Mark Rubin, M.D., an assistant professor of dermatology at UC-San Diego, added: "A scary part is that, if you look in the literature, every single injectable material that's out there has (produced lumps in the skin). There's nothing you can use that is completely safe."
"It is never going to be the primary filler in my practice," he says.
The filler Radiesse is made of synthetic calcium hydroxyapatite, a component of bones. It lasts about 12 months after it's injected.
"It's like injecting bone into the skin," said Gilbert, who favors shorter-lived fillers such as Restylane and Juvederm.
"Fillers that last four to eight months work the best and have the best safety profile," he said.
In contrast, dermatologist Marta Rendon of Boca Raton, Fla., and Spa Retreat owner Sandhya Gandhi, M.D., in Lake Forest, Calif., are fans of Radiesse.
"The neat thing about it is you have about 20 minutes to mold it (after it's injected)," Rendon says. "It's like silly putty."
Gandhi uses Radiesse to plump up patients' lips and to fill above the eyes for people who otherwise would need eyelid surgery.
The even longer-lived filler Artefill is made from microscopic sphere-shaped pieces of plastic, which is why it can remain in place in the body for five years or more.
That makes some physicians worry about what will happen when an aging patient's skin sags but the filler remains in its original location.
"Patients will age around those fillers," Gilbert says.
"Who knows what that is going to look like three or four years later?"