INTRODUCTIONGreek term "keramos" which means pottery.an article having a glazed or unglazed body of crystalline orpartly crystalline structure, or of glass, which body is producedfrom essentially inorganic, non-metallic substances and either isformed from a molten mass which solidifies on cooling, or isformed and simultaneously or subsequently matured by theaction of the heat.BIOCERAMICS.
I GENERATION BIOCERAMICSIn 1960’sBIO-INERTNESSInteraction with the living tissue as low as possible.Alumina & Zirconia
II GEN BIOCERAMICS1980’sBIOACTIVE or BIO-RESORBABLEFavorable interaction with bodyAble to form strong interaction with living tissuecrystalline calcium phosphates, bioactive glasses and glass-ceramicsbone tissue augmentation, bone cements or the coating of metallicimplants
III GEN BIOCERAMICSStart of 21stcenturyconcept replacement of tissues is been substituted withregeneration of tissues.Able to induce regeneration and repair of living tissues basedon genesporous second generation bioceramicsOrganic & inorganic hybrids, mesoporous of silica, stargels,templated glasses.
CERAMICS IN ARTHROPLASTYoxide ceramicsformed by closely packed crystals of Very small and very purecrystals oxides of aluminum or zirconium metalsSliding ceramics1930 Rock, 1stperson to consider the possibility of ceramics inA’plasty.1970 French surgeon Boutin implanted the first ceramic-on-ceramic cemented total hip joint in France
MANUFACTURING PROCESS Particulates of C. + H20 + organic binder Moulding Hot isostatic pressure. Evaporation of water, burning the binder by thermaltreatment Sintering with Cao / Mgo Final ceramic structure.
MATERIAL PROPERTIESHardnessWettabilityBiocompatiblityExcellent tribological propertiesChemical & corrosion resistantGood surface finish
HARDNESS:very resistant to scratches from the tiny particlesharder the surfaces coupled together, the less wear the couplingsystem producesWETTABILITY: Self lubricating, because of ionic structure which produceshydrophilic surface.Synovial fluids gets attracted & spreads out which minimizesadhesive wear.
BIO-COMPATABILITY Exist in highly oxidative state Chemically inert, resistant to oxidative degradation. Insoluble in water, hydrative degradation not possible.Results in less wear, smaller wear particle size, decreasedcytotoxity & osteolysis.
TRIBOLOGICAL PROPERTY wear rate of alumina-alumina bearing coupling is extremelylow (0.001 mm/year). If compared with metal-polyethylene(0.2 mm/ yr) 4000 times less fluid film lubrification - reduces the coefficient of clutch.
Evaluation I GENERATION:1974-1988Grain size – 4.5 micrometersburst strength of 46 KNImpuritieshigh rate of #
ALUMINAOld A. ceramic materials the crystals of aluminum oxideswere large, not assembled closely; there were manyimpurities and voids between them [5%].impurities - weak points for propagation of fracture cracks.The coarse structure and impurities were the cause of thefrequent fractures
Modern alumina [0.5% impurity]: HIPing process extrudesimpurities out off the material and packs the crystals very closetogether.very tough structure, tougher than the metallic stem on which it isseated, and even more tough then the natural thighbone.disadvantage of the modern alumina ceramic is lower toughness
high alumina ceramics : materials that have the minimalcontent of 97% of alumina.high purity alumina ceramics: percentage of minimal aluminais of 99%. HPA: commonly used for arthroplasty.Biolax forte.
Zirconia Toughened Alumina(ZTA) ceramicMixed-oxide ceramics.75% of alumina and the rest are zirconium, Yttrium and chromeoxides.superior strength and resistance to wear.Biolax deltabending strength around 1000 MPa, more than the double of thealumina standard (400 MPa).Burst strength - 100 KN
Zirconia ceramicone of the stronger ceramics introduced to reduce the risk of fracture.Pure zirconia is an unstablematerial showing three different crystalline phasesStabilisation of zirconia by adding oxides to maintain the tetragonalphaseSmaller Femoral heads [22 mm]
More smoother finishZirconia femoral heads should articulate only againstpolyethylene socketsIt ages in the body’s temperature and the surface of thezirconia ball roughens
Advantages as bearing materialSmoother surface & less co-efficient of friction & wear.Superior lubrication property.Harder & less susceptible to third body wearInert with no ion release.best used in young and active patients who have a high risk ofloosening and osteolysis in the mid to long term.
Oxinium materialsZirconium is a strong and biocompatible metal similar totitaniumThin layer of zirconium oxide is coated on the surface of thesolid zirconium metalfemoral head made out of Oxinium that articulates with apolyethylene cup
combines the benefits of metals and ceramics.It offers superior wear resistance on its surfacezirconium metal itself, with characteristics close to titanium, is amaterial without the risk of brittle fracture.oxidized zirconium is black
Ceramics for total kneesThe total knee joints doesn’t have congruent joint surfaces.Thus, in a total knee joint with both joint surfaces made fromceramic materials, there would appear large localized stresses thatwould destroy components made from the contemporary ceramicsdifficult to fabricate such a large yet thin ceramic component as isthe form of the femoral component
Bioactive ceramicsOsteoconductive propertyacting as a scaffold to enhance bone formation on their surfaceused either as a coating on various substrates or to fill bone defects.Calcium phosphate ceramics.hydroxyapatite (HA) and tricalcium phosphate (TCP).In solid form, neither of these materials exhibits adequate fatigueresistance for use as a load-bearing implant
Hydroxyapatite (Ca10(PO4)6(OH)2)Synthetic apatiteMost similar material from structural & chemical point of view tothe mineral component of bone.bone-graft substitute, HA coating to prosthesis.bonding mechanism - attachment at the surface of the HA ofosteogenically-competent cells which differentiate into osteoblasts
A cellular bone matrix is then formed at the surface of the HA.An amorphous area is present between the surface and the bonetissue containing thin apatite crystals.As maturation occurs, this bonding zone shrinks HA becomesattached to bone through a thin epitaxial layer, resulting in a stronginterface with no layer of fibrous tissue interposed between thebone and HA.
Such integration rarely, if ever, occurs with porous or smoothmetal implantshot plasma spray technique.optimal thickness of the coating- 50 micronsThinner coatings may not supply sufficient Ca and P long enough tobe effective,Thicker layers can experience sufficient stress under implant cyclicbending and shear and tensile loads to be subject to fatigue failure
Tricalcium phosphate (Ca3(PO4)2)exists in either alpha or beta crystalline forms.The beta form is the most stable.The rate of biodegradation is higher when compared with HA.Degradation occurs by combined dissolution and osteoclasticresorption.to stimulate early bone in-growth into porous surfaces.
Bone graft substitutesPorous coraline ceramicsChiroff et al, first recognised that, corals made from marineinvertebrates have a structure similar to both cortical & cancellousbone.Exoskeleton of genus porite [ICF- 190mm], structure similar tocortical bone.Genus gonipora – similar to cancellous bone
Hydrothermal exchange process converts delicate coralcarbonate in to hydroxyapatite without altering the internalstructure.Invaded & converted to mature lamellar B.Only surface resorption & no remodeling.Reconstruct metaphyseal defects.
Bioactive glasses.Bioglass 45S5bonding mechanism to bone - series of surface reactions ultimatelyleading to the formation of a hydroxycarbonate apatite layer at theglass surface.Greater production of bone, compared with HA.poor mechanical properties
wollastonite (CaOSiO2)glass ceramic developed by Kokubo et alosteoconductive properties similar to Bioglass 45S5increased mechanical strength.It has been used as a spacer at the iliac crest, for vertebralprostheses and as a shelf in procedures about the shoulder
Bioactive bone cementExplored in order to avoid complications related to PMMA debrisand to enhance fixation of the prosthesis.calcium-phosphate based bone cement and glass-ceramic bonecement.
Calcium phosphate cementsBiocompatible & resorbable cementInjectable cementsReplaced by creeping substitution with host bone.As bone void fillers with uniform & predictable drug eludingproperty.Deliver the antibiotics.N-SRS, ETEX alpha - BSM
Norian SRSN. skeletal repair system.Augmentation of fracture repair.[DHS, pedicle screw]Combination of monocalcium phosphate, tricalciumphosphate, calcium carbonate & a sodium phosphate solutionin to inj. PasteHardens with in minutes into dahllite [carbonated HA] in anonexothermic reaction.
ETEX alpha BSMCalcium orthophosphate cementDicalciumphosphate dihydrate, octocalcium P & manyprecipitating apatites.Poorly crystalline apatite which will mimic bone, aimingsuperior resorption & osteointegration.Easy intraop handling characteristics..
OSTEOSETMedical grade calcium sulphateHigh tech processing [retains all biological adv & consistent mech /resorption profile]Provide structural support & is bioabsorbable and biocompatible.Resorption profile matches with the rate at which hostenvironment can lay down bone around the compound.Available as pelletsAntibiotic delivery – aminoglycosides/ ideal.
FUTUREScaffold fabricated with a synthetic bioceramic which afterbeing supplemented with moieties of biological activity isimplanted in a living organism to induce tissue regeneration,