Diagnosis and Treatment Planning in Orthognathic Surgery

DIAGNOSIS AND TREATMENT PLANNING IN
ORTHOGNATHIC SURGERY
Dr.N.R.K.Anil Kumar,
II MDS,
Department of oral and maxillofacial
surgery.

Contents
 Introduction
 History
 Diagnosis and Treatment Planning
 Clinical evaluation
 Cephalometric evaluation

Introduction
 Malocclusion can be due to many possible
reasons but they can be treated by:-
1. Modification of growth
2. Orthodontic camouflage which produces a
dental compensation for the skeletal
compensation.
3. Surgical repositioning of the jaws and/or
dentoalveolar segments
The term orthognathic originates from the words
orthos and gnathos (Gr. orthos = straight;
gnathos = jaw). Orthognathic surgery refers to
surgical procedures designed to correct jaw
deformities.

HISTORY
 Hullihen is regarded as the first surgeon to
describe a mandibular orthognathic surgical
procedure. In 1849, he reported an anterior
subapical osteotomy.
 Jaboulay and Berard (1898), Kostecka (1931)
performed operations on condylar neck and
upper part of ramus by closed blind approach.
 Surgical treatment for mandibular prognathism
started in early 19th century.
 In 1959, Trauner and obwegeser introduced
sagittal split osteotomy as the beginning of a new
era of orthognathic surgery.

 American surgeons modify the technique for
maxillary surgery that has been developed in
europe
 Epker, bell and wolford developed lefort-1
maxillary downward fracture ,so that we can keep
the maxilla stable in all 3 planes of spaces.
 By 1980 progress has reached such an extent to
reposition either or both the jaws to move chin in
all 3 planes of spaces.
 Rigid internal fixation made it possible for comfort
and better immobilization was achieved.

Envelope of discrepancy
 Envelope of discrepancy shows how much of
change can be produced by various treatment
modalities.
3 5 25
2
5
15
5101
2
4
6
10
7 12 15
2
5
15
2510
4
6
10

INDICATIONS
 Severe skeletal class II &class III cases
 Skeletal open bite and deep bite cases
 Deep over bite in non growing individuals
 Extreme vertical excess or deficiency in maxilla or
mandible
 Severe dentoalveolar problem
 Extemely compromised periodontal situation
 Skeletal asymmetry

DIAGNOSIS AND TREATMENT
PLANNING

 There is no use of using a single diagnostic tool
to implicate appropriate treatment as edward
angle once hoped
 Untill recently, hard tissues of the facial skeleton
were the focus of diagnosis and treatment
planning
 It is now clear that the soft tissues are the
limiting factor in the changes that can be
produced in treatment and obtaining appropriate
soft tissue proportions is the primary goal of
treatment

Patient evaluation
 Patient concerns or chief complaints,
 Clinical examination,
 Radiographic imaging and analysis,
 Dental model analysis.

PATIENT’S CONCERNS
 What are your concerns or problems?/what do you think is wrong
 Have you had previous treatment for this condition,
and what was the outcome?
 Why do you want treatment?
 What do you expect from treatment?

History taking
 Personal information
 Chief complaint - Motivation questionnaires
 Medical history
 Dental and orthodontic history
 Pre-surgical growth assessment

Evaluation
 Esthetic facial evaluation
- frontal facial analysis
- profile analysis
- intra oral evaluation
 Cephalometric evaluation
 Panaromic / full mouth peripaical evaluation
 Masticatory muscle and TM joint evaluation

Frontal view
Assessment of facial proportions and symmetry.

 The ideal face in both
males and females is
vertically divided into
equal thirds by
horizontal lines at the
hairline, the nasal base,
and the menton

 0.30
 0.35
 0.35
 1 : 1.16 :
1.16

 Fronto temporal point (
0.65 )
 Zygion ( 0.75 )
 Gonion ( 0.66 )

 6 – 8 yrs of age
 Symmetry of canthi
 Eyelids – ptosis, entropion, ectropion
 Sclera, ocular imbalance
 Scleral show – mid facial defieciency
 Eyelid laxity – snap test

NOSE
 Both males & females show more growth in
vertical ht than anteroposterior projection of nose
but downward growth is greater in males
 Form and symmetry
 Location of deformity
 Alar base width (34 + / - 4 mm)
 A dorsal hump in the nose
develops when class I & II malocclusion
is present & is more pronounced in boys

• Alar width / nasion to
pronasale
= 3/5
• Cheek prominence
• 8 – 12 mm laterally
• 10 – 20 mm inferior to
lateral canthus
•Ears
• Upper 1/3rds just above
the canthal level.

Lips
 Width of lips equal to
interpupillary distance
 If asymmetry exists
- Cleft lip
- Facial nerve
dysfunction
- Dental skeletal
deformity
 Gull wing upper lip
has to be
differentiated from
vertical maxillary
Normal patient 3 3 3 3 3 3
Vertical maxillary
excess
6 6 6 6 6 6
Gull wing deformity 2 4 6 6 4 2

LIPS
 The height of center part of upper lip trails behind the
vertical height of the lower face in childhood & then
catches up during & after adolescence.
 Lip incompetence is common in children
 What looks like incompetent lips in childhood or early
adolescence is merely a reflection of incomplete soft
tissue growth
 Lip height
 Females :
Upper lip - till 14
Lower lip - continues to grow up to the age of 16
 Males : growth of both upper & lower lip continues
into late teens

 Lip thickness is maximum during the conclusion
of adolescent growth spurt & then decreases
during late teens.

Smile evaluation
 A balanced smile is achieved by appropriately positioning the teeth and gingiva in
the area that is displayed by lip animation during smiling (dynamic display zone).
 The amount of incisor and gingival display
 The transverse dimension / broadness of the smile
 The smile arc
 Buccal corridor
 Negetive space

Incisor and gingival display
The difference between social and enjoyment smile is not
the activity of orbicularis oris musculature but of orbicularis

Chin
 Tapered / squarish
 Pinch test – semiquantitative assessment of
subcutaneous fat
 Sub platysmal and supra platysmal fat -
differentiated

PROFILE VIEW
 Fore head
 Slopes anteriorly
 Accentuated at supra orbital rim
 Frontal bossing
 Supra orbital hypoplasia
 Glabellar angle
 Gl- N to N – prs
 132 + / - 15 degrees

Soft tissue proportions: profile
view.
 The prominent part of the forehead (glabella)
should be approximately the same as the base of
the nose, and the forehead should slope gently
posteriorly.
 The radix (the depth of the concavity at the base of
the forehead) should be prominent to obscure the
eyelash on the opposite side.
 Lateral orbital rims – 8 to12 mm
behind the anterior projection of globe.
 Infra orbital rim – 2mm anterior
to the globe.

 The contour of the alae
from the base of the
nose to its tip should be
well defined to form a
"scroll".
 The bridge of the nose
(nasal dorsum) should
then be a straight line
from the base of the
radix to the nasal tip
cartilage, and there
should be a slight
prominence of the tip
relative to the bridge.

Naso labial angle – 90 to 110
degrees
2
• Alar base has to be supported by
skeletal nasal bone.
• Nasal bridge – 5 – 8 mm ant to
globes
• Nasal tip ( prn ) – subnasale :
subnasale – alar base crease = 2:1
• If values of 1: 1 – maxillary
defeciency

Clinical facial examination - Profile view
 Mandibular area
 Lower lip prominence
 Soft tissue pogonion
prominence
 Neck – chin angle – 110
 Throat length contour – 50 mm
 Overjet

Labiomental fold
 The labiomental sulcus should form a shallow S
curve, with the upper and lower portions similarly
shaped. The prominence of the chin should be
slightly less than the prominence of the lower lip.
 The angle between the lower lip, chin, and
deepest point along the chin-neck contour should
be approximately 90 degrees

Cervico mental area
 Mandibular angle- Inferior border defenition
- well defined in profile
- skin laxity, cervical facial lipomatosis, high
mandibular plane angle are conditions – obscure
the defenition.
 Neck – chin angle and length
- normally 110 degrees
- PoG – neck chin angle : distance is 50 mm.

TMJ Examination
• The range of movements
• Deviation from normal movements
• Any pain during movement
• The joint sounds.

Intra-oral examination
Soft tissues
 General periodontal condition
 Tongue size, position and activity
 Mentalis muscle activity
 Finger or thumb sucking
Hard tissue
 Dental assessment

Periodontal evaluation
 Adequate attached gingiva
 Maintain bone around the necks of each of the teeth
at the interdental osteotomy sites

Dentition
 Vertical
 Overbite
 Plane of occlusion
 Curve of spee
 Horizontal
 Anatomical variation
 Crowding / spacing
 Overjet
 Transverse
 Crossbites

 Maxillary retrusion
 Mandibular retrusion
 Clockwise mandibular rotation
 Upper and lower denture base retrusion
 Overjet increase

Canting of bilateral structures, specially the lips
and the dentition.

Burstone's Analysis (COGS)
Burstone, Randal, Legan, Murphy &
Norton
(1978)

ANATOMIC LANDMARKS
 Sella (S)
 Nasion (N)
 Rhinion (Rh)
 Glabella (G)
 Orbitale ( O )
 Articulare (Ar)
 Pterygomaxillary fissure
(PTM)
 Posterior nasal spine
(PNS)

ANATOMIC LANDMARKS
 Prosthion (P)
 Anterior nasal spine
(ANS)
 Subspinale (A)
 Menton (Me)
 Gnathion (Gn)
 Pogonion (Pg)
 Mandibular plane
(MP)

ANATOMIC LANDMARKS
 Infradentale ( I )
 Supramentale (B)
 Condylion (C )
 Pronasale (P )

 The COGS appraisal describes
 Dental,
 Skeletal
 Soft tissue variations.

CRANIAL BASE
HORIZONTAL PLANE
(HP), which is a
surrogate Frankfort
plane,constructed by
drawing a line 7 o from
the line S to N.

 Ar- PTM :
 The greater the distance
between Ar-PTM, the
more the mandible will
lie posterior to the
maxilla, assuming that
all other facial
dimensions are normal.
 Therefore, one factor for
prognathism or
retrognathism can be
evaluated by this
measurement of cranial
base.

HORIZONTAL SKELETAL
PROFILE
 N-A –Pg (Angle):
gives an indication of
the overall facial
convexity. A positive
(+) angle of convexity
denotes a convex
face; a negative (-)
angle denotes a
concave face.

VERTICAL SKELETAL AND
DENTAL
 Middle third facial height :
Distance from N to ANS
 Posterior maxillary height :
PNS-N
 Lower third facial height :
ANS – GN
 Divergence of mandible
posteriorly : M.P-H.P
angle(clockwise or counter -
clockwise rotations of the
maxilla and mandible)

 U1 to NF: Anterior
maxillary dental height
 L1 to MP: Anterior
mandibular dental
height
These two
measurements define
how far the incisors
have erupted in relation
to NF and MP
respectively.

 Max. molar to NF :
Posterior maxillary
dental height
 Mand. Molar to MP:
Post mandibular
dental height

MAX-MAND. RELATION
 ANS-PNS: This
measurement along
with the N-ANS and
PNS– N gives a
quantitative
description of the
maxilla in the skull
complex.

 Ar - Go : Length of
Mandibular ramus
 Go - Pg : Length of
Mandibular body
 Ar - Go - Gn Angle :
Gonial angle that
represents the
relationship between
ramal plane and MP.
Vertical /Horizontal growth
 B - Pg : Distance from B
point to line perpendicular
to MP through Pg
describes chin
prominence.

DENTAL
 OP- upper HP:
 AB – OP:
 U1 to NF angle & L1
to MP angle: These
angulations determine
the procumbency or
recumbency of the
incisors.

BURSTONE’S ANALYSIS
CHARLS .J.BURSTON ET AL: JOS,VOL 36 , PG 269-277

STEINER’S ANALYSIS
S.N
o
Measurement Mean
1. SNA 820
2. SNB 800
3. ANB 20
4. SND 760
5. M.P to SN 320
6. U1 to N-A 4mm
7. U1 to N-A (angle) 220
8. L1 to N-B 4mm
9. L1 to N-B (angle) 250
10. Interincisal angle 1300
11. Occ. Plane to S-N (angle) 140
S-line: Upper lip: 0mm Lower lip: 0mm

WITS APPRAISAL
 AO is 2mm ahead of BO - skeletal class I

SCHWARZ ANALYSIS
Length of Mean
Anterior cranial
base
Mandibular base ACB + 3mm
Maxillary base mm
Ramus length mm
Ramus width mm

HOLDAWAY’S SOFT TISSUE ANALYSIS
Measurement Mean
Facial angle 90-920
Upper lip curvature 1.5-4mm (2.5)
Skeletal convexity
at point A
-2 to +2
H-line angle 7-150
Nose tip to H-line Upto 12mm
Upper sulcus depth 3-7mm
Upper lip thickness 15mm
Upper lip strain Same as ULS
Lower lip to H-line 0mm -1to +2mm
Lower sulcus depth 5mm
Soft tissue to chin
thickness
10-12mm

 The first horizontal plane connects the medial aspects
of the zygomaticofrontal sutures.
 The second horizontal plane connects the center of
the zygomatic arches.
 The third horizontal plane connects the jugal
processes.
 A fourth horizontal plane runs through the menton and
is parallel to the first plane.
Grummons article JCO 1987

Zygomaticofrontal sutural plane
Zygomatic arch plane
Jugal plane
Z plane through menton
Mandibular morphology
Volumetric comparison

Maxillo mandibular comparison of
assymetry

MSR-J maxillary width
MSR-Ag mandibular width
MSR-NC width of NC
Nasal septum
deviation
MSR-Co Asymmetry in
condyle
MSR-Me Mandibular
symmetry
LINEAR ASYMMETRY
MAXILLARY MANDIBULAR COMPONENTS

 Errors in cephalometric measurements
 Radiographic cephalometry is a two dimensional
representation of three dimensional object.
a)Radiographic projection error
Magnification
Distortion
b)Errors within measuring system
c)Errors in landmark identification
Quality of radiographic image
Precision of landmark definition
Reproducibility of landmark location
The operator and registration procedure

Limitations of cephalometric radiographic
analysis
 1)Growth pattern not taken into consideration
 2)Mean values are based on different
population
 3)Two dimensional representation of three
dimensional object
 4)Form and functions not taken into
consideration

A combination of various cephalometric
norms and variables should be compiled
to arrive at a proper diagnosis.Although
innumerable controversies exist in the
field of cephalometrics, it is still a very
significant & effective diagnostic tool.
Conclusion:

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”

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

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. These
lines will be used to
plan the vertical

3. Three vertical lines VC,
VB, VM are drawn from
upper base line (A) to the
lower baseline (A) on each
buccal segment.
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
Cuspal reference points
are used for transverse

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
Interrupted line is the
proposed osteotomy site.

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.

Diagnosis and Treatment Planning in Orthognathic Surgery

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