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Ceramics (2)


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Ceramics (2)

  1. 1. CERAMICS
  2. 2. INTRODUCTIONGreek 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.
  3. 3. I GENERATION BIOCERAMICSIn 1960’sBIO-INERTNESSInteraction with the living tissue as low as possible.Alumina & Zirconia
  4. 4. II GEN BIOCERAMICS1980’sBIOACTIVE or BIO-RESORBABLEFavorable interaction with bodyAble to form strong interaction with living tissuecrystalline calcium phosphates, bioactive glasses and glass-ceramicsbone tissue augmentation, bone cements or the coating of metallicimplants
  5. 5. III GEN BIOCERAMICSStart of 21stcenturyconcept replacement of tissues is been substituted withregeneration of tissues.Able to induce regeneration and repair of living tissues basedon genesporous second generation bioceramicsOrganic & inorganic hybrids, mesoporous of silica, stargels,templated glasses.
  6. 6. CERAMICS IN ARTHROPLASTYoxide ceramicsformed by closely packed crystals of Very small and very purecrystals oxides of aluminum or zirconium metalsSliding ceramics1930 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
  7. 7. 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.
  8. 8. MATERIAL PROPERTIESHardnessWettabilityBiocompatiblityExcellent tribological propertiesChemical & corrosion resistantGood surface finish
  9. 9. HARDNESS:very resistant to scratches from the tiny particlesharder 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.
  10. 10. 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.
  11. 11. 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.
  12. 12. Evaluation I GENERATION:1974-1988Grain size – 4.5 micrometersburst strength of 46 KNImpuritieshigh rate of #
  13. 13. II GENERATION:1990-1993Grain size – 3.2 microburst strength – 58 III GENERATION:From 1994grain size – 1.8 microburst strength – 65 KNImproved mech, HIP, Laser etching.
  14. 14. ALUMINAOld 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
  15. 15. 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
  16. 16. 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.
  17. 17. Zirconia Toughened Alumina(ZTA) ceramicMixed-oxide ceramics.75% of alumina and the rest are zirconium, Yttrium and chromeoxides.superior strength and resistance to wear.Biolax deltabending strength around 1000 MPa, more than the double of thealumina standard (400 MPa).Burst strength - 100 KN
  18. 18. Zirconia ceramicone of the stronger ceramics introduced to reduce the risk of fracture.Pure zirconia is an unstablematerial showing three different crystalline phasesStabilisation of zirconia by adding oxides to maintain the tetragonalphaseSmaller Femoral heads [22 mm]
  19. 19. More smoother finishZirconia femoral heads should articulate only againstpolyethylene socketsIt ages in the body’s temperature and the surface of thezirconia ball roughens
  20. 20. Advantages as bearing materialSmoother surface & less co-efficient of friction & wear.Superior lubrication property.Harder & less susceptible to third body wearInert 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.
  21. 21. Oxinium materialsZirconium is a strong and biocompatible metal similar totitaniumThin layer of zirconium oxide is coated on the surface of thesolid zirconium metalfemoral head made out of Oxinium that articulates with apolyethylene cup
  22. 22. combines the benefits of metals and ceramics.It offers superior wear resistance on its surfacezirconium metal itself, with characteristics close to titanium, is amaterial without the risk of brittle fracture.oxidized zirconium is black
  23. 23. Ceramics for total kneesThe 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 ceramicsdifficult to fabricate such a large yet thin ceramic component as isthe form of the femoral component
  24. 24. Oxinium total knee prosthesis
  25. 25. Bioactive ceramicsOsteoconductive propertyacting as a scaffold to enhance bone formation on their surfaceused 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
  26. 26. Hydroxyapatite (Ca10(PO4)6(OH)2)Synthetic apatiteMost 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
  27. 27. 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.
  28. 28. Such integration rarely, if ever, occurs with porous or smoothmetal implantshot plasma spray technique.optimal thickness of the coating- 50 micronsThinner 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
  29. 29. 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.
  30. 30. Bone graft substitutesPorous coraline ceramicsChiroff 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
  31. 31. 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.
  32. 32. Bioactive glasses.Bioglass 45S5bonding 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
  33. 33. wollastonite (CaOSiO2)glass ceramic developed by Kokubo et alosteoconductive properties similar to Bioglass 45S5increased mechanical strength.It has been used as a spacer at the iliac crest, for vertebralprostheses and as a shelf in procedures about the shoulder
  34. 34. Bioactive bone cementExplored in order to avoid complications related to PMMA debrisand to enhance fixation of the prosthesis.calcium-phosphate based bone cement and glass-ceramic bonecement.
  35. 35. Calcium phosphate cementsBiocompatible & resorbable cementInjectable cementsReplaced by creeping substitution with host bone.As bone void fillers with uniform & predictable drug eludingproperty.Deliver the antibiotics.N-SRS, ETEX alpha - BSM
  36. 36. Norian SRSN. skeletal repair system.Augmentation of fracture repair.[DHS, pedicle screw]Combination of monocalcium phosphate, tricalciumphosphate, calcium carbonate & a sodium phosphate solutionin to inj. PasteHardens with in minutes into dahllite [carbonated HA] in anonexothermic reaction.
  37. 37. ETEX alpha BSMCalcium orthophosphate cementDicalciumphosphate dihydrate, octocalcium P & manyprecipitating apatites.Poorly crystalline apatite which will mimic bone, aimingsuperior resorption & osteointegration.Easy intraop handling characteristics..
  38. 38. OSTEOSETMedical grade calcium sulphateHigh 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 pelletsAntibiotic delivery – aminoglycosides/ ideal.
  39. 39. FUTUREScaffold fabricated with a synthetic bioceramic which afterbeing supplemented with moieties of biological activity isimplanted in a living organism to induce tissue regeneration,