Could a chin osteotomy change my square-shaped face into longer, oval shaped face? (Photo)

 Thank you for the pictures. I agree with Dr. Eppley that you need vertical height and a small amount of projection to your chin. Either genioplasty or an implant can achieve this goal. Please seek in the valuation from either a board-certified plastic surgeon or board-certified or the maxillofacial surgeon.

Do you want oval shape face?My opinion is jaw angleplasty(mandibular angle reduction) and genioplasty.Operation take one hour and recovery take one month.

You are correct about the effects of a sliding genioplasty on your square lower face. By bringing the chin bone forward and down you will create a longer and more oval facial shape. Such  similar effect can also be created by a custom designed chin-jawline implant.