Dental Crowns: Materials and Selection Criteria

How zirconia, lithium disilicate, alumina and porcelain-fused-to-metal compare on strength and aesthetics, and which specific clinical indications guide material choice based on the position of the tooth being restored.

For decades the standard for dental crowns was porcelain-fused-to-metal (PFM): an underlying metal coping providing strength, covered by a layer of porcelain improving aesthetics. The historical limitation of this approach is well known to clinicians and longtime patients alike: as gums recede over time, the metal margin can become visible, creating that characteristic dark halo at the tooth's collar, particularly unpleasant in anterior areas. Hence the push toward metal-free materials, now the majority in modern practice.

Zirconia has established itself as the reference material for strength: its mechanical hardness makes it particularly suited for posterior teeth, subject to intense chewing forces, even though its translucency — much improved over first-generation zirconia — remains generally lower than that of lithium disilicate. The latter is instead the material of choice where aesthetics take priority: its natural translucency makes it hard to distinguish from a natural tooth, at the cost of slightly lower mechanical strength than zirconia, which is why it's more suited to single anterior teeth than extensive posterior bridges.

Clinical indications published in Dental Cadmos summarize this balance well: for restoring a single tooth, lithium disilicate or zirconia are recommended depending on whether the case prioritizes aesthetics or mechanics; for 3-4 unit bridges, zirconia is preferred, or porcelain-fused cobalt-chromium; for rehabilitating full arches, resin- or composite-veneered titanium is generally chosen, or porcelain-fused cobalt-chromium — both solutions designed to better distribute chewing loads over a large prosthetic span.

Alumina, less common but still present in the clinical arsenal, offers an intermediate combination of stability, corrosion resistance and light transmission particularly favorable for aesthetics, albeit with lower mechanical strength than zirconia — it's mainly used in cases where the tooth to be restored has no particular underlying discoloration, where alumina-ceramic offers an excellent aesthetic compromise. In any case, the final choice is never reducible to a table of generic indications: abutment color, available prosthetic space, patient occlusion and aesthetic expectations always remain variables to be evaluated case by case together with the dental laboratory.

On Oralzon you'll find zirconia and lithium disilicate blocks and discs, and porcelain-fused-to-metal alloys compatible with the main CAD/CAM systems, along with all the materials for the final aesthetic characterization of the crown.