Does The Thickness of Facial Implants Create The Same Change On the Outside?
Q: Dr. Eppley, you have written in regards to facial implants that the translation of bone augmentation to an exterior soft tissue facial change is not a 1:1 ratio. Does this mean that a 3mm malar implant may not necessarily provide 3mm of augmentation? If so, do implants tend to give more or less augmentation than their specified dimensions? Additionally, what is the reason for it not being a 1:1 ratio?
A: The reason that augmentation of bone (a hard substance) does not translate exactly to the exterior surface of the overlying soft tissue is the compressibility factor between the two different types of tissues. If the enveloping soft tissue was as hard as bone then augmenting the bone would create an exact 1:1 ratio translation. But the soft tissue of the face has varying thickness and is soft, thus pushing on it from below is somewhat ‘blunted’. Thus the ratio of bone surface change to external soft tissue change would be less than an exact 1:1 relationship. This would be influenced by the thickness of the overlying soft tissues. The thicker it is, the less is the 1:1 relationship, the thinner it is (less fat) the closer it is a to a 1:1 relationship. This phenomenon is well established in orthodontics and orthognathic surgery where these hard:soft tissue relationships have been studied by cephalometric analysis.
Dr. Barry Eppley