Biomaterial Application On Fiber Reinforced Polymer: A review

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Biomaterial Application On Fiber Reinforced Polymer: A review
Abstract
This paper glances through the application of Fibre Reinforced Polymer (FRP) in the biomedical
industry. It covers development, application and future prospect of FRP in medical world in a
very simple yet informative way. The study touches on various aspect of FRP such as its
biocompatibility, advantages and as well critical analysis. The study also describes various latest
technologies available in the market to test property of FRP and its suitability as a bio medical
material in a very lay man term. It also scrutinizes the challenges and critical issues of its
application in various purposes.
Keywords: Biomaterial, Fibre Reinforced Polymer (FRP) , Composite, Medical Application.
1.0
Introduction
FRP based material has been in used for many decades in various industries. FRP in bio
engineering was introduced to address the problems facing by medical practitioners. Usage of
metals such as stainless and titanium widely used in bone repairing for its bio compatibility
properties, however it
causes un necessary pain and inconveniences
as several surgeries
required to remove these metals over time[4]. This journal also pointed out other consequences of
using metal plates for bone repairing which could lead to uneven cells growth around the metals
plates a eventually causes porosis. Another disadvantage of this material in bone repairing is the
possibility of re-fracture of the bone where differential in stiffness between bones and metals
effects after the plate has been removed.
Bio engineering defined as application of concepts and methods of the physical science
and mathematics in an engineering approach towards solving problem in repair and
reconstructions of damaged, lost or deceased tissues. Any material that is used for this purpose
falls in to biomaterial class[6]. Biomaterial has long history date back to ancient civilization,
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where Chinese and Indians used wax, glues and tissues in reconstructing missing or defective
parts[5]. On the other hand, Polymer also known as plastic is made from petroleum based resins.
Petroleum based polymer however is not ideal for certain application such as in bone repairing,
because of its bio incompatibility.
In biomaterial development polymer alone may not give the desired/required mechanical
properties, one way of overcoming this problem is to reinforce it with fibres. By introducing
fibres into (resins) polymers, it enhance the mechanical properties of the polymer particularly its
strength and modulus[20] . Just like in the construction of building columns and beams, where
steel rods have been used to enhance the strength of concretes
Fibre in general can be divided in to 2 major groups and can be further break down in to
sub categories as shown in the Figure 1 below.
Fibre
Natural
Plant based fibre
Synthetic
Animal based Fibre
Figure 1: Groups of Fibre
2.0
Milestone of FRP in Medical Industry
Plastics such as vinyl, polystryne, phenoil and polyester were developed in 1900’s. The
drawback of these materials is its strength and rigidity. In 1935, Owen Corning introduced the
first fibre glass. With this fibre polymer and its application in developing bio material had begun.
In 1930‘s a documented report on biopolymers by the Micro-biologist, Lemoyne describing
polyhydroxybutyrate[9] was published marking the starting point of FRP development in bio
medical industry.
FRP was further developed in 1970s with technology advancement. Better plastic resins
and improved reinforcing fibers were developed. DuPont developed an aramid fiber known as
Kevlar, this fiber is still being used in developing dental bridges ,tendon ligament bone cement
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and many more applications[13]. Parallel to this development carbon fiber is introduced replacing
metals.
3.0
Characteristics of FRP
One of the mandatory requirement for biomaterial is sterilization and meet the reuired
characteristic. It is known that sterilization of FRP(particularly properties of carbon fiberreinforced Polyetheretherketone PEEK composites) material that would alter the micro
mechanical properties to the certain extend. It is crucial to analyse the changes in FRP material
as such changes in micro mechanical properties would affects in vivo behaviour of the material.
Test ought to be done to analyse the level alteration during such process. Two established tests
namely Nanoindention and nanoscratch are used for this purpose[6]. Sterilization is a mandatory
test for implant materials therefore the required parameter of FRP must be analysed first to
ensure its full potential. The characteristic of FRP has been summarised in the Table 1.
4.0
Application of FRP in biomedical industry
Various importance factors be must considered in material selection for biomedical
applications. In brief factors influence the selection summarized in the Table 1 below.
Factors
Description
1st level properties
Chemical/biological
characteristics
chemical absorption (bulk and
surface)
Physical characteristics
Density
2nd Level material
properties
Adhesion
Surface topology
Texture and roughness
Specific functional
requirement (Based on
application)
Bio functionality ( Non thrombogenic, cell
adhesion.etc),Bio-inert (nontoxic, non-irritant, non-allergic,
non- carcinogenic, etc),BioActive, Bio Stability (resistant
to corrosion, hydrolysis,
oxidation, etc) Bio degradation.
Form (solid, porous
,coating ,film, fibre, mesh,
powder), Geometry,
Coefficient
of thermal expansion,
Electrical conductivity,
colour ,Aesthetic,
Refractive index, Opacity
or trancesluency
Mechanical/structural
characteristics,
elastic modulus
Poisson's ratio
Yield Strength
Tensile Strength
compressive strength
Hardness
Shear modulus
Shear strength
flexural modulus
flexural strength
Stiffness or rigidity
Fracture toughness
Fatigue strength
Creep resistance
Friction and wear
resistance
Adhesion strength, proof
stress
Abrasions resistance
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processing and
fabrication
Characteristic of host
Reproducibility , quality, Sterilizablity, packaging, secondary process ability
Tissue ,organ, species, age ,sex, race, health condition, activity, systemic response
Medical /surgical procedure, period of application/usage.
Table 1 : Various factors Of Importance in Material Selection for Biomedical application
4.1
Hard Tissue Application.
The application of FRP in biomedical can be grouped into hard tissue and soft
tissue applications. Hard tissue application comprises of bone fracture repair, dental
application, total hip replacement, knee, ankle and other joint replacement. Usually the
material selection for hard tissue application is from resorbable and partially resorbable
FRP materials. Selection of FRP material should consider the mechanical properties of
the tissue. Two key areas to be considered in the selection can be summarized in the
Table 2 below:
Hard Tissue
Cortical bone (longitudinal direction)
Cortical bone (transverse direction)
Cancellous bone
Enamel
Dentine
Modulus
( GPa)
17.7
12.8
0.4
84.3
11.0
Tensile
Strength(MPa)
133
52
7.4
10
39.3
Table 2: Mechanical properties of hard tissues [5]
4.1.1
Bone Fracture Repair.
It can be divided in two types ; External Fixation and Internal Fixation. The
different between of these two types is the first does not require opening of the fracture
location and the later does. External repairing is done by keeping the bone fragments
aligned by using casts, splints, braces or other sort of supports.
FRP materials have been widely used in bone fracture repairing in both fixation
types. Material like carbon fibres (CF), polyetherethrketone (PEEK) , Epoxy ,etc are the
common material in manufacturing bone plates and screws.
[5]
The bone density is
proportionate to stress that applied to it, in other words the higher the applied stress the
denser the bone become. Bone weakening on the other hand generally is due to lack of
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stressing/exercising of the bone. Therefore, heavy loading may impact bone fractures and
there are many types of fractures depending on the crack, size, position and orientation[5]
The fundamental purpose of fracture fixation is to stabilize the fractured bone, and
facilitate speedy recovery of injured bone.[19] FRP is more widely used in manufacturing
breathable caste in which if compared to the conventional type it has many advantages,
comfort to anatomical shape, strong, stiff , water proof, radiolucent
are the most
prominent advantages of this material. Usually for external fixation materials from non
resorbable are used for example CF/Epoxy. [5] The internal fixation usually covers dental,
total hip replacement, knee replacement and done by implanting screws, plates,
intramedullary nails, wires and pins.
Figure 1: Picture of External Fixation. Adopted from indiamart.com.
Figure 2: Picture of Internal Fixation . Adopted from uihealthcare.org
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4.1.2
Joint Replacements
There have been many developments of material for joint replacement. Hip, knee,
shoulder and elbow are few examples of synovial joints. FRP materials have been used in
joint replacement, however there were too many complications in it such as stress
shielding, reduction of blood supply at the implantation site and the possibility of
corrosion wear and debris formation. [10]
FRP was proven to have high resistance to fatigue failure as their structural
stiffness strength that can be matched the modulli of bone.[1] It has been used in femoral
component ( total hip replacement) as it can be customized as per require stiffness and
strength.[3]
4.1.3 Dental application.
Typical application of FRP in dental treatment includes filling cavities
( dental caries), replacing fractured or decayed teeth, crown and bridge, prosthetic
and many more. The material that have been used for this treatment falls into biomaterial
as well and can be grouped in internal fixation. The selection of material depends on the
capability to resemble the physical, mechanical and aesthetic properties of natural tooth
structure. Amalgam, gold, alumina, zirconia, acrylic resins and silicate cements are
commonly used for restoring decayed teeth
[5]
.The problem with these materials is the
suitability in certain conditions such as amalgams and gold are used in restoration of
posterior (back) teeth not preferred for anterior teeth for cosmetics reasons.
The capability of FRP is to increase the mechanical properties and good aesthetic
attributes, that is why it has been widely used in dental application. The fibres enhance
the mechanical properties of the polymers and there is a good initial bonding of glass
fibres to polymer via an interface made from saline coupling agents[14]. Studies show that
Silica-Glass ?Fibre Reinforced poly methyl methacrylate (PMMA) based polymers has a
good mechanical properties in both wet and dry conditions
[14]
. The usage of traditional
material in the manufacture of brackets shows high strength and stiffness but poor
aesthetics. PMMA composite materials have been suggested as substitutes for this
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traditional/conventional type. Furthermore composite post insertion proves less time
consuming and making surgical procedure less traumatic for patients[19].
4.2
Soft Tissue Application
FRP based material implants in soft tissues application plays very important role,
where special requirement particularly strength and modulus in repairing connective
tissues need to be observed in orthopaedic and dentistry patients. The usage of FRP based
implants depends on the types of corrective surgery intended, for example the deformities
or defect which can be congenital, developed or acquired [5].
Composite material such as FRP can be a very convenient in such situations as the
desired mechanical properties can obtained by choosing the right characteristics of
composite materials. This is done by using micromechanics and lamination theory
approach. Finite Elements Models (FEM) is used to analyse the stress pattern in detail in
both natural and synthetic structure under the complex loading geometry
[16]
. Table 3
shows the two important parameters that ought to be considered in choosing or designing
FRP based implants.
Soft Tissue
Modulus
Tensile
(MPa)
Strength(MPa)
Articular Cartilage
10.5
27.5
Fibrocartilage
159.1
10.4
Ligament
303.0
29.5
Tendon
401.5
46.5
Skin
0.1-0.2
7.6
Arterial Tissue(longitudinal direction)
0.1
Arterial Tissue(transverse direction)
1.1
Intraocular lens
5.6
2.3
Table 3: Mechanical properties of soft tissues [5].
4.2.1.Connective tissues
Connective tissues is tissue that connect or holds synovial joints. The application
of FRP is widely used in connective tissues repairing, significant factor, particularly
elastic modulus and strength ought to be considered.
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In the current application FRP implants can be used in developing devices for
various purposes, which depends on the intended functions, among which are fillers
defect, enclose, store, isolate or transporting.
Fillers usually are required to do restoration of cosmetic defects and atrophy.FRP
is also being used in cartilage replacement, Articular cartilage which caused by
deterioration by osteoarthritis , now can be replaced by FRP implant made of Silicone
rubber(SR) and Polytetrafluoroethylene (PTFE) which believed to have the closest
characteristics of meniscus or fibrous [5].
4.2.2
Skin
Materials such as PLLA (Poly-L-Lactic acid), collagen areresorbable polymers
used in skin repair, particularly in facilitating the healing.
4.2.3
Arterial Blood vessels
FRP application in repairing blood vessel comes in the form of grafts. Graft is a
tubular structures that used to bypass vessels which is blocked /damaged to restore blood
circulation. Vascular graft is used to replace segments of the natural cardiovascular
system that are deceased or blocked. Typical example is to replace section of arteries in a
diabetic patient’s leg where blockage has occurred. PET or extruded porous wall tubes
PTFE and PU material widely used for this purpose[5].
6.0
Conclusion
In general, the application of FRP in bioengineering area are very wide. Since it
was first developed, various materials have been modified to substitute less efficient
traditional materials. It is apparent that in developing FRP materials two important
parameters that have to be considerd are biocompatibility and its structural strength. With
the advancement of technology new methods and manufacturing processes has been
developed, this have laid the path for more advanced materials for more complicated
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purpose. A lot of efforts have been put in develeoping high strength biodegradable
materials. This requires many researches and continuous improvement in developing the
latest technology.
Prepared by,
Pushpa a/p Jegannathan
CMET
Date: 13 December 2014
7.0
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