ceramic biomaterials - auburn university
TRANSCRIPT
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Ceramic Biomaterials
Lecture #17
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Ceramics
Refractory (maintain shape and composition at high temperatures)PolycrystallineNonductile virtually zero creep at room temperaturesUsually inorganic
SilicatesMetallic oxidesCarbides Refractory hydrides, sulfides, and selenides
Low heat conductivityHard
Moh scaleDiamond 10Talc 1
Alumina (Al2O3) 9Quartz (SiO2) 8Apatite (Ca5P3O12F) 5
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Traditional Uses of Ceramics
In form of pottery, used for thousands of yearsUntil recently use was limited
BrittleSusceptible to notching and microcrackingLow tensile strength (but high compressive strength)Low impact resistance
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Bioceramics
Augment or replace various body parts –especially boneDental crowns
Relative inertness to body fluidsHigh compressive strengthAesthetically pleasing appearance
CarbonsBlood interfacing applications – heart valvesTendons and ligaments
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Desired Properties of Bioceramics
NontoxicNoncarcinogenicNonallergicBiocompatibleFunctional for its lifetime in the host
Ceramics must meet or exceed these requirements to be termed a bioceramic
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Nonabsorbable (Relatively Bioinert) Bioceramics
Pyrolytic carbon-coated devicesDense and nonporous aluminum oxidesPorous aluminum oxides
Zirconia ceramicsDense hydroxyapatitesCalcium aluminates
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Uses of Bioinert Bioceramics
Reconstruction of acetabular cavitiesBone plates and screwsCeramic-ceramic compositesCeramic-polymer compositesFemoral heads
Middle ear ossicles(small bones in the ear, malleus, incus, and stapes – hammer, anvil, and stirrup)Reconstruction of orbital rimsTotal and partial hipsSterilization tubesVentilation tubesCardiovascular repair
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Alumina (Al2O3)
Source: bauxite and corundumCalcination of alumina trihydrateNatural alumina is either sapphire or ruby, depending on impurities presentGood wear propertiesUsed in orthopedics for over 25 years – joint replacement, total hip prosthesis
0.04Na2O
0.03Fe2O3
0.12SiO2
99.6Al2O3
Composition (weight%)
Chemical
Chemical composition of Calcinated Alumina
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Zirconia (ZrO2)
Derived from zirconZrSiO4
Y2O3 used for stabilization
Good wear and friction properties but not quite as good as alumina 0.64.0Grain size (µm)
5.953.8-3.9Density (g/cm3)
6.59Hardness, Mohs
1.0>0.4Flexural strength (GPa)
190380Elastic modulus (GPa)
ZirconiaAluminaProperty
Physical properties of alumina and zirconia
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Carbons
DiamondGraphiteNoncrystalline glassy carbonQuasicrystallinepyrolytic carbon
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Properties of Various Types of Carbon
4.80.66.3Toughness (N•m/cm3)
517172138Compressive strength (MPa)
282424Elastic Modulus (GPa)
1.5-2.01.51.5-1.9Density (g/cm3)
PyrolyticGlassyGraphiteProperty
Type of Carbon
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Strength and Modulus vs. Density for Pyrolytic Carbon
(GPa)
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Biodegradable or Resorbable Ceramics
Plaster of Paris used as a bone substitute –1892Biodegradable substitutes – 1969
Replaced by endogenous tissueAlmost all are variations on calcium phosphate
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Examples of Biodegradable/ResorbableBioceramics
Al-Ca-P oxidesGlass fibers and their compositesCoralsCalcium sulfates, incl. Plaster of ParisFe+++-Ca-P oxides
HydroxyapatitesTricalcium PhosphateZn-Ca-P oxidesZn-SO4
—Ca-P oxides
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Use of Biodegradable/ResorbableBioceramics
Drug delivery devicesRepair of bone damaged by disease or traumaFilling space vaced by screws, donor bone, excised tumors, and disead bone loss
Repairing and fusion of spinal and lumbo-sacral vertebraeRepairing herniated discsRepairing maxillofacial and dental defectsHydroxyapatite ocular implants
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Calcium Phosphate
Artificial boneImplantsSolid or porous coatingsMay be crystallized into hydroxyapatite
Ca10(PO4)6(OH)2
Mechanical properties vary greatly
3.16Density (theoretical, g/cm3)
0.27Poisson’s Ratio
3.43Hardness (GPa)
147Bending strength (MPa)
294Compressive strength (MPa)
4.0-117Elastic modulus (GPa)
ValueProperty
Physical properties of calcium phosphate
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Hydroxyapatite
Excellent biocompatibilityForms direct chemical bond with hard tissueOn implant, new compact bone forms within 4-8 weeks
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Aluminum-Calcium-Phosphate (ALCAP) Ceramics
Developed in 1980Unique
Tailor where resorbtiontakes place
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Corraline
Any of various red algae of the family Corallinaceaewhose fronds are covered with calcareous deposits Main component – calcium carbonate – gradually resorbedCan be converted to hydroxyapatiteRepair traumatized bone, replace diseased bone, correct bone defects
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Tricalcium Phosphate (TCP) ceramics
Correct peridontaldefectsAugment bony contoursCeramic matrix drug delivery systemsMore soulble than synthetic hydroxyapatiteGood bone ingrowth
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Zinc-Calcium Phosphorous Oxide (ZCAP) Ceramics
Zn, essential for human metabolismComponent of >30 metalloenzymesMay be involved in wound healingRepair boneDeliver drugs
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Zinc-Sulfate-Calcium-Phosphate Oxide (ZSCAP) Ceramics
Formed from zinc oxide, zinc sulfate, calcium oxide, and phosphorous pentoxideSet and harden on contact with bloodRepair bone defects
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Ferric-Calcium-Phosphorous Oxide (FECAP) Ceramics
Sets and hardens on contact with waterComplete resorptionwithin 60 daysPatients with anemia
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Bioactive or Surface Reactive Ceramics
Surface reactive ceramics, upon implant form strong bonds with adjacent tissue
Bioglas and Cervital TM
Dense and nonporous glassesHydroxyapatite
Coating of metal prostheses
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Uses of Surface-Reactive Ceramics
Coating metal prosthesesReconstruction of dental defectsFilling space voided by screws etc.Bone plates and screws
Middle ear ossiclesLengthening of rami –vertical part of jawCorrecting periodontal defectsTooth replacement
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Glass
Bioglas®SiO2 (42.1% - mol %)CaO (29.0%)Na2O (26.3%)P2O5 (2.6%)
Ceravital®SiO2 (40-50% - weight %)CaO (30-35%)Na2O (5-10%)P2O5 (10-15%)MgO (2.5-5%)K2O (0.5-3%)