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Kylie Jenner, 17, admitted to using temporary lip fillers. Reuters

Seventeen-year-old Kylie Jenner shocked “Keeping Up With the Kardashians” fans Wednesday when she admitted she’d been receiving temporary lip fillers for months. The youngest member of the Kardashian-Jenner family, Jenner had sidestepped plastic surgery claims last year when she suddenly appeared to have a fuller pout. She denied that she’d had any type of procedure done, reminding everyone that she was only 17.

But now Jenner has come clean, admitting that she did have some injections. "I have temporary lip fillers, it's just an insecurity of mine and it's what I wanted to do. I'm just not ready to talk to reporters about my lips yet because everyone always picks us [the Kardashians] apart,” Jenner said in a preview for Sunday’s episode of her family’s E! reality show.

Jenner said she was afraid to admit that her fuller pout wasn’t completely natural.

“I want to admit to the lips, but people are so quick to judge me on everything, so I might have tiptoed around the truth, but I didn't lie," she added.

Jenner, who is not yet 18, would have needed an adult's permission to undergo the procedure.

“Injectable facial implants, also known as dermal fillers, wrinkle fillers or facial soft tissue fillers, are medical device implants approved by the Food and Drug Administration for use in helping to create a smoother and/or fuller appearance in the face, including cheeks and lips,” the FDA says on its dermal fillers page.

What exactly did Jenner use to enhance her lips? The 17-year-old hasn't discussed it yet, but here are the most popular dermal fillers.

Juvederm

This filler is available for approximately $600 per syringe. It’s made of hyaluronic acid, a substance that naturally occurs in the body, and doctors say its pliable texture is why clients and plastic surgeons love it so much. The formula is also mixed with lidocaine, a numbing agent that makes the procedure virtually painless. Doctors say the effects last from six to eight months.

Collagen

Plastic surgeons and injectors typically use bovine collagen for this type of filler, which is marketed as Bellafill. The substance is also used for filling in acne scars and smile lines. Injections typically cost from $600-700 and lasts around three months.

Restylane

Restylane is another hyaluronic acid filler, and one of the most widely used. Recovery usually takes two to three days, but the treatment can cause severe bruising as an unwanted side effect. Plastic surgeons say that Juvederm is preferred over Restylane for young people, and that the substance is just a bit softer. Restylane falls into the same price range and will last about six months.