Orthognathic surgery

ORTHOGNATHIC
SURGERY
By
HARDIK LALAKIYA
3RD YEAR PG

CONTENTS
WHAT IS ORTHOGNATHIC SURGERY
GOALS OF ORTHOGNATHIC SURGERY
ENVELOPE OF DISCREPANCY
TIMING OF ORTHOGNATHIC SURGERIES
WHY ORTHOGNATHIC SURGERY
INDICATIONS

PATIENT EVALUATION
CEPHALOMETRICS {COGS} ANALYSIS
MODEL SURGERY
CLASSIFICATION OF DENTOFACIAL
DEFORMITIES
DISTRACTION OSTEOGENESIS
LATEST NAVIGATION BASED ORTHOGNATHIC SURGERY
REFERENCES

Patient
Orthodontist
Oral
Surgeon

WHAT IS ORTHOGNATHIC SURGERY?
• To correct conditions of the jaw and face related to structure, growth,
sleep apnea, TMJ disorders, malocclusion problems owing to skeletal
disharmonies, or other orthodontic problems that cannot be easily treated
with braces.
• Originally coined by Harold Hargis, it is also used in treatment of
congenital conditions like cleft palate. Bones can be cut and re-aligned,
then held in place with either screws or plates. Orthognathic surgery can
also be referred to as corrective jaw surgery.

GOALS OF ORTHOGNATHIC /ORTHODONTIC
TREATMENT OBJECTIVES – F.R.E.S.H.
• 1) FUNCTION 5) Economic
• 2) Reliable 6) Stability
• 3) Realistic 7) Satisfaction
• 4) Esthetics 8) Health

ENVELOPE OF
DISCREPANCY
Orthodontics
Orthodontics +
Growth
Modifications
Orthognathic
Surgery
Open Journal of Stomatology, 2014, 4, 184-196

• Keep in mind that the envelope of discrepancy outlines the
limits of hard tissue change toward ideal occlusion, other
limits due to the major goals of treatment do not apply.
• In fact, soft tissue limitations not reflected in the envelope of
discrepancy often are a major factor in the decision for
orthodontic or surgical-orthodontic treatment.
• Measuring millimeter distances to the ideal condylar position
for normal function is problematic, and measuring distances
from ideal esthetics is impossible
•

WHY ORTHOGNATHIC SURGERY?
1.When orthodontic treatment alone cannot correct a
problem.
2.To improve jaw function.
3.To enhance the long term orthodontic result (stability).
4.Reduction in overall treatment time.
5.Change in facial appearance.
6.Improved breathing.
7.Improved speech.
8.Improvement in jaw pain.

INDICATIONS
• Congenital anomalies

• Excessively large or small jaw dimensions in adults (in one
or more planes)

• Marked asymmetric jaw growth

• Anatomic limitations, which hinder the orthodontic
tooth movement

• Corticotomy to hasten the orthodontic movements.

INTRODUCTION
 Successful treatment of the orthognathic
surgical patient is dependent on careful
diagnosis
 Cephalometrics can be an aid in the diagnosis of
skeletal and dental problems and a tool for
simulating surgery and orthodontics by the use
of acetate overlays (Tracing sheets).

PATIENT EVALUATION
 Patient concerns
Past medical history
Sociopsychologic Evaluation
 Facial evaluation
- Frontal
- Lateral
 Nose evaluation
 Oral Examination
 TMJ evaluation
 Dental Model Analysis
 Radiographic evaluation
 Cephalometric evaluation

ESTHETIC FACIAL EVALUATION
• Patient position: The patient should sit upright in a
straight-backed chair with the examiner seated
directly opposite at eye level.
• Patients head in examined in two positions
• Natural head position
• With the Frankfort horizontal plane and pupillary plane parallel
to the floor.
• Once the head oriented properly, the mandibular
condyles should be seated in glenoid fossae with the
teeth lightly touching. And in centric relation and
occlusion
• Analysis in 2 views:
1. Front face analysis
2. Profile / lateral face analysis

FRONT FACE ANALYSIS
Form
Transverse dimensions(rule of
fifths)
Symmetry
Vertical relationships
Upper third
Middle third
Lower third
Lips

FORM
• Facial height : Bizygomatic width
• MALES - 1.35:1
• FEMALES – 1.3 : 1
• Bigonial width : 30% less than bizygomatic
width

RULE OF FIFTHS
• Face divided into five parts, each width approx the
width of the eye.
• In the middle fifth, the width of the fifth should
approximate the distance between the inner
margins of the irides of the eyes.
• The alae of the nose should coincide with these
lines.

FACIAL SYMMETRY
• Glabella
• Nasal Bridge
• Nasal tip
• Filtrum of upper lip
• Dental Midlines
• Pogonion

VERTICAL RELATIONSHIP
• Face divided into three
equal parts:
•Trichion to Glabella
•Glabella to Subnasale
•Subnasale to Menton

UPPER THIRD
• May be masked by hairstyle.
• Look out for craniofacial
deformities

MIDDLE THIRD
• Glabella to Subnasale
• Sclera should not be seen above
or below the iris in relaxed state.
– In mid face deficiency, sclera
seen below iris

LOWER THIRD OF FACE
• Middle third: Lower third= 5:6
• Upper lip length:
– Males=22+/-2 mm
– Females=2o+/-2 mm
• Detect and evaluate any midline shifts.
• Chin: symmetry, vertical relation and
shape.
1/3
1/3
1/3
2/3

CHEEKBONE-NASAL BASE-
LIP CONTOUR
• CC- Cheekbone area
• a- zygomatic arch
• b- middle area
• c- subpupillary area
• MxP- Maxillary Point-
• Most medial point on the
curve.
• Nb-LC-Nasal Base-Upper lip
contour

LIPS
• Extremely critical to overall esthetics.
• Lip symmetry should be evaluated.
• Asymmetry caused by
• eg, cleft lip,
• facial nerve dysfunction,
• underlying dentoskeletal asymmetry
• scarring due to previous trauma
• congenital unilateral microsomia or macrosomia).

• The lower lip generally exhibits 25% more vermilion
than the upper lip, and the lips should be 0 to 3 mm
apart in repose.
• In patients with closed bites, the lips and tooth-lips
relation should be evaluated with the lips relaxed
and the jaws moved apart until the lips just part
(closed bites may be due to maxillary vertical
deficiency or severe deep bites).
• Accentuation of Cupid's bow of the upper lip may
lead to exposure of only the maxillary central
incisors

AVERAGE VALUES IN THE
EVALUATION FROM FRONTAL VIEW
1.Forehead, eyes, orbits and nose are evaluated for
symmetry, size and deformity.
2.Normal intercanthal distance 32 ± 3 mm for whites 35 ±
3 mm blacks
3.Normal interpupillary distances 65 ± 3 mm.
4.The inter canthal distance, alar base width and
palpebral tissue width should all be equal.

5. Width of nasal dorsum should be one half the intercanthal
distance and width of the nasal lobules should be 2/3rd the
intercanthal distance.
6. A vertical line through the medical canthus and
perpendicular to the pupillary line should fall on the alar bases
± 2 mm.
7. The upper lip length is measured from sabnasale to upper lip
stomion (22 ± 2 mm for males and 20 ± 2 mm for females).

8. A normal upper tooth – to lip relationship exposes 2.5 ±
1.5 mm of incisal edge to lips.
9. The facial midline, nasal midline, lip midline dental
midline all should be in line and face should be
reasonably symmetric, vertical and transversely.
10. During smiling the vermilion of the upper lip should fall at
the cervicogingival margin with no more than 1 to 2
mm of exposed gingival. The amount of upper lip
elevation may be affected by
i. Anteroposterior positioning of maxilla and mandible
ii. Amount of overjet/overbite
iii. Angulation of the anterior dentition
iv. Occlussal plane angulation
v. Clinical crown length

11. The distance from glabella to subnasale and
subnasale to menton should be approximately in a 1:1
ration, providing that the upper lip length is normal.
12. The length of the upper lip should be 1/3rd the length
of the lower facial third, which is lower lip stomion to soft
tissue menton should be twice the vertical dimension of
the upper tip, provided that the upper lip is normal in
length.

PROFILE / LATERAL FACE ANALYSIS
• Upper third of the face
• Middle third of the face.
– Nose
– Cheeks/Zygomatic projection
– Paranasal areas
• Lower third of the face
– Lips
• Upper lip length
• Inter labial gap
– Labio-mental Fold
– Nasolabial angle
– Chin
• Mentalis habit
– Chin-Throat area
• Submental volume
• Mandibular angle pattern
• Static & dynamic
information
• Natural head position
• Incisor exposure with relaxed
lip
• Lip insufficiency
• Facial volume
• Smile line
• Hyperactive metalis
• Tongue position

UPPER THIRD OF THE FACE
• The supraorbital rims normally project 5 to 10
mm beyond the most anterior projection of the
globe of the eye.
• Check for
• Frontal bossing
• supraorbital hypoplasia
• Exophthalmos
• Enophthalmos.

MIDDLE THIRD OF THE FACE
• Middle third of the face
includes
–Nose
–Cheeks/Zygomatic
projection
–Paranasal areas

THE NOSE
Evaluation
• Scars, soft tissue thickness and
evidence of previous surgeries
noted
• includes functional and
esthetic examination of internal
as well as nasal structures

NOSE
• Dorsum
• Normal
• Convex
• Concave.
• The projection of the nasal bridge should be
anterior to the globes (5 to 8 mm).
• The appearance of the nasal tip is evaluated
for the presence of a supratip break and for
tip definition and projection .

• It is important to distinguish between a dorsal hump and a
turned down tip, since the implications for treatment are
entirely different.
• The possible effect of maxillary surgery on the nose should
be kept in mind when evaluating the proportions of the
base of the nose

AVERAGE PARAMETERS
FOR THE NOSE
 The nasal dorsal length should fill most of the middle
3rd of face.
 No more than 1/3rd of vertical length of nares should
be visible from the frontal view.
 The normal nasolabial angle ranges from 90 ± 105º.
 The normal nasal projection angle is 34º for females,
36º for males.

 The collumella should extend 3 to 4 mm below the lateral
alar rims.
 The distance from the base of he nose to anterior extent of
the nares, and that from the anterior aspects of the nares to
tip of the nose should be 2:1 ratio
 Intranasal examination done to find out any septal
deviation, any existing airway obstruction, hypertrophied
turbinates, nasal polyps, nasopharyngeal adenoids.

CHEEKS
• The globes
generally project 0
to 2 mm ahead of
the infraorbital rims,
while the lateral
orbital rims lie 8 to
12 mm behind the
most anterior
projection of the
globes

The cheeks should exhibit a general convexity from cheek-
bone apex to the commissure of the mouth.
This line starts just anterior to the ear, extending forward
through the cheekbone, then anteroinferiorly over the
maxilla adjacent to the alar base of the nose, and ending
lateral to the commissure of the mouth
Cheekbone-nasal
base-lip curve
contour

LOWER THIRD OF THE FACE
• Examination includes
• Lips
• Labiomental fold
• Nasolabial angle
• Chin
• Chin-throat area

• The protrusion, retrusion, and soft tissue
thickness of each lip is evaluated with the
lips in repose.
• The upper lip usually projects slightly anterior to
the lower lip.
• The lips positions relate to the underlying dental
position, such as maxillary dental protrusion or
lack of upper lip support caused by, for example,
• Class II, division 2 malocclusion
• excessive orthodontic retraction of maxillary incisors.

• An individual with an excessive increase in lower lip
vermilion and a deep labiomental fold often also has a
Class II, division 1 malocclusion.
• The subnasale-pogonion line, also called the lower facial
plane, is an important guide in assessing the lip position
and planning orthodontic and surgical positioning of the
incisors, as well as surgical positioning of the chin.
• The upper lip should be 1-3 mm ahead of this line
• The lower lip 1-2 mm ahead of this line.
• Extractions followed by retraction of incisors behind the
subnasalepogonion line should be avoided.

LABIOMENTAL FOLD
• The lower lip-chin contour should have a
gentle S-curve, with a lower lip-chin angle
of at least 130 degrees.
• The angle is often acute in cases of Class
II mandibular anteroposterior deficiency
because of impingement of the maxillary
incisor on the lower lip or macrogenia.
• The angle is flattened in individuals with
microgenia or lower lip tension caused by
Class III malocclusion.

NASOLABIAL ANGLE
• The nasolabial angle, which is measured
between the inclination of the columella and
the upper lip , should be in the range of 85 to
105 degrees.
• In females a slightly larger angle is acceptable,
while a smaller angle is considered esthetically
pleasing in males.
• Surgical or orthodontic retraction of maxillary
incisors should be avoided in individuals with
large nasolabial angles.

• Where crowding necessitates tooth extraction, the
nasolabial angle should influence the decision to
extract first versus second premolars.
• Surgical repositioning of the maxilla also affects the
nasolabial angle. In general, the maxilla should
never be moved posteriorly, especially in
combination with superior repositioning.
• This surgical movement leads to loss of lip support,
increase in nasolabial angle, increase in nasal
projection, and flattening of the nasal base.

CHIN
• 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

CHIN-THROAT AREA
• The presence of a "double" chin and adipose tissue should
be noted. The chin-throat angle (normally 110 degrees)
provides chin definition.
• The distance from the neck-throat angle to the soft tissue
pogonion should be approximately 42 mm.
• These observations are pertinent when considering
mandibular setback or advancement procedures,
genioplasty (advancement or reduction), or submental
liposuction.

AVERAGE VALUES IN THE PROFILE /
LATERAL FACE ANALYSIS
Most valuable in assessing vertical and
anteroposterior problems of the jaws:
1.The distance form glabella to subnasale and from subnasale
to soft tissue menton should be in a 1:1 ratio if the upper lip
length is normal.
2.With the maxilla in normal AP position and the upper lip in
normal thickness, ideal chin projection is 3 ± 3 mm posterior to
a line through subnasale that is perpendicular to a clinical
Frankfort horizontal.
3.The morphologic characteristics and relationships of the
nose, lips, cheeks and chin are evaluated.

4. The length of the upper lip should be 1/3rd the length of lower facial
height (third). Lower lip stomion to soft tissue menton should be
twice the vertical dimension of the upper lip if the upper lip is normal
in length.
5. Upper lip suprabasale should be 1 to 3 mm anterior to subnasale
6. A line perpendicular to Frankfort horizontal and tangent to the
globe should fall on the infraorbital soft tissues within 2 mm.

•Cephalometrics for orthognathic
surgery burstone 1978 april Journ. of oral surg
•Quadrilateral analysis- By Di-paolo AJO-
DO 1984 Dec
•Proportionate mesh analysis AJO 1987 JUN

•More recent venture into
Cephalometric treatment planning
and predictions has been
VIDEOIMAGING

COGS – CEPHALOMETRICS FOR
ORTHOGNATHIC SURGERY
• Developed at university of Connecticut
• Based on a system from Indiana University and
further developed by additions at Connecticut

PLANE OF REFERENCE FOR
COMPARISON
• A constructed plane called Horizontal Plane which
is surrogate Frankfort Horizontal plane constructed
by drawing a line 70 from SN plane
• Most measurements will be made from projections
either parallel or perpendicular to the Horizontal
Plane

COGS
Chosen landmarks and measurements can be altered by various
surgical procedures.
 The appraisal includes all facial bones and a cranial base
reference.
 Rectilinear measurements can be readily transferred to a study
cast for mock surgery.

H-P line
Baseline for comparison
of most data
Constructed plane
By drawing a line
7 ° to SN

Ar-N:length of the cranial base
It is not an absolute value,
Proportionate value , so that can be
correlated with mandibular ,maxillary lengths
Mean value is 50 ± 3
1) PTM – N
Males = 52.8 +/- 4.1 mm
females= 50.9 +/- 3.0 mm
Indicates-the position of Posterior border of maxilla in relation to
Nasion
Increases – more posterior position of maxilla
Decreases- anterior position of maxilla

3.Ar-PTM :
--Measure horizontal distance b/t
poterior aspects of mandible &
maxilla.
The greater the distance,the more the
mandible will lie posteriorly to maxilla
Males=37.1 ± 2 mm
Females = 32.8 ± 1.9 mm

B. HORIZONTAL SKELETAL PROFILE
1. N-A-Pg = angle of skeletal facial convexity
-- Measurement doesn’t indicate if
due to maxilla or mandible
+ angle-convex face
- angle –concave face
Mean :
Males : 3.9 ± 0.4 °
females: 2.6 ± 5.1 °

A perpendicular to HP drawn through N.
The inferior anatomic point is horizontally measured in
relation to the
superior structure, with + being anterior and – being
posterior.
2.N-A : horizontal position of A is measured to this
Perpendicular .
measurement describes the horizontal position of
Apical Base of the maxilla in relation to N
---to determine if anterior part of maxilla is
protrusive or retrusive.
Mean :
males= 0.0 ± 3.7mm ; females = -2.0 ± 3.7 mm

3.N-B : horizontal position of B is measured to this
Perpendicular
Indicates: apical base of mandible in relation to
nasion.
males= -5.3 ± 6.7 mm ; females= -6.9 ± 4.3
mm
4.N-Pg : prominence of chin
This describes the position of chin in relation to
nasion.
MEAN:
MALES = -4.3 ± 8.5 mm ; females = -6.5 ± 5.1

Diagnosis of:
• Horizontal maxillary hypolasia/hyperplasia
• Horizontal mandibular hypo/hyperplasia
• Horizontal genial hypo/hyperplasia
Used in planning of treatments:
• Augmentation /reduction genioplasty
• Ant mandibular horizontal advancement or
reduction
• Total mandibular horizontal advancement or
reduction

• c. Vertical skeletal dysplasia
1. middle 1/3 facial ht
(N-ANS) ╧ HP
Anterior components males= 54.7+/- 3.2mm
females= 50 +/- 2.4mm
Indicates any increase or decrease in middle facial third height

2. lower 1/3 facial
( ANS- Gn ) ╧ HP
males = 68.6 +/- 3.8mm
females= 61.3 +/- 3.3mm
Indicates – increased or decreased anterior lower facial third
height
3. posterior maxillary ht- PNS- N Value-50.6 +/- 2.2 mm
--- length of perpendicular line from HP
intersecting PNS
Indicates- Increase or decrease posterior maxillary height

4. MP-HP angle = relates the posterior facial divergence with respect
to anterior facial height.
Indicates – increase or decreased posterior facial divergence.

Helps in Diagnosis of:
• anterior , posterior or total vertical
maxillary hyperplasia or hypoplasia.
• clockwise or counterclockwise rotations
of maxilla and the mandible.

VERTICAL DENTAL DYSPALSIA
• Anterior component:
Anterior maxillary height : upper1-NF
• Mean value- 27.5 + 1.7 mm
perpendicular distance from incisal edge of upper incisor to NF is
measured
indicates - Increased or decreased upper anterior dental height
Anterior mandibular height : lower1 – MP
Mean value- 40.8 + 1.8 mm
a perpendicular line is dropped from the edge of lower incisor to MP
Indicated – increase or decrease lower anterior facial height.

• Posterior conponent:
Posterior maxillary height :Upper 6 – NF
perpendicular line is dropped from tip of mesiobuccal cusp of upper
first molar to NF
Indicates – Increased or decreased upper posterior dental heights
Posterior mandibular height : Lower 6 – MP
• Perpendicular line is dropped from mesiobuccal cusp of lower first molar to
MP
• indicates – increased or decreased lower posterior dental height

1. PNS- ANS: Total Effective Length of Maxilla
With ANS-N And PNS-N
Males = 57.7 ± 2.5 Mm
Females =52.6 ± 3.5mm
2. Ar- Go ( Linear): Length of Mandibular Ramus
Males= 52±4.2 Mm
Females =46.8±2.5mm
Variation in ramal height can be a causative factor for skeletal open
bite or deep bite.
3. Go- Pg (Linear): Length of Mandibular Body
Males = 83.7±4.6mm
Females = 74.3±5.8mm

. B- Pg : Prominence of chin relation to mandibular
Denture base
males = 8.9 ± 1.7mm; female = 7.2 ± 1.9mm
By comparing with N-Pg distance chin prominence
relation to face
5. Ar- Go- Gn ( gonial angle)
Mean value is 122 + 6.9 mm
Gonail angle also contributes to skeletal open or
deepbite

Diagnosis of:
• variations in ramus height that effect open bite
or deep bite
• increased dimension of mandibular body
length
• acute or obtuse Go angles
• assesment of chin prominence
• prominence of chin related to mandibular
denture base.
• by relating to N-Pog asses the prominence of
the chin in relation to the face.

ASSESSMENT OF DENTAL
ANOMALIES
• OP : line drawn from the buccal groove of both first permanent molars
through a point 1mm apical to the incisal edge of the central incisor in
each arch
1.OP angle: upper- HP,OP lower – HP
males= 6.2 ± 5.1mm
females =7.1 ± 2.5mm
Increased OP-HP is associated with skeletal open bite lip incompetence
and increased anterior facial height.
Decreased OP – HP is associated with skeletal deep bite decrease
anterior facial height and lip reduncy.

2.A-B: measuring the distance between projection of
point A and Point B on OP
This gives us relationship between maxillary and
mandibular apical bases in relation to OP
relationship of maxillary and
mandibular apical base to OP
males= -1.1±2.0mm
females = -0.4 ± 2.5mm

Diagnosis of:
• Increased OP-HP :skeletal open bite,lip
incompetence,increased facial hieght,retrognathia
• Decreased OP-HP:
• A-B: large A-B with point B posterior to point A ,mandibular
denture discrepancy that predisposes to class II
malocclusion.

3. upper incisor – NF angle done by intersecting a line passing
through the tip of incisal edge through the root tip of upper
incisor and NF line
males = 111.0 ±4.7°
females = 112.5± 5.3°
Gives us the inclination of upper incisors in relation to palatal
plane
4. lower incisor - MP angle intersecting a line joining the incisal
edge of lower incisors passing through its root tip and MP
males = 95.9 ± 5.2°
females = 95.9 ± 5.7mm
Indicates inclination of lower incisor in relation to MP

CEPHALOMETRIC LANDMARKS
• Glabella(G)- the most prominent point in the midsagittal
plane of the forehead.
• Columella (Cm)- The most anterior point on the columella of
the nose.
• Subnasale(Sn)- the point at which the nasal septum merges
with the upper cutaneous lip in the mid sagittal plane.

• labrale superius (Ls)-a Point indicating the
mucocutaneous border of the upper lip.
• Stomion superius(Stms)- the lowermost point on the
vermilion of the upper lip.
• Stomion inferius (Stm)- the uppermost point on the
vermilion of the lower lip.
• labrale inferius (Li)- a Point indicating the
mucocutaneous border of the lower lip.

• Soft tissue pogonion (Pg’): The most anterior point on
soft tissue chin.
• Soft tissue gnathion (Gn’). The constructed midpoint
between soft tissue Pogonion and soft tissue menton.
and can be located at the intersection of subnasale
to soft tissue pogonion line and the line from C to Me’.

• Mentolabial sulcus(Si)- the point of greatest concavity in the
midline between lower lip(Li) and chin(Pg’).
• Soft tissue Menton (Me’). The most inferior point on the contour of
the soft tissue chin; found by dropping a perpendicular from
horizontal plane through menton.
• Cervical point (C)- the innermost point between the submental area
and the neck located at the intersection of lines drawn tangent to the
neck and submental area.

•Angle of facial convexity
•Lower neck face angle
•Lower vertical height-depth ratio
•Anteroposterior maxillary
& mandibular measurements
•Vertical facial height
proportionality

• Facial convexity angle – by G-Sn line and Sn-Pg’ line
• Standard value – 12 + 4
• Any Increase or decrease in this value indicates convex or concave profile
• Maxillary prognathism- distance between sn and a line
perpendicular to HP passing through glabella gives maxillary prognathism
• Negative no. indicates retrognathism

•Mandibular prognathism - Distance between Pg and a line
perpendicular to hp passing through G gives mandibular prognathism.
•Vertical height ratio:- ratio between G-Sn and Sn-Me’
• Increased ratio suggest increased middle third height
Lower face throat angle: it is the angle formed by intersection
of Sn-Gn’ and Gn’- C
This angle affects treatment planning to correct anterio posterior facial
dysplasia

• Lower face vertical height depth ratio :- It is obtained by
diving Sn-Gn’ distance with C-Gn’
• - - larger than 1 value indicate patient has relatively short
neck.
• Nasolabial angle:- Formed by intersection of Cm-Sn line and
Sn-LS line
• Lower than normal nasolabial angle suggests proclination
of upper incisors or anterior maxillary base
• Higher than normal nasolabial angle suggest retroclination
of upper incisors or anterior maxillary base.

•Upper lip Protrusion : - It is perpendicular distance between Ls-
Sn-pg’line .
• Lower lip protrusion :- It is perpendicular distance between Li to Sn-
pg’ line .
• Mentolabial sulcus depth :- It is perpendicular distance between
deepest point on the Mentolabial sulcus to Li - Pg’ line.
• --- The depth of sulcus is affected by various factors which are – flared lower
incisors, flaccid lower lip tone, extruded upper incisors causing rolling of
lower lip and prominence of lip.

• Vertical Lip : Chin Ratio- it is ratio between Sn-stms and stmi -
Me’
• Whenever the value decreases vertical reduction genioplasty should be
considered
• Maxillary incisor exposure :- It is obtained by measuring the
distance between tip of upper central incisor and stms
• Increased incisor exposure would be may be due to vertical maxillary excess
Or short upper lip.

• Interlabial Gap :- It’s the distance between Stms and stmi
• Pt with vertical maxillary excess tend to have a large interlabial gap and lip
incompetence.

MODEL SURGERY
•Model surgery simulates actual surgery, in
the dental arch models of the patient. It gives
the three dimensional understanding of the
post operative relationship of the jaws.

MAJOR AIMS OF THE MODEL
SURGERY
1.To get the definite idea about the extent of bone /
arch advancement or reduction required in the
surgery.
2.To get a post-operative relationship of the jaws,
dentition and occlusion.
3.To decide about the post-surgical orthodontic
treatment.
4.As a vehicle for fabrication of splints for
stabilization after surgery.

ARMAMENTARIUM:
• 1) A fret saw and fine blades (size M2) or a 10cm (4 inch)
fine fiber or metal cutting disc mounted on a lathe.
•2) Hand-piece and motor.
•3) A steel fissure bur.
•4) A plaster bur or an Ash acrylic cutter pear.
•5) Surgical scalpel blades, NO.10 or 20.
•6) Plaster knife, Spatula, 15 cm(6 inch) rubber bowl.

•Bunsen burner, spirit lamp,or soldering iron.
•8) Wax knife and carver.
•9) Soft ribbon wax, hard modeling and sticky wax.
•10) 15cm (6inch)flexible ruler.
•11) Spring dividers(15cm /6 inch)
•12) Plane line hinge articulator, and face bow.

DIAGNOSTIC SET-UP
• A diagnostic set up is employed to
be sure that it will be possible to
get the teeth to fit together if a
given orthodontic treatment plan
is employed.

Diagnostic pre-orthodontic set-up showing the
proposed extractions and tooth movements.

Method:
Individually remove the tooth from the dental
cast and reset the tooth in soft wax so that
their alignment and interdigitation can be
observed.

METHODS OF MODEL SURGERY:
•Simple method
•Anatomically oriented model
surgery.

ANATOMICALLY ORIENTED
MODEL SURGERY
•In complex cases, especially where
multiple bimaxillary movements are
required, it is essential to use a more
refined technique such as the following
variant of a popular “North American
method”

TECHNIQUE:
• In this technique, in addition to the
impressions and sqash bite, a face-bow
recording is taken
• The working models are anatomically
trimmed and articulated on the semi
adjustable articulator using the face-bow
recording and then the standard squash bite

2. Horizontal and vertical reference lines are
drawn on the mounting plaster to register the
post-operative position of each maxillary and
mandibular segments before surgery.
Two sets of parallel horizontal lines A/A and
B/B are drawn on the upper and lower
models. These are easily done by rotating the
detached model with the felt pen

•The B lines should be just clear of the
apices of the teeth, and not less
than 15mm from the A lines. The
actual distance between the A and
B lines is then recorded on the
plaster. These lines will be used to
plan the vertical movements.

3. Three vertical lines VC, VB, VM are drawn from
upper base line (A) to the lower baseline (A) on
each buccal segment.
These lines pass through the buccal surfaces of
the upper cuspid, bicuspid and the distal cusp
of the last upper molar tooth., and they are
extended to their occluding partners.
These will help to indicate the anteroposterior
movements achieved by the model surgery.
Upper and lower midlines are also drawn.

Marked models with the recorded distances.

4. The vertical distances from the buccal
cusp tips of the three reference teeth to
their A base lines are recorded to help
calculate any vertical movements.
Transverse changes are recorded by the
inter-canine and inter-molar distances
measured across the palate and recorded
by taking reference points on the canine
tips and the mesiobuccal cusp of the first
molars.

Cuspal reference points are used for transverse changes.

When all the reference lines have been
drawn and the measurements completed,
the osteotomy lines are drawn
between A and B lines to
correspond with the bone cuts.
The plaster mounting assembly is then
sectioned at the osteotomy sites with a
saw or large abrasive disc and the
whole arch or segments are
repositioned in the planned post-
operative position

Interrupted line is the proposed osteotomy site.
osteotomy lines

After making the horizontal cut, rotate the dental
midline on the model to match the facial
midline on the mounting plaster.
This will rotate the model VB and VM on the deviated
side forwards and the contra-lateral side VB and
VM lines backwards.
Carefully mark their new positions.
Additional forward movements are then measured
from these new vertical references

Maxilla is reassembled with the wax after the
osteotomy cuts. Mandible closes in to the
intermediate occusal relationship. Intermediate
wafer is made at this stage.

Lower segmental set-down of 3mm is carried out with the forward slide
of 5mm to correct the interarch occlusal relationship.

Anterior view: models showing the upper midline split
to widen the intercanine width and the lower anterior
set-down.

CLASSIFICATION OF DENTOFACIAL
DEFORMITIES
•I-According to jaw involved
-maxilla
-mandible
-combination of both

• II- ACCORDING TO PLANE
- TRANSVERSE
- VERTICAL
- ANTEROPOSTERIOR

• ALSO CLASSIFIED AS-
- SKELETAL CLASS I
- SKELETAL CLASS II
- SKELETAL CLASS III

CLASS I DENTOFACIAL
DEFORMITIES
• CLASS I VERTICAL MAXILLARY EXCESS
• CLASS I VERTICAL MAXILLARY EXCESS WITH OPEN BITE

CLASS II DENTOFACIAL
DEFORMITIES
• CLASS II DENTOFACIAL DEFORMITIES SECONDARY TO MANDIBULAR
DEFICIENCY
• CLASS II DENTOFACIAL DEFORMITIES SECONDARY TO VERTICAL
MAXILLARY EXCESS
• CLASS II DENTOFACIAL DEFORMITIES SECONDARY TO VERTICAL
MAXILLARY EXCESS AND MANDIBULAR DEFICIENCY
• CLASS II DENTOFACIAL DEFORMITIES WITH OPEN BITE

CLASS III DENTOFACIAL
DEFORMITIES
- CLASS III DENTOFACIAL DEFORMITIES SECONDARY TO
MANDIBULAR PROGNATHISM
MAXILLARY DEFICIENCY
A-P
VERTICAL
TRANSVERSE
MAXILLARY DEFICIENCY AND MANDIBULAR PROGNATHISM
- CLASS III DENTOFACIAL DEFORMITIES WITH OPEN BITE

CONDITIONS COMMON TO CL I,
CL II AND CL III DEFORMITIES
• TRANSVERSE MAXILLO-MANDIBULAR DISCREPANCIES
• BIMAXILLARY PROTRUSION
CLASS I
CLASS II
CLASS III

TYPES OF SURGERY
• 1 MANDIBULAR SURGERY
• 2 MAXILLARY SURGERY
• 3 COMBINATION OF BOTH

MANDIBULAR SURGERY
• 1 RAMUS OSTEOTOMY
• 2 BODY OSTEOTOMY
• 3 COMBINATION OF BOTH
• 4 SUB APICAL OSTEOTOMY
• 5 GENIOPLASTY PROCEDURES

RAMUS OSTEOTOMY
• 1 OSTEOTOMY IN THE CONDYLAR NECK
• 2 VERTICAL OSTEOTOMY
• 3 VERTICAL OBLIQUE OSTEOTOMY
• 4 INVERTED ‘L’ OSTEOTOMY
• 5 SAGITTAL SPLIT OSTEOTOMY
• 6 HORIZONTAL OSTEOTOMY IN THE RAMUS

BODY OSTEOTOMY
•1 ANTERIOR BODY OSTEOTOMY
•2 POSTERIOR BODY OSTEOTOMY

CONDYLAR NECK OSTEOTOMY
• GIVEN BY BERARD IN 1898
• ADVANTAGES :
• 1. SIMPLE TO PERFORM
• 2. SHORTER OPERATING TIME
• 3. SCARRING IS NEGLIGIBLE
• 4. NO INJURY TO MANDIBULAR NERVE
• 5. TEETH NOT SACRIFICED

VERTICAL OSTEOTOMY
GIVEN BY CALDWELL AND LETTERMAN IN
1954
CORRECTION OF PROGNATHISM MORE
THAN 10 TO 12 MM.

VERTICAL OBLIQUE OSTEOTOMY
• ALSO CALLED AS SUB CONDYLAR OSTEOTOMY OR SUB
CONDYLOTOMY
• TWO TYPES :
• 1 EXTRA ORAL
• 2 INTRA ORAL
• MODIFICATION OF VERTICAL OSTEOTOMY
• EXTRA ORAL WAS GIVEN BY HINDS,ROBINSON AND THOMA IN 1957.
• MODERATE PROGNATHISM CORRECTED

INTRA ORAL OBLIQUE OSTEOTOMY
• WAS GIVEN BY WINSTANLEY IN 1968

SAGITTAL SPLIT OSTEOTOMY
• WAS GIVEN BY OBWEGESER IN 1957
• WIDE VARIETY OF CHANGES AND MOVEMENT POSSIBLE
• SURGICAL MODIFICATION OF TRAUMATIC FACTORS
• MODIFIED BY DAL PONT
• OTHER MODIFICATION DONE BY BELL AND SCHENDEL

HORIZONTAL OSTEOTOMY OF
RAMUS
• WAS GIVEN BY BLAIR IN 1907
• MODIFIED BY KAZANZIAN IN 1941

BODY OSTEOTOMY
• ANTERIOR BODY OSTEOTOMY
• POSTERIOR BODY OSTEOTOMY
• GIVEN BY BLAIR IN 1907

DISTRACTION OSTEOGENESIS
• Distraction osteogenesis is a technique that relies on
the normal healing process that occurs between
controlled, surgically osteotomized bone segments.
• De novo bone lengthening occurs by gradual,
controlled distraction. In contrast to traditional
approaches, the soft tissue envelope (the skin,
muscle, and neurovascular structures) is
simultaneously expanded, which stabilizes the
skeletal reconstruction.
• The technique today is an important part of the
reconstructive surgeon's armamentarium.

A NEW SYSTEM FOR COMPUTER-AIDED
PREOPERATIVE
PLANNING AND INTRAOPERATIVE NAVIGATION
DURING
CORRECTIVE JAW SURGERY
A new system for computer-aided corrective
surgery the jaws has been developed and
introduced clinically and it combines 3D
surgical planning with conventional dental
occlusion planning.
TITB-00229-2005.R2

• The developed software allows simulating the
surgical correction on virtual 3D models of the facial
skeleton generated from CT scans.
• Surgery planning and simulation include dynamic
cephalometry, semi-automatic mirroring, interactive
cutting of bone and segment repositioning. By
coupling the software with tracking system and with
the help of a special registration

REFERENCES
• 1) WIKIPEDIA : ORTHOGNATHIC SURGERY
• 2) ESSENTIALS OF ORTHOGNATHIC SURGERY 2ND EDITION –
JOHAN P. REYNEKE
• 3) THE CURRENT CONCEPTS OF ORTHODONTIC
DISCREPANCY STABILITY - OPEN JOURNAL OF
STOMATOLOGY, 2014, 4, 184-196

• 4) Facial Aesthetics: 2. Clinical Assessment Dent Update
2008; 35: 159-170
• 5) SHRIDHAR PREMKUMAR – 2ND EDITION
• 6) A NEW SYSTEM FOR COMPUTER-AIDED PREOPERATIVE
PLANNING AN INTRAOPERATIVE NAVIGATION DURING
CORRECTIVE JAW SURGERY - THIS WORK WAS FUNDED BY
THE SWISS NATIONAL CENTER OF COMPETENCE IN RESEARCH
"COMPUTER AIDED AND IMAGE GUIDED MEDICAL
INTERVENTIONS (CO-ME)", AND THE AO/ASIF FOUNDATION,
DAVOS, SWITZERLAND. ASTERISK INDICATES
CORRESPONDING AUTHOR.

Orthognathic surgery

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