Informed consent was obtained for experimentation with human subjects. The patient’s face and mouth were prepared, and general anesthesia was administered, where local anesthesia was infiltrated by lidocaine 2% and epinephrine 1:100,000.
Genioplasty incision was made at 5 mm distance from the mucogingival line.
After bone marking, chin osteotomy with Balcony fashion was performed in two parts; superior rectangular part (from ab to a’b’ level) and a trapezius part (from a’b’ to cd level) (Fig. 1).
Osteotomy should be started in the superior part along (ab) line 5 mm away from canine apexes and be continued to the inferior line (a’b’). Only bone cortex and minimal cancellous bone should be separated from the rest of the bone and lingual cortex with the aid of the sagittal saw. It can be performed with angulation of 30–45° to the labial surface of lower incisors down to (a’b’) line with a swiping movement (Figs. 1 and 2).
Angles of the rectangular part were 90°. In the inferior trapezius part, the osteotomy was continued from (a’b’) to (cd) level, which is the inferior border of mandible. Osteotomy along lines (a’c) and (b’d) was continued similar to a routine genioplasty osteotomy while maintaining adequate space from mental nerve and mental foramen (Figs. 1 and 2).
Note that the osteotomy at the level of (a’b’), the junction between upper and lower parts of the osteotomy design, should be done completely bi-cortically with maximum extension along (a’b’) level. Also, care must be taken to prevent unfavorable fractures of mono-cortical upper part. Meanwhile, c and d angles vary due to the level of augmentation required for the chin.
More acute angles lead to increased length of (a’c) and (b’d) lines and more extension beyond mental foramina, yielding a greater width along the inferior border, which is esthetically desirable in men [3]. On the other hand, if (c) and (d) angles are obtuse, it makes osteotomy lines (a’c) and (b’d) shorter, resulting in lower width in the chin and sharper view, which is esthetically desirable in women [3, 8].
The lengths of (bb’) and (aa’) are variable depending on the chin height, which is defined as the distance between the alveolar crest and Menton (Figs. 1, 2 and 3).
To determine the effect of this surgical technique on the depth of the mentolabial fold, the distance between the fold and the line perpendicular to the Frankfurt plane was measured in MeshLab® (http://meshlab.sourceforge.net, version 1.3.3), before and after surgery. For this purpose, facial 3D scans were also captured by Intel® RealSense™ before and after surgery (Fig. 4).