ANSWERS

How thick should a posterior crown be?

Posterior crown thickness depends on the material. Monolithic zirconia crowns require 1.0 to 1.5 mm occlusal reduction and 0.5 mm axial. Lithium disilicate (e.max) needs 1.5 to 2.0 mm occlusal and 1.0 mm axial. PFM crowns require 2.0 mm occlusal for metal-ceramic coverage.

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Why it works this way

Thickness by Material

The answer changes per material because flexural strength changes per material. Monolithic zirconia (1,200 MPa range for 3Y-TZP, higher for 4Y and 5Y formulations) tolerates 1.0 mm occlusal in non-bruxer cases and 1.5 mm where load is high. Lithium disilicate sits at roughly 400 MPa and needs 1.5 mm minimum occlusal, 2.0 mm preferred in second molar positions. PFM requires 2.0 mm occlusal to accommodate the metal coping plus ceramic overlay without compromising either layer. These ranges align with manufacturer IFUs (Ivoclar for e.max, 3M for Lava) and the 2019 ADA clinical guidance on monolithic restorations.

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Can zirconia crowns be made thinner than e.max?

Yes. Monolithic zirconia at 1,200+ MPa flexural strength tolerates 1.0 mm occlusal reduction in non-bruxer cases, where lithium disilicate (e.max) needs 1.5 mm minimum. This is why zirconia is the typical recommendation when a posterior prep comes in under-reduced. The trade-off is esthetics: traditional 3Y-TZP zirconia is opaque, though 4Y and 5Y formulations have closed most of the esthetic gap for posterior use.

What happens if a posterior crown is milled below the material minimum?

Chip-out, fracture, or debond, usually within 12 to 24 months. Posterior occlusal loads run 150 to 250 N in normal function and exceed 500 N in bruxers. Sub-minimum thickness concentrates stress at the thinnest point, which is typically the central groove. Dani Dental flags any case where prescribed material conflicts with available clearance before milling, and the assigned technician contacts the referring office directly to resolve.

Does Dani Dental adjust crown thickness for bruxism cases?

Yes, when the case prescription notes bruxism or wear facets are visible in the intraoral scan. The standard adjustment is +0.5 mm occlusal over the material minimum, and the material recommendation typically shifts to 4Y or 5Y monolithic zirconia for second molars. The technician on the case will note the adjustment on the work ticket so the referring office sees the reasoning, not just the result.

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