Background: Aesthetic chin deficiencies are common and most are not associated with a superior occlusal abnormality. But the converse is almost always true….when an occlusal abnormality exists there almost always is a chin deformity. Everyone knows that when the lower jaw is significantly underdeveloped the chin will be correspondingly horizontally short. And this is best treated by advancement of the entire lower jaw.
But many more minor bite deformities are either left untreated, as they are not a patient concern, or become orthodontically corrected. But the chin deformity remains. A classic example is the deep bite or when a patient has an overbite. This over closes the lower jaw creating a vertical chin deficiency and a flatter mandibular plane angle and shorter lower face. There is often a horizontal chin deficiency as well.
With a combined vertical and horizontal chin deficiency, standard chin inplants are no ideal. This will increase horizontal chin projection but the lower face will still look vertically short and the labiomental fold will get aesthetically deeper. S special type of chin implant, the vertical lengthening chin implant is one contemporary implant style option, but the historic approach is an opening wedge vertical lengthening bony genioplasty.
Case Study: This young female desired a chin augmentation and was aware that she needed a combined vertical and horizontal dimensional augmentations. She had a 50% overbite relationship and 4mms of overjet. Using a mirror she jutted her jaw forward to where it created the desired chin location. From this position the changes in chin position were measured based on the change in the bone by the lower incised edges compared to the stable upper static edges.
Under general anesthesia an intraoral sliding genioplasty was performed. The downfractured chin segments was advanced 8mms and vertically lengthened by 4mms by bending of a step chin plate. These were the measurements that were recorded by her preoperative jaw jutting maneuver. The resultant bony chin gap was packed with gelfoam collagen sponges prior to closure.
Jaw jutting can be an effective preoperative patient maneuver to establish the desired chin position when an overbite exists. This is because vertical lengthening is required which is required of very mandibular forward thrust. This allows such a sliding genioplasty (or custom chin implant) to achieve an aesthetic outcome that is within 1mm of the preoperative goal.
1) Bite abnormalities often correlate with aesthetic chin deformities.
2) An overbite relationship usually indicates some degree of a combined vertical and horizontal chin deficiency.
3) The dimensions needed for a sliding genioplasty chin augmentation can be determined by measurements taken from the new chin’s position when normalizing one’s bite.
Dr. Barry Eppley