Metals as biomaterials - Aalto · PDF fileMetals 1/ 55 Emilia Peltola, DSc Properties and challenges ... Can not be hardened via heat treatment and do not weld to a high standard.

Metals 1/ 55

Emilia Peltola, DSc

Properties andchallenges

Commonly used metalsStainless steel

Titanium

Cobalt alloys

Smart materialsShape memory metals

Magnetostrictive materials

Metals as biomaterials

Emilia Peltola, DSc

21.9.2015

Metals 2/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Contents

Properties and challenges

Commonly used metalsStainless steelTitaniumCobalt alloys

Smart materialsShape memory metalsMagnetostrictive materials

Metals 3/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Brainstorming I

What kind of properties do metals have?

To what kind of implants are metals best suitable for?

http://presemo.aalto.fi/biomaterials/

Metals 4/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Tensile properties of metals

Metals 5/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Applications

Biomet Zimmer

Metals 6/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Brainstorming II

I Why is biological environment particularly hostilefor metals?

I What is the consequence of the hostileenvironment?

Metals 7/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Ion concentrations in body

Metals 8/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Corrosion

This etched metallograp-hic micrograph demon-strates the pitting corro-sion of stainless steel.

Extensive corrosion onthe titanium stem of amodular hip prosthesis.

[Ratner et al., 2013]

Metals 9/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Failure of orthopaedic implants

Metals 10/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Requirements for metallic implantmaterials

I Must be corrosion resistantI Mechanical properties must be appropriate for

desired applicationI Areas subjected to cyclic loading must have good

fatigue properties

Metals 11/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Commonly used metals

Stainless steel Titanium CoCr alloys

Metals 12/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Metals 13/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Stainless steel

Stainless steels were the first metals to be used inorthopaedics in 1926.

Steel used in the hip implants until the end of 1970s

Metals 14/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Stainless steel

20Metals 14/ 55

Stainless steelStainless steel

Austenitic (FCC)Can be formed and welded with successful results.

Martensitic (FCT)Can be tempered and hardened and are thus highly useful insituations where the strength of the steel is more important than itsresistance to corrosion.

Ferritic (BCC)Can not be hardened via heat treatment and do not weld to a highstandard.

Metals 15/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Stainless steel

α ferrite; σ martensite; γ austenite

Metals 16/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Austenitic steel

Specially AISI 316L is used in implants (316 =Mo-containing ja L = low carbon)

I Ni stabilises the austenitic microstructure of steel(note: allergic reactions)

I Cr-containing steel produces a thin and relativelydurable passivating oxide layer

I Mo has a strong positive effect on pitting andcrevice corrosion resistance in chloride-containingsolutions

Metals 17/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Chromium oxide passivating film

Metals 18/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Grain boundaries

Metals 19/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Role of Mo

[Hospadaruk and Petrocelli, 1966]

Role of Mo

[Hospadaruk and Petrocelli, 1966]

20Metals 19/ 55

Stainless steelRole of Mo

Metals 20/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Steel: pros & cons

+ Good corrosion and fatigueresistance in short-termapplications

+ Low cost+ Easy to be machined- Tend to be corroded in

long-term applications- High modulus (stress

shielding effect)- Ni and Cr allergy

Typical applications: Temporary implants such asfixation screws and plates

Metals 21/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Titanium

I More flexible than SS and closer to the stiffness ofbone

I Good behaviour under fretting corrosion andfatigue although not specially good with respect towear

Metals 22/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Ti O phase diagram

What can you tell about the microstructure of titanium?

Metals 23/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Metals 24/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Ti alloying

Metals 25/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Mechanical properties

Alloy Micro-structure

E (GPa) YS (MPa) UTS(MPa)

cpTi α 105 692 785Ti-6Al-4V α/β 110 850–900 960–970AISI 316L – 205–210 170–750 465–950Co–Cr–Mo – 220–230 275–1585 600–1785Bone – 10–40 90–140

Metals 26/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Ti crystal structure

+ corrosion resistance, biocompatibility+ weldability- poor forgeability, low strength

α− β+ can be strengthened by heat treatment

+ high hardenability+ good ductility and toughness- high density- low creep strength- low tensile ductility in the aged state- low wear resistance

Metals 27/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Ti-6Al-4V

I Al is added to the alloy as α-phase stabilizer andhardener due its solid solution strengtheningeffect

I V stabilizes ductile β-phase, providing hotworkability of the alloy

Metals 28/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Titanium

I cpTi has the best corrosion durabilityI Ti6Al4V has improved strength

Ti and its alloys tolerate pit and crevice corrosion butare sensitive for fretting corrosion.

I e.g. under the heads of screwsI this is the most significant limitation for titanium as

a biomaterial

Metals 29/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Ti applications: joints

I since the 1970s

Metals 30/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Ti applications: dental

Metals 31/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Osseointegration

Metals 32/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Osseointegration

Per-Ingvar Branemark in 1952

Osseointegration

Per-Ingvar Branemark in 19522015

20Metals 32/ 55

TitaniumOsseointegration

• First Step: formation of a carbonated hydroxyapatite onsurface via ion exchange

• Second Step: collagen fibers of host bone insert intothe carbonated apatite layer

Metals 33/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Ti applications: vascular implants

I Heart valve (Starr-Edwards1961)

I Packaging of pacemakerI Artificial heartsI Stents (nitinol)

Metals 34/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Ti applications: others

Metals 35/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Ti: pros & cons

+ Light+ Greatest corrosion resistance+ Excellent biocompatibility+ Relatively low Young’s modulus- Lower shear strength- Low wear resistance- Expensive- High modulus (stress shielding effect)

Typical applications: stem of hip prostheses, dentalscrews (permanent implant)

Metals 36/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Alloys contain 19-21%chromium, 4.5-7% molybdenumand carbon (carbides: MoC, WC)

Mechanical properties aredependent on processing

Metals 37/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Cast and wrought cobalt-based alloys

Alloys E(GPa)

UTS (MPa) 0.2% σy(MPa)

F75/Cast, ann. 210 650–890 450–520F75/P/M HIP 250 1280 840F799/forged 210 1400–1590 900–1030F90/ann. 210 950–1220 450–650F90/44% cold w. 210 1900 1610F562/forged 230 1210 960–1000F562/cold w., aged 230 1800 1500F563/ann. 230 600 280F563/cold w. 230 1000–1310 830–1170F563/cold w., aged 230 1590 1310F1058 wire 230 1860–2280 1240–1450

Metals 38/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Cobalt alloying

I Cr increases corrosion resistanseI Mo is added to produce finer grains which results

in higher strength after casting or forging

Metals 39/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

CoCr: pros & cons

+ Long-term corrosion resistance+ Super fatigue and wear resistance+ Biocompatibility- Difficult to machine and thus expensive to process- High modulus (stress shielding effect)- Ni and Cr allergy

Typical applications: Permanent implants

Metals 40/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Brainstorming III

I Alloys are increasingly used versus pure metalsfor biomedical applications. What two majoradvantages do they impart?

I Bone compatibility of Ti and CoCr alloys isimproved by making porous implants. Why arethere no porous stainless steel implants?

Metals 41/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Strength of pure metals versus alloys

A pure metal

lateralforce→

Dislocation occurs especially at grain boundaries

An alloy

Packing of two different sizes of metal elementsprevents physical dislocation of the lattice structure

Metals 42/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Smart materials

I Shape Memory (Nitinol)I Magnetostriction (Terfenol-D)I Piezoelectric

Metals 43/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Shape memory metals

Metals 44/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Shape memory metals

Metals 45/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Nitinol stent

[Chen and Thouas, 2015]

Metals 46/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Magnetostriction video

Metals 47/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Metals 48/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Bone lengthening now...

Metals 49/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Bone lengthening in the future

*Synoste is a start-up from Aalto

Metals 50/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Future metallic biomaterials

Biodegradable metalsI Mg, MgAl, FeMn

Self-cleaning surfacesI Ag, ZnO, CuO, TiO2

NanoparticlesI drug delivery

Metals 51/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Muddy cards

Metals 52/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Next time: Ceramics

Properties of ceramics

I Inert ceramicsI Nearly inert, porous ceramicsI Bioactive ceramicsI Absorbable/degradable ceramics

Metals 53/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Recommended watching

Charnley’s hip replacement technique turns 50

Smart materials (3 of 5): shape shifting material, drugdelivering nano particles

Osseointegration

Metals 54/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

References

Chen, Q. and Thouas, G. A. (2015).Metallic implant biomaterials.Mater Sci Eng R, 87:1–57.

Hospadaruk, V. and Petrocelli, J. V. (1966).The pitting potential of stainless steels in chloride media.J. Electrochem. Soc., 113:878–883.

Ratner, B. D., Hoffman, A. S., Schoen, F. J., and Lemons, J. E., editors (2013).Biomaterials Science An Introduction to Materials in Medicine.Elsevier.

Metals 55/ 55

Emilia Peltola, DSc

Titanium

Cobalt alloys

Course book

I Chapter I.2.3 - Metals: Basic PrinciplesI Chapter II.4.4 - Degradative Effects of the

Biological Environment on Metals and CeramicsI Chapter II.5.6 - Orthopedic ApplicationsI Chapter II.5.7 - Dental Implantation

Metals as biomaterials - Aalto · PDF fileMetals 1/ 55 Emilia Peltola, DSc Properties and challenges ... Can not be hardened via heat treatment and do not weld to a high standard.

Documents

C The Korean Society for Biomaterials · 2013-08-04 ·...

InTech Biomaterials

Kesko CMD, EVP Lauri Peltola

BIOMATERIALS- INTRODUCTION

Orthopedic biomaterials

View Article Online Biomaterials Science€¦ · 1. + −,....

Ohjaa ja opasta -kortit Heli Peltola

Kantapään kautta (Piippo & Peltola)

Lindgren, Mari; Huttunen-Saarivirta, Elina ; Peltola ...

Biomaterials Science

BIOMATERIALS 1

BIOMATERIALS 2014 Polymeric Biomaterials, Bioengineering &.....

Energiatehokkuutta kuljetusketjuihin. Vesa Peltola

HCF 2016: Johanna Peltola-Thies

Hietanen-Peltola: Valtakunnalliset ohjeet ja toimintamallit....

Etelä- ja Keski-Pohjanmaan metsäohjelma 2016-2020 · Asko...