You absolutely should wait several weeks for all of the Voluma to be dissolved before injecting a new product. Voluma is thick and it can take several sessions of Vitrase to dissolve the product. Best, Dr. Green
You will need to wait after dissolving the filler before having Volbella reinjected as the hyaluronidase will still be taking effect days after having it injected. Your practitioner will advise you when you should come back for the Volbella injection.
No, I would wait for all the product to dissolve first and then consider redo with the other product.
Sorry to hear that you are having this problem. The use of Voluma for lip augmentation is starting to gain popularity among plastic surgeons and dermatologists because it lasts longer and plumps the lips nicely, but it is an "off label" use for the product, which means that the manufacturer has not yet provided enough data to the FDA for approval for use in that area. However, your dermatologist did nothing wrong, as off label use for products is legal. For example, Botox was initially only approved for use in the mid-brow, but was used off label extensively for other areas of the face until approval was given by the FDA. I agree with the plan of dissolving the Voluma with hyaluronidase and then using another product, but I would recommend a very conservative repeat augmentation with a shorter lasting product, like Juvederm Ultra plus in your case. It may take a couple of sessions. Good luck!