Foreign materials such as collagen add volume when they are injected into the lips. In the long run, however, they may give gravity a helping hand in causing the lips' downward slide.

"Adding more volume to the lips may make them heavier and cause the lips to drop even lower," Yuksel said.

Using a technique called "lip suspension," Yuksel inserts sutures through the inside of the nose to the underside of the upper lip, lifting the lip up and out. The procedure takes 10 to 15 minutes and is done under local anesthetic. Healing takes about two to four weeks.

The final result restores the upper lip to its more youthful position and makes it look fuller. For an even fuller look, fat or scar tissue harvested from the patient can be injected into the lip.

"Lip enhancement has long been the "foster child" of plastic surgery, because other areas of the face have received more attention," Yuksel said. "I think that is changing because more people are realizing that the lips are a central element of the face. They are one of the first things you notice when you look at someone."