To assure clinical success, the following minimum material thickness is recommended.

Preparation

Anterior Crown 1.5 – 2.0 mm incisal reduction 1.0 – 1.5 mm labial and lingual reduction Round the internal line angles Chamfer margin	Posterior Crown 1.5 – 2.0 mm occlusal/incisal reduction 1.0 – 2.0 mm axial reduction Round the internal line angles Chamfer margin

The optimal preparation is a shoulder or chamfered preparation with a circumferential step or chamfer which must be applied at an angle of >5° (horizontal). The angle of the preparation (vertical) should be 4° or larger. The inside angle of the shoulder preparation must be given a rounded contour.

Contraindication:

We do not recommend a feather edge, as it does not provide adequate reduction for the porcelain buildup, or the trough (or gutter) shoulder because the outer most edge may not be detected when scanned.