Prepared by Choice Dental · Updated
The three options
- Full-contour (monolithic) zirconia: the whole crown is milled from zirconia, then stained and glazed or polished. There is no veneering porcelain.
- Layered zirconia: a milled zirconia core is veneered with porcelain for more depth and translucency.
- Metal ceramic (porcelain-fused-to-metal, PFM): porcelain is fired onto a cast or milled metal substructure.
Aesthetics
Layered zirconia and metal ceramic allow the technician to build translucency and characterisation in porcelain, which is useful for anterior teeth. Full-contour zirconia has improved considerably with more translucent formulations and staining, but very high-translucency zirconias are generally weaker than conventional ones, so the choice is a balance between aesthetics and strength.
With metal ceramic, the metal substructure needs an opaque layer and can show as a grey line at the margin if the gingiva recedes.
Tooth reduction
Full-contour zirconia can usually be made thinner than a metal ceramic crown because there is no metal and porcelain to accommodate. Always follow the minimum thickness given by the material manufacturer and send a scan or impression that shows the reduction clearly.
Metal ceramic needs space for metal, opaque and porcelain, so it typically requires more reduction.
Strength, chipping and bruxism
Because full-contour zirconia has no veneering porcelain, there is no porcelain layer to chip. This is why it is widely used for molars and for patients with bruxism.
Both layered zirconia and metal ceramic can chip in the veneering porcelain under heavy loads. A protective night guard is worth discussing with patients who grind.
After occlusal adjustment, zirconia should be polished (or re-glazed): a rough zirconia surface increases wear on the opposing teeth.
Cementation
Zirconia cannot be etched with hydrofluoric acid like glass ceramics. It can be cemented conventionally where retention is good, or bonded with a resin cement after air abrasion and an MDP-containing primer, following the cement manufacturer’s protocol.
Metal ceramic crowns are usually cemented conventionally.
A simple way to decide
Every case is different — the dentist’s clinical assessment always comes first. Discuss borderline cases with the laboratory before preparing the tooth.
- Posterior crown, normal or heavy occlusion → full-contour zirconia
- Anterior crown where characterisation matters → layered zirconia or metal ceramic
- Long-span bridge → discuss the span, connector size and material with the laboratory
- Patient with bruxism → full-contour zirconia plus a night guard