Labs Flashcards
What percentage of gold is in high gold content alloys?
Over 75% types I-IV
What percentage of gold is in medium gold?
40-60%
What percentage of gold is in low gold?
15-20% (Ag 40-60% and Pd 40%
Palladium and silver
What alloys are used for metal restorations?
High gold content alloys Medium gold Low gold Ag-Pd (less than 2% Au) Co-Cr Ti alloys
Positives of metal restorations?
Conservation Accurate fit Robust, strong Easy to adjust Can support RPD Can act as bridge retainer Simpe production
How to make metal restorations?
CADCAM
Negatives of metal restorations?
Aesthetics
Biocompatibility of metals
Thermal conductivity - pulpal protection
Uses of metal restorations?
Crowns
Inlay
Onlay
3/4 crown
Types of metal ceramic restorations?
Metal ceramic crown
Porcelain fused to metal crown
Bonded crowns
Substructure materials for metal ceramic restorations?
Bonding alloys
Precious metal alloy
NiCr/CoCr alloy
CoCr or Ti used in the laser melting systems
How do bonding alloys differ to the alloys used for metal restorations?
Higher melting temp
Have a TEC to match the ceramic
Are rigid to prevent the ceramic debonding
Contain base metal to create metal oxide on the surface which is required for the metal-ceramic bond
Positives of metal ceramic restorations?
More aesthetic than all metal Strong Can act as retainer for bridge Can support RPD Design can incorporate attachments More conservative palatal prep
What does the quality of metal ceramic restorations depend on?
Support the ceramic correctly Polish/porosity Fitting surface Contact points Model - duplicate model Shape Shade
Production techniques for metal ceramic restorations?
Wax pattern produced by hand or CAD
Wax pattern converted to metal via lost wax casting
OR CAD may be produced by milling or selective laser melting of definitive alloy
Metal surface conditioned for ceramic bond
Ceramic is sintered onto the metal surface
Types of all ceramic restorations?
High strength substructure - Zirconia or alumina Resin bonded restoration - Feldspathic type ceramics Lithium disilicate - Stronger materials
Resin bonded restoration examples?
Crown, inlay, onlay, veneer, 3/4 crowns
Features of resin bonded restorations?
All ceramic with no substructure Material must be susceptible to etching HF used Feldspathic ceramic containing leucite Lithium disilicate
How to produce resin bonded restorations?
Sintering - use either refractory model or platinum foil to support the ceramic particles in the furnace
OR pressing technique: wax pattern is produced and lost wax process converts wax pattern into ceramic
OR production via milling
Material must be etched and restoration bonded
How do high strength ceramic restorations gain support?
Resin bonded restoration - support from tooth
PFM - support from metal substructure
High strength ceramic for support
High strength ceramic substructure production?
CAD CAM (previously slip-casting) Ceramics are sintered onto substructure
Zirconia substructure material examples?
Procera (alumina), Lava, Zircon Zahn
Zirconia features?
Very opaque but translucent options available
Milled 20% oversize due to shrinkage from firing
Examples of glass infiltrated substructure materials?
In ceram
- Spinell
- Zirconia
- Alumina
Spinell indications?
Translucent
Not as strong
Single anterior units only
Aluminia indications?
Reasonably translucent
Single units
Strong
Anterior bridges
Zirconia indications?
V strong
Bridge frameworks
Full contour restorations
RPD support
Positives of high strength ceramic restorations?
Aesthetics
V strong
Relatively simple to produce
Biocompatible
Negatives of high strength ceramic restorations?
Expensive equipment Confusing choice of materials and production methods Varying strengths Varying optical properties Most destructive
What must you warn the pt of regarding crowns?
10-20% of pulp devitalising - if occurs will need to do RCT (nerve is dead, remove nerve, clean the tooth and replace it with a filling)
Crowns may not last forever - replacing and maintenance
Anterior crown options?
All ceramic - large restorations, aesthetics important
Metal ceramic - large restorations, heavier occlusion, aesthetics less essential
Dentine bonded crown - aesthetics v important, suitable occlusion, minimal tooth restored, white, less tooth removed but weaker
Posterior crown options?
FGC - minimal tooth prep, least aesthetic, bruxism
All ceramic crown - high strength, most aesthetic
Metal ceramic crown (PFM) - strong, not as aesthetic as all ceramic crowns, less destructive
