Dr. Ayman Zaghal
BDS, DDS, ABOMFS, RCSED
• Oral & Maxillofacial Surgery BDS, DDS
• Arab Board of Oral & Maxillofacial Surgery
• Palestinian and Jordanian Board OMFS
• DDS Palestinian Ambassador and a Distinguished member of the Communication & Visual Strategy Committee
• Top 100Doc Class 2022 Global Summit
• Consultant of Oral and Maxillofacial Surgery at the Al-Makkassed Hospital (Jerusalem) and the H-Clinic (Ramallah)
• Owner and Head of the Jerusalem Smile and Jerusalem Eye Specialized Dental Centers
introduction
introduction
The chin plays a prominent role in facial aesthetics. When the chin is unbalanced in relation to the rest of the face, it can create disharmony. A strong chin can convey a sense of masculinity, whereas a weak chin can cause poor neck contours and premature ageing.
Repositioning the chin, also called genioplasty or mentoplasty, is a common procedure both for cosmetic and functional purposes. Osseous genioplasty is considered the gold standard. It is a safe and effective means of creating a beautiful and balanced facial profile. The surgeon cuts a portion of the chin bone and repositions it surgically. The overall harmony of the face is due to the contribution of the balance of its different aesthetic units, in which the chin plays a key role, even to the untrained eye. The lower third of the face is the most important area when evaluating aesthetics, and an imbalance in this structure, in terms of shape, size, symmetry or position, can have considerable results on the outcome.
Genioplasty is frequently combined with other procedures such as upper and lower jaw surgery to help improve the neck contour and soften the transition from jowl to chin. It is also often combined with rhinoplasty when the nose appears too strong in relation to the chin. Genioplasty can be either a straightforward surgical plan for isolated chin disharmony or an alternative to more complex jaw surgeries with camouflaging and decompensation of the dental arches.
Advances in facial reconstructive surgery have been associated with less morbidity and more predictable results. Computer-aided surgical simulation has greatly enhanced the efficiency and accuracy of orthognathic surgery for the correction of dentofacial deformities. Virtual surgical planning (VSP) improves the efficiency of the presurgical work-up and allows for illustrating the multidimensional correction at the dental and skeletal levels. It provides preoperative insight into the surgical intervention, and the fabrication of cutting guides and templates can help decrease intraoperative surgical inaccuracies. VSP is rapidly becoming the standard of care for surgical treatment planning of dentofacial deformities. It now allows for the fabrication of custom plates, patient-specific cutting guides and custom plates, permitting precise spatial positioning of the osteotomised jaw or chin during orthognathic surgery.
AI simulation has enhanced patient collaboration by actively engaging them in the planning process. It allows for discussing preferences and visualising outcomes, ensuring alignment between expectations and reality.
Piezosurgery has become an alternative tool and is increasingly used in orthognathic surgeries. Osteotomies are performed in close relationship with delicate anatomic structures. Saws, burs and chisels are traditionally used for cutting bones. Although these instruments are highly effective, they can damage the adjacent soft tissues and nerves. These rotating instruments are potentially injurious since the production of excessively high temperatures can impair bone regeneration and result in bone necrosis. Therefore, the need for less invasive surgery and greater precision compared to the standard bur and saw encouraged the development of piezosurgery. This device is used to cut the bone with minimum damage to the soft tissues such as blood vessels and nerves. Additionally, it provides excellent visibility due to its cavitation effect.
the clinical case
the clinical case
A 22-year-old female dental student with mandibular prognathism, long anterior lower facial height and a high mandibular plane angle could benefit from a single jaw BSSO surgery at the most. She underwent a long orthodontic treatment, camouflaging by extracting teeth, levelling, aligning and compensating to restore an optimum overbite and overjet.
She ended up with a strong chin, long anterior lower face and slight chin deviation. Data acquisition began with intra-oral and extra-oral facial scanning using Trios3 IOS (3shape – Denmark), a large FOV cone-beam computed tomography (CBCT) scan, OPG and lateral cephalometric radiographs, and high-quality frontal and lateral photographs.
A treatment plan was curated using clinical examination, cephalometric analysis and 3D measurements. This incorporated the patient desires and expectations, which included a reduction genioplasty both in the anteroposterior and vertical components.
Reduction genioplasty is performed under general anaesthesia with an incision through the mouth and typically involves making a cut through the bone and either sliding the chin back or removing a portion of the chin. The chin bone is then secured in place using plates and screws.
The osteotomy cut was planned digitally by computer-aided surgical simulation technology (3Matic Materialise software). Models, templates and guides were transferred to additive manufacturing. The cutting guide was planned to be supported on the teeth with a splint and a connector in an assembly manner.
“The chin plays a prominent role in facial aesthetics. When the chin is unbalanced in relation to the rest of the face, it can create disharmony. ”
The cutting guide was designed as a hole-transferring guide for the custom plate’s holes to verify its precise place after osteotomy and movement.
The patient-specific plates were 3D-printed using selective laser melting (BTK Dental – Italy).
A homogeneous layer of highly pure titanium powder was melted using a laser selectively, based on the 3D virtual model. This was the first case worldwide to use a BTK custom solution as an extra dental fixation for osteotomised bony segments.
Custom plating adds the benefit of selecting the screw’s size, location and trajectory, avoiding thin bone, undercuts and vital structures, especially after a long orthodontic treatment.
A piezoelectric device (Mectron, Italy) was used as an alternative cutting device. Precise delicate corticotomy marks through the guide slits were made first, then a complete safe cut was accomplished after removing the whole guide assembly.
Chin reduction in the anteroposterior direction is the most difficult and least indicated technique of facial bone sculpting. Overreduction causes a flat chin from the sublabial fold inferiorly, frequently with ptosis of the soft tissue, so it should be planned with caution. AI-assisted simulation of the postoperative soft tissue reflection gives a clue to the final soft tissue result.
“Custom plating adds the benefit of selecting the screw’s size, location and trajectory, avoiding thin bone, undercuts and vital structures.”
A posterior sliding genioplasty to reduce the chin also places the inferior component of the chin into the facial view from the anterior, which gives the chin an odd appearance. A reverse wedge osteotomy should be done to avoid this adverse result and still reduce the chin. Although the amount of reduction remains limited with this technique, a minimal vertical reduction by taking out a horseshoe segment of the chin with clockwise rotation of the distal segment and slight correction of the midline shift were used here to address the 3D components of the chin reasonably with a desired soft tissue reflection.
Finally, a custom plate was designed to perfectly adapt, move and fix the osteotomy segments to their final place.
Postoperative photographs overlay the pre-operative photographs and lateral cephalometric radiographs, revealing the desired soft tissue position in the profile and frontal views.
“The overall harmony of the face is due to the contribution of the balance of its different aesthetic units, in which the chin plays a key role.”
NOTES
Resources