ANSWERS

How strong is lithium disilicate?

Lithium disilicate (IPS e.max) has a flexural strength of 360 to 400 MPa, roughly three times stronger than feldspathic porcelain and on par with leucite-reinforced ceramics under high load. It handles single-unit crowns, veneers, inlays, onlays, and anterior bridges up to three units.

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Flexural strength: the number that matters

Lithium disilicate measures 360 to 400 MPa in flexural strength per Ivoclar's IPS e.max Press technical documentation (2023 edition). That puts it about 3x stronger than traditional feldspathic porcelain (around 100 MPa) and well above leucite-reinforced glass-ceramics (160 MPa). For context, natural enamel sits around 384 MPa, which is part of why e.max bonds and wears so predictably against opposing dentition.

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Is lithium disilicate stronger than zirconia?

No. Lithium disilicate runs 360-400 MPa flexural strength. Zirconia runs 800 MPa (translucent 5Y) up to 1,200+ MPa (3Y-TZP monolithic). Zirconia is roughly 3x stronger. The tradeoff is esthetics: lithium disilicate offers superior translucency and chameleon effect for anterior cases, while zirconia, especially older generations, reads more opaque. Material choice should follow the indication, not the spec sheet alone.

Can lithium disilicate be used for posterior crowns?

Yes. Monolithic lithium disilicate is indicated for single posterior crowns including molars, with documented 10-year survival rates at 96.7% per a 2020 Journal of Prosthetic Dentistry meta-analysis. The contraindication is posterior bridges of three or more units and bruxism cases with documented parafunction. Minimum occlusal thickness should be 1.5 mm for posterior monolithic restorations to stay inside the material's safe load envelope.

What is the minimum thickness for a lithium disilicate veneer?

Lithium disilicate veneers can be fabricated as thin as 0.3 mm in the press technique, per Ivoclar IPS e.max Press indications. For most anterior veneer cases, 0.5 to 0.7 mm is the working range that balances strength, esthetics, and prep conservation. Below 0.3 mm the material loses predictable handling during pressing and the bonded interface becomes the primary structural element rather than the ceramic itself.

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