The short answer is yes, and I have done it quite a few times already using robust HA lifting and volumizing filers. Because there is already the presence of a foreign body (I.e. the implant) at the site, absolutely sterile technique and skilled, precise placement of the filler is essential to avoid adverse reactions. You would be wise to make sure to consult with an experienced, board certified cosmetic dermatologist filler expert and best of luck. As a note to other readers of this answer, I would like to emphasize my preference for considering the use of robust HA fillers in general for chin projection augmentation, rather than relying on surgical implants. Implants are permanent. That is true, and that is the big attraction for this procedure. But there are changes, such as loss of fat, muscle and even bony tissue with aging in the surrounding area. So, what may look nice right after the surgery may not look so right five or ten years later, necessitating the removal and replacement of the implant (I.e. a second surgery) or the additional use of filler, as in this case--reason enough in my opinion to consider filler treatment first from the outset and avoiding the expense and downtime of surgery in the first place.