Should I Be Concerned About Bone Resorption With Chin Implants?
Q: Dr. Eppley, I have consulted with you in the past in regards to jaw/chin implants, and I just had a few questions for you in this regard.
I have read a lot of things about the difference between Medpor and silicone. The main concern I had was in reference to the issue of bone resorption. I know that there are many opinions out there, and I just wanted your experience and expertise as to what the pros and cons of each are.
I am especially worried about the issue of bone resorption, as I don’t want to cause myself a lot of pain and misery in 10 to 20 years. I read that silicone causes more bone resorption compared to Medpor. However, I also read that fixing the silicone implants with screws eliminates a lot of the pressure of the implants. Furthermore, I had read that bone resorption occurs at the chin. Would any occur with jaw implants as well? I would appreciate any clarity on this issue.
I also wanted to know which material feels more natural (if they do at all) when implanted.
A: The concern about bone resorption around any type of facial implant is overstated, largely clinically irrelevant and biologically misunderstood. It is not an active inflammatory response that is eating the bone away. Rather it is a passive bone remodeling response to the pressure of the implant on the underlying bone caused by the tight overlying soft tissues. It is simply put a biologic response to relieve the pressure of the tension band effect on the implant. This can result in a few millimeters or less of the implant settling into the bone which then stops once an equilibrium of pressure redistribution occurs. While largely reported in chin implants, probably because they are easy to evaluate by panorex and lateral cephalometric x-rays, this normal biologic phenomenon to an implant can occur anywhere in the body. Similar examples including breast tissue thinning with breast implants and gluteal muscle thinning in buttock implants.
You have to remember that putting a synthetic implant into the body is not natural and the tissues have grown and work based upon their natural tissue attachments and thicknesses. Once you introduce an implant into these tissues, the natural tissue volume and balance is altered and it will respond by adapting to it. A little bit of implant settling (tissue loss) is a very small price to pay for whatever aesthetic benefits that an implant may provide.
As for facial implants specifically, the chin seems to be the only location where this biologic response is seen. This is due to the natural tightness of the chin tissues and the thickness of the underlying chin bone. In most cases that I have seen, the chin implant is almost always placed or become displaced higher up on the chin bone over the thinner cortical bone.
I have seen this biologic phenomenon in both Medpor and silicone chin implants, which makes sense since both materials are non-resorbable polymers. It is just less reported with Medpor because the vast proponderence of chin implants done involve silicone materials both historically and currently.
I would not think that screw fixation would affect this biologic response either favorably or unfavorably.
Either Medpor or silicone facial implants can feel natural or unnatural based on their size, orientation on the bone, tissue location, thickness of the overlying tissues and the patient’s perception to them. Their physical characteristics (firm) are similar so their postoperative feel, all factors otherwise being the same, should be no different.
Dr. Barry Eppley