Alloy Denture Base Materials Flashcards
Name 3 noble metals which are resistant to corrosion in the mouth
- Gold
- Platinum
- Palladium
Describe 3 parts of the classifications of alloys according to American Dental Association
- High-noble
- Noble
- Base metal
Describe the gold content and noble metal content of a high-noble alloy
Gold content of 40% + and noble metal content of 60% +
Describe the gold content and noble metal content of a noble alloy
No requirement of gold content and noble metal content of 25%+
Describe the gold content and noble metal content of a base alloy
No requirement of gold content and noble metal content of less than 25%
What 4 things does adding base materials to noble metals cause?
- Increased strength
- Decreased flexibility
- Better wear resistance
- Cheaper
Describe Gold alloys as a material
- High density
- Expensive
- Very stable in oral condition
- Excellent biocompatibility
Describe cobalt-chromium compared with gold as a denture base material
- Harder
- x2 MoE
- Half as dense
- Proportional limit is reduced (brittle)
- Shrinks more on cooling
Name 4 main constituents of cobalt chromium
- Cobalt (60-65%)
- Chromium (25-30%)
- Molybdenum (4-6%)
- Carbon (0-0.4%)
Name 3 functions of cobalt in CoCr
- Strength
- Rigidity
- Hardness
Name 2 functions of chromium in CoCr
- Corrosion resistance
2. Tarnish resistance
Name 2 functions of molybdenum in CoCr
- Add strength
2. Reduce grain size
Name the function of carbon in CoCr
Raise strength and hardness but too much carbon can weaken the alloy
Name 5 materials where traces are found in CoCr to add strength
- Tungsten
- Boron
- Manganese
- Iron
- Silicon
Describe the properties of CoCr
- Good biocompatibility
- Casting shrinkage of around 2%
- Must use phosphate bonded investment material
- High MoE makes rigid in thin section
- Low ductility makes clasps prone to fracture
- Low density makes RPD light
Name 3 ways to form metals in dentistry
- Cast
- Wrought
- CAD-CAM
Describe casting materials in dentistry
Molten alloy poured into mould e.g crowns and RPD bases
Describe wrought alloys in dentistry
Alloy shaped by mechanical force (hot or cold pressing, drawing, milling) e.g NiCr for ortho wires, RPD clasps, endo files
Describe CAD-CAM as a method for shaping metals in dentistry
Reductive (formed from a block of material) or by addition (built up in thin layers)
Describe investing and casting procedures - Lost Wax Technique
- Pattern laid onto model duplicated in refractory model
- Sprues added and model invested
- Placed in a furnace and temperature raised
- Allow melted and cast into mould using centrifugal force
- Casting is sandblasted
- Fitted to master model and polished
Name 3 requirements of sprues in the lost wax technique
- Channel which allows molten alloy to flow into the pattern
- Sprue acts as a reservoir
- Sprue should be thicker than thickest section of casting
Name 2 methods of sprues
- Direct (on top)
2. Indirect (or inverted)
Describe titanium based alloys as a denture base material
- Good biocompatibility
- Rigid
- Low density
- Excellent corrosion resistance
- Very high casting temperatures
- Reactive with oxygen (must be cast in vacuum)
