CLASSIFICATION OF BIOMATERIALS
Drug Delivery
Devices
Skin/cartilage
Polymers
Bone
replacements
Orthopedic
screws/fixation
Metals
Dental
Implants
Ocular
implants
Synthetic
BIOMATERIALS
Ceramics
Dental Implants
Implantable
Microelectrodes
Semiconductor
Materials
Biosensors
METALIC BIOMATERIALS
Crystal structures and
strong metallic bonds orthopedic applications
material joint prosthesis and bone renewal
- the face and jaw surgery
Dental implant
- cardio-vascular surgery
Artificial heart parts, heart valve
Metals used as Biomaterials
Steel
Cobalt-containing alloys
Titanium and titanium containing alloys
Dental amalgam (XHg)
Gold
Nickel- 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
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
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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
Structure
Ceramic Structure: AmXn
ZnS
A: metal, +ve
CsCl
NaCl
X: nonmetal,
-ve
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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
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Mechanical Properties
B. Amsden
CHEE 340
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BIOCERAMICS
BIOINERT
BIOACTIVE
Bioactive ceramic, that allows the chemical bond
formation between tissue and implant
Bioinert ceramic, that doesn’t allow the chemical
bond formation between tissue and implant
MATERIAL
TISSUE
TOXIC
DEAD
Bioinert
Various thicknesses
of fibrous tissue
NON-TOXIC
Bioactive
binding of tissueimplant interface,
Soluble
Tissue replaces
İmplant place
Classification of Bioceramics According to
Tissue Responses
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 Hydroxyapatite
pores
Resorbable
ceramics
Absorption
Tricalcium
phosphate
Bioactive glasses
Ceramic implants are non-toxic
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
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 um
Wear: 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
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Glass and glass-ceramics:
Silica(SiO2) –based ceramics (Includes LithiumAluminum or Magnesium-Aluminum crystals )
Bioglass:
Instead of some silica groups, calcium, phosphorus
or sodium is present (SiO2, Na2O, CaO, P2O5)
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
SiO2
B
C
A
D
CaO
A: Bonding within 30 days
Na2O
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
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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
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
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Advantage of Bioceramics
The resistance to
Microorganisms,
Temparature,
Solvents
pH changes
High 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
Why Use Bioceramics?
General
Options
Toxic/
Imunogenic/
Disease
transmission?
Mechanical
Properties?
Bioactive?
Degradable?
Autograft
Allograft
Metals
Ceramics
Excellent
Moderate
Low
Polymers
Composites
Advantages to Bioceramics:
Disadvantage of Bioceramics:
• Biological compatibility and activity
• Brittleness – not for load bearing
applications
•Less stress shielding
•No disease transmission
•Unlimited material supply
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