The whitest shade of natural teeth is typically classified as B1 on the VITA classical shade guide, which is widely used in dentistry. B1 represents a very light, natural tooth color that some individuals may have naturally, though it's not the most common shade.
For artificial teeth, particularly in cosmetic dentistry, the whitest shade is often BL1 (Bleach 1) on the newer VITA shade guides, such as the VITA 3D-Master system. BL1 is significantly whiter than natural teeth shades and is commonly used for veneers, crowns, and other restorations to achieve an ultra-white, "Hollywood" smile.