Maybe the way the bracelet is shoved in her mouth and creating a warped smile is metaphorical of the way certain drugs force you to be happy, even though it might actually be an uncomfortable and unnatural happiness.
She is wearing the teeth to create a piece of art LIKE SHE ALWAYS DOES... DUHHHH!!!!
In this case, she is expressing a theme/message on how marijuana can harm you- hence she performed her song Dope.
I don't know why I love this look so much. It's definitely one of my favorites from this past months. I guess I like things that are disturbing and that generally make people feel uncomfortable .-.