.Society for
biomaterials.2017:2796-2807
11. Wally et al.Porous Titanium for Dental Implant Applications.
Metals 2015;5:1902–1920.
12. Pacifici et al. Metals used in maxillofacial surgery. Oral
Implantol. 2016, 9,107–111.
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