Background: Like all surgical implants used in the body, chin implants do have some long-term effects. This is particularly true when they are used improperly or are inadequately positioned. Long-term effects could be underlying bone resorption and loss of horizontal projection. This is most commonly seen with the chin implant is positioned too high and rests in thinner alveolar bone closer to or over the tooth roots.
Case Study: This is a 50 year-old female with the desire to improve her chin position. She had suffered with a short chin her entire life. But she had a history of having had a rhinoplasty and a chin implant in another country when she was 21 years of age. Despite this early surgery providing some improvement, she was still never really satisfied.
Because she was currently in orthodontics for teeth straightening (more older people are doing it than ever before, I have even see a 65 year-old in braces!), a lateral cephalometric x-ray was available for review. It clearly shows a small chin implant that is positioned above the most anterior point of the bone. The implant has eroded into the bone by about 50%, exhibiting a well-described phenomenon known as implant-related ‘pressure resorption’.
Her surgical options were to remove and replace her old implant with either a new larger one in a better position or to move the chin forward (advancement osteotomy) after implant removal. While either approach is a better option than what she had, the amount of chin advancement that she needed made a bone-based operation the best choice. (it could move the chin the furthest forward without using a lot of foreign-material to do it)
The operation was performed through an intraoral approach. The old chin implant was found exactly where the x-ray showed it to be, on the bone at the level of the labiomental crease significantly above where it should ideally be placed. It has settled into the bone over time from the pressure of the overlying soft tissues.
The implant was removed and a horizontal chin osteotomy was performed. The chin bone was brought forward as much as possible, keeping the back edge of the chin bone against the front edge of the bone above the moved segment. It was plated into this new position with a specially-designed chin plate with a built-in movement of 12mms forward.
While a bigger advancement could have been tolerated, the aesthetic change was a big improvement. It would have been possible to enhance the advancement even further by placing an implant in front of the osteotomized chin bone. When done together, I call this procedure an ‘extreme chin augmentation’.
Case Highlights:
1) In cases of severe chin shortness, a large implant over time will eventually settle some amount into the underlying bone.
2) Chin implants placed through the mouth can move upward from their desired position on the pogonion. This can be avoided by screwing them into position.
3) When the chin deficiency is large (> 10mms), it may be better to consider a chin osteotomy long-term rather than an implant in some cases.
Dr. Barry Eppley
Indianapolis, Indiana