When does Suncoast Ceramic Studio need prep shades (i.e. Stump shades)? And why?

We need prep shades when all-porcelain restorations are requested. This includes e.max press, e.max CAD and Empress. The shade of the prep can show through the porcelain restoration and alter the final shade. We make ingot or block selections based on the prep shade and the final shade requested, these choices will block out or utilize the underlying prep shade depending if the prep shade is dark or light.