Bristol Palin's "corrective" surgery: Did she need it?

(CBS/AP) Did Bristol Palin have plastic surgery? The 20-year-old daughter of former presidential candidate Sarah Palin says absolutely not. Her new face - thinner, with higher cheekbones and an angular jaw - is the result of surgery, she says, but not of the cosmetic sort.

She says she had corrective jaw surgery in December, one month after finishing third on "Dancing with the Stars."

"Yes, it improved the way I look, but this surgery was necessary for medical reasons," she told US magazine. "I wouldn't get plastic surgery unless I got in an accident or something terrible and got disfigured."

Palin said she had the procedure so her jaw and teeth could properly realign. While growing up, she wore braces and a device to help correct an overbite. But she said her dentist warned her that she'd have to have surgery one day.

Doctors call corrective jaw surgery orthognathic surgery and say it can help with a variety of problems, including difficulty chewing or biting food and swallowing. The surgery can also reduce chronic jaw pain and excessive tooth wear.

The surgery can take many forms, according to the website of the American Association of Oral and Maxillofacial Surgeons. In some cases, bone is added, taken away, or reshaped - with screws, wires, and rubber bands used to keep the jaws in the new position. Incisions are usually made in the mouth so that scars are not visible.

In many cases, the surgery dramatically enhances the patient's appearance. As for Palin, she told the magazine, "I look older, more mature and don't have as much of a chubby little baby face."