What procedure do you recommend for long jaw with wide square chin? (photos)

The chin shape and size can be changed with a reduction genioplasty; both width and height. It is difficult to provide more input without a full set of radiographs. You may benefit from mandibular angle implants.

What you are demonstrating is a classic inverted-t shaped bony genioplasty, also known as mini V line surgery. Besides the midline wedge of bone removed from the chin, some vertical length needs to be removed as well.

A genioplasty to alter the chin 3 dimensionally is quite straightforward. Additionally one can reshape the jawline from the angles to the chin depending upon the clinical review.