Cephalometrics for orthognathic surgery1 /certified fixed orthodontic courses by Indian dental academy

Cephalometrics for Orthognathic
Surgery
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in continuing dental education

 Taken from the AJO-DO 1984 Dec
(470-482): The quadrilateral
analysis - Di Paolo, Philip,
Maganzini, and Hirce
 --------------------------------
 The quadrilateral analysis: A
differential diagnosis for surgical

 Taken from the AJO-DO 1983 Dec (508-
520): Projecting the soft-tissue outcome
of surgical and orthodontic manipulation
of the maxillofacial skeleton - Kinnebrew,
Hoffman,
 --------------------------------
 Projecting the soft-tissue outcome of
surgical and orthodontic manipulation of
the maxillofacial skeleton

 Taken from the AJO-DO 1980 Dec
(657-669): Cephalometric diagnosis
and surgical-orthodontic correction
of apertognathia - Frost
 --------------------------------
 Cephalometric diagnosis and
surgical-orthodontic correction of
apertognathia

Ceph needs innovation not renovation
 Ao- 97 vol67 no.5

Factors Influencing the Predictability of
Soft Tissue Profile
Changes Following Mandibular Setback
Surgery
 (Angle Orthod 2001;71:216–227.)

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.

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

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

Soft tissue Cephalometric 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

TVL

NHP

The Arnett’s way

Arnett & Bergman....
(1993- Am. J. orthod. & Dentof Orthop. )
 Contributed 19 keys to facial
esthetics
 Used for comprehensive treatment
planning.
Backed by
Soft Tissue Cephalometric Analysis
(1999 - Am. J. Orthod. & Dentof. Orthop.)

“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

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
originally

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.
 This step is carried out exactly as
described by Bench, et al.2 After placing
the teeth in their ideal position we are
now ready to trace the new profile.

Thank you
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Cephalometrics for orthognathic surgery1 /certified fixed orthodontic courses by Indian dental academy

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