Topic 4 Ceramic Biomaterials PDF

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ceramics -> a) Treet high b) brittle - wear resistant MT 271 Application : - Zirconia , Hydroxy apatite -> Knee joints -> Dental implants ↳ Alumina , ZTA , Zirconia -> Bioactive glasses · Hydroxyapatite ↓ -> Calcium phosphate ↳ Bone has this is active active Bio -as made of it bone while ↳ on Ti Alz03 , Zirconia a re bio inect inert coating of Bone -> composite and couagen conagen & heac - silicon freectul toughnes · ceramic but classical is not too less not silica Topic 4 * semiconductor silicone sillico b oxide · polymac · ceramic · hard & - 11-si- si - Si brittle , I · glasses · ball in a heart ⑳ drying value. ablity · a had brittle not · high temp ball & soft What happens when Ceramic biomaterials Biomaterial enter the Body ? be zirconia need not -> bioinert coated by a material but still illilit an IR doesn't. Bioirent -> we may give antibiotics newcallyb Foreign to supress IR after georia apite red Bio active mall vial biomaterial - putting the Hydroch ever the trigger it to o. Does not als caD term IR recognize it eventually a long. , bone O leads clb Gimene Inect in the serve to adhering too. ⑧ that it can t can't S S B acevia - Bacteria directly b ind to - erqut bites off bone but bore it & kill it engulfs meetene by degreeding enzymes on it grows. together come ec form a firs & e "Inex doesn't imply there is no immune only see capsule may that also have a ⑦ Zirconia * immune ce just (ess mabrin etc. response finuous binding. capsule protein immure zimonia at otengetract it around it. & no more Immune so its engulfed resp Ome Common uses of bioceramics Bones of skulls are diff from bones of & so on the spire. maxillofacial orthopaedic &. -Hydroxyapatite.  What are ceramics? Ceramics are refractory, polycrystalline compounds, usually inorganic, including silicates, metallic oxides, carbides, hydrides, sulfides, etc. Oxides such as Al2O3, MgO, SiO2, etc. contain metallic and non-metallic elements. Ionic salts (NaCl, CsCl, ZnS, etc.) can form polycrystalline aggregates, but soluble salts are not suitable for biomaterials.  Structure of ceramics Classified according to the structural compounds: AmXn (A: metal and X: nonmetal element, and m and n are integers) Simplest case is AX structure (m=n=1). Types of AX structure based on relative size of the ions (rA / rX)  Crystal structure of ceramics For similar sizes of ions: simple cubic structure For large differences in sizes: f.c.c. structure Positive ions can be fitted in the tetragonal or octagonal spaces created among larger negative ions. Dark spheres: A+ and white sphere: X- Examples of ceramic structures  Physical properties Very hard High melting temperature Low conductivity of electricity and heat Brittle; difficult to deform plastically Applications of ceramic biomaterials Primarily for hard tissues: orthopedic and dental nee in soft tissues ? why not 9) brittle module b High Young Why? c) Orthopaedic a dental bones are made up Of ceramics & hence they are a better chemical match to them.  Anatomy of bone The outer surface is the membrane called the Periosteum.- this is a membrane rich in celly so soft & has lot of stem cells. Imore parly The outer bone region is called very - I more dense High content in Cortical bone (or compact bone) Xray's The inner bone is called Trabecular bone (spongy bone) A Medullary Cavity is often present  Anatomy of bone units that core self sustaining Volkmann’s & Haversian canals- basic nutritional and blood supplies for the bone. ↑ shielding stress. Bone is made of and replaced by Osteons including Osteocytes, -> desdebure nei - Osteoblasts & Osteoclasts. b mater into osteocytes I form bones &. allow to grow  Micro-structure of bone JECT9 ↳ classic composite with fibres of puteded in ceramics. collagers) mostles crane, Taton (2001) Nature vol. 412 p.491 Collagen (protein) and inorganic (calcium phosphate-based) minerals are the major components of bone Composition of bone Got eins age  Structure and composition of teeth Bone & teeth have a lot of mineveh making Four tissues form the teeth- them close to biocratics. Enamel: hardest part of the human halder than body; 95 % mineral, rest water and ↑ bone & brittle ↓ softer proteins Dentine: 70% inorganic materials, 20% organic materials, and 10% I progressively water SO ftes Cementum: 45% inorganic material, 33% organic material and 22% water Dental pulp: soft connective tissue containing blood vessels, nerves  Implant-tissue interactions Potential effects of implanting a biomaterial: Toxic material or leachable: tissue dies, not suitable as biomaterial Material is non-toxic but “inert”: fibrous tissue formed Material is non-toxic and biologically-active/ interactive: formation of interfacial bond Material is non-toxic and soluble in aqueous: material is resorbed and replaced with new tissue  Bioceramics classified by interaction with tissue Type 1: inert Type 2: inert micro-porous Type 3: bioactive Type 4: resorbable  Type 1- inert -> sould block of malerial - like a Zirconia Smooth Surface or Ana -> fibrous capsules on it form. problems = to the does not adhere · It etc places Morphological fixation-. body or if there · Biofilms may from ↳ is infection tear Poor interface bonding · micro-wear If we make gaps or wugh cells can adhere or surface , prone to loosening of the implant atuch to beter or to them adhering , leading So we make material inert microporous. an  Type 2- inert microporous Biological fixation- Micropores on the surface to promote in growth of the surrounding tissue Better performance than Type I  Type 3- bioactive fixation coal with a Bioactive matorial doesn't degrade too easily. Bioactive fixation- Primarily mechanical fixation, strengthen fixation by chemical coating Material is bioactive, formation of a chemical bond between the implant and the surrounding tissue  -> bioresorbable Rate atwhat na E I e type geradewat a to grow on it veryimpor out won type I bioactive en Type 4- bioresorbable will dissolve ou * Zinoria are furnaces & present etc Al2oz. in * Al2O3 in ecements degrade to give exc : a dissolved material dissones into the · Material blood etc. I new water , cells onto those gaps grow fixate etc. allowing them to The ceramic slowly dissolves in aqueous environment and replaced by growth of the surrounding tissue Particularly useful for tissue engineering scaffolds Less thermodynamically stable forms of CaP besides hydroxyapatite  Inert crystalline ceramics: Al2O3 Alumina: High-density (low porosity) Used at high-purity (>99.5% alumina) Applications: load-bearing hip prostheses and dental implants Excellent corrosion resistance 36 wit(inent Iner=> no bad immune resporte Biologically “inert” > X no im re response High wear resistance High strength Fine-grained polycrystalline alumina prepared by sintering fine crystals ISO standards for alumina bioceramics Properties of alumina bioceramics Alumina meeting ISO standards: ceramic ball cup of ulherhigh i leve rol not poly they used in joints & has amazing Good fatigue resistance 3 wear venitarce. ceps for hip joints & knee joints are made of these. Excellent wear resistance Coefficient of wear in alumina-alumina ball-socket of a hip prosthesis = 10 times lower (better) than metal–polyethylene surfaces High stress shielding leads to bone atrophy and prosthesis loosening  Inert crystalline ceramics: ZrO2 ↓ again used for Zirconia: cups in hip joints mainly. Properties equivalent or better than alumina Used to make head and acetabular cup in total hip joint replacement  Wear properties of zirconia Wear resistance against UHMWPE of zirconia better than alumina due to lower porosity Zirconia-zirconia wear resistance worse than alumina-alumina surfaces does not have the HA - & moduly strength ACO3 & 2002 : as slow or fast Metab -> cooling gives estaine solic ceramics owco etwire Bioactive and resorbable ceramics amorphous Bioactive veramics ceramics q I I calcius Bioglass Based Glass and glass-ceramics Calcium phosphate ceramics I combination Glass - mics of glass I - ~- 2..... 000 ceramics I glass alow........ 0 ⑧0 00 to reach a more thermodynamically no green & aless crystalline ceramics Atable state. slow cooling greein boundries for glas & amorphous in crystalline fast cooling.  Bioactive ceramics amorphous - Certain compositions of glasses, ceramics, glass-ceramics, and b composites can bind to bone crystalline b of amorphous mix & crystalline The common characteristic is a time-dependent, kinetic modification of the surface that occurs upon implantation. The surface forms a biologically active carbonated-hydroxyapatite - Jelly Like filous form layer that provides the bonding interface with tissues showt such shactures Optimal balance between dissolution reaction and precipitation reactions at the interface car quick have a dissolution in some bore cases forming a gap  Glass-ceramics Glass ceramics originally developed by S.D. Stookey of Corning Glass Works in 1960s. Glass-ceramics are polycrystalline ceramics made by controlled crystallization of glasses. Metallic precipitates added to nucleate and crystallize the glass into a amphoorphous grainless glass to glass ceramics fine grained ceramic I trigger to we add metal precipitates to allow nucleation. Possess excellent mechanical and thermal properties. Bioglass® is a glass and Ceravital® is a glass-ceramic developed for implants.  Formation of glass-ceramics · cramics may crack if raise qui O you temp too. usually glass & amorphous ceramics degrade Nucleating agents added for a bit feater & here are more resorbable nucleation of crystalline phase:. metallic agents (Cu, Ag, Au, Pt), TiO2, ZrO2, and P2O5 I The nucleation of glass is carried tohelp nucleation we out at temperatures much lower adI nucleating than the melting temperature. To obtain a larger fraction of the microcrystalline phase, the material is further heated to an appropriate temperature for maximum crystal growth. Crystallization usually > 90% with grain sizes of 0.1 to 1m  Bioglass and Ceravital By itself it is chemical mimic I some additional things bioinen so bore mineral it lao , P2US very sma - - make 4 S? We active using · Binest sodagene - L Multicomponent Primarily SiO2-CaO-Na2O-P2O5 I ceramics · add to make some it P2Os more & 10 bio active in nature. Many bioactive ceramics contain 45% SiO2 =>“45S” series Ca/P ratio= 5 for good bonding => “45S5” glass Glass ceramic ↑ glass- ceramic  Bioglass and Ceravital bonding SiO2-CaO-Na2O phase diagram for constant P2O5 Region A: bonding in 30 days with bone. -only SiOz e.g. Bioglass 46S5 Region B: nonbonding—too low - I diff prop of Sioz M20 & reactivity. e.g., Soda glass (window and , Ca0 Terrany bottle glass) phale diasrem Region C: nonbonding—too high reactivity. (resorbable in 10-30 days) -> Gogesses are in this Region D: bonding but does not form region glass (not practical to prepare) -targents ↑ give values only ↓Maso -- ↑ less CaO & 10 only more NazO Bonding to bone  Use of glass-ceramics use in we can ↳ & in The main drawback of the glass-ceramic: brittleness fining gaps coatings & we ther use don' load bearing in purposes Due to restrictions on the composition for biocompatibility (or osteogenicity), mechanical strength cannot be substantially improved. They cannot be used for major load-bearing implants such as joint implants. They can be used as fillers for bone cement, dental restorative composites, and coating material.  Many forms of calcium phosphate Bone Mineral = Ca-deficient carbonate- hydroxyapatite Hydroxyapatite is found in bone (ideal Ca/P ratio 10/6) CaP stability in solution generally increases with increasing Ca/P ratio Substitution of OH group with F ion gives greater chemical stability. ClP ratio is -> important lower the ratio , more is it water soluble.  Hydroxyapatite The form depends on- the Ca/P ratio, presence of water, impurities, temperature In a wet environment and at lower temperature (> a-TCP>> b-TCP> CDHA >>HA > FA work we enamel don't use this here  Factors affecting CaP resorption ↓ various rates of deqretion The rate of biodegradation increases as: 1. Surface area increases (powders > porous solid > dense solid) 2. Crystallinity decreases (amorphous phase less thermodynamically stable) 3. Crystal perfection decreases 4. Crystal and grain size decrease HA is already stable e 5. Ionic substitutions of Mg and Sr in HA 2+ 2+ so adding Mg2+] Suzt unstable mold make it Factors decreasing the rate of biodegradation: 1. F− substitution in HA ↓> stabilizes crystal structures the ler & hence causes resorption 2. Mg2+ substitution in β-TCP 3. lower β-TCP/HA ratios in biphasic calcium phosphates ne we can make biphasic calp that aid in racorption rates.  Bone cement Bone cements are used to firmly anchor artificial joints (hip joints, knee joints, shoulder and elbow joints) by filling the free space between the prosthesis and the bone. Traditionally made from polymethyl methacrylate (PMMA) - take a monomer do an New generation: Calcium phosphate cement (CPC) imite polymerisation -> but its bioinet abo & may release lot of heat ,  Bone cement New generation: Calcium phosphate cement (CPC) CPCs consist of a concentrated mixture of one or several calcium phosphate powders and water CPC chemical formulation is CaO-H3PO4-H2O that can experience a transformation from a liquid or pasty state to a solid state, and in which the end-product of the reaction is a calcium phosphate. Also used as bone substitutes; can be implanted by minimally- invasive surgery · 10-15min window for seal hydroxyapatite to the hole · add calle + Ocp => Hydroxy apatite ↓ ↓ does not => less ratio CalP => move Calp e dissone => rectio form easing. cement Ceramic-Tissue interfacial interactions Bone showed grow into it or this spechur Dequedation is stightly more for the bioactive glasses.