Chapter 2 Literature Review
2.1 Conventional Materials for Bioengineering Applications
Most of the current clinical applications involve complex structural and chemical functions, therefore, ceramic and metallic materials have been widely accepted for the development of implants. Recent researches on the impact of biodegradable polymers as well as the natural fibers to reinforce these polymers as biocomposites for different types of tissue engineering applications have explored. In this section, comparisons on various kinds of biomaterials on their background (such as clinical applications, advantages and disadvantages on using these biomaterials) are first addressed in Tables 2.1 and 2.2.
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Table 2.1 Examples and applications of different implant materials [Bartolo and Bidanda, 2008; Teoh, 2004; Ramakrishna et al., 2004].
Biomaterials Examples Applications
Metallic materials
Stainless steel, cobalt-based alloys, amalgams, titanium and titanium alloys,
nickel-titanium alloy (SMA), gold, platinum, silver
Artificial joints (hip ball and sockets), femoral stem, dental implants, tooth fixation (crowns and permanent bridges), artificial hearts, endovascular therapy, bone plates, staples, wires, pins, stents, pacemaker electrodes, artificial inner ears, intramedullary nail, disc prostheses, internal and external fixators (plates, washers and screws), spinal fusion, medical devices, surgical instruments (chisels, scalpels, pliers, forceps, etc.), hypodermic needles, craniofacial and maxillofacial treatments, self-expanding cardiovascular stents (SMA), guide wires for introduction of therapeutic and diagnosis devices (SMA), snare wires (SMA), vena cave filters (SMA), orthodontic arch wires (SMA), studs of earrings (silver), sanitizing agent (silver), burn therapy (silver), wound dressing (silver), urinary bladder catheters and stethoscope diaphragms (silver). crystalline or glassy forms of carbon and its compounds
Orthopedic and dental implants, hip and knee replacements, porous coating for femoral stems, porous alumina spacers, scaffolds, artificial tooth, bone filler, orbital implants within eye socket, crows, shoulder reconstruction surgery, coating for dental implants, knee joints and spinal implants.
Polymeric materials
Hydrogels, cellulose, collagen, chitin, chitosan, PE, PMMA, PP, PU, PTFE, PVC, PA, PC, PET, PEEK, polyacetal, alginate, gelatine, SR, PHEMA, PMA, PEA, PCL, PHB, PBT, PEG, PLA, PGA and co-polymers, Kelvar49, reconstituted collagen
Controlled drug delivery, artificial liver assist device, total hip replacement, vascular grafts, acetabular cups, tissue regeneration scaffolds, pins, rods, screws, disc prostheses, wound healing dressings, hemocompatible coatings, cell and DNA encapsulation, artificial tendon or ligament, catheters, facial reconstructive surgery,
endoprosthesis stent-graft, sutures, contact lenses, biosensors, blood tubings, blood storage bags, coating for breast implants, intra aortic balloons Composite polymer composite, HA-reinforced polymer
Subperiosteal orbital floor implants, middle ear implants, 3-D scaffold, screws and total hip stems, total knee replacement, dental resins, dental posts, dental arch wires, dental restorative material, sockets, bone cements, bone grafts, bone plates, spine rods, cage, expanding jacks, disc prostheses, finger joints, abdominal wall prosthesis,
tendon/ligament, cartilage replacement, external fixation, intramedullary nail
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collagen -reinforced polymer composite
Nanomaterials Carbon Nanotubes,
alumino-silicate (nanoclay)
Imaging, drug delivery, biosensors, tissue scaffolds, cellular sensing, cell tracking and
labeling, improving tissue matrices
Table 2.2 Advantages and disadvantages of different implant materials [Bartolo and Bidanda, 2008; Teoh, 2004; Ramakrishna et al., 2004].
Biomaterials Advantages Disadvantages
Metallic materials
High stiffness;
High tensile strength;
High fatigue strength and fracture toughness;
High ductility;
Good thermal conductivity;
Good electrical conductivity;
Oxidation resistance;
Corrosion and pitting resistance;
Wear and abrasion resistance;
Availability;
Flexibility;
Easily shaped machining and casting;
Non-magnetic;
Biocompatible;
Shape memory effect;
Relatively heavy in weight;
Poor durability;
Chromium releases;
Toxicity of corrosion products;
Production of polyethylene wear;
Excessively high rigidity;
Stiffness mismatch to tissues;
High specific gravity;
Fracture due to corrosion fatigue;
Lack of biocompatibility;
Inadequate affinity for cells and tissues integration;
Shielding of X-rays;
Intrinsically soft and ductile;
High processing cost.
Wear and abrasion resistance;
High fracture toughness;
Coating prolongs prothesis’s working life;
Accumulate less bacteria;
Lower rate of inflammation
Only be produced by high temperature sintering;
Production of polyethylene wear.
Polymeric materials
Light in weight;
Thixotropic and reversible;
Injectable and implantable;
Able to deliver delicate bioactive agents;
Promotion of tissue repair and regeneration;
Low mechanical properties;
Limitations to moderate load bearing applications;
Poor durability;
Shrinkage;
Difficulty to anchor to bone;
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Wear and abrasion resistance;
Low coefficient of friction; Accelerate wound healing;
Able to keep dryness on wounds;
Dressings adhere to wounds well;
Water-soluble;
Insoluble at physiological pH 7;
Gel-forming ability;
Ease of sterilization;
Easy processing;
Non-toxic residues upon biodegradation;
Chemically modification ability;
Enhance drug absorption;
Controlled release;
Non-reactive;
Resist the spread of infection;
Natural tissue-like properties;
In-situ formability;
Eliminate the utilization of toxic heavy metals;
Aesthetics;
Abrasion and wear of prostheses;
Strength deteriorate in long term (fatigue);
Generation of particulate matter may cause synovitis and inflammation;
Sensitive to hydrolytic and stress-induced degradation;
Lack anisotropy and non-linear compliance for vascular prostheses Too flexible;
Absorb liquid and swell;
Properties may be affected by sterilization processes.
Material properties can be tailored;
High stiffness;
High static and fatigue strengths;
Corrosion and fatigue resistance;
Good integration of biomaterials into tissues;
Aesthetics;
Easy forming;
More flexible;
Controllable porous size;
More comfortable to patients;
Chemically modification ability;
Generation of particulate matter may cause synovitis and inflammation;
Sensitive to hydrolytic and stress-induced degradation;
Absorb liquid and swell;
Properties may be affected by sterilization processes;
Have optimal fraction of reinforcements.
Nanomaterials Bioreactivity;
High strength;
High aspects ratio;
Good electrical and thermal conductivity;
Functional;
Clumping or aggregation for nano-scale reinforcements;
Carcinogenic.
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