Possible to get bone necrosis from chin implant? Best to place implant over or under periosteum?

Chin bone necrosis never occurs from a chin implant. Passive bone remodeling/adaptation occurs under many types of chin implants not just silicone. This is a normal biologic response. Placing a chin implant above or below the periosteum is irrelevant, the tissue response will be the same.

 Hi, I have performed many facial shaping procedures, including Chin Augmentation with dermal fillers or silastic chin implants, for over 30 years.  Chin necrosis is extremely unlikely with chin implant surgery as the blood supply to the chin bone is not disrupted.  When the chin is weak, this creates an imbalance making the nose appear larger, the mid face top heavy, the lower face looks short, de-emphasizes the lips and allows early formation of a "double chin".  
 Proper placement of a silastic chin implant adds forward projection to the chin thereby creating harmony and balance to the lower face.  Using the same incision, liposuction can be performed to reduce the fat and further shape the neck.  Excess skin, from below the chin, can also be removed through the same incision.  
 I have found that placement of a silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty (requires extensive tissue dissection, bone cuts and placement of metal screws and plates to secure the cut bone segments).  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  The silastic chin implant should be placed "below" the periosteum in my humble opinion which helps stabilize the implant.Hope this helps.