chapter 8 Design parameters 8.1 Biomaterials: Relative Properties 8.2 Bulk (Mechanical) and Surface Properties 8.3 Reactivity: Molecular Interactions 8.4 Bioadhesion(Tissue Bonding: Physical and Chemical mechanisms 8.5 Factors Affecting Biomaterials
CHAPTER 8 Design Parameters 8.1 Biomaterials: Relative Properties 8.2 Bulk (Mechanical) and Surface Properties 8.3 Reactivity: Molecular Interactions 8.4 Bioadhesion (Tissue Bonding): Physical and Chemical Mechanisms 8.5 Factors Affecting Biomaterials
8.1 BIOMATERIALS: RELATIVE PROPERTIES ADⅤ ANTAGES DISADVANTAGES METALS Stainless steel Strengt Potential for corrosion Ease of manufacturing High modulus of elasticity availability Cobalt-Chromium Strength Unknown long-term effects of Corrosion resistance Co and Cr ions Relative wear resistance High modulus Titanium(6A1-4V) Strength Low wear resistance Corrosion resistance CERAMICS Alumina Resistance to chemical degradation Low tensile and flexural strength Wettability Resistance to wear Calcium Phosphates(Slightly Soluble and resorbable Hydroxyapatite Bone-bonding Low tensile and flexural strength Slight solubility Slight solubility Whitlockite Bone-bonding Low tensile and flexural strength solubility Solubility Natural(resorbable) Bone Apatite Bone-bonding Low strengt Resorbabil
8.1 BIOMATERIALS: RELATIVE PROPERTIES ADVANTAGES METALS Stainless Steel Strength Ease of manufacturing Availability Cobalt-Chromium Strength Corrosion resistance Relative wear resistance Titanium (6Al-4V) Strength Low modulus Corrosion resistance CERAMICS Alumina Resistance to chemical degradation Wettability Resistance to wear Calcium Phosphates (Slightly Soluble and Resorbable) Hydroxyapatite Bone-bonding Slight solubility Whitlockite Bone-bonding Solubility Natural (Resorbable) Bone Apatite Bone-bonding Resorbability DISADVANTAGES Potential for corrosion High modulus of elasticity Unknown long-term effects of Co and Cr ions High modulus Low wear resistance Low tensile and flexural strength Low tensile and flexural strength Slight solubility Low tensile and flexural strength Solubility Low strength
POLYMERS Syntheti Thermoplastics PTFE ( Teflon Resistance to chemical degradation Low wear resistance Hydrophobicity Hydrophobic Low friction Does not display typical thermoplastic flow behavior UHMWPE Relatively high wear resistance Subject to oxidatio PET (Dacron) Subject to hydrolysis Low MW contaminants PMMA Polymerization in vivo Low fatigue strength ( for load-bearing appl PSF High strength thermoplast Water absorption (dec strength in water) PEEK High strength( PsF) Unproven C/PSF. C/PEEK Very high strength Unproven Relatively low modulus Elastomers PDMS High flex life Low wear resistance Ease of manufacture Release of low Mw PDms Range of mechanical properties Immunogenicity?
POLYMERS Synthetic Thermoplastics PTFE (Teflon) Resistance to chemical degradation Low wear resistance Hydrophobicity Hydrophobic Low friction Does not display typical thermoplastic flow behavior UHMWPE Relatively high wear resistance Subject to oxidation PET (Dacron) PMMA Polymerization in vivo PSF High strength thermoplastic PEEK High strength (> PSF) Low water absorption C/PSF; C/PEEK Very high strength Relatively low modulus Elastomers PDMS High flex life Ease of manufacture Subject to hydrolysis Low MW contaminants Low fatigue strength (for load-bearing applications) Water absorption (dec. strength in water) Unproven Unproven Low wear resistance Release of low MW PDMS Range of mechanical properties Immunogenicity?
Polyurethane High flex life Uncertain molecular structure- Range of mechanical properties property relationships Surface radically different from ulk(high mobility of"soft segments") Low MW contaminants Subject to hydrolysis, oxidation, d calcification Hydrogel P-HEMA Low reactivity Low strength Absorbable PLA/PGA Programmable absorption Uncertain biological response to Metabolizable degradation products bolus-release of metabolites Collag Replicates eCm components Immunogenicity Halt Replicates ECM component U Chitosan Substitutes for GAG(e.g, hyaluronan) Unproven PTFE polytetrafluoroethylene, UHMWPE, ultra high molecular weight polyethylene PET polyethylene terephthalate; PMMA, polymethyl methacrylate; PSF, polysulfone; PEEK, polyetheretherketone; PDMS polydimethyl siloxane; P-HEMA, poly hydroxyethyl methacrylate; PLA, polylactic acid; PGA
Polyurethane High flex life Uncertain molecular structureRange of mechanical properties property relationships Surface radically different from bulk (high mobility of "soft segments") Low MW contaminants Subject to hydrolysis, oxidation, and calcification Hydrogel P-HEMA Low reactivity Transparent Absorbable PLA/PGA Programmable absorption Metabolizable degradation products Natural Collagen Replicates ECM components Hyaluronan Replicates ECM component Low strength Uncertain biological response to bolus-release of metabolites Low strength Immunogenicity? Unproven Chitosan Substitutes for GAG (e.g., hyaluronan) Unproven PTFE polytetrafluoroethylene, UHMWPE, ultra high molecular weight polyethylene PET polyethylene terephthalate; PMMA, polymethyl methacrylate; PSF, polysulfone; PEEK, polyetheretherketone; PDMS, polydimethyl siloxane; P-HEMA, poly hydroxyethyl methacrylate; PLA, polylactic acid; PGA, polyglycolic acid
8.2 BULK (MECHANICAL) AND SURFACE PROPERTIES 8.2.1 Properties Dependent on Atomic Bonding in the Bulk and Surface of Materials BULK URFACE mechanical Mechanical Elasticity/Plasticity/Viscoelasticity Friction/Lubrication Wear(Abrasive and Fatigue) Chem -Corrosion -Oxidation hydroly zymolysiS Dissolution Bioadhesion Mechanical Chemica
8.2 BULK (MECHANICAL) AND SURFACE PROPERTIES 8.2.1 Properties Dependent on Atomic Bonding in the Bulk and Surface of Materials BULK Mechanical -Strength -Elasticity/Plasticity/Viscoelasticity -Wear (Abrasive and Fatigue) SURFACE Mechanical -Wear (Adhesive) -Friction/Lubrication Chemical -Corrosion -Oxidation -Hydrolysis -Enzymolysis -Dissolution Bioadhesion -Mechanical -Chemical