The rupture issue persists: The implants do not last a lifetime, and eventually they must be removed or replaced, according to the FDA. A 2000 Institute of Medicine report found rupture rates as high as 77 percent.

Women whose silicone implants ruptured have reported years of pain, swelling, numbness and other symptoms that they blame on the devices. Leaked silicone gel can migrate throughout the body, forming lumps. Implants also can cause infection and form hard, painful scar tissue that can distort the shape of a breast.

Some researchers also worry that the platinum used to manufacture the implants can seep into the body and cause harm. The FDA says there is no evidence of that.

Proponents say silicone-gel implants look and feel more natural than do those filled with saline, or salt water. Those implants are sold without restrictions.

"It's a hugely positive piece of news for plastic surgeons and for patients and for the company — all three — because it really allows us to turn a page and to work with what we have believed for a long time is a better technology and better device," said Dr. Scott Spear, head of plastic surgery at Georgetown University Hospital and an Allergan consultant.

Last year, the FDA told both companies their implants could be approved once they met additional, undisclosed conditions. Federal advisers had narrowly recommended that Inamed's implants not receive FDA approval, citing concerns about the long-term durability. The same advisers endorsed Mentor's implants.

In October 2003, FDA advisers had recommended allowing the implants to be sold again. The agency overruled that recommendation.

Breast implants have grown in popularity for augmentation, despite a history of lawsuits. Last year, 291,000 women had their breasts surgically enlarged in the United States, a 37 percent increase since 2000, according to the American Society of Plastic Surgeons.

The popularity of implants for reconstructive surgery shrank over the same five-year period by 29 percent, to 58,000 procedures, according to Society statistics. Last year, 39,000 women had their implants removed.

Overall, the use of breast implants has grown since 1992 despite the FDA's de facto ban on silicone-gel implants.

Just three years later, Dow Corning Corp., once the major manufacturer of silicone breast and other implants, faced 19,000 lawsuits, pushing it into Chapter 11 in 1995. The company emerged from Chapter 11 in 2004, after setting aside $2.35 billion to settle claims.

Allergan Inc. shares rose $1.76, or 1.6 percent, in trading that was almost double its average volume to close at $112.50 on the New York Stock Exchange. Mentor Corp. shares increased $1.47, or 3.19 percent, also in higher than average volume, to close at $47.58.