Old metal-supported crowns, which use base metals like nickel, chromium, or cobalt in their substructures, release metal ions over the years due to the effects of oral fluids and corrosion. These ions seep into the surrounding gum tissue, causing irreversible dark gray-purple discoloration similar to a tattoo. Even if the crowns are replaced with aesthetic zirconium crowns, this gray shade may continue to be reflected from the gum. In treatment, the crown’s step margin is first slightly moved away from the subgingival area; then, the layer of tissue with accumulated metal ions in the gum is gently removed using Er:YAG laser peel-off or electrosurgical techniques. In very deep cases, a free graft taken from the connective tissue of the palate is placed under the gray area (connective tissue graft) to thicken the gum and completely mask the underlying dark color.
