Orthognathic surgery

Surgery to treat facial disproportion or surgery for

correction of dentofacial deformities. Orthognathic
comes from the Greek orthos (straight) and gnathos
(jaw).
Dentofacial deformities could be congenital or acquired.
Malocclusion and associated abnormalities of the
skeletal components of the face can occur as a result of a
variety of factors, including inherited tendencies,
prenatal problems, systemic conditions that occur during
growth, trauma, and environmental influences.
 :Treatment objectives
Function: to establish a functional occlusion aiming to achieve
normal overbite/overjet and transverse relationships.
Aesthetics: to normalize facial balance and proportions in three
dimensions, in addition to provide stable results in the long-term.
Other possible benefits:
* Temporo-mandibular joint dysfunction…????
* Mouth opening
*Sleep apnoea
*Traumatic occlusions and dental health
Many areas of dental practice, in addition to orthodontics and
surgery, must be integrated to address the complex problems of
patients with dental deformities. This integrated approach, used
throughout the evaluation, pre-surgical, and postsurgical phases
of patient care, provides the best possible results for these
patients.
The management protocol for facial deformity should
comprise the:
History
Clinical examination
Investigations
Initial diagnosis
Treatment plan
Pre-surgical orthodontics
Surgery
Post-surgical orthodontics
When appropriate, restorative dentistry, psychological
intervention or support and speech therapy will be
required.
The most important phase in patient care centers on
evaluation of the existing problems and definition of
treatment goals. At the initial appointment a
thorough interview should be conducted with the
patient to discuss the patient's perception of the
problems and the goals of any possible treatment.
The patient's current health status and any medical
or psychological problems that may affect treatment
are also discussed at this time.
The involved orthodontist and oral and maxillofacial
surgeon should conduct a thorough examination of
facial structure, with consideration of frontal and
profile esthetics.
 Clinical examination
The patient is best assessed sitting upright in good light with
head in the natural head position and the Frankfort
horizontal parallel to the floor.

Facial evaluation
It is a critical point to remember that facial evaluation is not
the search for deviation from the norm of a single facial unit
but the search for proportion (e.g. a face that is vertically
excessive means that, in relation to the transverse
dimension, the face is excessively long and not that it is
longer than another face. By increasing only the vertical
dimension facial harmony is lost, but by increasing both
transverse and vertical dimensions harmony is restored.
Most soft tissue discrepancies are indicators of
underlying dental and/or skeletal deformities.
Knowledge of the soft tissue problems and the
relationship with the supporting hard tissue
elements (dental and skeletal) will give the clinician
a good idea of the orthodontic tooth movement and
surgical repositioning of the jaw(s) required for
correction of both the hard and soft tissue
problems. Some key soft tissue parameters used for
an overview of facial esthetics and the
interpretation and differentiations of the possible
underlying deformities are listed below.
 Frontal view
Facial proportions: The facial height is divided in three
main thirds. The upper facial third goes from the
hairline to the glabella, the middle third from the
glabella to the base of the columella, and the lower
third from the columella third to the deepest point of
the chin prominence. The lower third is subdivided in
an upper third from the columella base to the lip
commissure and two lower thirds from the lower lip to
the chin. Special attention should be given to the
presence of a gummy smile as well as the symmetry of
the smile. The amount of gingival exposure when
smiling and the amount of upper incisor exposure
under the upper lip in repose should be correlated.
Ideally, the upper lip vermillion should fall at the
cervico-gingival margin with no more than 2 mm of
gingival exposure during smiling. Keep in mind that,
although there are several factors to be considered,
the amount of incisor exposure or lack of exposure
under the relaxed upper lip is the prime indicator of
the amount of vertical reposition of the maxilla.
To analyze facial widths and symmetry, the face can
be divided in to fifths according to the drawing.
Facial form:
The relationship between the height and the width
of the face has an important influence on facial form
and harmony and should also be correlated with the
patient’s overall body build. The height-to-width
proportions are 1.3:1 for females and 1.35:1 for
males. The bigonial width should be approximately
30% less than the bizygomatic dimension and the
width and shape of the chin should form a
harmonious part of the overall facial contour.
Transverse dimensions: The normal inter-pupillary
distance should be 65 ± 3 mm while the inter-canthal
distance should measure 32 ± 2 mm. Vertical lines
drawn through the medial canthi should coincide with
the ala of the nose while vertical lines drawn through
the medial margins of the irides of the eyes should
coincide with the corners of the mouth. The
measurements will, however, give the clinician an
indication of harmony between the nose, the mouth,
and the eyes. The alar base width will be an important
consideration as Le Fort I osteotomy, especially
superior repositioning and advancement of the
maxilla, may increase the width of the base of the
nose. Surgical precautions should be taken to control
unwanted nasal changes following Le Fort I
osteotomy.
Facial symmetry: The symmetry of the facial midline
structures such as the forehead (glabella), nasal tip,
upper lip, maxillary dental midline, mandibular
dental midline, lower lip, and chin should be
assessed. The clinician should consider whether
orthodontic or surgical correction of the dental
midlines should be planned. The left-to-right
symmetry must be correlated with the facial midline
and the face should be reasonably symmetric
vertically and transversely. Keep in mind that no face
is perfectly symmetric. When evaluating the
symmetry of the face it is also very important to
assess the presence of any occlusal plane cants. The
occlusal plane should be parallel to the
inter-pupillary line.
 Profile view
Nasolabial angle: is measured between the
columella of the nose and the upper lip. The
angle should be 90 ± 10° and is a guide to the
upper lip support by the maxillary incisors. It is,
however, also influenced by the decreased
vertical dimension due to maxillary vertical
deficiency.
 Profile view

• nasolabial angle
The lip–chin–throat angle: is formed between
the lower border of the chin and a line
connecting the lower lip and soft tissue
pogonion (110 ± 10°). It is most commonly acute
in flat or concave profiles with class III
dentoskeletal patterns. An obtuse angle is seen
in class II malocclusion, mandibular
antero-posterior deficiency, and is often
exacerbated by microgenia.
• lip chin throat angle
Upper lip length: The upper lip length is
measured from subnasale to lower lip and should
be 20 ± 2 mm for females and 22 ± 2 mm for
males ensure when evaluating the lips that they
are in repose. During treatment planning it should
be kept in mind that the upper lip length will
increase with age.
Ricketts has projected a line from nasal tip to
soft tissue pogonion, and suggested the upper
lip be 4 mm and the lower 2 mm behind this
line. It is very useful in planning.
Labiomental angle is formed by the intersection
of the lower lip and the chin and is measured at
soft tissue B-point. The angle should be gently
curved (mean = 120 ± 10°).
• labiomental angle 120 +- 10
 Documentations of findings

It is recommended to record the clinical findings

on standardized documentation sheets.
Standard digital photography (profile, frontal
view, three quarter view, bird's eye view) are
taken and attached to the clinical
documentation. Standard photos, especially
profile pictures, are necessary to do a profile
outcome prediction.
Documentations
Dental examination
A complete dental examination should include
assessment of dental arch form, symmetry,
tooth alignment, and occlusal abnormalities in
the transverse, anteroposterior, and vertical
dimensions. The muscles of mastication and TMJ
function should also be evaluated. A screening
periodontal examination, including probing,
should assess the patient's hygiene and current
periodontal health status.
 Radiographic evaluation

The radiographs mostly used as routine in the diagnosis

of dentofacial deformities are lateral and postero-
anterior cephalometric radiographs, panoramic
radiographs, and periapical radiographs. Other
radiographic imaging modalities, such as TMJ
tomograms, magnetic resonance imaging (MRI), and
computed tomography (CT) scans, may be required as
determined by the needs of each individual case.
Although clinical evaluation must be the primary
diagnostic tool in determining surgical treatment of the
orthognathic patient, cephalometric analysis is a helpful
diagnostic guide.
Lateral cephalometric analysis
Cephalometry is done to evaluate the
proportions of the facial skeleton and to
compare an individual patient with norm.
Standard skeletal analysis is based on plain
X-Rays taken in the sagittal and frontal plane.
Typically the X-rays are analyzed with the help of
computer based programs. Protocols for analysis
differ to some extent. All of them are based on
reference points, lines, and angles which are
marked on the X-ray.
Hard tissue landmarks are as follows:
Nasion (N): the most anterior point on the frontal nasal
suture in the midsagittal plane.
Orbitale (OR): the lowest point on the inferior orbital rim.
Sella (S): the center of the sella turcica, as on the lateral
cephalogram, which is located by inspection.
Anterior nasal spine (ANS): anterior tip of the nasal spine.
A-point (A): the most posterior midline point in the
concavity where the lower anterior edge of the anterior
nasal spine meets the alveolar bone overlying the
maxillary incisor teeth.
B-point (B): the most posterior midline point in the
concavity of the mandible between the alveolar bone
overlying the lower incisor teeth and the pogonion.
Gonion (Go): the point is defined by using two lines, one
tangent to the posterior border of the mandibular ramus
and the other tangent to the lower border of the
mandibular corpus; found by bisecting the angle formed by
the two lines and extending the bisector through the
curvature of the mandibular angle.
Menton (Me): the most inferior point on the symphysis of
the mandible in the midline.
Porion (P): the most superior point of the external auditory
meatus (anatomic point); machine porion is the uppermost
point on the outline of the rods of the cephalometer.
Condylion (Co): the most postero-superior point on the
head of the condyle.
Gnathion (Gn): the lowest, most anterior midpoint on the
symphysis of the mandible.
Glabella (G): the most anterior point on the frontal bone.
The following constructed hard tissue facial planes are
mostly used:
Frankfort horizontal plane (FH): extends from porion to
orbitale.
Anterior cranial base (SN): formed by a line drawn from
sella to nasion.
Occlusal plane (OP): formed by a line drawn through the
mesial cusp contact of the first molar teeth and dividing
the incisor overbite.
Mandibular plane (MP): extends from gonion to menton.
Because the anatomic Frankfort plane (FH) does not
always correlate with the clinical impression of the
patient’s facial deformity, the authors prefer to use the
anterior cranial base (SN) as a horizontal reference line.
 Skeletal antero-posterior relationships

• Maxillary antero-posterior position. The analysis gives an indication

of the antero-posterior position of the maxilla in relation to the
anterior cranial base. The angle between the anterior cranial base (SN)
and a line drawn between the nasion (N) and A-point is measured and
should be 82° for a normal maxilla.
• Maxillary depth angle. The angle between the FH and NA also gives
indication of the maxillary antero-posterior position and should be 90°.
A line perpendicular to FH should therefore fall on A-point.
• Mandibular antero-posterior position. The SNB angle is measured
between SN and a line drawn between N and B-point and it relates the
antero-posterior position of the mandible to SN. This angle should be
80° for a normal mandibular position.
• ANB angle. This angle gives the clinician an indication of the
inter-relationship between the upper and lower jaw. In class II
mandibular deficient cases the angle will be increased while in class III
cases the angle will be decreased. An angle of 2° indicates a normal
relationship.
 Model analysis (study casts)
Plaster of Paris models from the maxilla and mandible are
taken and the actual centric occlusion of the patient is
recorded. The models are oriented in a semi adjustable
articulator after face-bow transfer.
The models allow analyzing the:
occlusion
shape of the dental arches
position
size and shape of the teeth
position of the jaws in relation to the skull base

Usually two sets of models are used. One is kept to analyze and
document the preoperative situation. The second set of
models is used to perform mock surgery.
 Pre-surgical Orthodontic Considerations
Obviously, not all malocclusions require correction with
surgery when the skeletal discrepancy is minimal and
orthodontic compensation does not adversely affect
dental or facial esthetics or post-treatment stability,
orthodontic treatment alone may be the treatment of
choice. However, in some cases an adequate occlusal
relationship cannot be achieved because of the skeletal
discrepancy; some patients may be treated with
orthodontic compensation for a skeletal abnormality,
resulting in an adequate occlusion but poor facial or
dental esthetics or a poor long-term prognosis for post
treatment retention. These patients should be
considered for surgery combined with orthodontic
treatment.
Treatment Timing
As a general guideline, orthognathic surgery
should be delayed until growth is complete in
patients who have problems of excess growth,
although surgery can be considered earlier for
patients with growth deficiencies.
 Orthodontic Treatment Objectives

Undesirable angulation of the anterior teeth occurs

as a compensatory response to a developing
dentofacial deformity. For example, a patient with
maxillary deficiency and/or mandibular excess often
has dental compensation for the skeletal
abnormality with flared upper incisors and retracted
or retroclined lower incisors. Dental compensations
for the skeletal deformity are corrected before
surgery by orthodontically repositioning teeth
properly over the underlying skeletal component,
without considerations for the bite relationship to
the opposing arch.
This pre-surgical orthodontic movement accentuates the
patient's deformity but is necessary if normal occlusal
relationships are to be achieved when the skeletal
components are properly positioned at surgery. The
surgical treatment then results in an ideal position of the
skeletal and dental components. The essential steps in
orthodontic preparation are to align the arches
individually, achieve compatibility of the arches or arch
segments, and establish the proper antero-posterior and
vertical position of the incisors. The amount of
pre-surgical orthodontics can vary, ranging from appliance
placement with minimal tooth movement in some
patients to approximately 12 to 18 months of appliance
therapy in those with severe crowding and incisor
malposition.
Presurgical orthodontic consideration
 Final Treatment Planning
After the completion of the pre-surgical
periodontics, restorative dentistry, and orthodontics,
the patient returns to the oral and maxillofacial
surgeon for final pre-surgical planning. The patient's
facial structure and the malocclusion are
reexamined. Pre-surgical digital photographs and
radiographs are obtained. Pre-surgical models, a
centric relation bite registration, and face-bow
recording for model mounting are completed. Model
surgery on a duplicated set of pre-surgical dental
casts determines the exact surgical movements
necessary to accomplish the desired postoperative
occlusion.
 Mock surgery and fabrication of splints
Based on the results of the clinical and cephalometric
analysis, a problem list and treatment plan are
generated. The mounted models can then be moved
into the planned position for correction of the
skeletal disorder. Keeping in mind that treatment of
facial bone abnormalities is usually a combined
endeavor for both surgeon and orthodontist, this
position has to be agreed upon by both parties. It is
important that all movements become visible in a
three dimensional fashion. This can be achieved using
reference lines scribed on the models before
performing the movements.
The models are fixed in the new positions with
wax or glue. Mock surgery is performed to
mimic the planned surgical procedure. It is also
a powerful tool to demonstrate the treatment
plan to the patient. Finally the reoriented
models after mock surgery are used to fabricate
the surgical splints that will be used in the
operating room to reposition the osteotomized
segments. Mock surgery can also be performed
using individual stereolithographic models. This
is indicated for severe and mostly asymmetric
deformities.
 Fabrication of splints
Splints are made of acrylic and used in
orthognathic surgery to intra-operatively
position a mobile osteotomized jaw against the
other stable jaw before an internal fixation
procedure is performed. In case of two-jaw
surgery two splints need to be fabricated. The
first one is used after osteotomy of the first jaw
as an intermediate splint, the other one after the
second jaw has been osteotomized as a final
splint. Usually the two splints are colour coded
to avoid confusion.