The singer is said to keep 20 new toothbrushes.
"We won't go anywhere without a stack of brushes," showbizspy.com quoted a source as saying.
"When she was a kid she had 13 cavities. So she now brushes her teeth six times a day."
The 27-year-old earlier revealed that her tooth-cleaning obsession was inspired by Britney Spears.
"I brush my teeth all the time. I wanted them to be, like, Britney Spears white. I used to grow up seeing her music videos and be like, ‘What does she do? Does she get a new set of teeth all the time? They're so white,'" she said.
"I'll brush my teeth [after] breakfast, lunch and dinner... I did have 13 cavities at one time, so you can imagine why I'm so freaked out. When I was a kid I didn't really go to the dentist a lot and when I finally went, they were like, ‘You might as well get a new set of teeth,'" she added.