Cephalometrics Guide Orthognathic Surgery Planning

Cephalometrics for Orthognathic
Surgery
www.indiandentalacademy.com

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).

HISTORY
 Earlier Cephalometric analysis
highlighting dentofacial patterns and
dysplasias are
 Wylie’s analysis (1947)
 Down’s analysis (1956)
 Steiner’s analysis
However,

Analysis to help diagnose and plan for
orthognathic surgeries came in late seventies
and early eighties.

 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

COGS – Cephalometrics for
Orthognathic Surgery
 Developed by Charles Burstone et al
 Presented first in Journal of Oral
Surgery. 1978 April
 Followed by Soft tissue Cephalometric
Analysis for Orthognathic surgery in
Journal of Oral Surgery. 1980

 Data derived from samples obtained from
Child Research Centre, Univ. of Colorado
school of medicine.
 Sample type: Northern european descent
 Sample Size = 27

16 females

11 males

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.

 Critical facial components can be examined.
 Standards and statistics are available for variations in
age and sex from 5 to 20
 Consists of a series of measurements that can be
computerised.

H-Plane

Cranial Base

Cranial Base
Males Females
Ar-Ptm ( || to
HP)
37.1 + 2.8 32.8 + 1.9
Ptm-N ( || to
HP)
52.8 + 4.1 50.9 + 3.0

Horizontal Measurements
N-A-Pg

Horizontal Measurements
Males Females
N-A-Pg angle 3.9 + 6.4 2.6 + 5.1
N-A ( || to HP ) 0.0 + 3.7 -2.0 + 3.7
N-B ( || to HP ) -5.3 + 6.7 -6.9 + 4.3
N-Pg ( || to HP) -4.3 + 8.5 -6.5 + 5.1

Vertical Measurements

Vertical Measurements
Males Females
N-ANS ( 1 to HP) 54.7 + 3.2 50.0 + 2.4
ANS-Gn ( 1 to HP) 68.6 + 3.8 61.3 + 3.3
PNS-N ( 1 to HP) 53.9 + 1.7 50.6 + 2.2
MP – HP angle 23.0 + 5.9 24.2 + 5.0
Upper incisor-NF(1 to NF) 30.5 + 2.1 27.5 + 1.7
Lower incisor-MP(1 to
MP)
45.0 + 2.1 40.8 + 1.8
Upper molar-NF (1 to NF) 26.2 + 2.0 23.3 + 1.3
Lower molar-MP (1 to 35.8 + 2.6 32.1 + 1.9www.indiandentalacademy.com

Maxilla and Mandible

Maxilla and Mandible
Males Females
PNS-ANS (|| to
HP)
57.7 + 2.5 52.6 + 3.5
Ar-Go (linear) 52.0 + 4.2 46.8 + 2.5
Go-Pg (linear) 83.7 + 4.6 74.3 + 5.8
B-Pg (|| to MP) 8.9 + 1.7 7.2 + 1.9
Ar-Go-Gn angle 119.1 + 6.5 122.0 + 6.9

Dental Measurements

Dental
Males Females
OP upper – HP angle 6.2 + 5.1 7.1 + 2.5
OP lower – HP angle
A-B ( 1 to OP) -1.1 + 2.0 -0.4 + 2.5
Upper incisor – NF angle 111.0 + 4.7 112.5 + 5.3
Lower incisor – MP angle 95.9 + 5.2 95.9 + 5.7

The Arnett’s way

Soft tissue Cephalometric
Analysis
 By William Arnett and Robert Bergman
AJODO 1999
 Sequale to Facial keys to orthodontic
diagnosis and treatment planning. Part I
and II
AJODO 1993

“We only treat what we are educated to
see. The more we see, the better the treatment
we render our patients”
-Arnett....

Arnett and Bergman.......
“When attention is directed only to bite
correction, facial balance may not improve and can
deteriorate. The orthodontist's job is to balance
occlusal correction, temporomandibular joint
function, periodonal health, stability, and facial
balance while moving the teeth to correct the
bite.”

Format for examination of face
 Natural head posture,
 Centric relation (uppermost condyle
position),
 Relaxed lip posture
 True Vertical Line ( TVL )

Arnett and Bergman
By examining the patient in this format,
reliable facial-skeletal data can be
obtained that enhances diagnosis,
treatment planning, treatment, and quality
of results.

Why the Natural head position?

Natural head posture is preferred
because of its demonstrated accuracy over
intracranial landmarks.
Natural head posture has a 2° standard
deviation compared with a 4° to 6° standard
deviation for the various intracranial landmarks
in use.

Why Centric Relation??

Why relaxed lip position??

 The patient should be in the relaxed lip position
because it demonstrates the soft tissue, relative to
hard tissue, without muscular compensation for
dentoskeletal abnormalities.
 Vertical disharmony between lip lengths and skeletal
height (vertical maxillary excess, vertical maxillary
deficiency, mandibular protrusion, mandibular
retrusion with deep bite) can not be assessed without
the relaxed lip posture.

Existing positions and needed changes in upper
incisor exposure, interlabial gap, lip length, and
proportion are lost in the closed lip position.
Closed lip position may be adequate for
normoskeletal cases but is totally inadequate for
skeletal disharmony assessment

What is TVL and Why TVL??

True Vertical Line ( TVL )
 It is a Vertical line passing
through the Subnasale with
natural head posture.
 It may be used to quantify
favorable or unfavourable change
in the profile after overjet
reduction and has a potential role
in post treatment analysis and
research

Analysis
 Data base: Based on 46 white models
 Males = 20
 Females = 26
 All models had natural class I occlusion
and reasonably well balanced facially

Metallic Markers are placed on
right side of face to mark key
midface structures. i.e
1. Orbital rim marker
2. The alar base marker
3. The subpupil marker

Analysis
Composed of five components
1. Dentoskeletal factors
2. Soft tissue structures
3. Facial length
4. Projections to TVL
5. Harmony values

Dento skeletal factors
 Have a large influence on the facial
profile.
 When in normal range individually
produce a balanced and harmonious
nasal base, lip, soft tissue A’ and B’,
and chin relationship.

Dento skeletal Factors
Females Males
Mx occlusal plane 95.6 + 1.8 95.0 + 1.4
Mx1 to Mx occlusal
plane
56.8 ± 2.5 57.8 ± 3.0
Md1 to Md occlusal
plane
64.3 ± 3.2 64.0 ± 4.0
Overjet 3.2 ± .4 3.2 ± .6
Overbite 3.2 ± .7 3.2 ± .7

Dento skeletal factors

Soft tissue structures
 Soft tissue thickness in combination with
dentoskeletal factors largely control lower
facial esthetic balance.
 Nasolabial angle and upper lip angle are
important in assessing the upper lip and may
be used by the orthodontist as part of the
extraction decision.

Soft Tissue Structures
Females Males
Upper lip
thickness
12.6 ± 1.8 14.8 ± 1.4
Lower lip
thickness
13.6 ± 1.4 15.1 ± 1.2
Pogonion-
Pogonion’
11.8 ± 1.5 13.5 ± 2.3
Menton-
Menton’
7.4 ± 1.6 8.8 ± 1.3
Nasolabial
angle
103.5 ± 6.8 106.4 ± 7.7
Upper lip angle 12.1 ± 5.1 8.3 ± 5.4www.indiandentalacademy.com

Soft tissue structures

Facial length
 The presence and location of vertical
abnormalities is indicated by assessing
maxillary height, mandibular height,
upper incisor exposure and overbite.

Facial Length
Females Males
Nasion’-Menton’ 124.6 ± 4.7 137.7 ± 6.5
Upper lip length 21.0 ± 1.9 24.4 ± 2.5
Interlabial gap 3.3 ± 1.3 2.4 ± 1.1
Lower lip length 46.9 ± 2.3 54.3 ± 2.4
Lower 1/3 of face 71.1 ± 3.5 81.1 ± 4.7
Overbite 3.2 ± .7 3.2 ± .7
Mx1 exposure 4.7 ± 1.6 3.9 ± 1.2
Maxillary height 25.7 ± 2.1 28.4 ± 3.2
Mandibular
height
48.6 ± 2.4 56.0 ± 3.0

Facial Length

Projections to TVL
 They are antero-posterior measurements of soft
tissue and represent the sum of the
dentoskeletal position plus the soft tissue
thickness overlying that hard tissue landmark.
 The horizontal distance for each individual
landmark, measured perpendicular to the TVL,
is termed the landmark’s absolute value.

Projections to TVL
Females Males
Glabella –8.5 ± 2.4 –8.0 ± 2.5
Orbital rims –18.7 ± 2.0 –22.4 ± 2.7
Cheek bone –20.6 ± 2.4 –25.2 ± 4.0
Subpupil –14.8 ± 2.1 –18.4 ± 1.9
Alar base –12.9 ± 1.1 –15.0 ± 1.7
Nasal
projection
16.0 ± 1.4 17.4 ± 1.7
Subnasale 0 0

Projections to TVL

Projections to TVL
Females Males
A point’ –0.1 ± 1.0 –0.3 ± 1.0
Upper lip
anterior
3.7 ± 1.2 3.3 ± 1.7
Mx1 –9.2 ± 2.2 –12.1 ± 1.8
Md1 –12.4 ± 2.2 –15.4 ± 1.9
Lower lip
anterior
1.9 ± 1.4 1.0 ± 2.2
B point’ –5.3 ± 1.5 –7.1 ± 1.6
Pogonion’ –2.6 ± 1. 9 –3.5 ± 1.8

Harmony Values
 Created to measure facial structure balance
and harmony.
 It is the position of each landmark relative to
other landmarks that determines the facial
balance.
 The harmony values represent the horizontal
distance between two landmarks measured
perpendicular to the true vertical

HV examines four areas of balance
 Intramandibular parts.
 Interjaw
 Orbits to jaws
 The total face

Intramandibular Relations
Females Males
Md1-Pogonion’ 9.8 ± 2.6 11.9 ± 2.8
Lower lip anterior-
Pogonion’
4.5 ± 2.1 4.4 ± 2.5
B point’-Pogonion’ 2.7 ± 1.1 3.6 ± 1.3
Throat length
(neck throat point
to Pog’)
58.2 ± 5.9 61.4 ± 7.4
These values assess chin projection relative to other
mandibular structures.

Harmony Values

Inter jaw Relations
Females Males
Subnasale’-
Pogonion’
3.2 ± 1.9 4.0 ± 1.7
A point’-B
point’
5.2 ± 1.6 6.8 ± 1.5
Upper lip
anterior-lower
lip anterior
1.8 ± 1.0 2.3 ± 1.2

Orbit to Jaws
Females Males
Orbital rim’- A
point’
18.5 ± 2.3 22.1 ± 3
Orbital rim’-
Pogonion’
16.0 ± 2.6 18.9 ± 2.8

Full Facial Balance
Females Males
Facial angle 169.3 ± 3.4 169.4 ± 3.2
Glabella’-A
point’
8.4 ± 2.7 7.8 ± 2.8
Glabella’-
Pogonion’
5.9 ± 2.3 4.6 ± 2.2

Note
Landmark values are dependent on TVL
placement.
HOWEVER

Harmony values are independent of
the position of the TVL thus making it
very reliable

SURGICAL-ORTHODONTIC
CEPHALOMETRIC PREDICTION TRACING
By Epker and Fish (1980 JCO)
adopted in part from the mechanics
developed by Ricketts for cephalometric
analysis, growth prediction and visual
treatment objective construction as
presented by Bench, Gugino, and Hilgers.
(Bioprogressive therapy)

Cephalometric Prediction Tracing for
Mandibular Advancements.
Why do prediction tracings for mandibular
surgery?

1) To accurately assess the profile esthetic
results which will result from the proposed
surgery,
2) To consider the desirability of simultaneous
adjunctive procedures such as genioplasty,
suprahyoid myotomy, etc.,
3) To help determine the sequencing of
surgery and orthodontics (i.e., if the surgery
is done first will it be more difficult or easier
to do the indicated orthodontics),

4) To help decide what type of orthodontics
might best be employed (i.e., extraction
versus non-extraction)
5) To determine the anchorage requirements
should extraction treatment be chosen

The Cephalometric x-ray from which the
prediction tracing is to be done should be
taken with the patient's lips in REPOSE

Step I: Trace the Stable Structures.
 The first step in
producing a prediction
tracing is to overlay a
piece of acetate paper
on the original
cephalometric tracing
and trace all structures
which will not be
significantly altered by
the surgery and/or
orthodontics

 For mandibular surgery,
these structures will include
the deep cranial features,
the maxilla, the maxillary
occlusal plane, the
mandibular ramus and the
profile to the base of the
nose. Draw in Frankfort
Horizontal and a line from
nasion to indicate the
optimum facial depth, i.e.,
89° in females, 90° in males

Step 2 - Add Skeletal Portion Changed by
Surgery
 Slide the prediction
tracing to the left and
rotate it slightly to
position bony pogonion
at the optimum facial
depth, keeping the
mandibular occlusal
plane in proper relation
to the maxillary occlusal
plane.

 Once a satisfactory
position is achieved,
trace the distal portion
of the mandible, the
corpus axis, and the
soft tissue chin in this
position (Fig. 2B).
 There is little change in
soft tissue chin
thickness, so the soft
tissue chin may be
drawn in just as it was
originallywww.indiandentalacademy.com

Step 3 - New A-Po Line.
 Construct a new line from
Point A to pogonion. If a
genioplasty is to be included
in the procedure, the anterior
portion of this altered chin,
be it bone or alloplast, is now
construed to be pogonion for
purposes of placing the
teeth.

Step 4 - Placing the Teeth.
 First the lower incisor is
placed in its optimum
position 1 millimeter
ahead of the A-Po line,
1 millimeter above the
occlusal plane, and at
22 degrees to the A-Po
line.

Step 4 - Placing the Teeth.
 Old and new mandibles are
then superimposed on
Corpus Axis at PM and the
change in lower incisor
position is noted.
Arithmetically adding twice
this change to the crowding
already present allows
calculation of the arch length
deficiency or excess. Thus,
the anterior-posterior
position of the lower first
molar can be determined
and the molar is traced in
this position.

 The upper first molar
is then placed in the
desired occlusion and
the upper incisor is
likewise placed in the
optimum position with
its long axis 5 degrees
more upright than the
new facial axis (dotted
line on the prediction
tracing) .

Step 5 - Tracing the New Lip Contours.
 Once the teeth are placed, the lip
contours are traced to correspond to
the new incisor positions.

 Once completed, the prediction tracing must be
viewed as a goal toward which one is working.
 Once the prediction tracing is as you like it, the
prediction tracing can be superimposed upon the
original tracings, registering on the structures not
significantly altered by the surgery and/or
orthodontics, and the previously stated five basic
reasons to do prediction tracings for mandibular
surgery can be deliberately and intelligently assessed

Cephalometric Prediction for Maxillary
Superior Repositioning.
 Why do prediction tracings for
maxillary surgery cases?

It is even more important to do prediction
tracings for maxillary surgery cases, especially
when the primary direction of movement is
vertical, to ascertain the effects of the prescribed
surgery on the mandible.

 The decision to superiorly reposition the
maxilla is made primarily from their esthetic
features. The amount of superior
repositioning is based upon the upper tooth
to lip measurement which is made clinically.
Still,

 We need to know if the maxilla should be moved
posteriorly or anteriorly along with the upward
movement
 We need to know what orthodontics will be
necessary.
 Furthermore, we need to know if autorotation alone
will produce an adequate chin or if we will wish to
add a genioplasty or consider simultaneous
mandibular advancement.
These questions can be answered from a prediction
tracing.

Step 1 - Trace the Stable Structures.
 As is the case with all
prediction tracings, we
again begin by tracing
the structures which will
not be modified either
surgically or
orthodontically

Step 2 - Determination of Ideal Vertical
Position for the Upper Incisor.
 the measurement of the amount of upper central
incisor exposed, i.e., that from stomion of the upper
lip to incisal edge, be made clinically with the patient
standing in a relaxed posture.
 This is the single most important measurement in
preparation for superior repositioning of the maxilla
and can be confirmed cephalometrically.

 Once the amount of incisor exposed beneath the upper lip
is determined, the "ideal" amount of superior repositioning
of the upper incisor can be determined by the formula
x= y-2
0.8
 where X is the amount of superior repositioning necessary
 Y is the amount of upper incisor showing.

This formula is used because the upper lip
tends to shorten approximately 20% of the
amount of superior surgical repositioning; thus, a
1:1 relationship between the amount of tooth
showing and the amount of repositioning
necessary does not exist.

 If the superior movement is to be accompanied by
posterior movement of the incisors and an acute
nasolabial angle is present, the lip will not shorten
quite as much as predicted.
 Conversely, with an obtuse nasolabial angle and
anterior movement of the incisor, the lip will tend
to shorten slightly more.

These slight variations may be
disregarded, unless the anterior-
posterior change is more than 6
millimeters.

Step 2 - Determination of Ideal Vertical
Position for the Upper Incisor.
 Once the desired amount
of vertical incisor
repositioning is
determined, draw a line
parallel to Frankfort
horizontal on the
prediction tracing to
represent the desired
vertical position

Step 3 - Autorotation of the
Mandible.
 Superimpose the original
and prediction tracings
and, keeping the
mandibular condyle in the
same position, rotate the
prediction tracing
clockwise until the occlusal
plane is 1 mm above the
line indicating the desired
position of the upper
incisor.

 Trace the mandible in this position. The corpus axis and
the occlusal plane are also traced in at this time
 The change in point A and the soft tissue chin
contour must be carefully studied at this time. To
allow easier observation of these features, one may
wish to trace, with dotted lines, the soft tissue chin,
the lower incisor, and Point A.

Step 4 - Genioplasty Determination
 The next feature which must
be noted is the new soft tissue
chin position. (This is where
the chin autorotates to.) If the
chin is adequate, then
genioplasty is not necessary.
 However, if the chin is still
weak, either mandibular
advancement or some type of
genioplasty must be added to
the treatment plan for optimum
esthetics.
 Conversely, if the chin is too
strong, then some procedure
to reduce it may be required.

Step 4 - Genioplasty Determination
 Cephalometric criteria
which may be used to
help determine optimum
anteroposterior soft-
tissue chin position.

 For bony genioplasties,
the ratio of anterior-
posterior soft tissue
change to bony change
is about 0.6:1, thus, if 5
millimeters more chin is
desired, a bony
advancement of 8
millimeters will be
required.

If alloplastic material is to be added, this
ratio approaches 1:1 thus 5 millimeters of
alloplast will produce 5 millimeters more soft
tissue chin.
Dann, J.A. and Epker, B.N.: Proplast Genioplasty: A
Retrospective Study of Treatment Results, Angle Orthodontist,
[47:173, 1977.]

 Once the amount of genioplasty has been
determined, the new A-Po line can be
constructed using the genioplasty as a
new pognonion and either the old Point A
or new Point A as discussed previously.

Step 5 - Placement of Teeth In
Ideal Positions.
 The lower incisor is placed in relationship to
the symphysis of the mandible, the occlusal
plane and the APO plane. The arch length
requirements and realistic results dictate its
location.

Step 6 - Nasal Outline
 With superior repositioning of the
maxilla, the nasal tip is generally
elevated slightly. This is more
pronounced if the maxilla is moved
upward and forward, less
pronounced if upward and
backward. The lower border of the
nose is relatively unchanged though
it too may be elevated a small
amount. Accordingly, the prediction
tracing should be placed on the
original with the fixed landmarks
superimposed and the nasal outline
traced with the aforementioned
alterations

Step 7 - Upper Lip.
The upper lip reacts to superior repositioning in
the following ways:
 The length from subnasale to upper lip stomion
shortens 1/5 of the amount of superior repositioning,
 The thickness increases by 1/3 of the amount of
incisor retraction, and
 The lip thins out slightly if the upper incisor is moved
forward, but in all but the most extreme instances this
is unnoticeable.

 To trace the new upper lip one should
superimpose on the fixed cranial structures
and study the change in incisor position. If the
upper incisor is retracted such that it lies
posterior to an imaginary line from the labial
surface to Point A on the original tracing, then
lip support has been reduced and one should
trace the new lip in the following manner:


 Divide the vertical distance from old incisor tip to new
incisor tip into fifths and the anterior-posteriordistance
into thirds.
 Move the prediction tracing down 1/5 and forward
2/3 and draw in the new lip vermillion.
 Connect the new lip vermillion to the previously
traced subnasale in an artistic manner.
 Subnasale is affected so little by superior
repositioning that for prediction it can be considered a
fixed point.

If the upper incisor has moved directly up the line from
the labial surface to Point A of the original tracing, then
lip support is unchanged and one should trace the new
lip in the following manner:
 Divide the vertical distance from old incisor tip
to new incisor tip into fifths. Move the
prediction tracing down 1/5 and trace the new
lip, connecting it to subnasale as above.

If, the upper incisor is forward of the line from labial
surface to Point A of the original tracing, then lip support
has been increased and the new lip is traced as follows:
 Divide the vertical distance from old incisor tip
to new incisor tip into fifths.
 Move the prediction tracing down 1/5. Then,
 While maintaining this vertical position, rotate
and slide the prediction tracing such that the
long axis of the upper incisor in the prediction
tracing is parallel to, and the labial surface is
flush with, the line from the labial surface to
Point A of the original tracing.
 Trace the new lip in this position This
effectively maintains the original lip thickness.

Step 8 - Lower Lip.
In most instances the lower lip vermillion is traced in the
same relation to the lower incisors as existed prior to
treatment.

Step 8 - Lower Lip.
Superimpose the lower incisor on the prediction tracing
over that on the original and trace the lower lip.
Where the lower incisors are retracted 5 millimeters or
more, the lip tends to thicken slightly.
Thus the lower incisors are not exactly superimposed,
but the prediction tracing is moved slightly to the
lingual of an exact superimposition (i.e., the lip
thickens slightly) and the lip traced in this position

Some artistic freedom must be employed when dealing
with a hypotonic lip.
the hypotonic lip may increase mildly in tonicity following
production of lip competence and added support for
the lip via augmentation genioplasty.
IN SUCH CASES
then the lip would be traced slightly thinner for
purposes of prediction

Step 9 - Chin.
 If no genioplasty is projected, the soft
tissue chin will be relatively unaffected by
treatment and should be traced by simply
superimposing on the mandibular
symphysis.)

 If a sliding genioplasty is done, the chin
is traced by first superimposing on the
original symphysis and then sliding the
prediction tracing back 6/10 of the
amount of the genioplasty and tracing
the new chin contour.

 If an alloplastic implant is added, the
new chin contour can be determined by
simply superimposing the alloplastic
implant on the original symphysis and
tracing the chin

 Once the tracing is
completed, we again
must study it to
determine if indeed we
have achieved a
satisfactory result.

 To once again gain optimum
appreciation for the proposed
changes superimposition of the
original and prediction tracing is
done again superimposing on
the structures not significantly
altered by the surgery and/or
orthodontics.

 Frequently, it is necessary to do several prediction tracings,
trying different surgical approaches to a problem (i.e., superior
repositioning vs. superior repositioning with genioplasty vs.
superior repositioning with mandibular advancement) before
one can determine which result is best.

Conclusion
 Certainly it is better to retreat a patient on paper than
to wish that a different surgical approach had been
employed after the fact

Cephalometrics Guide Orthognathic Surgery Planning

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