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There are many misconceptions of the body’s biologic response to the placement of the commonly performed chin implant. The chin bone, while not entirely different from the rest of the facial bones at the osseous level, is unique in being a singular bony prominence that creates the leading edge of the lower third of the face. The overlying soft tissue chin pad is firmly fixed to the bone as it tightly wraps around it.

Thus when a chin implant is placed, regardless of the material or route of insertion, there is certain amount of pressure placed on the bone through the implant by the tightness of the overlying soft tissue chin pad. As a result the body must alleviate this pressure through a normal biologic phenomenon known as passive settling. This means the implant will settle into the bone a bit until the pressure is relieved. This creates an imprint on the bone seen if the implant is physically removed or digitally removed on a 3D CT scan. This is a limited process that is not associated with inflammation.  The clear and sharp imprint of the implant on the bone indicates the lack of inflammation. 

This process has been historically misinterpreted as ‘bone erosion’ which is an active inflammatory process that dissolves bone and will not stop until the inciting agent (implant) is removed. The origin of this misinterpretation comes from looking at plain radiographic side view images of the chin (lateral cephs) where the implant can be partially seen into the bone. it is true that if the implant is high enough over alveolar bone, which is much thinner than the bone at the bottom of the chin, that implant settling may cause tooth sensitivity…but this is very rare.  Contemporary 3D CT scan images provide a more accurate biologic view of the implant-bone interface.

There is also another commonly seen biologic reaction to chin implants that is less spoken about but well known. This is bone overgrowth that occurs around the edges of the implant in varying amounts. This can be seen in 3D CT scans as well as during chin implant removals/replacement. I have even seen bone growing up through the preformed holes in certain styles of chin implants. Such bone overgrowths are a direct result of the subperiosteal elevation which is a stimulus for osteogenesis. The implant merely provides surface onto which the bone may form. Such a phenomenon would not happen if the implant was causing a true inflammatory reaction throughout its surfaces.    

Dr. Barry Eppley

Indianapolis, Indiana

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