"It's not something people should approach cavalierly," [Douglas Hamilton] said. "[Botox] you can turn over to a registered nurse who has been well-trained and not have problems. But only doctors, he added, should be injecting the permanent wrinkle fillers. Some doctors may rely on nurses, however, to administer the temporary ones. The new fillers differ in composition and durability. Two approved by the FDA in March, CosmoDerm and CosmoPlast, are made of collagen derived from human cells. Doctors say they last slightly longer than bovine collagen.