The paper presents a bibliographic study about the metallic biomaterials, synthesizing the aspects related to properties, applicability, obtaining methods. Biomaterials can be used as medical devices, implants and prostheses. The metallic biomaterials are classified, by chemical composition and structure, in: pure technical metals, metallic alloys and composites with metallic matrix. The material quality of an implant must respect the following criteria: biochemical criteria and biomechanical ones. According to the biochemical criterion, the applicability of a material is determined by its biocompatibility, and from the biochemical criteria, it is determined by the fatigue resistance, the most important parameter, but not the only one

Al Bakri Abdullah MOHD MUSTAFA

Andrei-Victor SANDU

Dragoș-Cristian ACHIȚEI

Mirabela-Georgiana MINCIUNĂ

Petrică VIZUREANU

The Annals of “Dunarea de Jos” University of Galati Fascicle IX Metallurgy and Materials Science

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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
No. 3 - 2017, ISSN 1453-083X 
 
 
 
 
 
INTRODUCTION TO METALLIC BIOMATERIALS 
 
Dragoș-Cristian ACHIȚEI1, Petrică VIZUREANU1, 
Mirabela-Georgiana MINCIUNĂ1, Andrei-Victor SANDU1, 
Al Bakri Abdullah MOHD MUSTAFA2 
“Gheorghe Asachi” Technical University of Iași, Romania 
e-mail: dragos_adc@yahoo.com 
 
ABSTRACT 
 
The paper presents a bibliographic study about the metallic biomaterials, 
synthesizing the aspects related to properties, applicability, obtaining methods. 
Biomaterials can be used as medical devices, implants and prostheses. The metallic 
biomaterials are classified, by chemical composition and structure, in: pure 
technical metals, metallic alloys and composites with metallic matrix. The material 
quality of an implant must respect the following criteria: biochemical criteria and 
biomechanical ones. According to the biochemical criterion, the applicability of a 
material is determined by its biocompatibility, and from the biochemical criteria, it 
is determined by the fatigue resistance, the most important parameter, but not the 
only one. 
 
KEYWORDS: biomaterial, alloys, nickel, chrome, steel, biocompatibility 
 
1. Introduction 
 
A biomaterial can be defined in two ways: a 
synthetic material used to replace a part of the human 
body or to function straight with a living tissue or an 
inert biological substance destined for implantation in 
the living systems [1]. 
The successful usage of a biomaterial depends 
on 3 main factors as: 
• properties and biocompatibility; 
• health state of the patient; 
• the efficiency of the surgeon who uses the 
implant. 
According to the chemical composition and 
physical structure, the metallic biomaterials are 
classified in: 
• pure technical metals; 
• metallic alloys; 
• composites with metallic matrix. 
 
Table 1. Biomaterials classification 
 
Medical device Implant Prosthesis Surgical alloy Artificial organ Biocomposite 
 
A. Metals are used in medical field, currently, as 
surgical implants, as dental materials and in the 
making of different devices. 
There are over 30 metallic elements used in 
medicine in the shape of: 
• implants and orthopedics and dentistry 
prosthesis: Al, Co, Cr, Fe, Mn, Mo, Nb, Ni, Sn, Ta, 
etc.; 
• precious and semiprecious dental alloys 
with: Ag, Au, Cu, Ga, In, Ir, Pd, Pt, Rh, Ru, Sn, Ti, 
Zn, etc.; 
• non-precious dental alloys: Al, B, Be, Cd, 
Co, Cr, Fe, Mn, Mo, Ni, Si, Ti, V, W. 
B. Alloys used like surgical implants in 
orthopedic and dentistry, are divided in: 
• austenitic stainless steels; 
• cobalt base alloys; 
• titanium base alloys. 
The most used alloys are the ones based on 
cobalt – chrome (cca. 70%), followed by titanium 
alloy; the last one has excellent biocompatibility 
properties [2, 3]. The dental alloys used for dental 
rehabilitation: 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
No. 3 - 2017, ISSN 1453-083X 
 
 
 
• crowns and connecting decks; 
• glued porcelain on metallic alloys; 
• wires for correcting teeth; 
• metallic teeth from dental alloys; 
• alloys for brazing dental works. 
There are over 1000 dental alloys, which are 
classified in 4 subgroups: 
• precious alloys with Au, Pt, Ag content; 
• semi-precious alloys with low Au content, 
but based on Pd; 
• non-precious alloys from stainless steel, Co-
Cr and Ni-Cr group; 
• titanium base alloys. 
C. Composite materials with metallic matrix – to 
which belong: 
• dental amalgam with Hg and Ga matrix; 
• cermets materials; 
• prosthetic components covered with 
different ceramic layers. 
The superficial layers deposited on implants 
gives them special properties like: corrosion 
resistance, esthetic aspect, hardness and facilitates the 
development of the living tissue in the area [4]. 
2. Aspects regarding metallic biomaterials 
 
2.1. Titanium and its alloys 
 
Titanium is an active element chemically wise 
and should corrode strongly in ambient conditions. 
In reality this phenomenon does not manifest 
due to TiO2 protector layer on its surface. 
At air heat, titanium and its alloys strongly 
interact with the gases from the atmosphere, resulting 
chemical combinations, which forms the protector 
layer.  When the temperature rises, the oxidation 
speed intensifies and the possibilities of an explosion 
happen. Also, the titanium mixes with the nitrogen 
and hydrogen, forming nitrides and hydrides [5]. 
Due to small density, associated with good 
mechanical properties, micro-alloyed titanium and its 
alloys are superior to the other metallic materials, 
having a higher resistance (30-40 daN/mm2) reported 
at density, which is superior to higher alloyed steels 
(15-35 daN/mm2). 
 
Table 2. Classification criteria of titanium 
 
After processing 
Plastic deformable alloys  
Cast alloys  
After properties 
High plasticity and medium resistance alloys 
Enough plastic and high resistance alloys 
High corrosion resistance alloys 
Super plastic alloys 
Amorphous alloys 
Shape memory alloys 
After the usage field 
For welding constructions 
For aviation and space technique 
For chemical industry 
For prosthetic devices 
After structure 
Alloy with Ti structure 
Alloys with + structure (biphasic) 
Alloys with Ti structure 
 
Titanium alloys which are used in surgical 
implants manufacture are Ti6Al4V. In specialty 
references there also appears titanium alloys: 
TiSnMoAl and Ti13V11Cr3Al. 
The TiSnMoAl alloy are known under HILITE 
50 commercial name and contain 4 %Al, 2 %Sn and 4 
%Mo, difference Ti and are characterized by a high 
usage resistance. 
 
Table 3. Chemical composition of Ti6Al4V alloy 
 
Al V Fe Other elements C Ti 
5.5-6.5 3.5-4.5 max 0.25 0.1 each 0.4 total max 0.08 Difference 
 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
No. 3 - 2017, ISSN 1453-083X 
 
 
 
Because of the high melting temperature, and 
also the sudden increase of chemical activity with the 
temperature, titanium alloys are elaborated in 
electrical arc furnace and through induction, only in 
protective atmosphere with vacuum or inert gases [6]. 
 
2.2. Cobalt – chrome cast alloys 
 
These alloys are open to oxidation during 
melting, and cast alloy is fragile and hard. The alloy 
has a high melting temperature. 
The cooling contraction is 1.9% and makes it 
difficult to achieve the dimensional accuracy asked 
by the pattern [7]. 
Because of that, these alloys are not 
recommended for precise castings, like teeth crowns 
or connecting decks, meanwhile their use as a support 
for melted porcelain is not recommended due to the 
oxidation suffered by the alloys at work temperature.  
Nevertheless, the materials have a good 
corrosion resistance and are highly tolerated in the 
mouth cavity. 
 
Table 4. General composition of a Co-Cr 
biomaterial 
 
Co Cr Mo C Ni 
65% 25% 5% 0.2-0.35 difference 
 
The chrome percentage improves the oxidation 
resistance of the alloys; if the value is over 30%, it 
will lead to difficulties at casting. 
The cobalt increases the elasticity modulus, 
resistance and hardness higher than nickel. 
The safest way to increase the Co-Cr alloys 
properties is to increase the carbon content. A change 
of only 0.02 %C modifies the properties in such a 
way that the alloy cannot be used in stomatology. 
In medicine the Co-Cr alloys are used as 
implantable devices. The Co-Cr alloys are metastable 
and crystalize in CFC system, and the carbides are 
present at grains boundary. 
The melting temperature is situated between 
1250-1450 oC and is over the melting capacity 
realized by a natural gas flame; their melting in 
electromagnetic induction furnace is recommended. 
 
2.3. Nickel – chrome cast alloys 
 
Ni-Cr alloys gained the attention of researchers 
with the limitations discovered at Co-Cr alloys: low 
ductility, high contraction at solidification and a rise 
tendency to oxidation. 
In the industry, these alloys are known as 
NIMONIC and have applications in reaction engine 
technology. 
 
Table 5. General composition of a Ni-Cr biomaterial 
 
Ni Cr Mo W Mn Be C 
68-80% 10-25% 0-13% 0-7% 0-6% 0-2% 0.1-0.2% 
 
With these elements we can find small amounts 
of Al, Ti, Co, B, Si. These alloys are excellent as a 
support for melted porcelain. 
The alloys crystalize in CFC system, and the 
cast material has a structure with big grains which 
indicate a dendritic structure. 
The solidification contraction is 1.5%, and the 
alloys melt naturally in induction furnaces and are 
casting in phosphatic forms. 
Because of the low temperature field, the Ni-Cr 
alloys provide a more precise casting which make the 
connecting decks and dental crown to have minimal 
flaws. 
 
2.4. Silver-palladium cast alloys 
 
Silver and palladium present total solubilization.  
While Pd has a high affinity for H2 and a high 
melting temperature (Ttop = 1552 °C), Ag has a 
lower temperature and is appropriate for base alloys 
casting.  
The cast Ag-Pd alloys are Ag-Pd-Cu ternary 
system, which can be multi-phasic or mono-phasic.  
To theses alloys, we can apply hardened heat 
treatments through precipitation. 
 
Table 6. General composition of a Ag-Pd 
biomaterial 
 
Ag Pd Cu Au Zn 
45% 25% 15% 14% 1% 
 
These values can vary according the required 
precision of final element. 
The cast precision takes in consideration the 
attention with which the melting is made, and also its 
realization in controlled atmosphere. 
Materials can be used as a support for melted 
porcelain, but we have to keep in consideration the 
porcelain affinity for silver, which leads to obtain a 
greenish color of them. 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
No. 3 - 2017, ISSN 1453-083X 
 
 
 
The alloys can be hardened through 
precipitation when the melted porcelain is deposit on 
them. 
 
2.5. Stainless steels 
 
The first stainless steel used in metallic implants 
was AISI 302 steel, which is harder than vanadium 
steel and has good corrosion resistance properties. 
The vanadium-alloyed steel cannot be used, 
because it has an inadequate corrosion resistance. 
After, it was introduced AISI 302 steel alloyed 
with molybdenum to improve the corrosion resistance 
in salt water. This alloy is AISI 316 steel. 
The carbon content was reduced from 0.08% to 
0.03%, to obtain a good corrosion resistance in 
chlorine solution. 
The steel becomes AISI 316L steel. 
Chrome is a major element in corrosion resistant 
stainless steels. The minimal concentration is 11%. 
Chrome is a reactive element, but its alloys can 
passivate, having an excellent corrosion resistance 
 
Table 7. Chemical composition of AISI 316 and AISI 316L stainless steels 
 
% C Cr Ni Mo Mn Si P S Fe 
AISI 316 0.006 17-20 12-14 2-4 2 0.75 0.03 0.03 Rest 
AISI 316 L 0.002 17-20 12-14 2-4 2 0.75 0.03 0.03 rest 
 
These stainless steels can be used for metallic 
implants. 
They cannot be hardened through heat 
treatments but can be hardened through cold 
processing. 
The AISI 316 steel is nonmagnetic and presents 
a higher corrosion resistance than another stainless 
steel, also molybdenum alloying increases pitting 
corrosion resistance in salt water. 
Although it is known like a toxic element, nickel 
is found in chemical composition like alloying 
element which stabilizes the austenite at ambiance 
temperature and more, increases the corrosion 
resistance [8, 9]. 
The austenite stability at low temperature is also 
influenced by the chrome content. 
The austenitic stainless steels suffer a gardening 
process in exploitation, that being the reason why it 
cannot be cold processed without intermediary heat 
treatments. 
The heat treatment cannot determine the 
appearance of chrome carbides at grains boundary, 
carbides which can cause the corrosion phenomena 
formation. 
ASM International recommend the AISI 316L 
steel usage to implants manufacture. 
In stomatology, the stainless steels are used to 
fabricate wires and crowns for partial teeth. 
 
3. Conclusions 
 
Biomaterials release ions and metallic particles 
in the human body, which will concentrate in urine, 
blood, nails, hair and tissue around implants. 
There is danger for allergic reactions or 
immunological and inflammatory reactions. 
The dental alloys based on precious or semi-
precious metals are inert and perfectly biocompatible. 
Out of biomaterials, titanium and its alloys are 
the materials which correspond to mechanical, 
chemical and biological requirements. 
Some metals like beryllium, nickel and mercury 
are already considered prohibited in the human body. 
Nickel is considered one of the most dangerous 
metals used like biomaterial. 
The metal effects like chemical element are 
different from its compounds, oxides and organic 
compounds; these increase the risk of pathological 
reaction production in human body. 
It is recommended the usage of implants or 
prosthesis superficial covered with various protective 
films, which are inert to the human body and 
sometimes can facilitate the development of bone 
cells. 
 
References 
 
[1]. Jiang X. J., Yu G., Feng Z. H., et al., Abnormal beta-phase 
stability in TiZrAl alloys, Journal of Alloys and Compounds, vol. 
699, p. 256-261, 2017. 
[2]. Hu Shunbo, Jia Fanhao, Marinescu Cornelia, et al., 
Ferroelectric polarization of hydroxyapatite from density 
functional theory, RSC Advances, vol. 7, issue 35, p. 21375-21379, 
2017. 
[3]. Mareci D., Cimpoesu N., Popa M. I., Electrochemical and 
SEM characterization of NiTi alloy coated with chitosan by PLD 
technique, Materials and Corrosion-Werkstoffe und Korrosion, vol. 
63, issue 11, p. 985-991, 2012. 
[4]. Elshalakany Abou Bakr, Ali Shady, Amigo Mata A., et al., 
Microstructure and Mechanical Properties of Ti-Mo-Zr-Cr 
Biomedical Alloys by Powder Metallurgy, Journal of Materials 
Engineering and Performance, vol. 26, issue 3, p. 1262-1271, 2017. 
[5]. Li Yong-Hua, Chen Nan, Cui Hai-Tao, et al., Fabrication 
and characterization of porous Ti-10Cu alloy for biomedical 
application, Journal of Alloys and Compounds, vol. 723, p. 967-
973, 2017. 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
No. 3 - 2017, ISSN 1453-083X 
 
 
 
[6]. Franco Arias L. M., Kleiman A., Vega D., et al., 
Enhancement of rutile phase formation in TiO2 films deposited on 
stainless steel substrates with a vacuum arc, Thin Solid Films, vol. 
638, p. 269-276, 2017. 
[7]. Hu Shunbo, Jia Fanhao, Marinescu Cornelia, et al., 
Ferroelectric polarization of hydroxyapatite from density 
functional theory, RSC Advances, vol. 7, issue 35, p. 21375-21379, 
2017. 
[8]. Izquierdo Javier, Bolat Georgiana, Cimpoesu Nicanor, et 
al., Electrochemical characterization of pulsed layer deposited 
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[9]. Mareci D., Cimpoesu N., Popa M. I., Electrochemical and 
SEM characterization of NiTi alloy coated with chitosan by PLD 
technique, Materials and Corrosion-Werkstoffe und Korrosion, vol. 
63, issue 11, p. 985-991, 2012. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Introduction to Metallic Biomaterials

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Introduction to Metallic Biomaterials

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