Members of a U.S. advisory panel voiced mixed opinions about the safety of Mentor Corp.‘s silicone breast implants on Wednesday as they debated whether to recommend approval of the devices.

The advisers to the Food and Drug Administration were set to vote later on Wednesday on whether to back Mentor’s silicone implants and the end of a 13-year-ban on the products for most women.

On Tuesday, most panel members said Inamed Corp.‘s silicone breast implants appeared safe in the short term, but they later voted 5-4 to recommend against approval.

Inamed shares fell more than 4 percent on Wednesday, while Mentor shares gained more than 2 percent.

Views on whether Mentor’s implants would be safe over their expected lifetime were mixed, said Dr. Michael Choti, the panel chairman.

“Up to ten years, many, but not all, (panelists) felt assured” that Mentor’s implants were safe, Choti said.

The FDA will consider the advisory panel’s input when deciding whether to lift sales restrictions imposed in 1992 amid concerns that leaking silicone could cause disabling diseases.

Mentor officials said they had more information than Inamed about when and why implants break, as well as research showing implants improve self-confidence for women who got them to rebuild breasts after cancer surgery or others who sought bigger breasts for cosmetic reasons.

Improving self-confidence “is as integral to health and well-being as any medical issue,” Mentor Chief Executive Josh Levine told the panel.

Studies have failed to find a connection between silicone implants and Rheumatoid Arthritis, lupus and other chronic diseases that many women tie to the devices.

The implants can cause pain and other local complications, and they can break and require new operations to replace them.

In a Mentor study of about 400 women, 1 percent of implants ruptured over three years. The breaks did not cause symptoms but were detected by MRI scans.

Mentor also pointed to about 100 women who were treated by a British surgeon and followed for 12 years. Those patients had no ruptures until at least seven years after implantation.

But FDA reviewers said Mentor’s conclusions about the lifetime of implants were “of limited value” because the data had several limitations, including a short tracking period of two to three years for most of the women.

Many women and plastic surgeons say silicone implants look and feel more natural than saline breast implants - the only option for most women in the United States. Supporters say women should be able to choose silicone implants if they are fully informed of the risks.

Implant makers also say today’s silicone implants are more durable than older versions, and the gel is stickier and less likely to migrate.

In the United States, only breast cancer survivors and others needing reconstruction or implant replacements can now receive silicone implants, through clinical trials.

According to the American Society of Plastic Surgeons, more than 264,000 cosmetic implant procedures and nearly 63,000 breast reconstructions were performed in 2004.

Inamed, which is being bought by Medicis Pharmaceutical Corp., said on Tuesday it will keep collecting data on its breast implants. The FDA rejected an earlier application from the company for silicone implants in January 2004.

Inamed shares closed down more than 4 percent at $63.51 on Nasdaq. Mentor shares gained 2.2 percent to close at $35.33 on the New York Stock Exchange.