Teeth (2008)

High school student Dawn works hard at suppressing her budding sexuality by being the local chastity group's most active participant. Her task is made even more difficult by her bad boy stepbrother Brad's increasingly provocative behavior at home. A stranger to her own body, innocent Dawn discovers she as a toothed vagina when she becomes the object of violence. As she struggles to comprehend her anatomical uniqueness, Dawn experiences both the pitfalls and the power of being a living example of the vagina dentata myth.