Sliding genioplasty revision adding projection?

Once the bone is fully healed from the original genioplasty, you can perform a second one. It depends on the aesthetic goal you are trying to achieve (how many mm advancement, if you want more width ect...). It is possible an implant may get you the desired outcome, but implants also come with cons. As you know, a genioplasty will be a life-long procedure. If you and your surgeon have discussed a plan and outcome, I almost always suggest a genioplasty over and implant.

When the chin is very recessive, typically 10-15 mm, I prefer to perform a genioplasty then gain additional horizontal length with a silicone chin implant. The implant can be customized during the procedure to obtain the most aesthetic result. I wait 4-6 months between procedures.

The answer would depend on how much more horizontal projection you desire. If it just a few more millimeters than a chin implant overlay should be done. But if it more than a few millimeters a secondary sliding genioplasty is what is needed. It is all about how the tight soft tissue chin pad will respond to the additional horizontal projection is needed.