You will almost certainly look different to some degree; quite how different depends on the extent of your original problem and how much the jaw(s) have had to be moved.
Orthognathic surgery aims to balance the bony framework of the face, so that all the features are in proportion to one another, producing a pleasing facial appearance and teeth that chew better.
The vast majority of patients are delighted with the results, and although there may be some difficult times during the treatment, once it is completed the benefits will often last a lifetime!
