Multilayer Zirconia

Multilayer zirconia is judged by colour difference, translucency, contrast ratio, and fracture load. In one in-vitro comparison, Perfit STML had higher translucency, while Dental Direkt had lower translucency and higher opacity. The measured result also changed with the anatomical region.

Multilayer systems are used for monolithic dental crowns and are designed to mimic natural tooth gradients. Highly translucent materials may suit a natural incisal appearance when the underlying substrate is favourable; a more opaque material or masking may be needed when that substrate is discoloured.

The material choices include 3Y-TZP multi-layered zirconia, 4Y-PSZ super-translucent zirconia, and 5Y-PSZ ultra-translucent zirconia. Lithium disilicate is an alternative with more predictable aesthetic outcomes than third-generation dental zirconias in the cited review.

A layered crown can reproduce a cervical-to-incisal shade gradient, but the result depends on the zirconia system, the tooth region, and the colour of the underlying substrate. Two multilayer products should therefore be treated as different optical materials, not interchangeable names.

Fracture behaviour under biting load remains an uncertainty for multilayer monolithic zirconia crowns. Tested samples included 1.0, 1.5, and 2.0 mm thicknesses and different tooth positions, with outcomes recorded as cracks, partial fractures, complete fractures, or no fracture. Broader reviews also identify unresolved issues for strong, aesthetic, sufficiently stable long-span fixed prostheses.