My daughter is 15, since her wisdom teeth were removed a year ago, she keeps getting greyish staining between her teeth an along her gum line on top and bottom. This is new, has never happened before. I take her for a cleaning every two months and the staining comes off, but within 3 weeks it’s back. No one can tell us why and it’s very frustrating. She has impeccable oral hygiene, no cavities, and no high stain food in her diet at all. We’ve even tried a “white diet” and it still came back. She’s had blood work to test iron level, everything was normal. If anyone has any ideas, it would be greatly appreciated!