Denti Tech Services
Four material families cover nearly every crown and bridge a lab produces — and strength plus thickness decide among them.
Start with the number that matters most: flexural strength. High-strength zirconia in 3Y and 4Y grades reaches about 1,300 MPa, the most translucent 5Y zirconia sits near 550 MPa, and lithium disilicate of the IPS e.max type runs 400-530 MPa. ISO 6872 sets the ceramic-class floors at 500 or 800 MPa, and ISO 13356 standardises the zirconia material itself.
Zirconia's range exists because of yttria. The blanks are doped with 3-5 mol% yttria; higher yttria content lowers flexural strength while raising toughness, so a bridge framework and an anterior crown come off the same mill from different grades. Sintered density is 6.04-6.33 g/cm³ regardless of grade.
Lithium disilicate is the aesthetic workhorse with a hard ceiling. At roughly half the strength of high-strength zirconia it is indicated for single crowns, veneers and inlays or onlays — and explicitly not for long-span bridges or heavily loaded molars, where fracture risk stops being theoretical.
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Porcelain-fused-to-metal and full-metal restorations answer a different question. The Ni-Cr or titanium coping is cast, and porcelain is fired in 3-4 cycles between roughly 700 and 1,000 °C, which is why they take 1-2 weeks of lab time. They persist where a metal substructure is specifically requested.
Thickness often decides before strength does. Zirconia needs about 1.0-1.5 mm on axial walls and 1.5-2.0 mm over cusps; lithium disilicate needs 1.0-1.5 mm anterior and 1.5-2.0 mm posterior. Where the preparation cannot deliver that room, the material conversation is already over — under-reduction is the leading cause of chairside fracture.
Practical shorthand: molar or span, high-strength zirconia; single anterior tooth with room to spare, lithium disilicate or translucent 5Y zirconia; metal substructure requested, PFM and a two-week schedule. The working days for each option are itemised on the turnaround page, and the records to send with the case are listed on the scan-to-seat page.
Further reading