Zirconia and lithium disilicate – the two major ceramic types

Where metal and acrylic were long the standard, fully ceramic materials are today the first choice for much of the visible prosthetic work. Two materials dominate: zirconia (zirconium dioxide) and lithium disilicate, a glass ceramic. Both are made in CAD/CAM workflows, but they behave very differently, and the choice between them determines both appearance and durability.

§Zirconia - strength in the ceramic family

Zirconia is known for its high flexural strength, which far exceeds most other ceramic materials, making it a popular choice for crowns, bridges and constructions in the chewing area where the load is greatest. Zirconia is typically milled in a pre-sintered, "green" state where the material is softer and easier to machine, but at the same time made in an oversize that compensates for the shrinkage of approximately 20–25 percent that occurs during the subsequent sintering in a high-temperature furnace. Zirconia can be used monolithic (in one piece, without layering) or as a core that is layered with more translucent ceramic for a more natural appearance.

§Lithium disilicate - aesthetics in the ceramic family

Lithium disilicate is a glass-ceramic known for its high translucency and aesthetic appearance, which is closer to the light transmission of a natural tooth than zirconia. The material can either be pressed in an oven from a ceramic blank or milled digitally in a softer, partially crystallized state and then finally crystallized in an oven, where both strength and color are fixed. Bending strength is lower than zirconia's, but on the other hand the aesthetics are often better, which makes the material a preferred choice for visible front teeth and single crowns.

§How a choice is made between them

The choice depends on what the task requires most: strength or aesthetics. For a bridge in the chewing area where the load is high, zirconia's strength weighs most heavily. For a visible front tooth where natural light transmission is crucial for the result, lithium disilicate's aesthetics often weighs most heavily. Many laboratories therefore use both materials side by side and choose from case to case.

• 01Placement in mouth: the chewing area places greater demands on strength than the front tooth region.
• 02Aesthetic requirements: a visible front tooth often requires higher translucence than a molar.
• 03The thickness of the structure: thin structures require more strength per millimetre of material.
• 04Number of joints in the bridge: longer bridges with more intermediate joints place higher demands on material strength.
• 05The dentist's prescription and the patient's wishes always enter into the final decision.

Neither of the two materials is universally "best" — they solve different tasks well. The dental technician who knows both materials' strengths and weaknesses thoroughly can advise the dentist professionally and choose the material that gives the patient the best and most durable result.

“Ceramic does not lie — if you choose the wrong material for the task, it will show sooner or later.”