CSAR 14.3 - Material choices for fixed prosthodontics Flashcards
What advantages and disadvantages of the indirect restorations - pressed/cast (lost wax technique)?
+ very accurate
- risk of porosities
- need technician
What advantages and disadvantages of the indirect restorations - hand layered?
+ best aesthetics
- weaker as usually feldspathic ceramic
What are the advantages and disadvantages of monolithic restorations?
\+ Stronger \+ More conservative prep \+ Cheaper - Limited aesthetics - Can only character with stains
What are the advantages and disadvantages of bi-layered restorations?
+ Opportunity for better aesthetics
+ Can combine the best qualities of 2 materials – one coating for strength and other for aesthetics
- Potential weak point at material interface
- Risk of chipping/ fracture
- Need for greater preparation
Why would a metal collar on a crown be used?
Means less tooth tissue needs to be removed
What is the difference between high translucency zirconia and zirconia?
Zirconia – need layering
High Translucency Zirconia – better aesthetics, don’t need layered (but can also layer), weaker
What are the advantages and disadvantages of milling for indirect restorations?
+ use high strength materials
+ no porosities
- accuracy limited with size of cutting bur
- expensive equipment
What is the advantage of using monolithic zirconia compared to layered?
Monolithic has biological advantage saving tooth tissue as doesn’t need to be layered
What material is Emax?
Lithium disilicate
Why would monolithic lithium disilicate be preferred for posterior teeth?
Fracture strength is greater, therefore feldspathic would weaken it
Why would monolithic lithium disilicate layered with feldspathic porcelain be preferred for anterior teeth?
Adds character/aesthetics
What are the pros and cons of using indirect composite as a material for a crown?
+ Easier to adjust and repair
+ Cheaper
+ Can mill in thinner section that ceramic without fracture
+ Good when supported by enamel
- Flexible, therefore greater strain on bonding causing failure
- If into dentine, same prep as ceramic (stronger)
- Weaker than Emax
Give an example of a precious metal used for a crown?
Type 4 Gold
Palladium rich casting alloy
Give an example of a non-precious metal used for a crown?
Cobalt chromium
Nickel chromium
Give an example of a glass ceramic used for a crown?
Feldspathic porcelain
Lithium disilicate
Give an example of a polycrystalline ceramic used for a crown?
Zirconia
Give an example of a resin based material used for a crown?
Indirect composite
When would a translucent material be a good or bad option for a crown?
Good - greater aesthetics is core is a favourable colour
Bad - if tooth is black
Name an opaque (passive) lute.
Zinc phosphate
Zinc polycarboxylate
GIC
Name an aesthetic (active) lute.
Light cure resin
Dual cure resin
Self adhesive resin cement - needs resistance form as bond strength is low
What is the strength of a material as its translucency increases?
Increased translucency = decreased strength
Order these crown materials from low to high strength?
Zirconia, Lithium disilicate, Metal, Feldspathic porcelain, High translucency zirconia, Composite resin
Low to high: Feldspathic porcelain Composite resin Lithium disilicate High translucency zirconia Zirconia Metal
What are the advantages of an adhesive restoration?
- More conservative
- Less reliant on resistance and retention form
- Advantageous when limited clinical crown height
What are the disadvantages of an adhesive restoration?
- Harder to temporise
- Need to be able to isolate
- Bond is unpredictable/vulnerable in dentine margins
- Cementation much more technique sensitive
