What is causing this groove to form? (Photo)

At least from the one photo provided, there appears to be volume deficit in the lower third of the face that is like the underpinning of the changes seen in the photo. A robust HA volumizing filler placed injected in the region of the posterior angle of the jaw in the cheek and along the jawline will likely significantly improve the changes in the lower third of the face around the chin region. For the particular dent that troubles you, the use of a more superficially placed low viscosity, malleable, cohesive HA filler will likely elevate and smooth this quite easily. I gave up using fillers, like Radiesse and Sculptra, many years ago, since advances in HA filler technology led to longer lasting HA fillers nearly rivaling the durability of these other fillers, and possess the significant advantage of being able to be easily dissolved with hyaluronidase should the need ever arise. You would be wise to consult with an experienced, board certified cosmetic dermatologist filler expert. Hope this helps and best of luck.

Even though sculptra can be used to restore volume of the face, there’s nothing better than using your own fat, which is removed from another area on your body, where the fat is stubborn and then placed into the face. With fat grafting, when done by an expert Plastic surgeon, the results are extremely natural and practically permanent, I hope this helps and good luck from New York City Plastic Surgery