Kim Kardashian Still Wears Her Retainer

 Jason LaVeris/FilmMagic

Nerd alert!

Kim Kardashian may look glam on the red carpet — but she still wears her orthodontics while chilling at home.

"I have the rest of the night off…robe, pony tail, retainer, face mask and book editing all night…sexy fun!" joked the reality star, 29, on Twitter. (She's been working on a tome with her sisters, Kourtney, 31, and Khloe, 26, called Kardashian Konfidential.)

PHOTOS: Kardashians as kids!

Soon, Kardashian could be applying face masks to others: "I want 2 go 2 beauty school so bad," she also Twittered late Wednesday.

The E! reality star recently posed in her lingerie with 16-year-old Justin Bieber for an Elle magazine shoot.

PHOTOS: Kardashians' hot bikini bods

"It was so much fun," Kardashian tells the new issue of Us Weekly of taking the pics in the Caribbean earlier this summer. "Bahamas and the Biebs!"

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"He is a very sweet kid," continues Kardashian, who received death threats when Bieber jokingly Twittered she was his "girlfriend" after they met at the White House Correspondents' dinner in May. "A great guy!"

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