what makes the gums turn blue
Gum discoloration of this type is called an amalgam tattoo, which is caused when tiny pieces from a filling or cap wedge themselves into the gums. This issue often looks like a blue or black tattoo in the mouth, and it too is harmless. Smoking, certain medications such as minocycline, antimalarial agents, or tricyclic antidepressants, or metal-based crowns or fillings may also cause gum discoloration.