implant material Flashcards
why does stainless steel have good corrosion resistance
Cr form surface oxide, better corrosion resistance
Low Carbon content, decrease in carbide content, hence better corrosion resistance
Why is good about titanium based alloys
light
good mechanical properties
good corrosion resistance due to titanium solid oxide layer
what are the type of ti-based alloy
alpha–> non heat treatable
alpha beta–> heat treatable to varying extent
beta–> heat treatable, high strength, excellent cold forming qualities
is ti implant fracture common
no
what is the main mechanism of Ti implant fracture
metal fatigue from high cyclic occlusal loading
what are some factors promoting corrosion in body
water, dissolved O2, proteins, chloride, hydrochloride, low pH
how does an oxide layer minimises corrosion
minimises release of metal ions.
how is passivation done( to enhance oxide layer)
via immersion in 40% nitric acid/ anodisation
what are the advantages of ceramic implants
- improved mechanism properties esp Y-TZP–> higher mechanism strength and higher fracture toughness
- high corrosion resistance
- does not cause allergy
- good colour
what are the disadvantages of ceramic implants
- brittle
- can only be cemented
- it is a single piece implant, must replace everything if component fails
what are the properties of Y-TZP
excellent corrosion and wear resistance, high flexural strength
how does the atom particle change when there is a crack
from tetragonal to monoclinic structure, causes substantial increase in volume and induce surface compressive stresses, crack tip close, enhance resistance to further propagation
what is low temperature degradation
slow surface transformation of metastable tetragonal to stable monoclinic structure in the presence of water/ water vapour
what does LTD generate
microcracking, which enable further water penetration, crack propagation and phase destabilisation. cycle repeat as stress neighbouring grains also transform leading to further increase in volume and stress
