Restylane and hyaluronan fillers
Restylane is a filler that, along with hyaluronan, has in recent years emerged on the beauty scene to be hailed as more durable alternative to collagen, which typically lasts about three months.
Hyaluronan is extracted from the combs of roosters. Pfizer, which manufactures the stuff, breeds its own roosters with monster combs (at one point they were bred to be so large that the roosters were unable to hold their heads up). Restylane is essentially the same thing as hyaluronan, but it based on a synthetic alternative to the rooster combs called NASHA (non-animal stabilized hyaluronic acid).
Studies show that both last a little longer than collagen: about six months compared to three months for Zyplast.
One study on the durability of hyaluronan found that only 8% of patients retained two-thirds of the level of correction after 12 months. The majority of patients found the treatment declined between three to six months.
As for hyaluronan versus restylane, there isn't much to choose between them.