Metal-ceramic restorations Flashcards
What are the different metal-ceramic restorations?
Metal-ceramic crowns
Porcelain fused metal crowns
Bonded crowns - bond between the metal and ceramic
What are the different sub-structure materials in metal-ceramic restorations?
Bonding alloys
Precious metal alloy
NiCr or CoCr alloy
CoCr or Ti used in the selective laser melting systems
How do the bonding alloys used for metal-ceramic restorations differ to that used for all metal restorations?
They have a higher melting temp
Have a TEC to match the ceramic
Are rigid to prevent the ceramic debonding
Contain base material to create metal oxide on the surface which required for the metal ceramic bond
What are the advantages of metal-ceramic restorations?
Aesthetically better than all metal Strong in comparison to all-ceramic Can act as retainer for bridge Can support RPD Design can incorporate attachments
What are the disadvantages of metal-ceramic restorations?
Aesthetics in comparison to all-ceramic restorations
Technically difficult to produce
Bond between the metal and ceramic is weak
Concerns regarding biocompatibility
How are metal-ceramic restorations produced?
Wax pattern is converted to metal via lost-wax casting
Wax pattern is produced by hand or CAD
Alternatively CAD may be produced via milling or selective laser melting or definitive alloy
Metal surface is conditioned for ceramic bond
Ceramic is sintered on the metal surface
What is the depth of the ceramic on the substructure?
1mm of ceramic
What is the design of the substructure?
Produce pattern to full contour of the crown
Reduce by 1mm - for 1mm of ceramic
Varying thickness of substructure
Even thickness of ceramic
What is the depth of the substructure?
Metal substructure are produced as a 0.3mm thick metal coping
How much of the crown does the substructure make up?
Why it is an advantage for the metal to make up more of the crown?
May form part of the exterior contour of the crown
Minimal reduction
Strong contact points
Ease of adjustments
Incorporation of rest seats or milled surfaces
What does the clinician prescribe when it comes to deciding the extent of the metal work?
Occlusal and proximal contact material
Position of the ceramic finishing edge
Material for the margin: may be produced in ceramic
What qualities?
Support the ceramic correctly Polish/porosity Fitting surface Contact points Model Shape Shade
