When is the optimal time to select the shade (color) of a porcelain crown restoration?

Shade selection for porcelain restorations should be performed at the beginning of the appointment, before any dental treatment begins. This is critical for two reasons: (1) Dehydration: tooth preparation and rubber dam placement cause the teeth to dehydrate and appear lighter/more opaque than their true color. Once the tooth is dehydrated, shade matching becomes inaccurate. (2) Lighting and fatigue: color perception deteriorates with prolonged exposure to dental operatory lighting. Shade assessment should be done in natural or color-corrected light, with fresh eyes. The patient should also be in their regular clothing (not covered by a dental bib), and makeup should be noted. Shade guides should be moistened before use to simulate natural tooth hydration.