Surgical orthodontics / dental crown & bridge courses

Contents:
Introduction
Historical aspect
Envelop of discrepancy
Indications for surgical orthodontic
treatment.
Diagnosis and treatment planning.
www.indiandentalacademy.com

Collection of data base
Systemic evaluation of patient
Cephalometric evaluation
Prediction tracing
Mock Surgery
Bibliography.

Cephalometry is an excellent tool for
quantifying, classifying and communicating
patient data.
It is useful as a treatment-planning tool
through the construction of prediction tracings
to study profile changes and to allow the
planning of extractions and orthodontic
mechanics to meet the treatment objectives.

The shape of the face depends mostly on the basic
skeletal architecture. Thus skeletal analysis is
mandatory for identifying and classifying any deformity.
Innumerable analysis has been proposed to study the
skeletal relations. Among them some are;
Burstone's analysis ( COGS for both hard and soft
tissue)
Dipaolo's (Quadrilateral analysis)
Sassouni analysis
Peter Ward Booth analysis

The first step in the diagnosis of the
orthognathic surgical patient is to determine the
nature of the dental and skeletal defects.

Patients who require orthognathic surgery usually
have facial bones as well as tooth positions that must be
modified by a combined orthodontic and surgical
treatment. For this reason, a specialized cephalometric
appraisal system, called Cephalometrics for
Orthognathic Surgery (COGS), was developed at the
University of Connecticut. This appraisal is based on a
system of cephalometric analysis that was developed at
Indiana University, with the addition of clinically
significant new measurements.

The baseline for comparison of most of the data
in this analysis is a constructed plane called the
horizontal plane (HP), which is a surrogate Frankfort
plane, constructed by drawing a line 7° from the line S
to N. Most measurements will be made from projections
either parallel to HP or perpendicular to HP.

CRANIAL BASE
First, it is necessary to establish the length
of the cranial base, which is a measurement
parallel to HP from Ar to N. This measurement
should not be considered an absolute value but a
skeletal baseline to be correlated to other
measurements, such as maxillary and
mandibular length, to obtain a diagnosis of
proportional dysplasia.

Ar-pterygomaxillary fissure (Ar-PTM) is
measured parallel to HP to determine the
horizontal distance between the posterior aspects
of the mandible and maxilla. 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
causal factor for prognathism or retrognathism
can be evaluated by this measurement of the
cranial base.

HORIZONTAL SKELETAL PROFILE
A few simple measurements should be made on
the skeletal profile to assess the amount of
disharmony. We call this the horizontal skeletal profile
analysis because all the measurements are made
parallel to HP. This is very practical because most
surgical corrections primarily made in the
anteroposterior direction.
The first measurement quantitatively describes
the degree of skeletal convexity in the patient. The
angle of skeletal facial convexity is measured by the
angle formed by the line N-A and a line A to Pg. The N-
A-Pg (angle) gives an indication of the overall facial
convexity, but not a specific diagnosis of which is at
fault -the maxilla or mandible

A perpendicular line from HP is dropped through N
and the inferior anatomic point is horizontally measured in
relation to the superior structures
The horizontal position of A is measured to this
perpendicular line (N-A). This measurement describes the
apical base of the maxilla in relation to N and enables the
clinician to determine if the anterior part of the maxilla is
protrusive or retrusive.
The measurement and related measurements are
important in the planning of treatment of anterior maxillary
horizontal advancement or reduction, and of total maxillary
horizontal advancement or reduction.
Point B and Pog [ pogonion ] are measured in the same way.

VERTICAL SKELETAL AND DENTAL
A vertical skeletal discrepancy may
reflect an anterior, posterior, or complex
dysplasia of the face. Therefore, the vertical
skeletal cephalometric measurements are
divided into anterior and posterior
components.

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MAXILLA AND MANDIBLE
The total effective length of the maxilla is the
distance from PNSANS that is projected on a line parallel
to the HP. The ANS-PNS distance, with the previous
measurements N-ANS and PNS-N, give a quantitative
description of the maxilla in the skull complex.
Four measurements relate to the mandible
Ar to Go
Go-Pg
Go angle [represents the relationship between the ramal
plane and MP]
B-Pg [Distance from B point to a line perpendicular to
MP through Pg.]

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. .
.

DENTAL
Various angles measured are,
Occlussal plane angle
1-NF angle
Lower incisor-MP angle
AB-OP

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..

SOFT TISSUE CEPHALOMETRIC ANALYSIS FOR
ORTHOGNATHIC SURGERY:
Charles J. Burstone in 1980 developed a
soft tissue cephalometric analysis for
orthognathic surgery.

SOFT TISSUE ANALYSIS
Facial form
To describe the soft tissue
profile of patient, angle of facial
convexity, or facial contour
angle, G - Sn - Pg is evaluated.
G -Sn - Pg : 12° 4°

G-Sn
G-Pg
.
. .
A line
perpendicul
ar to
horizontal
plane (HP) is
dropped
from
glabella and
the
relationship
of the
maxilla and
mandible is
related to it
to determine
if the
problem is
maxillary or
mandibular.

Vertical height ratio 
G - Sn / Sn - Me (HP):
In vertical
dimension, anterior facial
proportionality is assessed
by taking the ratio of
middle third facial height
to lower third facial height
measured perpendicular
to HP. The ratio less than
1 denote a
disproportionality large
lower third of face .
Normal: 1
G-Sn
Sn-Me

Lower face - throat
angle (Sn - Gn - C):
It is formed by
intersection of the lines
Sn - Gn and Gn - C.
An obtuse lower face
neck angle warns the
clinician not to use
procedures that reduce
the prominence of
chin.
Sn-Gn-C

Nasolabial angle (Cm - Sn - Ls) :
It is important in
assessing antero-posterior
maxillary dysplasia. An acute
nasolabial angle will often allow
us to surgically retract the
maxilla or retract the maxillary
incisors.
Obtuse nasolabial angle
suggests a degree of maxillary
hypoplasia.
Cm - Sn - Ls: 102°  8°

Upper lip protrusion Ls to (Sn - Pg) :
3  1 mm
Lower lip protrusion Li to (Sn - Pg) :
2  1 mm
It is evaluated by drawing a
line from subnasal to soft tissue
pogonion and amount of lip
protrusion or retrusion is measured
by perpendicular linear distance from
this line to the most prominent point
of both lips.

.
.
Labio-mental sulcus Si to (Li
– Pg) 4  2 mm
It is measured from the
depth of the sulcus
perpendicular to Li- Pg line.
Sulcus of about 4 mm is
average in pleasing lower lip to
chin contour.

Vertical lip chin ratio Sn-Stms / Stms-Me: 0.5 mm
Lower third of face (Sn - Me) is divided into length of
upper Sn - Stms. It should be approximately 1/ 3rd the
total and distance Stms - Me is about 2/3rd.
Sn - Stms/Stms - Me should be 1: 2 ratio and if it
becomes smaller than one half- vertical reduction
genioplasty is considered.

Interlabial gap - 3 mm:
Vertical distance between the upper lip and
lower lip with then lip in rest position is normally
3mm. In vertical maxillary excess tend to have large
Interlabial gap, lip In competency results.

Dipaolo R.J’s quadrilateral analysis
Various parameters used in this analysis are
1.Maxillary Bony Arch Length
• measured from ANS to PNS along the
palatal plane.
• The anterior point is the foot of the
perpendicular from point A to palatal plane.
• The posterior point is the foot of the
perpendicular from most inferior position of
Ptm to palatal plane.

. .

2.Mandibular Bony Arch Length
• linear measurement along
mandibular plane (Go-Gn).
• The anterior point is the foot of the
perpendicular from point B to Go-Gn.
• The posterior point is the foot of the
perpendicular from point J to Go-Gn.

.
.

3. Point J
• Located at the deepest point of the
curvature formed at the junction of anterior
portion of ramus and corpus of mandible .
• It is the posterior limit of denture base .
• This point is located by bisecting the angle
formed by a line drawn tangent to the
anterior border of the ramus and the
superior aspect of corpus of mandible.

4. Anterior Lower Facial Height or ALFH
• vertical linear measurement from anterior
limit of maxillary corpus to anterior limit of
mandibular corpus.

5. Posterior Lower Facial Height or PLFH
• Vertical linear measurement from posterior
limit of maxillary corpus to posterior limit of
mandibular corpus.

6. Anterior Upper Facial Height or AUFH
• vertical linear measurement from anterior
limit of maxillary corpus projected on palatal
plane from nasion.

7. Angle of Facial Convexity
• measurement of the skeletal profile formed by
intersection of ALFH with AUFH and relates the
quadrilateral to the upper face.
• 1650-1780.
.

8.Sagittal Angle
• intersection of horizontal planes of the
quadrilateral i.e.., the max bony arch length
and mand bony arch length .
• 23010
.

9.Sagittal Ratio:
• A mathematical expression that identifies
and locates the angular , vertical and saggital
relation of max corpus to mand corpus.

Skeletal measurements

Dental measurements
1. Upper incisor position
• determined by drawing a line parallel to
ALFH through point A.
• perpendicular from this line to the
anterior most point on the max incisor is
measured in mm.
• 5 1 mms.

5 1 mms

2. Lower incisor position
ALFH through point B.
anterior most point on the mand incisor
is measured in mm.
• 0  2 mms.

0  2 mms

3. Pogonion line
ALFH through pogonion.
anterior most point on the mand incisor
is measured in mm.
• 2 mm anterior or posterior to the
pogonion line.

Sassouni Analysis
• It was given by Viken Sassouni in 1955.
• It was the first analysis to emphasize
vertical as well as horizontal relationships
and the interaction between vertical and
horizontal proportions.
• 100 Films of Philadelphia Center for Research in
Child Growth (49 males, 51 females)
• Age 7-15

Planes
•Mandibular base plane:- tangent
to inferior border
•Occlusal plane:- mesial cusp of
permanent 1st upper and lower molars and
incisal overlap of upper and lower centrals
• Palatal plane:- from ANS to PNS.

•Anterior cranial base plane or basal plane:-
parallel to axis of upper contour of anterior
cranial base and tangent to inferior border
of sella turcica.
•Ramus plane:- tangent to posterior
border of ascending ramus

Arcs
•Anterior arc :- it is a arc of a circle
between anterior crainal base and
mandibular plane with O as center and O-
ANS as radius.
•Posterior arc:- it is a arc of a circle
between anterior crainal base and
mandibular plane with O as center and
OS’ as radius.

Sassouni Norm
• He said in well balanced faces that
horizontal planes:-
– Anterior cranial base
– Palatal plane
– Occlusal plane
– Mandibular plane
Converge at a singe point in well
balanced faces and their inclination reflect
vertical proportion of the face.

• If they intersect relatively close to the face and
diverge quickly as they pull anteriorly, the facial
proportions are long anteriorly and short posteriorly
which predisposes to open bite (skeletal open bite).
• If they are nearly parallel, converge far away and
slightly diverge anteriorly, then there is skeletal
predisposition towards anterior deep bite (skeletal
deep bite)
• He evaluated antero-posterior position of face and
dentition by noting relationship of various points to
arcs drawn from area of intersection of planes.

Sassouni Norm
• The arc from pt. O to ANS as a radius
passes through
– Pog
– Incisal edge of maxillary central incisor
– Nasion
– Frontoethmoid junction
• If circle has a center O then the arc that
passes from the posterior wall of sella
turcica will pass through gonion.

Relationship between angles
formed at point “O”
• Mandibulocranial angle – unique for each
face
• Palatocranial angle/ palatomandibular
angle – 1/1
• Occlusopalatal angle/ occlusomandibular
angle – 1/1 to 1/2

Teeth axis & facial planes – Maxilla
• Axis of 6 & 1 – bony orbital contour
• Angle M’ – equals angle I’ + 100

Teeth axis & facial planes –
Mandible
• Angle R - equals angle i
• Ramal plane; lower incisor axis; occlusal
plane - isosceles triangle
• Angle m’ - equals angle i’ + 5
• Axis of lower 7 - parallel axis lower
incisor

Peter Ward Booth
analysis - 1980

ORTHODONTIC SURGICAL
CEPHALOMETRIC PREDICTION TRACING
(Epkar and Fish, 1994):
One of the most important planning tools
in surgical cases is the cephalometric
prediction tracing. Once the problem is
recognized and the type of surgery provisionally
decided, prediction tracing is done accordingly.

Types of prediction tracings ;
1) Orthodontic surgical
2) Surgical
Orthodontic surgical tracing is used for overall
treatment planning and illustrates the effect of both
orthodontic tooth movements and surgical skeletal
changes.

The orthodontic surgical tracing is done for the
following reasons :
To assess accurately the profile esthetic results of the
proposed surgery and orthodontics.
Determine desirability of adjunctive surgical
procedures such as genioplasty.
To help determine the sequencing of surgery and
orthodontics.
To help decide if extractions are necessary.
To determine which teeth to extract if extraction
treatment is required.
To determine the anchorage requirements.

Certain points to be kept in mind during prediction
tracing are;
With the antero-posterior movement of the incisors,
60-70% change is seen in lips. With the vertical
movement of incisors, associated with soft tissue
changes are minimal but lip rotation is almost equal to
the rotation of mandible.
In mandibular advancement, lip movement is 60-70%,
but the soft tissue chin movement is almost as equal to
the base movement.

In maxillary advancement, the nose tip
is slightly elevated, but the change is usually
temporary. In maxillary retro positioning, the
movement of the base of the upper lip is only
20% of that of point A. The lower lip rotates
along with the mandibular rotation.
In surgery of chin, the soft tissue reacts
about 60-70% to forward advancement.

Currently, there are three methods of prediction
tracing.
A) It involves repositioning acetate tracing. of the various
bony and skeletal segments over the original tracing to
duplicate the movement of potential treatment
procedures.

B) In Second technique appropriate landmarks from the
cephalometric tracing are digitized and entered into a
computer using commercial programs.
C) The third method involves overlying the digitized
image of the lateral cephalometric tracing on to a video
image of patient. The surgical predictions produced
from the digitized cephalometric tracing can be
integrated with the video image so that the prediction
includes not only a line drawing but also a
corresponding facial image.

Mandibular advancement:
First the bony and soft tissue landmarks are
traced. Frankfort horizontal plane is drawn and
then a line is passed from nasion through point A
and extending inferiorly. Point A is frequently in its
normal relation (900 maxillary depth).
Begin the prediction by tracing the distal
portion of the mandible, the soft tissue chin, and
the occlusal plane on clean acetate paper. A lightly
dotted line is used for soft tissue chin and the
corresponding part of mandible. It makes easier to
add genioplasty whenever required.

In deep bite cases, occlusal plane is made
between functional plane and molar incisor
occlusal planes. The choice must be made
carefully as it affects the esthetics the amount
and direction of advancement and the
necessary orthodontic treatment.
Functional occlusal plane
Wolford L.M., Chemello B.D. and Hilliard F.
(1994) quoted that deep bite is frequently
associated with excessive curve of spee in lower
arch and a reverse curve of spee in the upper
arch

Molar incisor occlusal plane:
The patient with deep bite has two divergent
molar incisor occlusal planes. One from maxillary
incisor to maxillary molar and another from
mandibular molars to mandibular incisors.
If mandible has to be advanced along these
divergent planes, then rotate clockwise the distal of
mandible, so that both planes get coincide. The teeth
are advanced more than pogonion and lower face height
is increased by the amount of excessive overbite.

After tracing the fixed structures, draw A -
Pog line and the facial axis on the prediction.
This line is used to place the teeth in their ideal
position.
Ideal position of lower incisor determined
by Rickets, is with the incisal edge 1 mm ahead
of the A - Pog line and the long axis at 22° to A -
Pog line.

SUPERIOR REPOSITIONING OF THE MAXILLA AND
ADVANCEMENT GENIOPLASTY:
Routine tracing of pretreatment cephalogram with
skeletal, dental and soft tissue landmarks done.
Then to start with prediction - fresh tracing of the
patients cephalogram without analysis line made.
Construct subnasal perpendicular this tracing to allow
assessment of changes in chin and lip position. For soft
tissue chin and mandible use dotted lines, as it is easier
to add genioplasty.

Note : Accurate tracing of condyle is important
as it serves as center of rotation for mandible,
Functional occlusal plane ( molar-premolar) is
used.
Then the prediction is rotated
counterclockwise around the condyle keeping
the condyle in fossa, until the functional
occlusal plane is 1-3mm below the upper lip
on tracing .Where to place the occlusal plane
is based on the amount of upper tooth
exposed before treatment.

Then hold the prediction and draw the fixed
structures,observe the anteroposterior position of
chin. The soft tissue chin optimally lies 2 - 6 mm
behind the subnasale perpendicular on tracing.
If chin is deficient at this time augmentation
genioplasty is done. There the bone to soft tissue
ratio is 1 : 0.7.

For augmentation genioplasty, draw a
horizontal line parallel to FH plane on
symphysis. Then superimpose the tracing on
prediction. Slide the prediction until the bony
chin of the tracing projects anteriorly. Then
hold the prediction and draw the new chin
position, relative to both subnasale
perpendicular and the forehead and nose. Then
draw A - Pog line and it should be coincident
with this line. Place the teeth in their ideal
position. Superimpose the Prediction on tracing
and soft tissue can be compared.

TWO JAW SURGERY (MAXILLARY SUPERIOR
REPOSITIONING AND MANDIBULAR
ADVANCEMENT)

Selection of articulators
• Isolated mandibular surgery
• Face bow transfer and mounting the
models in semidjustable articulators are
not always required. Since the condyle is
separated from the dentition in all isolated
mandibular surgeries.
• Simple hinge articulators can be used.

• Isolated maxillary surgery
• Face bow transfer to relate the maxilla to
cranial base and mounting the models in
semiadjustable articulators is mandatory
except the surgeries for trasverse
correction of maxilla and maxillary sub
apical surgery with no vertical change.

• Bi jaw surgery:
• Face bow transfer to relate maxilla to
cranial base
• Occlusal registration to relate mandible to
maxilla and mounting the models on
semiadjustable articulators for model
surgeries.

MODEL SURGERY :
-Model surgery simulates the actual surgery, in
the dental arch model of the patient
-It gives a three dimensional understanding of
the postoperative relationship of the jaws.
Why Model surgery is performed ???

The basic reason to perform the model surgery is
1) To determine if the indicated surgical procedure will
produce an occlusion that can be simply and safely
perfected by subsequent orthodontic treatment.
2) To get a definite idea about the extent of bone / arch
advancement or reduction required in the surgery.
3) To get a postoperative relationship of the jaws,
dentition and occlusion.
4) To decide about the post surgical orthodontic
treatment.
5) As a vehicle for fabrication of splints for stabilization
after surgery

There are two basic types of feasibility model
surgery.
Whole arch
Segmental
Whole arch feasibility model surgery is done
by hand articulating dental models into the
best possible occlusion.

Segmental feasibility model surgery is done
by sawing the upper lower or both dental
models into the dento-osseous segments to
be produced at surgery and re-assembling
them into the best possible occlusion while
using any simple hinge type articulator to
help hold the model bases.

Technique:
The models are duplicated, trimmed to
simulate the anatomy and arbitrarily mounted
on an articulator using a wax bite to ensure
proper occlusion. The roots of the teeth
adjacent to planned interdental osteotomies
are drawn on cast.

The teeth and the alveolus are
sectioned from the upper model base
along a reference line made
approximately 5 mm above the tooth root
apices. Then the maxilla is sectioned into
the appropriate segments taking care not
to cut through the tooth roots.

The anterior segments are placed
into its best occlusal relationship with the
lower teeth and held in this position with
soft Wax. The objective is to establish a
class I canine occlusion with normal
overbite and overjet. Sometimes, it is
necessary to section the anterior segment
between the central incisors to increase or
decrease inter-canine width, close the
midline diastema etc.

In Lefort I osteotomy, models are
articulated in an anatomical articulator
with face bow transfer. An anatomical
articulator is necessary because the
repositioning of maxilla always result in
some rotatory movement of mandible.

References
• Phillips C, Proffit WR. Psychosocial
aspects of dentofacial deformity and its
treatment (Chapter 3). In: Proffit WR,
White RP, Sarver DM, eds. Contemporary
Treatment of Dentofacial Deformity. St.
Louis: Mosby; 2003.
• Proffit WR, White RP, Sarver DM, eds.
Contemporary Treatment of Dentofacial
Deformity. St. Louis: Mosby; 2003.

References
• Di Paolo RJ, Markowitz JL, Castaldo DA (1970)
Cephalometric diagnosis using the quadrilateral
analysis. J Clin Orthod 4:30-5.
• Di Paolo RJ, Philip C, Maganzini AL, Hirce JD
(1984) The quadrilateral analysis: a differential
diagnosis for surgical orthodontics. Am ] Orthod
86:470-82.
• Sassouni V (1955) A roentgenographic
cephalometrics- Am J Orthod 41:735-64.
• Sassouni V (1958) Diagnosis and treatment
differential diagnosis and treatment. Angle Orthod
44:433-63.

References
• Sassouni V (1969) A classification of skeletal
facial metric analysis of cephalo-facio-dental
relationships, types. Am J Orthod 55:109-23.
• Sassouni V (1970) The class II syndrome:
planning via roentgenographic cephalometry.
Am} 40:334-41.
• Epker, Integrated orthodontic and surgical
correction; St. Louis: Mosby, 2nd ed; 2003.
• Burstone CJ, James RB, Legan H, Murphy
GA, Norton LA (1979) Cephalometrics for
orthognathic surgery. J Oral Surg 36:269-77.

References
• Blakey GH III, White RP Jr. Mandibular
surgery (Chapter 10). In: Proffit WR, White
RP, Sarver DM, eds. Contemporary
Treatment of Dentofacial Deformity. St.
Louis: Mosby; 2003:312-344.
• Sarver DM, Rousso DR. Plastic surgery
combined with orthodontic and
orthognathic procedures. Am J Orthod
Dentofac Orthop 126:305-307, 2004.

References
• Kiyak HA, West RA, Hohl T, et al. The
psychological impact of orthognathic
surgery: A 9-month followup. Am J Orthod
81:404-412, 1982.
• Coben SE (1955) The integration of facial
skeletal variants. Am J Orthod 41:407-34.
• Coben SE (1961) Growth concepts. Angle
Orthod 31:194-201.

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