CEREC crowns are milled from solid blocks of ceramic, zirconia, or ceramic-resin hybrid materials. The specific block your dentist chooses depends on which tooth needs the crown, how much natural tooth structure remains, and how visible the crown will be when you smile. Each material has distinct trade-offs between strength, appearance, and how much tooth needs to be removed.
Glass Ceramic
Glass ceramic is the most common material category for CEREC crowns, and it comes in several formulations. The two you’re most likely to encounter are lithium disilicate and leucite-reinforced porcelain. Lithium disilicate is the stronger of the two, with flexural strength ratings around 350 to 500 MPa depending on the specific product and whether it undergoes a secondary firing step. That’s roughly two to three times stronger than traditional feldspathic porcelain, which makes it suitable for both front and back teeth.
What makes glass ceramic popular for CEREC work is its ability to mimic the way natural teeth interact with light. Natural enamel is partially translucent, and glass ceramic blocks replicate that quality better than most alternatives. Blocks come in high-translucency and low-translucency versions. High-translucency options look the most lifelike but let more of the underlying tooth color show through, which matters if the prepared tooth is discolored or has a metal post. Low-translucency and medium-opacity versions block more of that underlying color at the cost of looking slightly less natural.
Dentsply Sirona, the company behind the CEREC system, currently offers glass ceramic blocks under names like CEREC Tessera and Celtra Duo. Other compatible brands include IPS e.max, which is widely considered the benchmark for lithium disilicate crowns.
Zirconia
Zirconia crowns are the toughest option available for the CEREC system. Zirconia is a crystalline oxide of zirconium, and in dental terms it behaves more like a metal than a ceramic: it resists cracking under heavy biting forces and is extremely difficult to chip. Standard zirconia blocks can exceed 1,000 MPa in flexural strength, making them the go-to choice for molars that absorb significant chewing pressure or for patients who grind their teeth.
The traditional knock against zirconia was that it looked chalky and opaque compared to glass ceramic. That’s changed significantly. CEREC now offers multilayer zirconia blocks (marketed as CEREC MTL Zirconia) that graduate from a more opaque, stronger core near the gumline to a translucent, enamel-like layer at the biting edge. This mimics the natural gradient of a real tooth, where the base is darker and the tip is more glassy. There’s also CEREC Zirconia+, a standard zirconia option for situations where maximum strength matters more than aesthetics.
One practical difference: zirconia crowns often require a sintering step after milling, where the crown is heated in a small furnace to reach full hardness. Some newer formulations have shortened this process considerably, but it can still add time to what’s otherwise a single-appointment workflow.
Nano-Ceramic Resin (Hybrid Blocks)
Hybrid blocks blend ceramic particles into a resin matrix, creating a material that behaves differently from pure ceramic. One well-known example, Lava Ultimate, packs roughly 80% ceramic content (a mix of zirconia and silica nanoparticles) into a cross-linked polymer base. The result is a block that’s less brittle than glass ceramic, with a flexural strength around 200 MPa, higher than feldspathic porcelain but lower than lithium disilicate or zirconia.
The practical advantage is gentleness. Hybrid materials absorb shock rather than transmitting it directly to the tooth underneath, which can reduce post-operative sensitivity. They’re also easier on opposing teeth. Pure ceramic crowns can gradually wear down the natural enamel they bite against, while resin-containing materials have wear rates closer to natural tooth structure.
Because hybrid blocks are less prone to cracking during try-in and adjustment, dentists can sometimes prepare the tooth more conservatively, removing about 0.5 mm less tooth structure than a typical all-ceramic crown requires. That’s a meaningful difference when you’re trying to preserve as much healthy tooth as possible. These blocks also polish to a high gloss that holds up over time, unlike older composite materials that tended to dull.
The trade-off is longevity and stain resistance. Resin-containing materials are more susceptible to discoloration from coffee, wine, and other staining agents than pure ceramic or zirconia. They’re also not as strong, so they’re typically recommended for smaller restorations or teeth that don’t bear heavy chewing loads.
Feldspathic Porcelain
Feldspathic ceramic blocks like VITA Mark II were among the first materials designed for the CEREC system and are still available. This is essentially traditional porcelain in a millable block. It offers excellent aesthetics, particularly for front teeth where color matching is critical, and it’s the easiest material for a dentist to characterize with surface stains and glazes.
The limitation is strength. Feldspathic porcelain is the most brittle option in the CEREC lineup, so it’s best suited for inlays, onlays, and veneers rather than full crowns on back teeth. When used for front tooth crowns that don’t endure heavy biting forces, it can produce some of the most natural-looking results of any CEREC material.
How Your Dentist Picks the Right One
The choice comes down to three variables: location in the mouth, cosmetic priority, and how much tooth remains. Back teeth that handle heavy chewing forces generally get zirconia or lithium disilicate. Front teeth where appearance matters most often get glass ceramic or feldspathic porcelain. Teeth with minimal remaining structure benefit from zirconia’s superior strength, while teeth that still have a solid foundation can work well with any of the options.
Thickness plays a role too. At just 0.5 mm, different materials transmit dramatically different amounts of light. A study evaluating 15 CEREC-compatible ceramics found contrast ratios (a measure of opacity) ranging from 0.35 to 1.00 at that thickness, meaning some blocks are nearly transparent while others are completely opaque. Your dentist factors in the color of your prepared tooth, any posts or core buildups, and the shade of your surrounding teeth when selecting not just the material category but the specific translucency grade within it.
If you’re told your CEREC crown will be “all ceramic,” it’s worth asking which type. A zirconia crown and a lithium disilicate crown are both technically all-ceramic, but they differ significantly in appearance, strength, and how they wear against your other teeth over time.