For more than a decade, silicone breast implants have been banned in the United States, pulled from the market amid claims that they made women ill. By the mid-1990s, the devices had become a symbol of what many regarded as corporate America's indifference to women's health, with one company, Dow Corning, eventually filing for bankruptcy protection.

Now, silicone implants are poised for a comeback. With no fanfare, longtime implant maker Inamed Inc., formerly known as McGhan, has taken the first step toward returning the gelfilled devices to the marketplace. On New Year's Eve, the company quietly asked the Food and Drug Administration to allow it to again sell silicone breast implants. A rival firm expects to make a similar request soon, and a third company hopes to follow. Manufacturers also are testing a thicker, gumdrop-like gel that doesn't leak. Inamed's filing sets the stage for a new examination of silicone gel. Although some of the debate is expected to echo the original, this time the FDA will be ruling in a markedly changed climate -- and will have safety data in hand.

At the time the silicone implants were pulled from the market, an estimated 1 million to 2 million women had gotten them. No one denies that some implants ruptured, requiring repair or removal, and that some women became ill. "We know there hasn't been a breast implant manufactured that doesn't sometimes rupture," said Dr. David W. Feigal, the FDA's top regulator of devices. Even Inamed's patient literature tells women they may need additional surgery at some point to replace or remove the breast implant.

But scores of studies have failed to prove that implants cause the connective tissue diseases, such as rheumatoid arthritis, lupus and scleroderma, which thousands of women claimed in class-action lawsuits against the manufacturers. In a 1996 book, Dr. Marcia Angell, then executive editor of the New England Journal of Medicine, said that unscrupulous trial lawyers had manipulated the science to convince women -- and an unquestioning media -- that silicone implants were dangerous. Then came a widely publicized report from the prestigious Institute of Medicine. That report, released in 2000, found that women with silicone implants were no more likely to have connective tissue disorders than women without implants.

The furor temporarily dampened the demand for breast implants. But as plastic surgery has become more acceptable, the number of women seeking the devices has grown as well. And with it has come an increasing dissatisfaction with saline implants, the only option available to most women.

Meanwhile, even as Inamed and Mentor Corp., both headquartered in Santa Barbara, continued to produce saline implants, they were working to improve the durability of silicone implants -- laying the groundwork to ask regulators to reconsider their decision. They've changed both the composition and design of silicone implants and their outer coverings, or shells. They've made the shells thicker and more durable, to guard against silicone leakage, and they've added an extra membrane to keep silicone from bleeding through the shell.

The focus of yet-to-be scheduled hearings before an FDA advisory panel, which could come as soon as this summer, is likely to come down to whether today's silicone implants are safe enough. Much of the attention will focus on the rate of complications: Implants don't last a lifetime and can cause infection, rupture and capsular contracture -- the painful shrinkage of the scar tissue that forms around implant shells. When saline implants rupture, the salt water is absorbed by the body. When silicone implants rupture, the gel can migrate outside the chest, causing lumps called granulomas; longterm effects aren't known.

Nevertheless, many women gravitate to the more natural look and feel of silicone .

"A good silicone you can't feel, and a good saline you can always feel," said Dr. Debra Johnson, a plastic surgeon in Sacramento. " Silicone is not a perfect implant. It feels oh-so-nice, but if it breaks, it's a bit of a hassle.... Free silicone in the tissues can be nasty to get rid of."

Introduced in 1962, silicone implants went unregulated until 1988, when the FDA asked manufacturers to provide evidence they were safe.

But in January 1992, after multimillion-dollar jury awards and hundreds of lawsuits, FDA Commissioner David A. Kessler called for a moratorium on the sale of silicone implants, noting that women still had access to saltwater-filled implants. That April, Kessler made an exception: Women who had undergone a mastectomy would be able to get silicone implants through research studies; otherwise healthy women later were allowed to enter the studies. The mushrooming controversy and FDA action had a temporarily chilling effect, but demand has since grown dramatically. The American Society of Plastic Surgeons reported 32,607 augmentations and 29,607 breast reconstructions the year Kessler restricted silicone . In 2001, less than 10 years later, the group reported 206,354 breast augmentations and 81,089 reconstructions. Feigal, director of the FDA Center for Medical Devices and Radiological Health, said regulators will review all prior studies of implant safety, including an FDA-sponsored report published in 2001 that found a higher rate of fibromyalgia among women who had silicone leaks from implants that were at least 8 years old.

"The [Institute of Medicine] report didn't find convincing evidence about connective tissue diseases, but commented quite extensively about local complications," he said. Depending on the agency's satisfaction with manufacturers' silicone studies and two years of patient follow-up (90,000 women have gotten the implants through research studies), the FDA could approve the sale of silicone gels next year. It could also request further studies.