Cephalometric superimposition

IntroductionIntroduction
A cephalometric super imposition is an
analysis of lateral cephalograms of the
same patient taken at different times.
These super impositions are used to
evaluate a patient’s growth pattern
between different ages and to evaluate
changes in dentoalveolar and basal
relationships after a course of
orthodontic or surgical treatmentwww.indiandentalacademy.co
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Early method -- Comparison of linear
and angular measurements from
consecutive cephalograms
Serial superimpositions from
cephalograms that have been taken at
different times
To determine the effect of growth or
treatment, tracings of the head films
are superimposed on those landmarks
least affected by growth.www.indiandentalacademy.co
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The placement of metallic implants for
subsequent use as stable structures
(BJORK, 1968).
Information gathered from these implant
studies are useful in identifying areas
which are relatively stable or where the
changes are of relatively small magnitude.
When tracing serial films, start with the
smallest age and follow the child towards
maturity or start at the most mature stage
and work backwards -- Allows examiner
to observe gradual morphological changes.
Broadbent (1975)
www.indiandentalacademy.co
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For superimpositions to be accurate they
should be taken under identical
conditions of
Magnification,
Head position,
Radiological exposure and
Tracing of the superimpositions must be
accurate (locate precisely the outlines of
the relevant structures and to eliminate
the confusing, unusable details).www.indiandentalacademy.co
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DefinitionsDefinitions
Validity
Validity or accuracy is the extent to
which, in absence of measurement
error, the value obtained represents the
object of interest.
Reproducibility
Reproducibility, or precession, is the
closeness of successive measurements
of the same objectwww.indiandentalacademy.co
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Uses of CephalometricUses of Cephalometric
superimpositionsuperimposition
Evaluate a patient’s growth pattern
between different ages
Evaluate changes in dentoalveolar and
basal relationships after orthodontic or
surgical treatment
Differentiate the changes due to growth
and that due to treatment
Construction of VTOwww.indiandentalacademy.co
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Color-coding for tracingColor-coding for tracing
To facilitate identification of
consecutive cephalograms (American
board of orthodontists,1990)
Pretreatment – black
Progress – blue
End of treatment – red
Retention – green
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When evaluating the dentofacial changes
that occur as a result of growth or
treatment, specific areas that should be
observed for alteration include:
Changes in overall face
Changes in the maxilla and its dentition
Changes in the mandible and its
dentition
Amount and direction of condylar
growth and
Mandibular rotation
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Evaluation of the overall
changes in overall face
Cranial structures have been used for super
impositions based on the fact on that both
the neurocranium and its related cranial
base achieve most of their growth potential
at a relatively early age. Therefore, this part
of the cranium is considered to be relatively
stable.
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Basion Horizontal (Coben,Basion Horizontal (Coben,
1955)1955)
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Broadbent triangleBroadbent triangle
(Broadbent, 1931)(Broadbent, 1931)
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Basion – Nasion planeBasion – Nasion plane
(Ricketts, 1979)(Ricketts, 1979)
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Sella-nasion line (AmericanSella-nasion line (American
Board of Orthodontics, 1990)Board of Orthodontics, 1990)
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Disadvantage of above methods – They
incorporate areas of the cranial base that
continues to change during most of the
growing years.
Growth at the spheno-occipital synchodrosis
Bone remodeling at the Nasion -- (Knott,
1971)
Bone remodeling at the Sella -- (Melsen,
1974).
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Basion – influenced by the remodeling
processes on the surface of the Clivus
and anterior border of foramen magnum
and displacement of occipital bone due
to growth at spheno-occipital
synchodrosis (Melsen, 1974).
Bolton point – It is frequently obscured
by the mastoid process in the teenage
years (Broadbent, 1975).
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Best fit of anterior cranial base (NelsonsBest fit of anterior cranial base (Nelsons
(1960) cephalometric study and Melsen’s(1960) cephalometric study and Melsen’s
(1974) histological investigation)(1974) histological investigation)
Identified various bony surfaces in the
anterior cranial base that are suitable
for accurate superimpositions. They
include
Anterior wall of sella turcica
The contour of cibriform plate of
ethmoid bone
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Details in trabecular system in ethmoid
cells
Median border of orbital roof
Plane of sphenoid bone (planum
spenoidale)
Registration should be done on the
midpoint between the right and left
shadows of the anterior curvatures of
the greater wing of the sphenoid bone
where they intersect the planum.
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They compared the above methods and
concluded that this study does not
suggest a preference among the various
methods but the use of best fit of the
anterior cranial base may be better than
the others as it takes into consideration
the detailed individual anatomy of the
cranial base, rather than simplifying this
anatomy into lines or planes
Ghafari, Engel, and Laster (May, 1987)
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Uses of overall superimpositionsUses of overall superimpositions
Provide an overall assessment of the
growth and treatment changes of the
facial structures
Amount and direction of maxillary and
mandibular growth or displacement
Changes in maxillary-mandibular
relationship
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Relative changes in soft tissue
integument (specifically the nose, lips
and chin)
Provide information on the overall
displacement of the teeth
It does not provide for an assessment of
the changes in the position of the teeth
within the maxilla or mandible. In order
to obtain this information, maxillary and
mandibular superimpositions are
required. www.indiandentalacademy.co
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Grid analysis (Weislander AJOGrid analysis (Weislander AJO
1993)1993)
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Changes in the maxilla andChanges in the maxilla and
its dentitionits dentition
Maxillary superimposition
The purpose of maxillary
superimposition is to evaluate the
movement of maxillary teeth in
relation to the basal parts of maxilla
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Superimposing along the palatal planeSuperimposing along the palatal plane
registered at ANS (Broadbent 1937, Mooreregistered at ANS (Broadbent 1937, Moore
1959, Salzmann 1960, Ricketts 1960,1959, Salzmann 1960, Ricketts 1960,
Mcnamara 1981).Mcnamara 1981).
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Superimposition on the nasal floorSuperimposition on the nasal floor
with films registered at anterior surfacewith films registered at anterior surface
of maxilla. (Downs 1948, Brodie 1949)of maxilla. (Downs 1948, Brodie 1949)
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Superimposition along the palatalSuperimposition along the palatal
plane registered at pterygomaxillaryplane registered at pterygomaxillary
fissure (Moore 1959)fissure (Moore 1959)
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The methods of maxillary superimposition
that use the palatal plane are compromised
because of the remodeling of the palatal
shelves.
The hard palate undergoes continuous
resorption on its nasal surface and
apposition on the oral side making most of
these methods of superimposition
unsatisfactory.
Both points ANS and PNS undergo
significant anteroposterior remodeling
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Superimposition on the outline ofSuperimposition on the outline of
infratemporal fossa and posterior portion ofinfratemporal fossa and posterior portion of
hard palate (Reidel 1974)hard palate (Reidel 1974)
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Superimposition registering the maxilla onSuperimposition registering the maxilla on
the common Ptm co-ordinate, maintainingthe common Ptm co-ordinate, maintaining
the basion Horizontal relationship (Cobenthe basion Horizontal relationship (Coben
1986).1986).
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Superimposition on the best fit of internalSuperimposition on the best fit of internal
palatal structures (McNamara 1981)palatal structures (McNamara 1981)
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Superimposition on metallicSuperimposition on metallic
implants (Bjork and skieller 1976).implants (Bjork and skieller 1976).
They found that remodeling involves
resorptive lowering of the nasal floor --
greater anteriorly than posteriorly.
The zygomatic process did not undergo the
same remodeling changes .So they
recommended the use of headfilm tracing
superimposition on the anterior surface of the
zygomatic process of the maxilla.
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Structural superimposition on the anteriorStructural superimposition on the anterior
surface of the zygomatic process of thesurface of the zygomatic process of the
maxilla. (Bjork and Skieller 1976) with themaxilla. (Bjork and Skieller 1976) with the
second head film oriented so that thesecond head film oriented so that the
resorptive lowering of the nasal floor isresorptive lowering of the nasal floor is
equal to the apposition at the orbital floor.equal to the apposition at the orbital floor.
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Compared the popular “Best fit” method
with that of implant and structural
superimposition methods
Best fit method significantly underestimates
the vertical displacement of molar teeth by
30% and that of incisors up to 50%.
No statistically significant differences were
found between the structural and implant
methods in the vertical plane.
Nielsen (AJO 1989)
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In the horizontal plane the structural
method on average demonstrated
posterior displacement of the
reference points by 0.5 mm.
Hence it has been concluded that the
structural method for superimposing
head films is a valid and reliable
method for determining maxillary
growth and treatment changes.
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Disadvantage of using theDisadvantage of using the
structural methodstructural method
The zygomatic process of maxilla is
characterized by double structures, which
make it difficult to identify accurately and
hence to trace the construction line.
If the anterior surface of the zygomatic process
is short, superimposition can create rotational
effect, which can cause tooth movements to be
misinterpreted. So quality head films are
required.
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Doppel (AJO 1994)Doppel (AJO 1994)
Compared various superimposition
methods and concluded that for clinical
purposes this method of maxillary
superimposition more closely
approximates implant superimposition.
Anterior and posterior contours of
zygomatic arches are superimposed
allowing the floor of the orbit to be raised
more than the palatal plane in a ratio of
1.5:1 www.indiandentalacademy.co
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Changes in the mandible andChanges in the mandible and
its dentitionits dentition
It is used to evaluate the movement of
mandibular teeth in relation to the basal parts
of the mandible
Lower border of the mandible and on the inner
table of symphysis (Salzmann 1960, 1972).
Disadvantage -- Lower border undergoes
significant remodeling during growth (Bjork
1963).
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Superimposition on the mandibularSuperimposition on the mandibular
planeplane
It has low degree of validity, but of
high degree of reproducibility.www.indiandentalacademy.co
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Implant studies, Bjork (1963,Implant studies, Bjork (1963,
1969) and Bjork and Skieller1969) and Bjork and Skieller
(1983)(1983)
Indicated relatively stable structures that
could be used for superimposition purposes.
Anterior contour of the chin
The inner contour of the cortical plates at
the inferior border of the symphysis and
trabecular structure in the lower part of
symphysis.
The contour of mandibular canal
Lower contour of mineralized molar germwww.indiandentalacademy.co
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Evaluation of Amount and direction ofEvaluation of Amount and direction of
condylar growth and mandibular rotationcondylar growth and mandibular rotation
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Visual treatment objectiveVisual treatment objective
(VTO)(VTO)
It is a visual plan to forecast the normal
growth of the patient and the anticipated
influences of treatment, to establish the
individual objectives we want to
achieve for that patient.
The treatment plan must take advantage
of beneficial aspects of growth and
minimize any undesirable effects of
growth, if possible.www.indiandentalacademy.co
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After setting up teeth ideally within the
anticipated or “grown” facial pattern,
the orthodontist must decide what
mechanics and orthopedics must be
used to achieve these goals.
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To effectively forecast and draw an
effective treatment design the steps that
should be followed are:
Understand the individual patients basic
facial, skeletal and dental structures
(Ricketts analysis).
An analysis of normal growth
change and treatment design
Evaluation of growth and treatment
results
VTO
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Ricketts VTORicketts VTO
Uses of Ricketts VTO
Monitoring and measuring the
treatment progress
Helps in orthodontists self
improvement
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Construction of VTOConstruction of VTO
The various steps that should be followed in
the construction of a VTO are
Cranial base prediction
Mandibular growth prediction
Maxillary growth prediction
Occlusal plane position
Location of dentition
Soft tissue of the face
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CranialCranial base predictionbase prediction
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1mm/year
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Mandibular growth predictionMandibular growth predictionMechanics
Convexity reduction – Opens 1°/5mm
Molar correction –Opens 1°/3mm
Overbite correction –Opens 1°/4mm
Cross bite correction –Opens 1°-1½°
Facial axis closes with extraction
Open or close with headgear
Facial pattern
S.D on the dolicofacial pattern Opens
1° www.indiandentalacademy.co
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2mm/year
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Maxillary growth predictionMaxillary growth prediction
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Maximum range of point A changes with
various mechanics
HG -8mm
Class II elastics -3mm
Activator -2mm
Torque -1 to -2mm
Class III elastics 2 to 3mm
Facial Mask 2 to 4mm
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Occlusal plane positionOcclusal plane position
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Location of dentitionLocation of dentition
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4mm www.indiandentalacademy.co
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Soft tissue of the faceSoft tissue of the face
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Take the VTO and superimpose on the
five-superimposition areas to establish
individual objectives for the patient.
The Five superimposition areas are used
to evaluate the following in the face in
order:
The chin
The maxilla
The teeth in the mandible
The teeth in the maxilla
The facial profilewww.indiandentalacademy.co
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Superimposition area 1Superimposition area 1
Basion-Nasion at CC point.
Establishes Evaluation area 1 (Evaluate
the amount of growth of the chin in mm
and change in an opening or closing
direction that may result from the
mechanics used).
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Superimposition area 2Superimposition area 2
Basion – Nasion at Nasion.
Establishes Evaluation area 2 (Changes
in the maxilla).
The Basion - Nasion – Point A angle
does not change with normal growth.
Any change in this angle is due to the
effect of mechanics.
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Superimposition Area 3Superimposition Area 3
Corpus Axis at PM.
Establishes Evaluation Area 3 (evaluate
weather we are going to intrude, extrude,
advance or retract the lower incisors which
help us determine the type of mechanics
that must be used)
Evaluation Area 4 (evaluate the lower
molars to determine what type of anchorage
we need and weather we wish to advance,
upright or hold the lower molars).www.indiandentalacademy.co
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Palate at ANS.
Establishes Evaluation Area 5 (Evaluate
what we are going to do with upper
molars – hold, intrude, extrude, distalize
or bring them forward)
Evaluation Area 6 (Evaluate what we are
going to do with upper incisors – Intrude,
extrude, retract, torque or tip them)
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Esthetic plane at crossing of
occlusal plane.
Establishes Evaluation Area 7
(evaluate the soft tissue profile).
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VTO (Visualized treatmentVTO (Visualized treatment
objective) -- Holdaway (1984 AJO)objective) -- Holdaway (1984 AJO)
Systems based on hard-tissue
measurements or reference lines alone
may produce disappointing results.
Develop facial profile outline that is
harmonious with the skeletal type of the
patient under study.
Plan the dental repositioning necessary
to bring about the desired change.
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Step I
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.75mm/yearStep II
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3mm/yearStep III
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Step IV
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Step V
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40%
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Step VI
50%
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Step VII
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15
10
Step VIII
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4
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Elimination of lip strain -- 4 mm
Upper lip change -- 4 mm.
Maxillary incisor rebound -- 1.5 mm.
Total incisor repositioning -- 9.5mm.
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Step IX
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Arch length loss
from reposition --2 x 4 = 8 mm
Model discrepancy -- 2 mm
Total discrepancy -- 10 mm.
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Lower molar must be moved forward 2.5 mm.
Step X
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Step XI
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Step XII
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TEMPLATE ANALYSISTEMPLATE ANALYSIS
Johnston JCO 1987Johnston JCO 1987
Templates exist in two forms
Schematic (Michigan,Burlington)
Anatomically complete (Broadbent-
bolton, Alabama)
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Schematic (Michigan)
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Each template is, in effect, a compact set
of oriented rulers graduated in years (6
to 16 years). Thus any patient with this
age range can be analyzed with a single
template.
The types of superimpositions that
should be used to assess overall facial
form and to measure the size of
component parts includes
Cranial base superimposition
Regional superimpositionwww.indiandentalacademy.co
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Cranial base superimposition:
The choices of reference planes are
SN registered at S
FH registered at PtV
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Regional superimposition:
To determine relative size (measured
in years) of any craniofacial dimension
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THE PROPORTIONATE TEMPLATE
Jacobson AJO 1979
The tracing of the individual with
disharmony is compared with a normal
tracing or template and they are
systematically compared.
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Tracing with template superimposed on
mid S-J point and B-Na parallel
Maxilla and mandible
sagittal and vertical
Mandibular plane
Soft tissue lips
Chin
Nose www.indiandentalacademy.co
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Superimposition on palatal plane
registered on Ptm
Length
Incisor inclination
Incisor height
Molar height
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Body length
Ramus height
Gonial angle
Incisor height and
inclination
Molar height
Superimposition on mandibular plane
registered at pogonion
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Superimposition on the lines representing
the vertical dimensions
Upper facial height
Lower facial height
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Superimposition on the occlusal plane
Vertical dimension of the dentitionwww.indiandentalacademy.co
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The cephalometric superimposition
methods used for visualizing, planning, and
predicting surgical orthodontic outcomes
are
Tracing overlay method
Template method
Surgical treatment objective (STO)
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The purpose of S.T.O.
To establish orthodontic and pre-
surgical orthodontic goals.
To develop surgical objectives
To create the predicted facial profile,
which can be used as a visual aid in
patient consultation.
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Tracing overlay method
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Template method
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ConclusionConclusion
• If the tracings are not accurate and
the superimpositions and not made
on radiographic structures that have
been proved to be relatively stable
and reliable, the superimposition can
be manipulated to show anything the
operator wants to show.
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Cephalometric superimposition

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