classification of biomaterials
DESCRIPTION
Skin/cartilage. Drug Delivery Devices. Ocular implants. Bone replacements. Orthopedic screws/fixation. Synthetic BIOMATERIALS. Metals. Ceramics. Polymers. Dental Implants. Dental Implants. Semiconductor Materials. Biosensors. Implantable Microelectrodes. - PowerPoint PPT PresentationTRANSCRIPT
CLASSIFICATION OF BIOMATERIALS
Metals
Semiconductor Materials
Ceramics
Polymers
Synthetic BIOMATERIALS
Orthopedic screws/fixation
Dental Implants
Dental Implants
Bone replacements
BiosensorsImplantable Microelectrodes
Skin/cartilageDrug Delivery Devices Ocular
implants
METALIC BIOMATERIALS
Crystal structures and strong metallic bonds - orthopedic applications
- the face and jaw surgery
- cardio-vascular surgery
material joint prosthesis and bone renewal
Dental implant
Artificial heart parts, heart valve
Metals used as Biomaterials
SteelCobalt-containing alloysTitanium and titanium containing alloysDental amalgam (XHg)GoldNickel- titanium alloys
Corrosion;
The undesired chemical reaction of metals with their surruondings that forms oxygen, hydroxide and other compounds then degradation
Corroding Metal X Biocompatible
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Ceramic Biomaterials (Bioceramics)
The class of ceramics used for repair and replacement of diseased and damaged parts of the musculoskeletal system are referred to as bioceramics.
OBJECTIVES To examine chemical/physical properties of ceramics To introduce the use of ceramics as biomaterials To explore concepts and mechanisms of bioactivity
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Ceramics
(keramikos- pottery in Greek)
Ceramics are refractory polycrystalline compounds Usually inorganic Highly inert Hard and brittle High compressive strength Generally good electric and thermal insulators Good aesthetic appearance
Applications: orthopaedic implants dental applications compromise of non-load bearing for bioactivity
BIOCERAMICS
Bioceramics;
Repair the parts of body that injured or lost their function, restructuring or special ceramics are designed to replace ;
- polycrystalline structure ceramic (alumina),
- bioactive glass,
- bioactive glass-ceramics,
- bioactive composites…
Using Areas of Bioceramics
Glasses,Diagnostic devices, Thermometers,Tissue culture vessels.
Filling materials, Gold-porcelain coating,Prosthetic parts
Health Sector
Dental
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Structure
Ceramic Structure: AmXn
A: A: metal, +vemetal, +ve
X: X: nonmetal, nonmetal, -ve-ve
CsCl NaCl
ZnS
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Nature’s Ceramic Composites
Natural hard tissues are “ceramic”-polymer composites:
» Bones, Teeth, Shells Tissue = organic polymer fibers +
mineral + living cells Mineral component (Ceramic)
» Bone: hydroxyapatite (HA) – Ca5(PO4)3OH
Mineralization under biological conditions:
» Many elemental substitutions
» Protein directed crystallization
» Unique characteristics – crystal morphology and solubility
Synthetic calcium phosphates are used as biomaterials – “bioactive”
Synthetic HA Bone HA
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Types of Ceramics
nearly bioinert
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Bioactivity vs. Biocompatibility
Biocompatibility : Objective is to minimize inflammatory responses and toxic effects
Bioactivity - Evolving concept: The characteristic that allows the material to form a bond with
living tissue (Hench, 1971) The ability of a material to stimulate healing and trick the
tissue system into responding as if it were a natural tissue (Hench 2002).
Advantages: Bone tissue – implant interface, enhanced healing response, extends implant life
Biodegradability: Breakdown of implant due to chemical or cellular actions If timed to rate of tissue healing transforms implant to scaffold
for tissue regeneration Negates issues of stress shielding, implant loosening, long
term stability
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Classification based on tissue attachment
B. Amsden CHEE 340 14
Mechanical Properties
BIOCERAMICS
Bioactive ceramic, that allows the chemical bond formation between tissue and implantBioinert ceramic, that doesn’t allow the chemical bond formation between tissue and implant
BIOINERT BIOACTIVE
MATERIAL TISSUE
TOXIC DEAD
Bioinert
NON-TOXIC
Bioactive
Soluble
Various thicknesses of fibrous tissue
binding of tissue-implant interface,
Tissue replaces
İmplant place
Classification of Bioceramics According to Tissue Responses
Ceramic implants are non-toxic
Implant Type Tissue response
Example
Nonporous, dense and inert ceramics
The formation of very fine fibrous tissue
Alumina, Zirconia
Porous inert ceramics
The tissue growth in pores
Hydroxyapatite
Resorbable ceramics
Absorption Tricalcium phosphate
Bioactive glasses
Bioceramics According to Structural Functions
Oxide ceramics, inert structure, polycrystalline ceramics consisting of metal ions in the plane formed by the dissolution of oxygen ions
Alumina (Al2O3) orthopedic applications
Zirconia (ZrO2) femoral prosthese
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Inert Ceramics: Alumina
History: since early seventies more than 2.5 million femoral heads implanted
worldwide. alumina-on-alumina implants have been FDA monitored over 3000 implants have been successfully implemented since 1987
Smaller the grain size and porosity, higher the strength E = 380 GPa (stress shielding may be a problem)
High hardness: Low friction Low wear Corrosion resistance Friction: surface finish of <0.02 umWear: no wear particles generated – biocompatible
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Inert Ceramics: Aluminum Oxides (Alumina – Al2O3)
Applications orthopaedics:
»femoral head»bone screws and plates»porous coatings for femoral stems»porous spacers (specifically in revision
surgery)»knee prosthesis
dental: crowns and bridges
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Alumina
Bioinertness Results in biocompatibility – low immune response
Disadvantage:»Minimal bone ingrowth»Non-adherent fibrous membrane » Interfacial failure and loss of implant can occur
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Inert Ceramics: Zirconia, ZrO2
zirconium; named from the Arabic, zargun = gold color
Fabrication:• Obtained from the mineral zircon• Addition of MgO, CaO, CeO, or Y2O3 stabilize
tetragonal crystal structure (e.g. 97 mol%ZrO2 and 3 mol%Y2O3)
• Usually hot-pressed or hot isostatically pressed
Applications:
• orthopaedics: femoral head, artificial knee, bone screws and plates, favored over UHMWPE due to superior wear resistance
• dental: crowns and bridges
Glass and glass-ceramics: Silica(SiO2) –based ceramics (Includes Lithium-Aluminum or Magnesium-Aluminum crystals )
Bioglass: Instead of some silica groups, calcium, phosphorus or sodium is present (SiO2, Na2O, CaO, P2O5)
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Bioactive Ceramics: Glass Ceramics
Glass: an inorganic melt cooled to solid form without crystallization an amorphous solid Possesses short range atomic order Brittle!
Glass-ceramic is a polycrystalline solid prepared by controlled crystallization of glass
Glass ceramics were the first biomaterials to display bioactivity (bone system):• Capable of direct chemical bonding with the host tissue• Stimulatory effects on bone-building cells
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Bioactive Ceramics: Glass Ceramics
Composition includes SiO2, CaO and Na2O
Bioactivity depends on the relative amounts of SiO2, CaO and Na2O
Cannot be used for load bearing applications
Ideal as bone cement filler and coating due to its biological activity
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Bioactive Ceramics: Glass ceramics
B
AC
D
SiO2
CaO Na2OA: Bonding within 30 days
B: Nonbonding, reactivity too low
C: Nonbonding, reactivity too high
D: Bonding
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Bioactive Ceramics: Glass Ceramics
Bioactive: capable of direct chemical bonding with the host biological tissue
Glass:
• an inorganic melt cooled to solid form without crystallization
• an amorphous solid
• possesses short range atomic order BRITTLE!
Glass-ceramic is a polycrystalline solid prepared by controlled crystallization of glass LESS BRITTLE
Calcium-phosphate ceramics ; their structure is the form of multiple oxides of calcium and phosphate atoms
Hydroxyapatite Ca5(PO4)3OH,
Tricalcium phosphate, Ca3(PO4)2
Oktacalcium phosphate CaH(PO4)3.2OH
In medicine and dentistry
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Biodegradable Ceramics: Calcium (Ortho) Phosphate
Structure resembles bone mineral; thus used for bone replacement Coating of metal implants to promote bone ingrowth Different forms exist depending on Ca/P ratio, presence of water,
impurities and temperature
7 different forms of PO4 based calcium phosphates exist - depend on Ca/P ratio, presence of water, pH, impurities and temperature
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Calcium Phosphate
• Powders
• Scaffolds
• Coatings for implants – metals, heart valves to inhibit clotting
• Self-Setting bone cement
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Calcium Phosphates
Uses repair material for bone damaged trauma or disease void filling after resection of bone tumors repair and fusion of vertebrae repair of herniated disks repair of maxillofacial and dental defects ocular implants drug-delivery coatings for metal implants, heart valves to inhibit clotting
Advantage of Bioceramics
The resistance to Microorganisms,Temparature, Solvents pH changesHigh pressures is the advantage in health and dental aplications
Bioceramics are used repair or renewal of a hard
connective tissue in the skeleton
The elderly, the bones are very brittle
slow-moving cracks, uncertainties to durability in different strokes and pressures
The most important reasons for limiting the use of bioceramics,
Interaction of bioceramics with tissues
All materials placed on live tissue, takes response from tissue
TISSUE - IMPLANT
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Why Use Bioceramics?
GeneralOptions
Toxic/ Imunogenic/ Disease transmission?
Mechanical Properties?
Bioactive? Degradable?
Autograft
Allograft
Metals
Ceramics
Polymers
Composites
Excellent
LowModerate
Advantages to Bioceramics:
• Biological compatibility and activity
•Less stress shielding
•No disease transmission
•Unlimited material supply
Disadvantage of Bioceramics:
• Brittleness – not for load bearing applications