How do prejowl chin implants affect the face? Do they make the same visual changes as a normal (non-prejowl) chin implant?

Hello gps111,Prejowl and chin implants are very different and address different issues.  A chin implant enhances the forward projection of the chin, and typically have wings that extend along the lower edge of the mandible to provide a natural anatomic contour.  Prejowl implants project more along those wings to fill the fold in front of the jowl.  I would discuss these options in more detail with your surgeon.   I hope that is helpful!
All my best!  Dr. Elizabeth
AtlantaFaceAndBody.com
"This answer was solicited without seeing the person, and should not be construed as medical advice."

  It is important to understand that there are pre-jowl implants, and pre-jowl-chin implants.  There is a big difference between the 2 types of implants.  In addition, each 1 of those implants are manufactured in a large variety of both sizes and shapes.  In our practice for over 25 years, we use these implants which are manufactured by implant tech.  For many  before and after examples and diagrams of the implants themselves, please see the link and the video below

 No, not even close.  Pre-jowl chin implants are much thicker along the outer segments of the implant which are typically called the "wings".  The wings are very thick in pre jowl implants, some of which have almost zero forward chin projection.    This is exactly the opposite to an extended anatomical chin (EAC) implant, which in my experience and humble opinion creates the most natural looking augmentation to the chin.  The EAC implant provides forward projection to the chin which is required to correct a "weak chin".  The implant then tapers along the wings in a similar way that the chin tapers and flows into the jaw.  I believe pre jowl implants have an extremely limited application and have used this implant once or twice in 30 years.  Both cases were in older patients with weak chins that had significant indentations on the sides of their chin.  I have performed many facial shaping procedures, including Chin Augmentation with dermal fillers or silastic chin implants, for over 30 years.  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.   
Hope this helps.