I have layered Artefill in the same area as Juvederm and Perlane (as these products were fading) and have seen no problems at all. I would not place Artefil too soon after HA fillers, but after several weeks, when the HA filler is set/smooth, it should pose no problems.
What Are the Risks of Mixing a Temporary Filler with Artefill?
Doctor Answers 3
Safe to use both Artefill and other fillers in the same areas
There are no problems using Artefill in areas where other fillers have been injected and visa versa. In fact, I often will layer a thinner filler such as Juvederm Ultra over Artefill or Radiesse to treat finer lines that overlie deeper lines and wrinkles.
Mixing temporary fillers with Artefill
I presume you are not trying to mix them in the same syringe, but just inject a temporary filler after Artefill? If so there is not any risk above and beyond the risk of adding a filler without Artefill. Artefill in fact has a temporary filler mixed in with it, bovine collagen. As long as you utilize an experienced injector it should be safe.