WASHINGTON - Plastic surgeons expect breast implants filled with silicone gel to supplant those containing salt water as the most popular choice of the nearly 300,000 US women a year who have their breasts surgically enlarged. In this country, silicone-gel implants now account for only an estimated 10 percent to 15 percent of the breast augmentation market, with saline implants making up the rest. A 14-year virtual ban on silicone-gel breast implants - now ended - had restricted their use to women taking part in research studies. With the Food and Drug Administration's lifting of that ban, surgeons expect the saline-to-silicone ratio to reverse slowly and eventually match the overwhelming edge silicone has elsewhere in the world where the two types of devices are sold side by side. "I don't know how rapidly it will flip, but it definitely will," said Dr. Scott Spear, chairman of plastic surgery at Georgetown University Hospital and a consultant to manufacturer Allergan Inc. Proponents say silicone-gel implants look and feel more natural than do those filled with saline, which are sold without restrictions. Allergan and a second California company, Mentor Corp., won FDA approval late Friday to resume general sales of their silicone implants, despite lingering safety questions. "There is reasonable assurance that Allergan and Mentor silicone-gel breast implants are safe and effective, and there is adequate information to enable women to make informed decisions," said Dr. Daniel Schultz, FDA's medical device chief. Though "reasonably safe," the silicone-gel breast implants won't last a lifetime. The women who get them probably will need surgery again, the government warned. Dr. Sidney Wolfe, a longtime opponent, called the implants "the most defective medical device FDA has ever approved." And a lawmaker called on Congress to investigate the FDA's approval process. The FDA approved the implants for women 22 and older, and for women of all ages undergoing breast reconstruction surgery. About 291,000 women had their breasts enlarged last year, according to the American Society of Plastic Surgeons. Another 58,000 had them reconstructed. The twin approvals came with conditions, including a requirement that the companies complete 10-year studies of women who have already received the implants to check for leaks, as well as begin new decade-long studies of the safety of the devices in 40,000 women. The FDA set the age minimum because women's breasts aren't fully developed before then. FDA warned that the implants are not without risk and that women may not immediately know if their implants break. That means women with the implants will need to undergo regular MRIs to catch those so-called "silent ruptures." Silicone-gel breast implants first went on the market in 1962, before the FDA required proof that all medical devices be safe and effective. Thirty years later, they were banned amid concerns about their safety. At the time, there were worries about a possible connection to a variety of diseases, including cancer and lupus. Alarming cases of ruptures added to the concern. Since then, most studies have failed to find a link between silicone breast implants and disease. A pair of implants typically make up about $1,800 of the roughly $5,000 to $8,000 cost of breast augmentation surgery. They are about twice the price of saline implants, said Allergan president Michael Ball.