Many women are aware that implants can break down over time, requiring replacement just like car tires. Both saline implants, made out of a saltwater solution, and silicone implants, made out of gelatinous silicone, can form minute tears in their rubbery shells, causing ruptures. In the case of such defects that require product replacement, both manufacturers, Allergan Inc. and the Mentor Corporation, offer guarantees. Mentor has a 10-year guarantee to replace implants and defray some surgical fees; Allergan's warranty includes lifetime implant replacement and up to $1,200 for fees for the first 10 years.

Dr. Mark L. Jewell, a plastic surgeon in Eugene, Ore., who is a past president of the American Society for Aesthetic Plastic Surgery, said he warns his patients that breast augmentation surgery automatically guarantees a second operation at some future date. He added that many patients in clinical studies had elected to have follow-up operations to change implant type, size or position.

"Women are used to having their hair or nails done on a regular basis to maintain their appearance," said Dr. Jewell, who has conducted clinical trials for both implant manufacturers and is a consultant for Allergan, the manufacturer behind the ads running in Elle. "Ultimately, breast implants may also be a matter of maintenance."

But a rupture is only one of the local complications that may engender additional surgery. Like cocoons that grow around larvae, scar tissue can form around implants; and sometimes that scar capsule hardens and squeezes the implant, causing pain and deforming breasts. And saline implants can cause visible, tactile rippling beneath the skin.

Nearly 11 million cosmetic plastic surgery operations were performed in the United States in 2006, up by 7 percent from 2005, the group said. It also said more than 5.2 million reconstructive plastic surgery procedures were performed last year, mostly removal of tumors.

The most popular cosmetic choice was breast augmentation, with 329,000 reported in 2006. This is the first time "breast jobs" have passed nose reshaping surgery, performed on 307,000 people in 2006.

The group reported an 8 percent rise in minimally invasive cosmetic procedures such as injections to fill out wrinkles, with more than 9 million such operations. Botox treatments were by far the most common, with more than 4 million treatments in 2006.

Because the implants made of silicone gel are softer than the saline implants currently available, plastic surgeons said they would quickly become preferred among the more than 300,000 women in this country who have breast implants each year. Critics of the decision lambasted it and said that longstanding safety concerns had not been resolved. But supporters of the implants, including leading surgeons, applauded it.

"For us, it's a triumph of science," said Dr. Richard A. D'Amico of Engelwood, N.J., president-elect of the American Society of Plastic Surgeons. "We’ve always felt that the science would bear out the use of the implants." Dr. Daniel G. Schultz, director of the F.D.A.'s Center for Devices and Radiological Health, said that the agency's review, based on company-sponsored studies as well as long-term use of the implants abroad, had determined that their sale is in the best interest of women.

But Dr. Schultz warned that no device is foolproof and that there was a possibility that women would have to have the implants replaced at some point, sometimes because they rupture. Studies have found that the majority of women with silicone implants would have a rupture at some point. According to the federal agency, one study found that 69 percent of women had a rupture. "Women should know that breast implants are not lifetime devices," he said in a telephone briefing for reporters last night. "Women having these procedures done need to be prepared for the fact that there is a likelihood they will require additional surgery," he said. He also recommended regular M.R.I.'s to monitor the devices for "silent rupture," which can occur without a woman’s knowledge. He said the first M.R.I. should be performed when the implants are 3 years old. Because many of the procedures are cosmetic, it was not clear whether those M.R.I.'s would be covered by insurance.

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Defending the decision to lift the ban, Dr. Schultz said, "we have been looking at this data continuously for the last 10 years. We have been watching as data had been collected, we have been watching as data has accumulated. We believe that from a scientific standpoint, the decision that we'e making tonight is, in fact, in the best interest of American women."

But he said the agency would require the companies to conduct post-approval studies involving a total of 80,000 women to continue monitoring the safety of the implants. He said that information would be collected about rates of rupture, cancer and autoimmune diseases and effects of the implants on reproduction. That would enable the agency to evaluate concerns about the implants in a large number of women.