Vertical lengthening: Is there any size limit for custom made total jawline implant? Age 20 male. (Photo)

Hi, I have performed many facial shaping procedures, including Chin Augmentation with dermal fillers or silastic chin implants, for over 30 years.   Looking at your face it has equal vertical segments = upper, mid and lower face.  In my experience this is typically the case.  When the chin is weak, this causes the lower vertical segment of the face to appear weak creating the "illusion" of a shortened vertical dimension.  Take a look at the attached video "before" and "after" placement of silastic chin implants illustrating that point.  Providing vertical lengthening of your lower face would throw the face out of balance and would "not" provide the forward projection required to correct the weak chin. Your photo sows a chin that is quite weak, even with the beard.  I suspect that the mandibular angle are also weak.  When the chin is weak, this creates an imbalance making the nose appear larger, the mid face top heavy, the lower face looks short, de-emphasizes the lips and allows early formation of a "double chin".  
 Proper placement of a silastic chin implant adds forward projection to the chin thereby creating harmony and balance to the lower face.  Using the same incision, liposuction can be performed to reduce the fat and further shape the neck.  Excess skin, from below the chin, can also be removed through the same incision.  
 I have found that placement of a silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty (requires extensive tissue dissection, bone cuts and placement of metal screws and plates to secure the cut segments of bone).  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  In my opinion, you are a good candidate for chin implant surgery.   There are numerous shapes and sizes of silastic chin implants, some of which are rather old shapes that do not yield the desired "natural" aesthetic results.  The EAC (extended anatomical) in a size small is the most common implants that I use in women ( size medium in men ).  Proper placement and using the appropriate approach (placing the incision under the chin and not inside the mouth) are also key to obtaining the best aesthetic result.  When shaping the face with facial implants a philosophy of "more isn't better" is the proper and most effective mentality.  I prefer placement of a  silastic chin implant through a small, curved incision under the chin (submental) instead of through the mouth for the following reasons:
*The submental approach is sterile while the intra-oral approach is not.
*The submental approach requires limited dissection as it is much closer to where the chin implant needs to be placed along the center (front) and lower most sections of the chin on each side (where the wings are placed).  The intra-oral approach by contrast requires dissection all the way down the entire section of the chin in order to reach the same areas for chin implant placement.  This leads to several issues in my humble opinion.  The attachment of the chin muscle to the bone must be cut during the tissue dissection, the sensory nerves (mental) and motor nerves (marginal mandibular nerve) that move the muscles of the lips and mouth) are all in much greater jeopardy of injury because of the added dissection required.
*The added areas of dissection with the intra oral approach allows upward migration of the implant as well as an increased risk of nerve injury. In my opinion and experience there is no need to secure a silastic chin implants with sutures and screws when the following conditions are met:
 * Select a silastic chin implant ( I prefer the EAC) that doesn't have too much projection (thickness) as this becomes a problem stabilizing the implant under the periosteum when the implant is too thick.
 * Place the implant through a small curved incision under the chin which allows direct access to the periosteum (under the mentalis muscle) while preserving the muscle attachments.  This prevents upward migration of the implant which can occur when the intra-oral approach is used that severs the muscle attachments.
 * While the center or body of the chin implant should be placed at a perpendicular angle the chin bone in order to provide the proper forward projection to the chin, the "wings" of the implant should be at a lower level and follow the inferior (bottom) edge of the jaw line on either side of the chin.  When properly dissected and placed, this will be below the mental nerve foramen and be just wide enough of a dissection to accommodate the tapering wing.  There isn't enough room in this technique to allow the wings to migrate upward and contact the mental nerve.  In contrast if the dissection, along the sides of the chin (jaw line) are performed too high...this will place the mental nerve in danger and if the side dissection is too wide, the wings will have a space within which to migrate upward.
 * We have all of our chin implant patients avoid touching and feeling their chin implant for 1 month post op.  We also ask that they sleep on a U-shaped airline pillow for the same time.
  Our experience when following the technique described above is that the silastic chin implant does not need to be secured with sutures or screws and does not move.  I have placed silastic chin implants in military, SWAT, LE, professional fighters, as well as actors and many regular people who are active.  In addition, I have had the opportunity on numerous occasions to replace silastic chin implants (placed by others) that had been screwed into the bone.  During the replacement it was evident that the metal screws pushed right through the soft silastic implant as it was tightened down on the hard chin bone.  Which makes perfect sense.  So in the long run, these fixation methods alone are no guarantee that the implant won't move.  Proper placement, proper implant pocket creation and meticulous closure of all the tissues layers is what is required in my humble opinion.
Hope this helps.