New data from Inamed Corp. and rival Mentor Corp. on their silicone breast implants are of “limited value” in assessing the risk of ruptures, U.S. regulatory staff said in reports made public on Wednesday.

The Food and Drug Administration released the staff evaluations ahead of a three-day advisory panel meeting next week on whether silicone breast implants should return to the market after they were banned for most women in 1992 over health concerns.

Many women and plastic surgeons say the silicone devices have a more natural look and feel than saline-filled breast implants.

Although studies have failed to find a link between silicone implants and chronic diseases such as cancer, lupus and Rheumatoid Arthritis, some are convinced that leaking silicone can cause sickness.

“These data are of limited value to address the rupture rate over the lifetime of the device due to the short duration of follow-up,” the FDA staff wrote about Mentor’s information, adding it was also “of limited value to address the local health consequences of rupture due to the small number of ruptures observed.”

The reviewers made similar comments about studies by Inamed, which is being acquired by Medicis Pharmaceutical Corp.

Officials for both companies could not immediately be reached for comment.

Inamed shares were off $1.12 at $66.98 in early afternoon trading on Nasdaq. Medicis shares were off 81 cents at $28.82 and Mentor shares were up 2 cents at $32.78, both on the New York Stock Exchange.