Chin augmentation is a common aesthetic facial reshaping procedure that is second only to rhinoplasty. It has been traditionally performed by the placement of a preformed implant. While many different chin implant styles have been used over the years, the basic concept of an alloplastic chin augmentation is the same.
The emergence of injectable methods for facial augmentation using a variety of injectable fillers and fat has now become an accepted treatment approach for chin augmentation. While no injectable material offers an assured and permanent outcome as that of an implant for chin augmentation, it does provide an opportunity for patients to non-surgically ‘wear’ the result for awhile to determine if it suits them.
An interesting but relevant issue when using injectable fillers for chin augmentation is how do they compare volumetrically. To create an injectable chin augmentation effect, what volume of injectable filler is needed to compare to what a chin implant does? It is not a fair comparison if one is ‘testing’ an injectable filler and the volume injected does not equal what that of the effect that a chin implant does.
Comparing facial implants and injectable fillers is done using volumetric displacement. Based on the Archimedes principle of displacement, volume of displaced water would equal to the volume of the implant. (provided that they sink in water and all chin implants do) Using the most commonly used extended anatomic chin implants (Implantech) of small, medium, large and extra large, their weights in grams and volume displacement were as follows:
Small Chin Implant 2.1 grams 1.3cc
Medium Chin Implant 2.7 grams 1.7cc
Large Chin Implant 3.4 grams 2.2cc
X Large Chin Implant 4.0 grams 2.7cc
The volume displacement of all injectable fillers is on the syringe so the comparison to chin implants is straightforward. It shows that a 1cc syringe of any of the hyaluronic acid-based fillers (e.g., Juvederm) would be less than even a small chin implant. A small anatomic chin implant more favorably compares to 1.5cc of Radiesse. Larger chin augmentation effects requires up to 3ccs of injectable filler regardless of the type.
There are other variables that affect how any of these materials create an external facial augmentation effect. The most significant would be how well does the material push on the overlying soft tissues or push off of the bone to create their effect. This is known as G Prime Force or their elastic modulus. It is quite clear that implants are stiffer than any liquid material and would have a higher resistance to deformation. (thus creating more outward effect given a similar material volume) Therefore it is probable that comparing volume displacements alone overestimates the effect of injectable fillers compared to that of chin implants.
Dr. Barry Eppley
Indianapolis, Indiana