• Successful treatment of the orthognathic surgical patient is dependent on
• Cephalometrics can be an aid in the diagnosis of skeletal and dental
problems and a tool for simulating surgery and orthodontics treatment.
• While patients seeking about facial cosmetic surgery often focus on
structures such as the nose, the eyes, and the laxity of their skin, but the
lower third of the face is an area that could be surgically modified to
improve overall facial appearance and harmony.
• The profile of a patient can be significantly altered with either a chin
augmentation or reduction procedure. This, in turn, has a significant
effect on overall facial symmetry.
What is deformity?
• Jaw deformities are a common condition, ranging from mild abnormalities to
more severe defects that can be surgically corrected. In some instances, the upper
or lower jaw — or both — may grow too little or too much, resulting in
malocclusion, the improper alignment of the teeth in relation to the first molars.
• The chin represents one of the most recognizable structures on the human face.
Numerous methods to alter the contour and appearance of the chin and lower
facial esthetic subunit have been described in the past.
• Chin deformity can be corrected by genioplasty approaches.
HISTORY OF GENIAL PROCEDURES
• Hofer in 1942 described horizontal sliding osteotomy.
• Trauner & Obwegesser in 1957 described horizontal sliding osteotomy
with intraoral incision.
• Reichenbach in 1965 described wedge osteotomy & vertical shortening
• Chin augmentation, known as genioplasty, is performed to enhance chin
projection and improve facial proportions and aesthetics . It is performed
through incisions hidden in the mouth by using either alloplastic
materials (a chin implant) or by creating a bone cut in the chin and
sliding the chin forward (osteoplastic genioplasty). These procedures
may be done alone or in combination with other cosmetic procedures.
• The chin should, however, be evaluated in all three dimensions. The width of
the chin should be assessed in relation to the overall facial shape.
• A narrow chin often has a knobby appearance, and if surgical advancement of
the chin is planned, widening of the chin should be contemplated.
• The labiomental fold, chin shape, relation to the dental midline, symmetry,
and cant of the lower border should be considered.
The primary sensory innervation to the chin area is from the paired mental
nerves that exit the body of the mandible near the apices of the premolar teeth.
The primary motor component to the muscles associated with the anterior
aspect of the chin are from the buccal and marginal mandibular branches of the
facial nerve. These muscles include the depressor labii inferioris, depressor
anguli oris, mentalis and orbicularis oris muscles.
Salient nerve anatomy as described by Hwang et al. showing the position of
the mental nerve in relation to the mental foramen and inferior border of
the mandible. A: 5 ±1.8 mm, B: 4.5 ± 1.9 mm, C: 9.2 ± 2.7 mm
• The primary muscle involved with the genioplasty procedure itself is the
mentalis muscle, which provides the primary vertical support to the
• The depth of labiomental fold may dictate which technique is suitable.
Alloplastic implants tend to deepen the mentolabial sulcus. The
mentolabial sulcus becomes less pronounced in a vertical lengthening of
• Position of mental foramen is utmost importance during surgery. The
mentalis muscle elevates the chin at a place just below the tooth roots.
• The arterial supply to the muscles of the chin area is from the inferior
labial arteries, which are terminal extensions from the facial arteries.
Biologic foundation of osseous genioplasty
• When carrying out an osseous genioplasty, a horizontal osteotomy below
the roots of the anterior teeth and the mental foramen on either side is
• After osteotomy, the distal segment of the chin remains attached to a
• Healing is optimal when the circulation of blood to bone and its
enveloping soft tissue is continuously maintained.
• In 1988, Bell and colleagues completed microangiographic and
histologic studies in adult rhesus monkeys that indicated that an intraoral
pedicle flap that involved an osteotomy of the inferior border of
mandible maintains circulation and osseous viability after manipulation
and repositioning of the chin segment.
• According to Bell’s experimental work, circulation to the dental pulp
should not be affected during the process.
CLASSIFICATION OF CHIN DEFORMITIES
• Class I macrogenia
c. Combination of both
• Class II microgenia
c. Combination of both
• Class III combined
a. Horizontal macrogenia with vertical microgenia
b. Horizontal microgenia with vertical macrogenia
• Class IV asymmetric chin
a. Short anterior facial height
b. Normal anterior facial height
c. Long anterior facial height
• Class V Witch’s chin(soft tissue ptosis)
• Class VI Pseudomacrogenia
• Class VII Pseudomicrogenia
• Carefully evaluate the teeth and the height of the mandible prior to
surgery. Long teeth with a short mandibular height is a relative
contraindication for an osseous genioplasty or an aggressive bony
A combination of Down’s, Steiner’s and Tweed’s analysis is used to assess the
relationships of skeletal and dental structures so that an accurate diagnosis of dental
and anomalies can be made. The information obtained from this analysis is considered
when performing sagittal or vertical changes in chin position.
Soft Tissue Analysis
• Gonzales-Ulloa and Stevens in
which a line is constructed
perpendicular to the Frankfort
horizontal and passing through the
soft tissue nasion.
• Merrifield’s ‘Z’ angle is a line
from the soft tissue chin tangent
to the most procumbent lip,
which forms an angle with the
• Ricket’s as a line from the tip
of the nose to the chin.
• In asthetically pleased profile,
upper lip was 4 mm and lower
lip 2mm behind the asthetic
• Holdeway suggested a
tangent line to the chin and
• This line forms an angle with
a line between the nasion and
• Degree = 7 to 9
• Zimmer’s aesthetic plane- from
the anterior nasal spine to
Down’s ‘B’ point and
demonstrated that the nose and
lips as well as the chin.
• Steiner’s aesthetic plane,
from the middle of the
columella, midway between
the curves of the upper lip
and nasal tip.
• Lastly, the skin of the lower face should be examined in both frontal and
profile views, noting the quality, thickness, and laxity as well as any
• Because these factors can impact outcome, a patient’s expectations
should be managed by discussing these factors in the preoperative
• Infiltration with vasoconstrictor
The area of dissection is infiltrated with a local anesthetic containing a
vasoconstrictor 10 minutes before surgery.
• Mucosal incision-
The mucosal incision is placed roughly 5 mm superior to the buccal
sulcus in the labial mucosa from canine to canine.
Care must be taken to identify the branches of the mental nerve,
which are often visible.
Placement of the incision must provide for a soft tissue cuff of
mucosa and muscle to suture and should be placed well away from the
attached mucosa of the teeth to prevent gingival recession.
• Muscular incision
– The incision is then completed down to the bone.
– The mental nerve should be avoided.
• Periosteal stripping
⁻ Stripping of the periosteum should strive to maintain the periosteum
intact, and avoid total denudation of the chin as this will result in
unpredictable soft tissue changes
• The procedure is done for the correction of an anterior open bite.
• Hofer (1936) demonstrated an anterior mandibular alveolar osteotomy
to advance anterior teeth in correction of a mandibular dentoalveolar
In 1959, Kole modified this procedure employing Hofer’s osteotomy
generally use some form of bone graft in the alveolar defect if significant
movement of the fragment is planned.
• Michelet and associated described this techenique in 1974.
• A U shaped monocortical osteotomy is created on the center of the
• Lateral extensions are developed below the mental nerves, which
connect to the superior aspects of the tenon corticotomy.
• Full thickness osteotomies are completed on the lateral extensions and
only through the lingual cortex on the superior aspect of the tenon.
• The resultant full thickness of bone behind the tenon facilitates the
mortising of the tenon and lag-screw fixation.
Advantages of Chin Osteotomy
i. Very versatile procedure
ii. Corrects vertical problems
iii. Stable over time
iv. Increases submental length and cervicomental angle
v. Advances genial-tongue-hyoid position, of benefit in sleep apnea
Disadvantages of Chin Osteotomy
i. Requires osteotomy, adding risk from surgery and anesthesia
ii. Vascular injury risk
iii. Airway problem risk
iv. Not easily reversible
v. Increased expense for anesthesia, OR time and fixation materials
when compared to implants
• Genial procedure or genioplasty afford the surgeon the ability to make
small but necessary changes or dramatic alteration in the overall form of
the lower third of the face.
• This can be accomplished with detailed preoperative planning and
application of good surgical technique.
In addition to the historical aspects associated with procedures, I feel surgeons must have a sound knowledge of the relevant anatomy as well.
Improper repositioning of the mentalis muscle can result in unsightly disfigurement of the chin known as a “witch’s chin” deformity
A variety of cephalometric analysis have been proposed for the evalusion of a pts profile..
Placement of reference marks. (1) The incision is placed in the buccal sulcus leaving at least 5 mm of nonkeratinized mucosa superior to the incision. (2) The mental nerve is identified and protected. (3) Reference marks are placed to assist in accurate repositioning of the genial segment.
(a) The horizontal osteotomy is performed using an oscillating saw. (b) Care should be taken to perform the osteotomy at least 5 mm below the root apex of the canine tooth and the mental foramen. (c) Ensure that the osteotomy is carried through the lower border of the mandible.
The height of the osteotomy will influence the shape of the chin. (a) A high osteotomy will make the labio-mental fold more obtuse (c) and shallower. (b) A lower osteotomy will augment the tip of the chin (d) and increase the depth of the labio-mental fold.
The horizontal osteotomy is performed at least 5 mm below the apex of the canine root and the mental foramen.
Advancement genioplasty along a high angle will reduce the height of the chin, and the opposite will occur with a setback procedure.
Vertical reduction genioplasty. (a) A predetermined segment of bone is removed from the genial segment. (b) The genial segment is repositioned superiorly and fixated.
Vertical augmentation genioplasty for incresing the height . (a) The genial segment is repositioned inferiorly and the defect grafted. (b) The amount of vertical increase is predetermined and the segment fixated with 2 bone plates (an H- or X-shaped plate)
Widening the posterior aspects of the chin. (a) The position of the horizontal osteotomy is marked. (b) Before the horizontal osteotomy is performed, a bone plate is placed over the center of the genial segment. (c) The centerline osteotomy is performed and the genial segment mobilized.
Widening the posterior aspects of the chin. (a) The centerline osteotomy is completed and the genial segments widened using the bone plate as a hinge. (b) A small bone graft is placed in the defect.
Narrowing the posterior aspects of the chin. (a) Following mobilization of the genial segment, the centerline osteotomy is completed. (b) A small triangular segment of bone is now removed from the posterior aspect of the genial segments and the genial segments are narrowed by using the bone plate as a hinge.
Widening the anterior aspect of the chin. (a) The genial segments are moved laterally to a predetermined width and fixated. (b) A bone plate is placed across the midline defect to fixate the segments. (c) A bone graft is placed into the defect and the graft fixated by the bone plate. (d) The anterior aspect of the chin is made squarer.
(a) A predetermined amount of bone is removed from the center of the genial segments. (b) Guided by the reference marks, the defect is closed by
moving the segments medially.
(a) The genial segments are fixated across the midline and to the mandible.
Correction of horizontal chin asymmetry. (a) The osteotomy is performed on a horizontal plane and the genial segment moved to the right, in this case. (b) The clinician is guided by the reference marks.
Correction of a chin cant. (a) The left side of the genial segment is repositioned inferiorly using the positioning wire. (b) A bone graft placed in the defect.
The propeller genioplasty. (a) The facial midline is marked on the superior aspect of the chin. (b) The first osteotomy is performed
parallel to the lower border of the chin. (c) The second osteotomy is performed parallel to the horizontal. (d) Mark the center of
the lower genial segment. (e) The bone segment will be rotated by 180.
The propeller genioplasty. (a) The dental and facial
midline. (b) The rotated bone segment. (c) The centerline reference
mark of the genial segment.
A standard anterior subapical osteotomy is performed after which a portion of the lower border is removed as in a genioplasty & wedged into the space produced between the dentoalveolar segment.
This newly formed chin is then reshaped & wound closed in layers.
Schematic diagram showing chin and facial midlines (A), horizontal flip around the AP axis (B), the flip interchanges points 1 and 2 (C), niche for pedicle (arrow), and the genial segment fixed in an overriding position buccal to the stable portion of the mandible (D).