Surg analysis ii /certified fixed orthodontic courses by Indian dental academy

Surgical analysis and prediction
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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Surgical analysis

Hard tissue analysis

Soft tissue analysis
SOFT TISSUE CEPHALOMETRIC
ANALYSIS- Arnett et al

CEPHALOMETRICS FOR
ORTHOGNATHIC SURGERY
QUADRILATERAL ANALYSIS
MC NAMARA ANALYSIS

prediction

SOFT TISSUE CEPHALOMETRIC
ANALYSIS - Legan, Dallas, Burstone et al
TOMAC: AN ORTHOGNATHIC
TREATMENT PLANNING SYSTEM
SOFT-TISSUE ANALYSIS- TONY G.
McCOLLUM,
VIDEO IMAGING


SOFT TISSUE
CEPHALOMETRIC
ANALYSIS- Arnett et al


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

In 1999 Arnett et al purposed the Soft
Tissue Cephalometric Analysis (STCA) ,
with particular emphasis on midface
structures that do not show on standard
cephalometric analysis.
In particular, orbital rim, subpupil,and alar
base contours were noted to indicate
anteroposterior position of the maxilla.

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Soft Tissue Cephalometric Analysis
(STCA) can be used to diagnose the
patient in five different but interrelated
areas;
dentoskeletal factors,
soft tissue components,
facial lengths,
True vertical line (TVL) projections,
and harmony of parts.

Dentoskeletal factors,
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

Dentoskeletal factors have a large
influence on the facial profile.
These factors, when in normal range will
usually produce a balanced and
harmonious nasal base, lip, soft A’, soft B’,
and chin relationship.


Dentoskeletal factors:
 maxillary occlusal
plane
upper incisor to
maxillary occlusal plane,
lower incisor to
mandibular occlusal
plane,
overbite, and overjet
are measured.


female


male

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

The dentoskeletal factors, to a large
extent, control esthetic outcome
How accurately the orthodontist and
surgeon manage the dentoskeletal
components greatly influences the
resulting profile.


2.Soft tissue structures


Tissue thickness of
upper lip, lower lip, B
to B’, Pog to Pog’, and
Me to Me’ are
depicted.
Soft tissue thickness
in combination with
previously described
dentoskeletal factors
largely control lower
facial aesthetic
balance.

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Soft tissue structure; ideal values
Upper lip thickness –female-12.6 ± 1.8mm
male-14.8 ± 1.4 mm
Lower lip thickness -:female;13.6 ± 1.4 mm
male; 15.1 ± 1.2mm .
Pogonion-Pogonion’ --female; 11.8 ± 1.5 mm
male;13.5 ± 2.3mm .
Menton-Menton’ --female;7.4 ± 1.6 mm
male--8.8 ± 1.3 mm.


Upper lip angle and nasolabial angle are depicted.
Clinical significance; These soft tissue structures are altered
by movement of the incisor teeth. Therefore these angles
should be studied before orthodontic overjet correction to
assess the potential for changes out of normal range.

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Upper lip angle-- female 12.1 ± 5.1
male 8.3 ± 5.4 degree

Nasolabial angle-- female-103.5 ± 6.8
male- 106.4 ± 7.7 degree


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3.Facial length
Soft tissue lengths
include facial height
(Na’ to Me’), lower
one-third height (Sn
to Me’), upper lip
length (Sn to upper
lip inferior), lower
lip length (lower lip
superior to Me’),
and interlabial gap
(upper lip inferior to
lower lip superior).

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Facial height --female-124.6 ± 4.7mm; male137.7 ± 6.5mm
Lower 1/3 of face —female;-- 71.1 ± 3.5 mm
male;-- 81.1 ± 4.7
Upper lip length –female-21.0 ± 1.9mm male24.4 ± 2.5 mm
Interlabial gap– female- 3.3 ± 1.3mm male-2.4 ±
1.1 mm.
Lower lip length– female- 46.9 ± 2.3mm;
male-;54.3 ± 2.4mm

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Additional essential
vertical
measurements
include:
Relaxed lip upper
incisor exposure,
maxillary height (Sn
to Mx1tip),
mandibular height
(Md1 tip to Me’)
and overbite.


Ideal values
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Maxillary incisor exposure –female-4.7 ±
1.6mm male-3.9 ± 1.2 mm
Maxillary height —female- 25.7 ± 2.1mm
male- 28.4 ± 3.2mm .
Mandibular height –female-48.6 ± 2.4mm
male-56.0 ± 3.0mm


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4.TVL projections
are anteroposterior
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.


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When midface
retrusion is diagnosed
the TVL is moved 1 to
3 mm anterior.
Midface retrusion is
defined by clinical
factors (long nose,
deficient midface
structures, poor incisor
upper lip support) and
cephalometric factors
(upright upper lip
and/or thick upper lip)

Soft tissue profile
points measured to
TVL are Glabella
( G’), nasal
tip ( NT), soft tissue
A’ point ( A’),
upper lip anterior
( ULA),
lower lip anterior
( LLA), soft tissue
B’ point ( B’), and
soft
tissue Pogonion’
( Pog’).


Ideal values
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Glabella –female 8.5 ± 2.4mm male –8.0 ± 2.5 mm
Nasal projection –female-16.0 ± 1.4 mm–male-17.4 ±
1.7mm .
A point’ –female;-01 ± 1.0 mm male;–0.3 ± 1.0mm .
Upper lip anterior--female -3.7 ± 1.2 mm male-3.3 ±
1.7mm .
Lower lip anterior- female 1.9 ± 1.4mm, male-1.0 ± 2.2
mm
B point’ –female-5.3 ± 1.5m male –7.1 ± 1.6mm .
Pogonion’ –female-2.6 ± 1.9mm male –3.5 ± 1.8 mm.


Midface, points
measured with respect
to the TVL are soft
tissue orbital rim( OR’),
cheekbone height of
contour ( CB’), subpupil
( SP’), and alar base
(AB’).
Hard tissue measured
to the TVL are upper
incisor tip and lower
incisor tip.


Ideal values
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Orbital rims –female;-18.7 ± 2.0mm male; –22.4 ±
2.7mm
Cheek bone- female –20.6 ± 2.4mm male –25.2 ±
4.0mm
Subpupil- female –14.8 ± 2.1mm male; –18.4.0 ± 1.9mm
Alar base- female –12.9 ± 1.1 mm male–15.0 ± 1.7 mm
Subnasale
female 0mm male 0mm
Mx1 female–9.2 ± 2.2 mm male;–12.1 ± 1.8mm
Md1 female–12.4 ± 2.2mm male–15.4 ± 1.9 mm


5.Harmony values
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The harmony values were created to measure
facial structure balance and harmony. Harmony
or balance between different facial landmarks is
an important component of beauty.
It is the position of each landmark relative to
other landmarks that determines the facial
balance.
Harmony values represent the horizontal
distance between 2 landmarks measured
perpendicular to the true vertical line (TVL)

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Harmony values examine four areas of
balance:
A) intramandibular parts,
B) interjaw,
C) orbits to jaws, and
D) The total face.
These harmony groupings are essential to
excellent dentofacial outcomes.


A)

intramandibular parts,

Relationships
between structures
within the mandible
that determine
balance are
measured,
lower incisor to
Pog’, lower lip to
Pog’, soft tissue B’ to
Pog’, and neck throat
point to Pog’ are
depicted.

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Intramandibular relations IDEAL VALUES
Md1-Pogonion’ –female 9.8 ± 2.6mm male
11.9 ± 2.8mm .
Lower lip anterior-Pogonion’---female 4.5 ±
2.1mm male- 4.4 ± 2.5mm .
B point’-Pogonion’—female 2.7 ± 1.1mm
male 3.6 ± 1.3 mm.
Throat length (neck throat point to Pog’) –
female 58.2 ± 5.9mm male 61.4 ± 7.4mm

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Analysis of these structures
indicates chin position relative
to other mandibular structures
and which, if any, structure is
abnormally placed.
For example, excessive
distance from mandibular
incisor tip to the chin may
indicate an upright lower
incisor, or hard tissue
pogonion enlargement, or
increased thickness of the chin
soft tissues (Pog to Pog’).
All of these possibilities are
examined within the
intramandibular harmony
group, and a diagnosis is
made so that treatment can be
rendered to harmonize
structures within the mandible

B) interjaw,
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Next, interjaw harmony is
examined.
These relationships
directly control the lower
one third of facial
aesthetics. : relationships
between the upper and
lower jaw soft tissues that
determine balance are
measured
Values indicate the
interrelationship between
the base of the maxilla
(Sn) to chin (Pog’), soft
tissue B’ to soft tissue A’
and upper to lower lips.


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Interjaw relations
Subnasale’-Pogonion’--female 3.2 ± 1.9
mm male--4.0 ± 1.7 mm
A point’-B point’ --female 5.2 ± 1.6 male
6.8 ± 1.5mm
Upper lip anterior-lower lip anterior female;
1.8 ± 1.0mm male -- 2.3 ± 1.2mm


C ), Orbital rim to
jaws: relationships
between the soft tissue
orbital rim and upper and
lower jaw that determine
balance are measured,
soft tissue orbital rim to
upper jaw at soft tissue A’
point and lower jaw at
Pog’.


Ideal values
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Orbital rim’- female A point’ 18.5 ± 2.3mm
male 22.1 ± 3mm
Orbital rim’-Pogonion’ –female 16.0 ±
2.6mm male- 18.9 ± 2.8mm


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D ) Total face
harmony:
relationships between
the forehead, upper
jaw, and lower jaw that
determine balance are
measured,
The upper face,
midface, and chin are
related via the facial
angle (G’-Sn-Pog’).
Then
the forehead is
compared to two
specific points,
upper jaw (G’-A’) and
chin (G’-Pog’).
These three measures
give the broad picture
of facial balance. www.indiandentalacademy.com

Ideal values
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Full facial balance
Facial angle —female 169.3 ± 3.4 male
169.4 ± 3.2 .
Glabella’-A point’ –female 8.4 ± 2.7mm
male 7.8 ± 2.8mm .
Glabella’- Pogonion’ –female 5.9 ± 2.3mm
male 4.6 ± 2.2mm


SOFT TISSUE CEPHALOMETRIC
ANALYSIS - Legan, Dallas, Burstone et
al


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Means & standard deviation derived from
40 orthodontically untreated white adults
(20 men, 20 women).
Class I occlusion, Vertical facial
proportions within normal limits.


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Facial convexity –
given by angle G –
Sn – Pg’.
Smaller value –
Class III profile.
Clockwise angle –
Positive.
Counterclockwise
angle – Negative.


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Maxilla & mandibular
are related to a line
dropped from glabella
perpendicular to
horizontal reference
plane.
Maxillary – Distance to
subnasale from this
line.
Gives amount of
maxillary excess or
deficiency in A-P
dimension.
Anterior to line –
Positive, Posterior negative



This & other related A-P measurements
are important in planning treatment for
anterior maxillary advancement or
reduction and for total alveolar or lefort I
maxillary horizontal advancement or
reduction.


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Mandible –
distance from
perpendicular
line dropped
from glabella to
Pg’.
Gives an
indication of
mandibular
prognathism or
retrognathism.


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This measurement must be evaluated in
conjunction with others to distinguish
between
microgenia—small hard tissue chin,
micrognathia—small mandible
retrognathia—average sized mandible
positioned posteriorly
Thin soft tissue chin or
combination of these

Lower face throat angle (Sn – Gn’ –C)
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Formed by
intersection of lines
Sn-Gn’ & Gn’-C.
Critical in planning
treatment to correct
A-P dysplasias.
In case of obtuse
angle, clinicians
should not use
procedure that
reduce prominence
of chin.

C

CLINICAL APPLICATION
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Class III patients with short ,heavy throats
& obtuse angle usually not have
mandibular setbacks.
Alternatives – maxillary advancement,
mandibular subapical procedure,
mandibular setback with advancement
genioplasty, compromise tooth position.


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Vertical – ratio
of distances G
– Sn & Sn –
Me’ should be
approx. 1.
Less than one
indicates
larger lower
third of the
face


Lip position

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Nasolabial angle –
between Cm-Sn-Ls.
Important
measurement in A-P
maxillary dysplasias.
Acute angle allow us
to surgically retract
maxilla or maxillary
incisors or both.
Obtuse angle –
maxillary
advancement or
proclination of
incisors.


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A-P lip position –
line is drawn from
Sn-Pg’ & amount of
lip protrusion or
retrusion is
measure as
perpendicular linear
distance from this
line to most
prominent point of
both lips.


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Labiomental sulcus –
from depth of sulcus
perpendicular to LiPg’ line.
Sulcus of about 4mm
provides pleasing
lower lip to chin
contour.
Uprighting lower
incisors,intruding
maxillary
incisors,chelioplasty
can help in reducing a
deep sulcus.

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Distance of upper lip
to maxillary incisor
(Stm – 1) is a key
factor in determining
vertical position of
maxilla.
Normal – 2mm of
incisor display.
Patients with vertical
maxillary excess tend
to show a large
amount of upper
incisor with lips in
repose.

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Vertical maxillary deficiency – No incisor
display with lips relaxed, edentulous look.
Orthodontically extruding maxillary teeth
or surgically positioning the maxilla
inferiorly – preferable treatment in patients
with short face.
INTERLABIAL GAP – Approx. 3mm .
Patients with maxillary excess have large
interlabial gaps & lip incompetency.

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Raising maxilla – shortens facial height,
allow patient to close lips without muscle
strain.
Patient with maxillary deficiency – no
interlabial gap, have lip redundancy with a
rolling out of upper & lower lips.


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Lower third of face (SnMe’) – divided into
thirds.
Length of upper lip (Snstm)is one third of total
distance of sn-Me’.
Stm-Me’ is about two
thirds.
Sn-stm/stm-Me’ is 1:2
When it becomes
smaller than half
vertical reduction
genioplasty is
considered.


TOMAC: AN ORTHOGNATHIC
TREATMENT PLANNING
SYSTEM SOFT-TISSUE
ANALYSIS- TONY G.
McCOLLUM,




TOMAC an acronym for the author’s name
is a surgical orthodontic treatment
planning and prediction system designed
to identify the best possible soft tissue
profile by testing the effects of various
orthodontic and surgical options.


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Line from
glabella to
subnasale –
Upper facial
contour
plane.
Line from
subnasale to
pogonion –
Lower facial
contour
plane.


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The acute angle
between these
planes is the facial
contour angle,
which describes
the degree of
anteroposterior
discrepancy of the
total face.
Normal value –
according to
Burstone is -11º ±
3º.

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The facial contour
angle (FCA) is highly
relevant to the analysis
because it measures
the convexity or
concavity of the face
Varies according to
facial type, with
leptoproscopic (long
face) individuals
tending to be more
convex, around -16°,
euryproscopic (short
face) patients tending
to have more acute
angles : -7°.

Nasolabial angle
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

The nasolabial angle is
formed by the
intersection of a line
originating at
subnasale and tangent
to the lower border of
the nose with a line
from labrale superius to
subnasale
Indicates the protrusion
of the upper lip relative
to the nose but can
also be a reflection of
the up or down tip of
the nose.

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Male-100-110
degree
Female-110-120
degree
Tip of the nose is
more elevated in
the females than
in males creating a
more obtuse angle.

Nasofacial angle
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Formed by the
intersection of a
tangent to the radix
and the tip of the nose
with a line drawn from
glabella to pogonion.
Describes the
protrusion and slope of
the nose relative to the
total facial profile.
Norms- 30-35 degree
O’ Ryan et al
36-40 degree Powell
et al

Lower lip chin throat angle
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This angle is formed by
a line drawn labrale
inferius and tangent to
pogonion intersecting
with a tangent to the
throat that passes
through throat point
and soft tissue menton.
determine the position
of the lower lip in
relation to the chin.
Norms-110 SD 8
DEGREE
Prognathic mandibleacute
Retrognathic mandibleobtuse

LINEAR MEASUREMENTS
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Lip protrusion- Bustone’s
B line is taken as
reference. Drawn from
subnasale to pogonion
Upper lip-+3.5 sd 1.4 mm
Should be used in
conjunction with
nasolabial angle
Lower lip +2.2 mm sd 1.6
mm.
Should be used in
conjunction with lower lip
chin throat angle

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Chin length

Measured from
constructed soft tissue
menton to the intersection
of tangents to the chin
and the throat.
Difficult to measure
accurately, because it is
subject to a number of
variables amount of fat
present, the posture of the
head and the shape of the
mandible and throat.
Norms 38-42mm in
females
40-45mm in males.


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Upper facial height—
measured from eye
point to subnasale
makes up two fifth
Middle facial height or
upper lip lengthsubnasale to stomion
and contributes one
fifth.
Female 20mm male 24
mm
lower facial height or
lower lip length-from
stomion to constructed
menton makes up final
two fifth.
Must be used in
combination with
interlabial gap and
maxillary incisor
exposure.

Interlabial gap
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

Is the space
between the upper
and lower lips when
they are relaxed
with the head in a
normal upright
position and the
teeth in centric
occlusion. Range
3mm
>3mm excessive
lower facial height

Maxillary incisor exposure
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Should be 1-2mm in males
and 3-5 mm in females
when lips are relaxed.
This is a critical
measurement on which
much of the vertical
planning for surgicalorthodontic treatment
depends
Excessive exposure —
increased maxillary height,
Under exposure- maxillary
height deficiency or teeth
attrition
Lip length increases with
age as much as 1mm
(Nanda, Ghosh) – taken into
consideration while planning
the correction of vertical
maxillary excess.

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Measured in both relaxed
and lip together postures.
Measurement is made
from the point of maximum
thickness of the upper lip
just below subnasale to the
underlying bone
usually about 3mm below A
point. This measurement is
compared with that from
the incisor crown to the
vermillion border.
The norm is 14mm –upper
measurement
15mm-lower resulting in
1mm of taper.
Clinical significance lip
taper appears to be more
prevalent in older patients
and must be allowed for
when retracting proclined
maxillary incisors. www.indiandentalacademy.com

Lip taper

Prediction


Soft tissue changes from various
surgical procedure


To predict the soft tissue profile it is vital to
have an in depth knowledge of the soft
tissue reactions caused by different
surgical movements of the jaws.


Mandibular advancement
•Soft tissue pogonion
advances in an almost 1:1
(100%) ratio with hard tissue
pogonion.
•The inferior labial sulcus
responds in a. 69:1 (70%)
ratio with hard tissue B Point.
•Labrale inferius advances in a
.77;1 (75%) ratio with the
lower incisor tip.

Mandibular setback
•Soft tissue pogonion
advances in an almost
1:1 (100%) ratio with
hard tissue pogonion.
•The inferior labial sulcus
responds in a .77:1
(75%) ratio with hard
tissue B Point
•Labrale inferius
responds in a .79;1
(75%) ratio with distal
movement of the lower
incisor tip.


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

The lower lip shortens slightly and
becomes more protrusive by curling out
and the labiomental fold becomes more
accentuated.
Only minor effects occur in the upper lip
and the nasolabial angle.


Mandibular advancement
The soft tissue chin advances
in harmony with the underlying
bony chin.
The thickness of the lip also
plays a role the thicker the lip
the less it will advance and the
thinner the lip the more it will
respond.
The lower lip advances less
than the soft tissue chin
because of its status before
surgery, when it can be
curled,everted and already
forward.

Mandibular setback
The lower lip shortens
slightly and becomes
more protrusive by
curling out and the
labiomental fold
becomes more
accentuated.
Only minor effects
occur in the upper lip
and the nasolabial
angle.


genioplasty




In Enhancement as well as reduction
genioplasties the soft tissue chin follows
the bony contour in a 1:1 ratio.
The chin advancement in particular has no
influence on the lower lip at labrale inferius
but the labial sulcus deepens. Therefore
genioplasties should only be performed if
they complement and balance lip position .


Maxillary advancement
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The nose tip responds in a ratio of .26:1 (25% of
the hard tissue movement) measured at
maxillary incisor anterius.
Subnasale advances in a .52:1 (50%) ratio with
maxillary incisor anterius and in a .56:1 (55%)
ratio with subspinale (A point).
The superior labial sulcus moves horizontally in
a ratio of. 69:1 (70%) with maxillary incisor
anterius;in other words the middle of the upper
lip becomes less concave as it flattens.

Maxillary advancement

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
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Labrale superius responds in a .55:1 (55%) ratio
with maxillary incisor anterius.
Labrale superius and stomion superius move
vertically in a .1:1 (10%) ratio with the maxillary
advancement.
Thin lips(<15mm) advance 2.8 times farther than
thick lips.
As a whole as the maxilla advances the nose tip
advances slightly the alar bases widen
marginally, subnasale advances ,the superior
labial sulcus flattens and labrale superius
advances.

Maxillary impaction
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Undesirable nasal tip elevation due to superior
repositioning. 1 mm of elevation for every 6mm
of superior repositioning.
The alar bases widen with maxillary impaction.
And nasolabial angle decreases.
The upper lip elevates superiorly with impacted
maxilla by 40%. Will shorten more if the maxilla
is advanced as well as impacted


autorotation


The soft tissue chin follows the
autorotation of the mandible in an approx.
1:1 ratio. The lower lip becomes slightly
recessive at labrale inferius and
labiomental angle increases.


TOMAC VTO




TOMAC is a unique surgical-orthodontic
treatment planning system. The essential
underlying principle is that the soft-tissue
profile is changed first, setting a goal
toward which hard-tissue changes are
adapted.
The TOMAC VTO is constructed in three
stages:

Test VTO

Pre surgical VTO

Surgical VTO


Test VTO


This is where the various orthodontic and
surgical options are tested and the optimum
combination is visualized. In the
anteroposterior plane, the facial contour angle
(FCA) is changed to the chosen ideal. The
upper and lower jaws, or both, are traced in
their new positions according to the softtissue reactions to surgical movements, and
the teeth are then decompensated
accordingly.





Line from
glabella to
subnasale –
Upper facial
contour
plane.
Line from
subnasale to
pogonion –
Lower facial
contour
plane.

TEST VTO


Presurgical-Orthodontic VTO




This is constructed from the information in
the test VTO.
Any necessary incisor decompensations,
molar adjustments, and soft-tissue
changes become the orthodontic
objectives prior to the surgical procedure.


SURGICAL VTO




The surgical VTO is constructed over the
presurgical VTO, with the surgical cuts
diagramed on the tracings of the jaws.
The simulated surgical movements are
governed by the decompensated positions
of the incisors. The soft-tissue profile is
then drawn according to the expected
soft-tissue/hard-tissue ratios of movement

VIDEO IMAGING


In the VTO of an orthognathic surgery
case, the clinician classically has used
acetate templates of the teeth and jaws to
predict orthodontic and surgical
movements to attain their esthetic and
functional goals, and the final profile is
determined by the reaction of the soft
tissue to the hard tissue movements





Cephalometric digitizing programs are
useful in automating these predictions
Video imaging technology allows the
orthodontist to gather frontal and profile
images and modify them to project overall
esthetic treatment goals










The advantage that video cephalometric planning often
offers is that
(1) it allows facial visualization for better comprehension
of the facial response to the dental and/or soft tissue
manipulation involved in a particular treatment plan;
2) it allows quantification of the planned dental and/or
osseous movements to reduce the guesswork as to the
facial response to our orthodontic treatment plan; and
(3) it allows the clinician to test various treatment plans
before deciding on the final plan. This is the essence of
the video imaging concept because it allows us, at least
in adult or surgical cases, to determine beforehand the
facial result of proposed treatment.


Computer prediction of hard tissue profiles in
orthognathic surgery. Loh S,
Yow M. 2002


The purpose of this retrospective study was to analyze
the accuracy of computer predictions by CASSOS
(Computer-Assisted Simulation System for Orthognathic
Surgery) 2001 software (2000 SoftEnable, Technology).
Forty adult patients who had undergone orthognathic
surgery were evaluated. Pre- and postsurgical lateral
cephalographs were scanned into the computer,. A
customized cephalometric analysis consisting of 14
measurements was used in this study. Predicted and
actual postsurgical hard tissue landmarks were
compared.







Results showed good correlation between repeated
digitization for all measurements. There were no
statistically significant differences in 10 of the 14
measurements.
The differences that were statistically significant were in
angular measurements for SNA angle, upper incisor to
maxillary plane angle (U1-MxP), interincisal angle (U1L1), and upper incisor to anterior cranial base angle (U1SN).
The greatest mean difference measured was the
interincisal angle (U1-L1) which, although statistically
significant, was clinically insignificant. This investigation
showed that CASSOS 2001 software provides accurate
hard tissue prediction for orthognathic surgical
procedures.

The predictability of maxillary repositioning in
LeFort I orthognathic surgery.
Jacobson R, Sarver DM. (ajo 2002)




The purpose of this retrospective study was to evaluate
the surgical accuracy of maxillary repositioning by
comparing the objectives obtained from cephalometric
prediction tracings with the actual skeletal changes
achieved during maxillary and maxillomandibular
procedures.
The sample consisted of 46 patients from the files of 1
orthodontist. Presurgical and immediately postsurgical
cephalometric radiographs were digitized, and the
original surgical prediction was reproduced with
Dentofacial Planner (Dentofacial Software, Toronto,
Ontario, Canada) software.







Vertical and horizontal measurements to several skeletal
landmarks were used to assess the differences between
the predicted maxillary position and the actual maxillary
postsurgical position.
Statistical differences were found for some
measurements, particularly those related to the vertical
placement of the posterior maxilla..
To assess the overall fit of individual predictions, authors
calculated an average discrepancy for each patient; 80%
of the actual results fell within 2 mm of the prediction,
and 43% fell within 1 mm of the prediction


Predictability of soft tissue profile changes
following bimaxillary surgery in skeletal class III
Chinese patients.
J Oral Maxillofac Surg. 2004.


The aim of this study was to evaluate the accuracy of
soft tissue profile predictions generated by a recently
developed computer program (Computer-Assisted
Simulation System for Orthognathic Surgery [CASSOS]
2001, SoftEnable Technology, Ltd, Hong Kong) in
Chinese skeletal Class III patients treated with
bimaxillary surgery








Comparison of the predicted and actual changes found
that 16 of the 32 soft tissue measurements were
significantly different ( P <.05).
Most of the significant prediction errors were observed in
the upper and lower lip region. The software tended to
underestimate the vertical position of both the upper and
lower lip and overestimate the horizontal position of the
lower lip.
However, the mean differences were relatively small,
with the greatest mean difference being 2 mm in the
vertical position of stomium inferius. The CASSOS 2001
program produced a clinically useful prediction of soft
tissue profile changes following bimaxillary surgery in
skeletal Class III Chinese patients.

conclusion




Surgical analysis offers the opportunity to identify
treatment goals in the vertical and anteroposterior
planes, allowing the clinician to be more confident
in making the difficult decision of whether a case
can be treated by orthodontics alone or requires
orthognathic surgery.
Our ability to predict the outcome of any
orthognathic procedure relies on the surgeon's
ability to accurately reproduce the desired skeletal
movements and on our understanding of the soft
tissue changes associated with those movements.





In the future, computerized tracing and video
imaging techniques in three dimensions may be
faster and more efficient than conventional
tracing methods.
With soft-tissue responses to hard-tissue
movements better understood than in the past,
these and other influential factors could be
incorporated into computerized technology, to
provide extremely accurate treatment planning
information.

REFERENCES:_
1.

2.

3.
4.

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Legan H, Burstone CJ: Soft tissue
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Di Paolo RJ, Philip C, Maganzini A: The
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Di Paolo RJ, Philip C, Maganzini A: The
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Johnston LE. --A simplified approach to
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





15. Sarver, D.M.:-- Video imaging: A computer
facilitated approach to communication and
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