Ceramic Biomaterials - Auburn University

Ceramic Biomaterials

Lecture #17

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

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

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

Desired Properties of Bioceramics

NontoxicNoncarcinogenicNonallergicBiocompatibleFunctional for its lifetime in the host

Ceramics must meet or exceed these requirements to be termed a bioceramic

Nonabsorbable (Relatively Bioinert) Bioceramics

Pyrolytic carbon-coated devicesDense and nonporous aluminum oxidesPorous aluminum oxides

Zirconia ceramicsDense hydroxyapatitesCalcium aluminates

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

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

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

Carbons

DiamondGraphiteNoncrystalline glassy carbonQuasicrystallinepyrolytic carbon

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

Strength and Modulus vs. Density for Pyrolytic Carbon

(GPa)

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

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

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

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

Hydroxyapatite

Excellent biocompatibilityForms direct chemical bond with hard tissueOn implant, new compact bone forms within 4-8 weeks

Aluminum-Calcium-Phosphate (ALCAP) Ceramics

Developed in 1980Unique

Tailor where resorbtiontakes place

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

Tricalcium Phosphate (TCP) ceramics

Correct peridontaldefectsAugment bony contoursCeramic matrix drug delivery systemsMore soulble than synthetic hydroxyapatiteGood bone ingrowth

Zinc-Calcium Phosphorous Oxide (ZCAP) Ceramics

Zn, essential for human metabolismComponent of >30 metalloenzymesMay be involved in wound healingRepair boneDeliver drugs

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

Ferric-Calcium-Phosphorous Oxide (FECAP) Ceramics

Sets and hardens on contact with waterComplete resorptionwithin 60 daysPatients with anemia

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

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

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%)