Is it possible to get osteonecrosis from a silicone chin implant? How would you notice if so? Is there any symptoms or will the bone crack or dissapear suddenly? How can this be avoided? Also, where is the right placement of a chin implant- over or under periosteum? Someone in here says over because periosteum helps protect the bone from erosion. Others says under. So, where is safest to place chin implants to avoid bone erosion, bone necrosis and migration of the implant?