2- Metallic Biomaterials Flashcards
Biomaterials are used for what two functions?
functional performance, biocompatibility
Biomaterials can be divided into 4 materials? Name them.
metals, ceramics (including glasses), composites, polymers
What properties of meals make them widely used?
there strength and toughness
Name 3 implant metals that are generally biocompatible.
SS Steel, Titanium, Cobalt alloys
Name Problems with current metal implants (3)
some people may be allergic to the ions released, the wear particle can cause inflammation, and imlplant loosing.
Name where metals are used?
bone and joint replacement, dental implants, cardiovascular devices, surgical instruments
Packing- state how order packing relates to energies
dense, ordered packed structures tend to have lower energies
unit cell
smallest repetitive volume which contains the complete lattice pattern of a crystal
Metallic crystal structures…. 1. how are they packed. why? is bond energy low or high? why?1
they are densely packed. THis is because only one element is usually present, so all radii are the same, metallic bonding is not directional, it is low in energy because the nearest neighbor distances tend to be small
define solidification and the 2 steps
the result of casting of molten material.
- nuclei form
- nuclei grow to form crystals- grain structure
Name two categories for types of imperfections in metal crystaline structure
point defects; line defects
name 2 types of point defects
vacancy atoms (missing atoms), interstitial atoms(extra atoms), substitutional atoms
name types of line defects
dislocations
When metals mix they form in what two ways?
substitution(replace atoms), intersitial(just adds between atoms)
name types of metal fabrication (forming)
forging(hammering; stamping), rolling (hot or cold rolling), drawing (rods, wire, tubing), extrusion (rods, tubing)
name types of metal fabrication (casting)
casting-mold is filled with metal. metal melted in furnace, may alloy added. then cast in mold
Name types of metal fabrication (misc)
powder metallurgy, welding
name components of 316 SSL
–Fe 60-65 wt%
–Cr 17-19 wt %
–Ni 12-14 wt%
–C max 0.03%
SSL why add chromium?
corrosion resistance by formation of surface oxide
SSL why add nickel
improve strength by increase face center cubic phase
SSL why reduce carbon content…?????
well it is reduce to .03%. when this is reduce it has better resistance to in vivo corrosion….. by reducing carbide Crv23Cv6 formation at grain boundry…. carbide impairs formation of surface oxide
what may SSL316 release?
NI^+2, Cr^+3, Cr^+6
name a colbalt alloy used for implants
ASTM F799
What is added to colbalt alloys?
W(tungsten) and NI (nickel)
Titanium: how much in TI, grade for?
name components in Ti-6Al-4V ELI (ASTM F136)
Ti 89%
Al 6%
V 4%
where is Ti-6Al-4V ELI (ASTM F136) used?
hip and knee implants, screws and fittings, dental implants, pacemaker housing
what is special about Ti-6Al-4V ELI (ASTM F136)?
IT PERMITS BONE GROWTH AT THE INTERFACE
Comparison SSL to others
cheap high strength, ductility, and toughness corrosion can be a problem less bone bonding then others may produce nickel ion sensitiviy
Comparison Co/Cr/Mo alloys to others
hardest to fabricate
cast forms-lower cost, higher modulus
wrought or forged forms- highest cost, highest strenth/wear resistance
may produce colbalt or chromium ion sensitivity/toxitcity
Comparison Titanium Alloy (Ti-6Al-4v) vs (Titanium metal
Ti alloy is stronger than Ti metal
both have relatively low moduli
neither is as wear resistant as SS or Co/Cr/Mo alloys
both have best corrosion resistance of all metals, expecially pure Ti
both have excellent bone bonding, best of all metals
name some dental metals
amalgam, gold, nitiol
what is uniquie about nitiol
dental metal, it shape memory alloy… remember stiches
