Surface Modification on Titanium alloy for Biomedical

Surface Modification on Titanium alloy for Biomedical Application A.Shah aFaculty

of Technical and Vocational, Universiti Pendidikan Sultan Idris, 35900 Tanjong Malim, Perak, Malaysia . Email: [email protected] Phone Number: 605-4505404

Siti Nurul Fasehah Ismail bFaculty

of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia. Email:[email protected]

H.Mas Ayu cFaculty

of Mechanical Engineering, Universiti Malaysia Pahang, 26300 Pekan, Pahang, Malaysia. Email: [email protected] Phone Number: 609-4246316

R.Daud cFaculty

of Mechanical Engineering, Universiti Malaysia Pahang, 26300 Pekan, Pahang, Malaysia Email: [email protected] Phone Number: +609-4246332

Abstract Surface modification techniques have been proven to enhance resistance towards corrosion, to slow the process of wearing, to reduce metal ions release, as well as the process of biomaterial osseointegration. Not only that, these techniques could extend the longevity in materials related to implant, primarily because of its response towards the host of body. Generally, these techniques can be further broken down into physical, mechanical, and chemical approaches. As such, this paper presents further information pertaining to the numerous types of methods for modifying surfaces, along with their benefits and drawbacks. Additionally, several other significant aspects are detailed as well in this paper, for example, the materials and biomaterials used for implant, as well as a number of issues concerning the usage of alloy, biomaterial and titanium. Keywords: Biomaterial, titanium alloy, surface modification, Medical Engineering, surface treatment, corrosion resistance, wear resistance, osseointegration.

1.0 Introduction The use of biomaterials has witnessed extensive applications, especially within the medical field associated in supporting internal and replacing tissues, for instance, implantation for orthopedic cases, as well as replacement of dental roots and joints. Nonetheless, the aspect of biocompatibility has been emphasized so as to ensure the longevity of these biomaterials for prolonged functional. With that, the term ‘biocompatibility’ is defined as ‘the capability of a selected material in performing a certain function with a suitable host Uwais et al. (2017). In fact, some biomaterials that have been employed in the medical field are composite, polymer, ceramic, and metals. For instance, some metals that have been extensively applied as implants to function as artificial joints in the orthopedic are Ti alloys, stainless steel (316LSS), and alloys based on Co-Cr Gibon et al. (2017). Nevertheless, some limitations of these metals are the process of wear, osseointegration, and corrosion. Hence, the technique of modifying surface serves as an approach to address several issues, aside from enhancing the operational of tribological and the biomedical material in term of its mechanical features, Shah et al. (2017). In fact, the typical approaches employed as methods for treating

surfaces in the biomedical field for implant cases are Chemical Vapor Deposition (CVD), Ricci et al. (2017), Physical Vapor Deposition (PVD) Shah et al. (2016b,Shah et al. (2016a), ion implantation Qin et al. (2017), coating with plasma spray, Sathish et al. (2011), nitriding, Cassar et al. (2010), application of sol gel, Ayu et al. (2017), as well as thermal-based oxidation, Sun et al. (2016). With that, this paper describes materials and biomaterials for implantation, several problems concerning looks into Ti alloys, biomaterials, and titanium, as well as the approach of modifying the surface of titanium alloy. 2.0 Implant biomaterials In1969, the inception of biomaterials was initiated at the Clemson University location at South Caroline. In fact, the notion ‘biomaterial’ denotes a material that is either natural or artificial used to form implant structure for replacement of certain biological frame so as to restore or to maintain its functional Geetha et al. (2009). Apart from that, biomaterial can also be referred as a material that responses towards biological frame in treating, examining or substituting organs, tissues or even functions of the body Williams (2009). As such, the biomaterials applied for implants are categorized as transient and permanent, based on reaction time towards the host. Table 1 presents some biomaterial implementation for implant purposes. Besides, the classification of biomaterials is of four types, as given in the following: i)

polymers with covalent bond (silicone, nylon, polyester, rubber, and polytetrafluoroethylene)

ii)

metals with metallic bond (Au, stainless steel, Ag, titanium and its alloys, as well as Co-Cr alloys),

iii)

ceramics with ion bond (alumina zirconia calcium phosphates that are comprised of carbon and hydroxyapatite),

iv)

composites with polymer and ceramics combined or non-artificial elements such as ivory, bone, and wood (bone cement with fiber reinforcement, and wire that is carbon-carbon, Müller et al. (2008).

Table 2 shows both benefits and drawbacks, including biomaterial usage, in implant cases. Since past these few decades, biomaterials that are based on metals have been extensively applied in implantology and orthopedic implant due to their maintain mechanical and biocompatibility in bone healing period Shadanbaz and Dias (2012). Basically metallic biomaterials widely used for implant materials are cobalt chromium (Co-Cr) alloys, stainless steel (316 L), and titanium and its alloys. However, Cobalt chromium and steel release metal ions such as Cr, Co, and Ni due to the corrosion of the implant subjected to body fluids. Besides having metal ions release, steel and Co-Cr have a higher elastic modulus than bone, which can lead to stress shielding and loosen of an implant,Nakai et al. (2011). In this case, the bone density is decreased using implant that promotes stress shielding through elimination of normal stress on bone. Figure 1 show the attributes of biomedical alloys based on elastic modulus. Besides, due to some features, such as having higher strength, lower density, hiked resistance for corrosion, being inertive towards bodily fluids, higher biocompatibility, lower modulus, and ease of being attached other tissues; the alloys of titanium have appeared to be a material with high potential for implant purposes, Fukuda et al. (2011); Suresh et al. (2012); Wei et al. (2011).

3.0 Issues pertaining to biomaterials In orthopaedic implants, the reaction of biomaterials to the environment found in the human body is an important factor used to determine if these implants will fail or succeed. This is because; biological responses are deemed to happen upon implants. Initially, the surface of implant goes through water molecules adsorption, followed by protein, and lastly, cell. Furthermore, the responses that are of biological relies on several features of the surface, for instance, energy, topography, roughness, and, chemistry, Geetha et al. (2009). Table 3 depicts the categories for biomaterials in accordance to reactions of tissues based on bioactiveness, bio inertness, and

bioadsorption. Bioactiveness rejects growth of new bone on surface due to response of ions towards tissue, thus generating a chemical osteogenesis bond Sarandha (2007). Meanwhile, bio-inertness refers to acceptance of a material upon implant because the host responses positively via enclosure of fibril layers that takes a capsule shape, thus permitting a closer apposition between surfaces and bone that could generate osteogenesis. Therefore, the features of biocompatibility, mechanical properties, osseointegration, as well as resistance towards wear and corrosion determines the failure or success of an implant, Ramsden et al. (2007). 3.1 Mechanical Properties Mechanical properties are embedded in biomaterial design prior to implementation. In the case related to orthopedic, lower elastic modulus is sought to decrease the effects of harmful stress shielding. Hence, in implementing a fastener and a stent, the resistance of fatigue and strength is essential, Kent et al. (2011). In precise, several mechanical attributes, for example, tensile strength, Young’s modulus, fatigue life and its fretting, wear, and ductility, are needed for implant cases related to substitution of tissues that are hard Niinomi (2008). In fact, a number of researchers have enhanced the biomaterial mechanical features for implant purposes. For example, Majumdar et al. (2011)

examined the impact of heat upon Ti-13Zr-13Nb mechanical attributes for

implementation involving load bearing. As a result, upon heating at 800 ºC and quenching of water, the material tested proved adequate for implant cases due to enhanced alloys of Ti-13Zr-13Nb in terms of Young’s modulus, tensile strength, and hardness. Meanwhile, Luo et al. (2011) determined the effect carburization had upon mechanical attributes in biomedical properties, in which they discovered that samples with coating displayed improved toughness for fracture, hardness, and plasticity, in comparison to samples that were not coated. On the other hand, Jouanny et al. (2010) produced a film made of titanium oxide via reactive sputtering generated by frequency of radio on plates of titanium alloy. As a result, it was revealed that a tougher rutile structural and a decreased coefficient friction had been exerted by titanium oxide that had anatase. The following section elaborates several modifying surface approaches.

3.2 Biocompatibility The notion ‘biocompatibility’ extensively reflects the demands in terms of biological for successful biomaterial application in the medical arena, which also signifies the drawback of excessive responses from tissues, Guelcher and Hollinger (2006). In fact, the capability of a material in generating successive responses from the tissues after implant process Ratner et al. (2004) relies upon the material itself, as well as the material degradation that occurs in the body of host. Response from host reflects the responses exerted by a system due to the existence of additional material. Table 3 tabulates the human body responses in adherence to several types of biomaterials. On the other hand, materials that are biodegradable can decompose easily in the host body, which is an aspect sought in biomaterials, aside from being biocompatible Izman et al. (2012a).

3.3 Wear Resistance Wear rate is one of the tribological behaviours required, especially in load bearing applications. Strength, hardness, and toughness are important properties that influence wear resistance. A decreased resistance for the aspect of wears leads to loose biomaterial implant that generates debris which affect surrounding tissues. Meanwhile, as for alloys made of titanium, the effect of wear is on the materials’ resistance towards corrosion. Due to friction caused by constant rubbing, the oxide surface layer of the biomaterial wears off, thus exposing to risks, Diomidis et al. (2011) of bodily fluids that promotes corrosion. As such, studies pertaining to surface layer have always looked into enhancing wear resistance in biomaterials. Thus, the impact of TiN coat via plasma spray and PVD methods upon dry wear had been examined, which resulted that samples with TiN coat via plasma spray method displayed better performance for resistance of wear when compared to the other method, Nolan et al. (2006). In fact, Gispert et al. (2007) compared the performances displayed by thin coats of TiCN, TiNbN, and TiN upon stainless steel with lubrication for wear, which exhibited exceptional results when TiN

was combined with TiCN for decreased rate of wear for metal implant purposes. Meanwhile, the comparison of wear rates between Diamond-like Carbon, micronite in Bovine calf serum, and TiN, Hoseini et al. (2008) indicated positive results with TiN and micronite coatings being exceptional. On top of that, Subramanian et al. (2011) examined the resistance of dry wear against Ti/TiN and TiN coating upon samples made of stainless steel, where the coating of Ti/TiN exhibited better results primarily because of its decreased friction coefficient. Besides, a substantial number of studies have looked into TiN coats closely linked to wear of dry sliding, but only a handful have associated Tin coating with fluids of the body in simulation.

3.4 Osseointegration Osseointegration can be defined as the formation of bone tissue around an implant without the growth of fibrous tissue at the bone implant interface Rautray et al. (2011). In precise, it is the capability for the growth of natural tissue upon a fixed implant in the host. Nonetheless, when the material surface fails to amalgamate with the bone, mainly because of micro motion, fibril tissues are generated that loosens the implant. In fact, some identified reasons for the occurrence of osseointegration are surface roughness, chemistry, and topography. Besides, materials that are bioactive and bioinert in nature are demanded for enhancement of implant osseointegration. Apart from that, the methods of modifying surface, for instance thermal spraying, blasting, and chemical etching, have been extensively employed to enhance dental implant osseointegration, Liu et al. (2004).

4.0 Titanium and its alloy Although William Gregor from Cornwall, United Kingdom first discovered titanium in 1791, its application was only extensively used at post Second World War Lütjering and Williams (2007). The categories of titanium are alpha alloy, alpha-beta alloy, and

unalloyed. In precise, alpha alloy has alpha phase and it is comprised of alpha stabilizers, whereas alloys are made of 5% to 10% of beta phase or near alpha alloy and 2% of beta 2%.stabilizers. Meanwhile, α + β alloys consists of more beta stabilizers, by at least 10% to 30%, in the microstructure. On the other hand, beta alloys possess substantial amount of beta stabilizer, which could be retained via fast cooling. On top of that, N, O, and Al are alloy elements that stabilize the alpha phase, hence known as alpha stabilizers. Increment in alpha elements leads to increment in temperature of beta transus, while extra elements (Cr, Fe, Mo, V, and Nb are beta stabilizers) decreases the temperature Geetha et al. (2009). 4.1 Unalloyed titanium Unalloyed or Commercial Pure Titanium (CP-Ti) has been widely employed due to its exceptional resistance against corrosion and response towards tissue, although poor in strength and weak in wear resistance Davis (2006), thus inadequate for heart-related implants, Zhao et al. (2011). Nonetheless, unalloyed titanium can be applied for piping, heat exchangers, as well as valves and pumps within the petrochemical and chemical fields, Askeland and Phule (2009).

4.2 Alpha and near alpha alloy The use of alpha alloys has been proven to enhance CP-Ti for they are comprised of Ti, Al, and Zr, which could be employed at increased temperatures and cryogenic implementations. In fact, near alpha or alpha alloys contain the following: Ti-0.3Mo0.8Ni,

Ti-5Al-2.5Sn,

Ti-8Al-1Mo-1V,

and

Ti-6Al-2Nb-1Ta-0.8Mo.

However,

enhancement in terms of Young’s modulus, strength, and resistance towards corrosion is sought Geetha et al. (2009) for usage in casings of gas turbine engines, structural elements, skins for airframe, and compressor blades for jet engine, Askeland and Phule (2009).

4.3 Alpha-beta alloy The production of alpha-beta alloys enhances and substitutes alpha alloys. In fact, Ti6Al-4V appears to be the most extensively employed alpha-beta alloy in both aerospace and biomedicine arenas Atapour et al. (2011). Its structure is stronger than CP-Ti, while its Young’s modulus is lower than both stainless steel and Co-Cr-Mo. One drawback of the Ti-6Al-4V alloy is its higher Young’s modulus, in comparison to bone, which could lead pain in thighs and stress shielding in femur. In addition, aluminium and vanadium are toxic materials to the human body Miura et al. (2011). Hence, beta titanium alloys are produced with improved stress shielding, as well as better wear and corrosion resistance, aside from the main reason; safe for humans Geetha et al. (2009). 4.4 Beta alloy The beta alloys contain small quantity of alpha stabilizers so as to improve strength, corrosion resistance, and high creep resistance against intermediate temperatures. Besides, its iron, vanadium, and chromium stabilizers enable high temperature endurance. In fact, some instance of such alloys are Ti-10V-2Fe-3Al, Ti-15V-3Cr-3Al3Sn, Ti-15Mo-2.7Nb-3Al-0.2Si, Ti-3Al-8V-6Cr-4Mo-4Zr, and Ti-13Zr-13Nb for usage in springs, airframe elements, pipes, fasteners, as well as commercial products. Besides, its low value for Young’s modulus, which is near similar to that of bone, is a plus point. Moreover, alloys of Ti-13Zr-13Nb are preferred due to enhanced wear resistance and corrosion for implants in biomedical arena, Geetha et al. (2004); Majumdar et al. (2010); Munuera et al. (2007).

5.0 Surface modification method on titanium alloy The prior section depicts several biomaterial demands. Besides, the methods of modifying surface could be applied to improve wear and corrosion resistance, biocompatibility, osseointegration, and mechanical features. Several functions of the surface modification methods are listed in the following: i.

Improves antibacterial effect

ii.

Improves bioactivity that promotes cell growth upon implantation

iii.

Enhances implant hardness to improve wear resistance, especially at rubbing joint applications.

iv.

Enhances implant fatigue strength

v.

Generates a passive layer to enhance extra ion release upon reacting with host body

vi.

Removes dust and other contaminants from an implant for biomedical applications.

Many methods of surface modification are available to enhance implant surface, which are: i) ii) iii)

Mechanical approaches: machining, grinding, polishing, and blasting Chemical approaches: sol gel, anodic oxidation, and chemical vapor deposition Physical approaches: thermal spray, physical vapor deposition, and ion implantation.

A list of surface modification methods, along with their objectives, is given in Table 4.

5.1 Mechanical Treatment Treatments of mechanical surface include shaping, physical treatment, and surface material removal. In fact, treatment upon surface is carried out so as to remove contamination on surface, to obtain a certain topography or roughness, and to enhance bonding Liu et al. (2004). As for the biomedicine field, biomaterial surface topography enhances response at the cellular level. Hence, varied treatments performed at the surface shift the chemical composition and the topography of implant material, thus promoting osseointegration Al-Radha et al. (2012). Blasting is a well-known mechanical treatment for surface, where high pressure is generated by employing air that is compressed to shoot particles of dry sand via nozzle so as to eliminate dirt or burr found on the item surface, Robber H. Todd (2004).

Meanwhile, sand blasting using abrasive elements, such as silicon carbide (SiC), alumina (Al2O3), biphasic calcium phosphates (BCP), hydroxyapatite, and ß-Tricalcium phosphate, Citeau et al. (2005), creates rough surface for biomaterial application. For example, Jiang et al. (2006) discovered improvement in the aspects of fatigue and corrosion in CP-Ti via SiO2 particles blast. Meanwhile, the impact of sandblasting upon alumina and ZrO2, titanium oxide plasma, and machining upon Ti dental implants osseointegration had been investigated. As a result, ZrO2 sandblasting exhibited the highest failure for bone growth, when compared to the rest, Bacchelli et al. (2009). In short, mechanical treatment appears to be an alternative to enhance Ti alloys due to shift in its surface structure.

5.2 Sol Gel Additionally, the method of sol gel enhances surface implants. The sol in gel sol refers to a suspension that is colloidal with tiny particles in continual liquid, while gel generates a solid and continual skeleton that promotes a phase of continuous liquid Brinker and Scherer (1990). In fact, sol gel is a non-intricate and non-expensive material used as coating for asymmetrical shapes, which is close to coatings of biomimetic Shadanbaz and Dias (2012). Polycondensation, gelation, hydrolysis, drying, aging, crystallization, and densification are some of the processes of sol gel Piveteau et al. (2001). Meanwhile, coating via sol gel is preferred for Ti alloys, primarily because of low temperature for processing that hinders transition between alpha and beta phases Metikos-Hukovic et al. (2003). The benefits of sol gel coating are: i.

Generation of gel that promotes excellent matrix to entrap varied organic and inorganic compounds, as well as biologically-significant molecules Shadanbaz and Dias (2012).

ii.

Generation of pure products that serves as organo-metallic precursor of desired ceramic oxides, which can be mixed, dissolved in certain solvent, and hydrolyzed into a sol.

iii.

Generation of a thin bond coating that adheres to metallic substrate and top coat.

Basically, five parameters are embedded upon producing sol gels with high quality, which are: i) precursors, ii) control of hydrolysis reaction, iii) water/alkoxide mol ratio, iv) precursor concentration (organics and water inclusion), and iv) catalyst amount and type.

5.3 Thermal oxidation The process of anodizing or oxidation of anodes applies electrode responses for diffusion of oxygen ions in metal to form films of oxide upon surface of anode. Besides, oxidation of anode could generate varied types of oxide layers for a variety of materials, for instance, H2SO4, H3PO4, or acetic acid, which can serve as electrolytes in oxidation of anode. Some aspects that may affect both chemical and structure properties include temperature, current, anode potential, and composition of electrolyte. Moreover, this process is apt for application in biomedical arena due to its generation of structures that are porous, enhanced fretting corrosion, as well as rates of wear Kumar et al. (2010). For example, Ou et al. (2011) investigated the impact of oxidation of anode upon Ti30Nb-1Fe-1Hf and CP-Ti. As a result, the oxide films were indeed porous with three layers. Meanwhile, another study proved that oxidation of anode enhanced CP-TI wear rates and fretting corrosion Kumar et al. (2010). Nonetheless, the surface has to be prepared prior to anode oxidation, in which surface that is clean is produced via chemical pickling and degreasing. As for the impact of pre-treatment before anode oxidation, pickling enhanced the oxide layer’s fatigue life upon an Al alloy, Shahzad et al. (2011). In short, anodizing is adequate for implementation the demands resistance against corrosion and wear. On top of that, its production of porous structure could enhance osseointegration. On the other hand, oxidation based on thermal appears effective to generate crystalline oxide film, along with oxygen dissolution below film. The process of oxidation is a chemical response between oxygen and metal. Via excitation of atoms through

provision of energy that are of external. The surface absorbs oxygen molecules, which are then dissolved. This forms and promotes the growth of oxide layer until no further response Khanna (2004). Besides, the process of oxidation relies on some aspects, as given below: i.

Temperature

ii.

Metal pre-treatment and preparation of surface

iii.

Pressure

iv.

Composition of gas

v.

Reaction time Kofstad (1988)

Izman et al. (2012b) discovered the formation of rutile structure upon samples oxidized with big-sized and nodular-shaped particles at 850 ⁰C when examining the influence of oxidizing temperature upon morphology and structure of oxidation based on thermal for alloy of Ti-13Zr-13Nb. Meanwhile, López et al. (2010) compared the effect of biological upon oxidation based on thermal for Ti-7Nb-6Al, Ti-13Nb-13Zr, and Ti-15Zr-4Nb. As a result, Ti–7Nb–6Al alloys appeared to offer the most effective biological reaction upon complete oxidation. Meanwhile, Ti-13Zr-13Nb was found to give better response as a received specimen. The study concluded that thermal oxidation for Ti alloy serves to address issue related to wear and corrosion, mainly because of the rutile structure generated upon the substrate.

5.4 Chemical Vapor Deposition The common versatile Chemical Vapor Deposition (CVD) procedure is suitable for producing powders, coatings, fibers, and monolithic elements. In this synthesis process, the chemical sample reacts with vapor phase upon a substrate that is heated for formation of a deposit that is solid. Moreover, coatings of CVD incorporate multiple engineering and scientific fields, such as plasma physics, thermodynamics, chemistry,

kinetics, and fluid dynamics. Besides, the CVD could generate both metal and nonmetal coatings, apart from several compounds, for instance, nitrides, oxides, carbides, and intermetallic, Pierson (1999). Nevertheless, diamond emerges as the most wellknown element for coating via CVD as it is employed for cutting tools, acoustical coating, wear areas, photonic and semiconductor devices, optical equipment, and implants for the biomedical field, Liu and Dandy (1995). As for implants in the biomedical sector, many investigations have looked into the coating behavior in bodily fluids. For instance, Amaral et al. (2009)

examined the

aspects of cell viability and adhesion, proliferation, as well as cell growth pattern of Nanocrystalline Diamond (NCD) upon Si3Ni4. The findings indicated that coating of NCD exhibited an adequate surface meant for attachment of cell, proliferation, and spreading. On the other hand, Swain and Pattanayak (2008)) examined the impact of a film made of hydrogen amorphous silicon carbon (a-SiC:H) deposited by Hot Wire Chemical Vapor Deposition (HWCVD) upon silicon so as to ensure the aspect of wettability. As a result, the a-SiC: H-coated silicon sample exerted enhanced performance for both wettability and biocompatibility aspects. Thence, the process of CVD could generate coatings of diamond to enhance the aspects of biocompatibility in materials for implant due to the production of nanostructure elements.

6.0 Conclusions Biomaterials that are metal-based have been extensively employed for implant purposes due to their exceptional biocompatibility and mechanical attributes within the period of healing bone. Nevertheless, metals have shortcomings, for example, low resistance against wear and corrosion, release of metal ion, as well as fibril tissues. Therefore the method of surface modification addressed these issues. Besides, with advancement of technology and material types, the methods of surface modification have to undergo progress. In fact, the option for the most viable method for surface modification is essential to generate an implant material with high quality. Apart from surface modification, the material type employed to produce implant surgery is also a significant aspect to weigh in.

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Figure and Table caption Table 1 Surgical use of biomaterial Park and Lakes (2010)

Table 2 Class of Materials Used in the Body Park and Lakes (2010)

Table 3 Classification of biomaterials based on its interaction with its surrounding tissue Geetha et al. (2009).

Table 4 Surface modification methods used for titanium and its alloys implants Liu et al. (2004) Figure 1: Elastic modulus of metallic biomaterials Geetha et al. (2009)

Table 1 Surgical use of biomaterial (Park and Lakes, 2010) Permanent implants System

Application

Muscular skeletal system

Joints in upper (shoulder, elbow, wrist, finger) and lower (hip, knee, ankle, toe) extremities, permanently attached artificial limb

Cardiovascular system

Heart (valve, wall, pacemaker, entire heart), arteries, veins

Respiratory system

Larynx, trachea, and bronchus, chest wall, diaphragm, lungs, thoracic plombage

Digestive system

Tooth fillings, esophagus, bile ducts, liver

Genitourinary system

Kidney, ureter, urethra, bladder

Nervous system

Dura, hydrocephalus shunt

Special senses

Corneal and lens prosthesis, ear cochlear implant, carotid pacemaker

Other soft tissues

Hernia repair sutures and mesh, tendons, visceral adhesion

Cosmetic implants

Maxillofacial (nose, ear, maxilla, mandible, teeth), breast, eye, testes, penis, etc.

Transient implants

Extracorporeal assumption of organ function

heart, lung, kidney, liver, decompressive-drainage of hollow visceraspaces, gastrointestinal (biliary),genitourinary, thoracic, peritoneal lavage, cardiac catheterization

External dressings and partial implants

temporary artificial skin, immersion fluids

Aids to diagnosis

catheters, probes

Orthopaedic fixation devices

general (screws, hip pins, traction), bone plates (long bone, spinal, osteotomy), intertrochanteric (hip nail, nail-plate combination, threaded or unthreaded wires and pins), intramedullary (rods and pins), staples, sutures and surgical adhesives

Table 2 Class of Materials Used in the Body (Park and Lakes, 2010) Materials

Advantages

Polymers (nylon, silicone rubber, Resilient, Easy polyester to fabricate polytetrafuoroethylene, etc),

Metals (Ti and its alloys, Co–Cr alloys, Au, Ag stainless steels, etc.)

Strong, tough ductile

Disadvantages

Examples

Not strong Sutures Deforms with time, May degrade

sutures, blood vessels, other soft tissues,hip socket, ear, nose

May corrode Dense Difficult to make

Joint replacements, dental, root implants, pacer and suture wires, bone plates and screws

Ceramics (alumina zirconia, calcium phosphates including

Very biocompatible

hydroxyapatite, carbon) Composites (carbon– carbon, wire- or fiberreinforced bone cement)

Brittle, Not resilient, Weak in tension

Dental and orthopaedic implants

Difficult to make

Bone cement, Dental resin

Strong, tailorMade

Table 3 Classification of biomaterials based on its interaction with its surrounding tissue (Geetha et al., 2009). Classification

Response Formation of thin connective tissue

Biotinert materials

capsules (0.1–10 lm) and the capsule does not adhere to the

Examples

Effect

Polymer-poly tetra fluorethylene (PTFE),

Rejection of the

polymethyl metha acralyte (PMMA), Ti, Co–Cr, etc.

failure of the implant

implant leading to

implant surface Formation of bony tissue around the Bioactive materials

implant material and strongly integrates with the implant surface

Bioreabsorbable materials

Replaced by the autologous tissue

Bioglass, synthetic calcium phosphate including hydroxyl apatite (HAP)

Polylactic acid and polyglycolic polymers and processed bone grafts, composites of all tissue extracts or proteins and structural support system

Acceptance of the implant leading to success of implantation

Acceptance of the implant leading to success of implantation

Table 4 Surface modification methods used for titanium and its alloys implants (Liu et al., 2004) Surface modification methods

Modified layer

Objectives

Rough or smooth surface formed by subtraction process

Produce specific surface topographies; clean and roughen surface; improve

Mechanical methods a. Machining b. Grinding c. Polishing

adhesion in bonding

d. Blasting Chemical methods a. Chemical treatment i.

Acidic treatment

ii.

Alkaline treatment

iii.

Hydrogen peroxide treatment