It's been there for a year already I've tried using hydrogen peroxide but nothing,what is it?
certain types of bacteria in the mouth will cause the tartar or calculus to turn greenish in colour. This usually happens when plaque accumulates around the gums. If left unbrushed it will harden and form this greenish tint. The good news is that a registered hygienist or a professional cleaning at your dental office will remove this tartar and improve the health of your teeth and gums!
