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(THIS IS A RE-POST OF DR. OTERO’S LINKEDIN POST.)
Dear colleagues and friends,
I have spent almost a year doing a clinical fellowship with Prof. Maurice Mommaerts at the European Face Centre in Brussels, a referral for hemifacial microsomia and surgery. I have noticed that patients are increasingly aware of facial asymmetries, although many of them are not related to malocclusions. I would love to hear how these patients are treated in other clinics.
I will describe the treatment options we currently use for unilateral or bilateral jaw angle deficiency, which detailed in an interesting paper by Büttner and Mommaerts (2015). The causes of facial asymmetries will not be discussed here. Let us assume there is no malignancy or progressive disease underlying the asymmetry.
A well-defined jawline is a sign of strength, youth, health, and sexual attractiveness. The jawline is less attractive when one or more of the following are present: overlying saggy skin, excess fat deposits, masseteric hypertrophy, or inadequate bone structure. The ideal proportions have varied over time and between cultures. In the contemporary Western world, the most attractive jawline angle in the profile view is considered to be 130° (±2°) for men and 126° (±2°) for women. It should have a gentle but well-defined slope that starts at the height of the nasal ala at 65–75° degrees from the Frankfort horizontal plane (Mommaerts, 2016). In the frontal view, the male jaw width should be similar or slightly less than the distance between the left and right, with the vertical position of the angle at the level of the lip commissure. For women, the intergonial width is generally smaller, aiming for an oval shape, but this depends on the patient’s wishes and sociodemographic factors. Scientific data about this are limited.
When jaw definition is lacking, we have the following options:
1- For a transverse deficiency, hydroxyapatite and calcium carbonate are mixed with fibrin sealant and inserted through a standard sagittal split osteotomy incision as an implant for minor cases.
2- When performing a bilateral sagittal split in orthognathic surgery, the condylar segment is rotated clockwise which vertically lengthens and accentuates the jaw angle. If a step is noticed between the two segments at the lower border of the ramus, calcium-phosphate cement works well covering the gap provided the osteotomy is left undisturbed long enough for it to set.
3- For more significant jaw angle deficiencies we use a three-dimensional (3D) custom-made titanium implant. After verifying the facial asymmetry by computed tomography (CT), the DICOM images are segmented through ProPlan CMF® software, and then they are exported in STL format. The software allows this conversion if you do not use any of its additional features (e.g., performing osteotomies for orthognathic surgery).
The STL file is imported to Geomagic Freeform®, a relatively user-friendly software for processing 3D objects, which allows clay-like thanks to the haptic mouse. We establish a sagittal half and mirror it to the side that is likely to need treatment. There is an option for Boolean subtractions to precisely determine the volume needed to restore facial harmony. In cases where there is no optimal side, the angles are planned as explained above.
The file is sent to the company that makes the custom-made titanium implants. You will receive a 3D PDF to verify your design. After your approval, you will receive the titanium implant along with a 3D-printed plastic mandible so that you can test the fit. If the implant is too long, you receive a two-piece implant with matching notches (like puzzle pieces) that snap to its original shape. Please see the video above (reproduced with permission by ).
The incision is placed approximately 15 mm lateral to the oblique line of the mandible, starting at a midpoint of the occlusal plane up to the second premolar. Standard subperiosteal dissection is performed to completely expose the mandible angle. It is important to have a visual reference (e.g., the cusp of a molar) and fix the implant with two or three monocortical screws placed in an accessible area. We then use a quick cone beam CT to confirm that the implant is in the correct position. The wound is closed in layers, with Vicryl 4-0 sutures, followed by 3-0 sutures in a watertight manner. For successful healing, the incisions must be closed without tension.
This department has placed custom-made 3D-printed titanium facial implants in 24 patients (to correct asymmetries of the zygoma, frontal bone, orbital floor, and jaw) in the last 3 years. Two of these implants needed to be removed. In both cases, we believe the reason for failure was that the implants were too large: one has been replaced with a smaller implant, and the other one will soon be replaced in the same way.
Previous studies report a high rate of success with facial implants composed of alloplastic materials, such as polyetheretherketone (PEEK) or . Another option bone grafts, but they have disadvantages such as donor site morbidity and unpredictable resorption. Titanium appears to be a good material for bioactivity and osteointegration. increase in tension over the jaw angle produces a facelift effect highly appreciated by most patients.
Please share your approach to treating these patients!
Dr. Joel Joshi Otero is an Oral and Maxillofacial surgeon trained in Seville, Spain. He later worked for three years as a Specialist in Hamad Medical Corporation (biggest governmental hospital in Qatar). Afterwards, he got accepted for further training and sub-specialized in Facial Cosmetic Surgery with Professor Maurice Mommaerts in the European Face Centre in Brussels, Belgium. This one-year fellowship is granted by the European Association of Oral and Cranio Maxillo-Facial Surgery.
Büttner, M and Maurice Y Mommaerts: Contemporary aesthetic management strategies for deficient jaw angles. news 2, 1–3 (2015).
Mommaerts, Maurice: The ideal male jaw angle — An Internet survey. Journal of Cranio-Maxillofacial Surgery 44, 381–391 (2016).