Metal-ceramic restorations

Question 1

Advantages

Answer 1

Aesthetically better than metal
Strong in comparison to all-ceramic
Can act as a retainer for a bridge
Can support RPD
Design can incorporate attachments

Question 2

Disadvantages

Answer 2

Aesthetics compromised to all-ceramic restorations
Technically difficult to produce
Bond between metal and ceramic is the weak point
Concerns regarding biocompability

Question 3

Production

Answer 3

Substructure produce in wax either by hand or CAD
Wax pattern converted to metal via wax casting
Substructure may be produced via milling or selective laser melting of definitive alloy
Metal surface conditioned for ceramic bond
Ceramic sintered on to the metal surface

Question 4

Substructure design

Answer 4

Design should leave 1mm for the ceramic
Ideally produce a full contour crown, then reduce by 1mm resulting in an even thickness of ceramic
Inferior substructures are produced as a 0.3mm thick metal coping
-ceramic makes up the remaining substructure
-this result in weak restorations
The metal substructure may form part of exterior contour of the crown
-this allows for minimal reduction, strong contact points, easy adjustment, rest seats and milled surfaces

Question 5

Substructure design: clinicians should consider design of the metal substructures for…

Answer 5

Occlusal contact
Better wear properties
Ceramic strength

Question 6

Substructure design: also consider…

Answer 6

Ceramic finishing edge
Material for the margin
Material for proximal contacts
Provision of guide planes or rest seats for RPD
Retainer for a bridge 
Material for production