Metal Mouth Message Board

I went for my 3rd adjustment yesterday, and today whilst cleaning i noticed that the bracket on my bottom tooth right at the back has no lig on? I was wondering if it's likely the ortho done this purposely, or is it more likely the lig had popped of and i just hadn't noticed?

Sometimes they use wires instead of coloured elastics at the back when I have adjustments. The wire blends in with all that metal.