The ideal preparation for PFMs is a chamfer margin preparation. If a porcelain labial margin is prescribed, then a shoulder margin preparation is required.
Feather-edge margin preparations are indicated for full-cast restorations.
If an adjustment is required on the ceramic, use a fine diamond with water and air to keep the crown cool.
To contour the ceramic, polish with a pink rubber wheel and diamond polishing paste (Brasseler, Shofu, Vident).