The Food and Drug Administration lifted a 14-year ban on the use of silicone gel breast implants in the United States.

The federal agency approved implants manufactured by two California companies, Mentor and Allergan, for breast reconstruction and cosmetic breast augmentation, but limited cosmetic use of the implants to women ages 22 and older.

The decision appeared to end a controversy over the safety of silicone implants that lasted more than two decades and resulted in thousands of lawsuits by women who claimed the implants leaked and caused a number of diseases, including cancer and rheumatoid arthritis. The dispute led to the bankruptcy of the manufacturer Dow Corning, a federal moratorium on the use of the implants, and, finally, findings by both the Institute of Medicine and the Food and Drug Administration that the devices do not cause major illnesses.

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.

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.