Symposium on Materials Challenges For Safety and Reliability 4th World Materials Research Institute Forum IMR-CAS, Shenyang Biomedical titanium alloys for improved implant reliability and compatibility Rui Yang, Yulin Hao and Shujun Li Shenyang National Laboratory for Materials Science Institute of Metal Research, Chinese Academy of Sciences 23 May 2011
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Biomedical titanium alloys for improved implant ... · Biomedical titanium alloys for improved implant reliability and compatibility Rui Yang,g, j Yulin Hao and Shujun Li Shenyang
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Symposium on Materials ChallengesFor Safety and Reliability y y
4th World Materials Research Institute ForumIMR-CAS, Shenyang
Biomedical titanium alloys for improved implant reliability and compatibility
Rui Yang, Yulin Hao and Shujun Lig, j
Shenyang National Laboratory for Materials ScienceInstitute of Metal Research, Chinese Academy of Sciences
23 May 2011
Earliest application of biomedical materials
• Artificial toe made of wood and leather found on a mummyD t d t l t 4000• Dated at least 4000 years ago
• Used by its carrier for both aesthetic and functional values
2
Current problem of orthopaedic implants Stress shielding: Reduction in bone stress in vivo following the introduction of orthopaedic implants and it causes loss of bone and loosening of the implant.
Statistical significance of correlation between severe t hi ldi d i i fl i f t
3
stress shielding and various influencing factors.
Z. Wan, L.D. Dorr, T. Woodsome, A. Ranawat and M. Song, J. Arthroplasty 1999; 14: 149
The alternative design does not work
Overhauling implant design has greater effect on stress distribution than anything possible by altering material properties but newthan anything possible by altering material properties, but new
design is not considered safe(bars show changes in absolute values of the major principal strains,
% of the intact femur, after implantation)
4R. Decking, W. Puhl, U. Simon, L.E. Claes, Clin. Biomech. 2006; 21: 495
% of the intact femur, after implantation)
mented and cementless implant
Survival of cemented and cement-less hip prostheses in Finland (1985 1999)
portunities for low-modulus implant materials
alleviate short-m/long-term designm/long term design nflict
reduce sensitivity of plant performance to
dividual factors
allow incrementalallow incremental provement to current signs
Survival of hip prostheses in Finland 1985-1999, by age of patient
anium alloys as implant materials: story and current problemsstory and current problems
ee generations of development: Problems to be solved:g pTi-6Al-4V (Aerospace alloy)Ti-6Al-7Nb (Removes poisonous elements)
(by alloy design)1. Some alloys still contain
i l t ( Al)Ti-13Nb-13Zr (To reduce modulus) poisonous elements (e.g., Al)2. Elastic modulus still too
high compared to human ar 7 alloys are approved by M for surgical implant (only 3 roved in China *):
ghard tissue
(by surface engineering)1 Bi ti it t id lTi *
Al-4V *Al-2.5V
1. Bioactivity not ideal2. Relatively poor wear
resistanceAl-7Nb*F
3. Corrosion resistance can be further improved
st recent developments: m Metal (Toyota) vs Ti2448 (IMR)m Metal (Toyota) vs. Ti2448 (IMR)
Ti2448 Gum MetalTi2448 Gum Metal
P ti Ti2448 G M t l
H. Ikehata et al. MRS Bullitin 2006; 31: 688et al., Acta Biomater. 2007; 3: 277.
ta type biomedical titanium alloys: mmary of recent developmentmmary of recent development
Ti-29Nb-13Ta-4.6Zr Ti-15Mo
Ti-13Nb-13ZrTi-35Nb-5Ta-7Zr
GUM METALTi-12Mo-6Zr-2Fe
Ti-15Mo-3Nb-0.3O
"
Ti-V Ti-Nb Ti-Mo
Ti 24Nb 4Z 8S
Fedotov, Proc. of 2nd World erence on Titanium (1973)
ficulty in reducing elastic modulus
MetalsAlloys
GraphiteCeramicsSemicond
Composites/fibers
strength and elastic ulus of metals tend to ease or decrease
Al oxide Carbon fibers only
600800
10001200
400 TungstenSi carbide
Diamond
ySemicond
Ti
ultaneously
ngth must be maximised
Platinum
Silver Gold
Tantalum
Zinc, Ti
Steel, NiMolybdenum
Si crystal
Gl d
Si nitrideAl oxide Carbon fibers only
Aramid fibers only
80100
200
400
Cu alloys
Tungsten
<100>
<111>
AFRE(|| fibers)*
CFRE(|| fibers)*
Ti: ~110GPa
rder to ensure the ue life and thus the bility of the implant
Magnesium,AluminumSilver, Gold Glass-soda
Concrete
CFRE*
GFRE*
Glass fibers only
20
406080
Tin GFRE(|| fibers)*
AFRE(|| fibers)
Bone:
hanisms such as stress-ced martensitic sformation are
8Graphite
AFRE( fibers)*
CFRE*
46
10
Polyester
PSPET
CFRE( fibers)*
GFRE( fibers)*Bone: <30GPa
sformation are ficient in this task
problem must be
1
PC Epoxy only
0 8
2
HDPEPP
PS
E GP
problem must be led from a more amental level
k modulus of Ti-TM binary alloys: Predictions
method was proposed to estimate the bulk modulus of Ti-TM nary alloys based on first principles computationnary alloys based on first principles computation
followed by Nb, Ta, was predicted to lower the bulk modulus of c Ti
oice of primary binary system: Ti-Nb
does not change the e/a ratio of Ti (same group)is high melting thus difficult to process and also too expensiveNb is a suitable primary system: intrinsic minimum of E at e/a ~4.15
4 wt.% Nb)Ti-NbTi Nb
moving the modulus peak
Both Zr and Sn reduce Ms for "wt.% of Nb, Zr, Sn reduces Ms by 7 6K 41 2K 40 9K ti l7.6K, 41.2K, 40.9K, respectivelyr + Sn suppress the r and Sn are potent strengtheners for i alloy
Alloy T, C MS, C Phase E, GPa
Ti-24Nb ~700 380~400 ++ ~90
ect of alloying on phase stability: Computation
A+first principles mputation enable sonably accurate atment of solid
tiutionsth Nb and Sn are bilizing elements h respect to the ase and can vent formation of phases neutral
ect of Sn on elastic properties of 24Nb 4Z b d ll24Nb-4Zr based alloysminimum of bulk modulus (B) and Poisson’s ratio () at 9wt % Sn was identified9wt.% Sn was identifiedr the 7.9wt.%Sn alloy, the bulk modulus (B) approximately uals the shear modulus (G)
ery short linear elastic stage; mostly non-linear elatic deformation; bsence of “double yielding”y glastic strain recovery of 3.3% occurs at 4% applied strainensile strength ~850MPaignificant elastic softening was found (decrease of incipient Young’significant elastic softening was found (decrease of incipient Young s
February 2008: Tests of biochemical compatibility authorised by the State Food and Drug Administration of China completed
June 2009: Clinical trials of bone plates and nails in human body completed
M h 2010 Cli i l t i l f i l fi ti l t dMarch 2010: Clinical trials of spinal fixation completed
nical trials: Ankle bone repair
nical trials: Shoulder bone repair
nical trials: Tibia repair
nical trials: Spinal fixation
mmary
A new titanium alloy Ti2448 for biomedical use was developed– High strength (850 MPa) /excellent fatigue properties– Lowest bulk modulus of structural metals (23.9 GPa), and incipient
Young’s modulus almost matching that of human bone (~40 GPa)– Superelastic deformation up to 3.3%– Good biocompatibility
New mechanisms of elastic deformation: lattice distortionNew mechanisms of elastic deformation: lattice distortion, reversible motion of dislocation loops nucleated homogeneously
The alloy has passed biochemical compatibility tests authorised by e a oy as passed b oc e ca co pat b ty tests aut o sed bythe State Food and Drug Administration of China, and has completed clinical trials of typical implants in hospitals
Low modulus ensures improved biomechanical compatibility and safety of implants; High recoverable strain enables high fatigue strength and thus improves life-time and reliability
knowledgements
G d t St d tGraduate StudentsDr Caiyun Zheng, Dr Yanwei Zhang, Dr Siqian Zhang, Dr Edward G. ObbardDr Edward G. Obbard
Collaboration withWego GroupProfessor Zheng Guo, The Fouth Military Medical University Professor Yue Zhu, China Medical UniversityProfessor Yue Zhu, China Medical UniversityProfessor Manling Sui, Beijing Polytechnical University