In the three years since plastic surgeon Jennifer Walden began practicing on the Upper East Side, she has performed hundreds of breast augmentation surgeries. About three-quarters of those procedures involved firm saline-filled sacs, devices that many say look and feel less natural than their more viscous silicone gel counterparts.

On November 17, the Food & Drug Administration lifted its ban on silicone gel breast implants for first-time cosmetic use, approving two brands of these implants for reconstructive and most cosmetic surgeries — a decision that Dr. Walden and many of her colleagues are applauding. “My reaction was one of excitement, because it does offer such a nice, natural option for women,” she said. “If it were me, if it were my mother or my sister, I’d recommend silicone.”

New York is a “hotbed for plastic surgery,” Dr. Walden said, adding that each year tens of thousands of city residents go in for cosmetic enhancements ranging from Botox injections to buttocks lifts to breast implants. Now New York doctors must decide how to guide their patients through the decision between saline and silicone implants.

For the past 15 years, the only women who could opt for the more life-like silicone gel implants were those seeking reconstructive surgery, suffering from certain medical conditions, or replacing existing gel implants. All of these patients were required to enroll in clinical trials.

“Surgeons are generally happy that the FDA has taken this stance,” the chief of plastic surgery at Manhattan’s St. Luke’s-Roosevelt Hospital, Mark Sultan, said. “It gives patients more choices, and allows us to provide them with better results in many instances. That’s the prevailing thought.”

Dr. Sultan said that just because these implants have become more widely available doesn’t mean that they’re the best choice for the approximately 365,000 American women who get breast implants each year. The choice should be made on a patient-by-patient basis, he said. “There are some definite advantages to saline: Incisions are, generally, smaller; mammograms tend to be more accurate, and leaks are less likely to cause tissue inflammation.”

Silicone gel breast implants hit the market it in 1960s. In the decades that followed, many women sued implant manufacturers, alleging that the devices had ruptured and caused them to develop autoimmune diseases and other illnesses. In 1992, the federal ban went into effect. Three years later, an implant-maker, Dow Corning, filed for bankruptcy, faced with crushing class-action lawsuits involving hundreds of thousands of women who claimed their breast implants had made them sick. However, the results of several clinical studies have turned up no evidence that silicone gel implants are dangerous.

A 64-year-old Queens resident who asked only to be identified by her first name, Barbara, decided on silicone implants when she went in for breast augmentation surgery in 1975. She had them supplanted with saline implants 18 years later, after the news broke of silicone’s possible health hazards. “They looked great, they felt great, but I was really swept up in the fear,” she said of the silicone implants.

Barbara, a patient of Dr. Walden, has since had to get two pairs of saline implants removed — one ruptured, and the other caused an infection — and plans to have a pair of silicone gel implants put in early next year. “I was thrilled to hear that the silicone was back on the market,” she said.

Dr. Walden, who was involved in the clinical trials for the new implants, said the new generation of implants is sturdier than its predecessors. Their filling is so cohesive that even in case of a rupture, “the gel stays in the implant pocket, and does not leak or seep into the tissue.”

“It’s kind of like Jell-O — it shakes, but it won’t move,” she said.

In order to detect ruptures, the FDA is recommending women with silicone gel implants to get an MRI three years after the augmentation surgery, and once every two years thereafter. The administration will also be conducting a 10-year, 40,000 patient post-approval study.

The Washington-based National Women’s Health Network disapproves of the FDA’s decision to lift the ban.

“We know they rupture after some period of time, but no one is saying at what point they’ll need to be replaced,” the Network’s program director, Amy Allina, said. “And what happens to a woman’s health as a result of a rupture? Women should have answers to those questions before they put these in their body.”

The two California-based companies whose silicone gel implants were approved earlier this month by the FDA are Allergan, which also manufactures Botox, and Mentor. (The FDA has limited purely cosmetic use of the silicone implants to women 22 or older.) Both companies require physicians wishing to purchase the silicone gel implants to complete Web-based forms that review indications, safety procedures, preoperative planning principles, and operative techniques.

Some surgeons still have concerns, however. The online certification process sets the bar too low, a plastic and reconstructive surgeon who practices in Great Neck, Peter Neumann, said. “Filling out a questionnaire is not a safeguard,” Dr. Neumann, who was also involved in the products’ clinical trials, said. “Science shows silicone implants are 100% safe, but opening up their use to any doctor who wants to put in an implant — that’s a very dangerous situation. My feeling is that doctors need to be trained, that they should be required to take a course, or else new problems may occur. We may be opening up a Pandora’s Box.”

An instructor of plastic surgery at Albert Einstein College of Medicine, Zachary Gerut, said he’s read clinical studies about silicone gel implants and doesn’t believe there’s any evidence that they cause autoimmune diseases, or other illnesses. “The absence of evidence isn’t the evidence of absence,” Dr. Gerut, who practices in Hewlett, said. “Do I believe they’re safe? Absolutely, but I’m not going to say to my patients, ‘This is safe.’ I’m going to say, ‘You’re going to decide if this is safe for you.'”

Dr. Gerut said saline, unlike silicone, is undoubtedly safe. “You’re putting something in your body that’s already there,” he said. “If they leak, it’s no more dangerous than drinking a bottle of club soda.”