Dental Superimposition Techniques

SUPERIMPOSITION
TECHNIQUES
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


Contents
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Introduction
Methods of assessing dentofacial changes
Method of superimposing radiographs
Maxillary super-impositions
Mandibular superimpositions
Ricketts superimposition for treatment design
Ricketts four-step method

Introduction
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In 1931 Broadbent (USA) and Hofrath (Germany)
- cephalometric technique using a cephalostat.
Treatment planning.
Evaluation of treatment results by quantifying the
changes brought about by treatment
Predicting growth related changes


What is cephalometric
superimposition ?
“A cephalometric superimposition is an analysis
of lateral cephalograms of the same patient taken
at different times”.
Uses:
 Evaluate a patients growth pattern at different ages



Method of superimposing
radiographs

Superimposing on a stable plane
or structure

Registration on a stable
landmark


Validity and reproducibility


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Validity: It is the extent to which the value
obtained represents the object of interest.
 Planes and landmarks should be anatomically
valid and should agree with the anatomic
structures they represent
Reproducibility: It is the closeness of successive
measurements of the same object.


Methods of assessing
Dentofacial changes
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Brodie and broadbent -Dentofacial growth
patterns are established at a very early age and
thereafter are subject to proportional changes.
Downs and Rickkets -several angles and
dimensions change with age but in an orderly and
progressive manner
Hellman -suggested that the infant face is
transformed into that of an adult face by increase
in size by changes in proportion and by
adjustment in position.

Dentofacial changes


Areas studied :
 Changes in the overall face
 Changes in the maxilla and it’s dentition
 Changes in the mandible and its dentition
 Amount and direction of condylar growth
 Mandibular rotation


Dentofacial changes
Color coding suggested by ABO:
 Pretreatment – Black
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Progress – Blue

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End of treatment – Red

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Retention - Green

Evaluation of overall changes
in the face


Superimposition methods:
 Broadbent triangle
 Sella nasion line
 Basion horizontal
 Basion nasion plane
 De Costers anterior cranial base reference line
 Viazis cranial base triangle
 Frankl’s occipital reference base

in the face


Objectives
 Overall assessment of growth and treatment
changes of the facial structures
 Amount of change in direction of displacement
and growth of maxilla and mandible.
 Changes in soft tissue
 Changes in maxillo mandibular relationship
 Overall displacement of teeth.

in the face
Superimposition at registration point
R with Bolton-nasion planes parallel

Broadbent triangle

Among the first structures
used for superimposition
 On observations of dried
skulls and a comparative
study of cranial base planes
(Bolton-nasion, porionnasion, sella-nasion) in
persons 3 to 18 years of age.
 Bolton point maybe obscured
by Mastoid


in the face
Sella nasion plane:




.

SN is a frequently used
reference line that has been
reported to be relatively
stable.
Both points S and N are
located in the mid sagittal
plane and are displaced a
minimal degree by
movement of the head.


Steiner -SN with registration
point
 At sella to evaluate sagittal
changes in mandibular
positions and
 At nasion to evaluate the
position of the maxilla
through changes in the
angle SNA


in the face
Sella nasion plane:
 Unlike Steiner, Björk
used sella as
registration point to
assess changes in
position of both jaws.


in the face

Basion horizontal
 Coben
 Basion is used as the
registration point.
 The SN planes are made
parallel by the help of the
Basion horizontal line and it’s
constant relationship with SN.
 A coordinate grid system is
used to superimpose the
radiographs.


in the face
Basion - Nasion plane:
 Suggested by Ricketts


He considered Ba-N plane as
a line of separation of the
face from the skull and hence
a basic cranial axis for
growth and structural
reference.


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Based on studies of
laminograph sections,
Ricketts suggested that
the cranial base angle,
while constant on
average, exhibits a
change of 5° in either
direction over a 3-year
period


in the face
De Coster line
 He advocated tracing the
inner contour of the
frontal bone through the
cerebral aspect of the
ethmoid , the
planumsphenoidale and
the anterior aspect of the
sella turcica.
 Ajodo1953;39;304-306

in the face
Viazis cranial base
triangle
 The anterior wall of
sella turcica and the
cribriform plate
(laminar cribrosa)
remain unchanged
after age 5.
 Jco;25;565-570



Superimposition on the
anterior wall of sella turcica
and the stable TC (cranial
base) line, with registration
on T point, provides a
practical and reliable
formation in both the
anteroposterior and vertical
planes.


in the face
Viazis cranial base triangle
 First priority - to
registering on T point,
followed by
superimposing on the
inner structure of the
triangle, and finally
superimposing on the TC
line. This "best-fit"
approach meets the
realistic expectations of
any superimposition
technique.

Frankl’s occipital reference
base

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Among the basal structures of the neurocranium,
the occipital bone around the foramen magnum is
the first to ossify (between the third and fourth
year of life).
Minimalpostnatal growth of this structure and
surrounding tissues is seen.

Frankl’s occipital reference
base




Landmarks – O’ and
O”
Reference plane –
based on natural head
posture and parallel to
the ground


in the face
Reliability of the various cranial base reference
planes used.
For meaningful interpretations of
superimpositions they have to be registered on
stable reference landmarks.
 Cranial base superimpositions are subject to error
due to the continued growth of the sphenoccipital
synchondrosis (Knott).
 Bone remodelling at sella and Nasion are also
responsible for further errors.

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Nasion position can change in a vertical direction
(Nelson and Knott).
Melsen’s study’s on human autopsy material has
shown that the position of sella may change in a
downward or a downward and backward direction.
She also showed that the position of Basion
changed due to remodelling of the clivus.
The Bolton point could be difficult to locate in
children due to the shadow of the mastoid process

Growth changes in position of Nasion and sella


Reference structures for
overall face superimpositions.


Nelson’s and Melsen’s - stable structures in the
anterior cranial base.
 Anterior wall of sella turcica
 The contour of the cribriform plate of the
ethmoid
 Trabecular system of the ethmoid air cells
 The median border of the orbital roof
 Planum sphenoidale

Evaluation of changes in maxilla
and its dentition in relation to the
maxilla
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Superimposition along the
palatal plane registered at
ANS
Broadbent, Moore,
Salzman, Ricketts,
McNamara
Compromised by
remodelling of the palatal
shelves and ANS- Bjork
and Skeiler

maxilla
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Superimposition on
the nasal floors with
films registered at the
anterior surface of the
maxilla
Downs and Brodie.


maxilla
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Superimposition
along the palatal plane
registered at the
pterygomaxillary
fissure
Moore


maxilla
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Superimposition on
the outline of the
infratemporal fossa
and the posterior
margin of the hard
palate.
Reidel


maxilla
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Superimpostion
registered at the
common Ptm
coordinate
maintaining the basion
horizontal
relationship.
Coben

maxilla
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superimposition on the
best fit of the internal
palatal structures.
McNamara


maxilla
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superimposition on
metallic implants
Bjork and skeiller


maxilla
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The structural
superimposition on the
anterior surface of the
zygomatic process of
the maxilla
Bjork and Skeiler


maxilla


Neilsen on a study of various maxillary
superimposition techniques concluded that:
 The best fit method significantly under estimates the
vertical displacement of skeletal and dental
landmarks
 With the implant method and the structural method
ANS showed twice as much vertical displacement
as PNS

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Structural method and implant methd did not
show any significant differences
The structural method is a valid method of
assessing maxillary growth and treatment
changes


Mandibular superimposition
Stable areas
 Anterior contour of the
chin
 The inner contour of the
cortical plates at the inferior
border of the symphysis
 Contours of the mandibular
canal
 Lower contour of the
mineralized molar tooth
germ

Mandibular superimposition
technique


Methods to assess growth Vs
treatment changes




Differentiate between changes produced due to
growth and changes produced due to treatment.
Assess treatment changes against the background of
natural growth of the individual


Methods to assess growth vs
treatment changes


Rickett’s eleven factor summary analysis



Four position analysis
The analysis is based on Rickkets short term growth
forecasting, data which was obtained on patients – both
male and female of different ages and growth patterns
undergoing orthodontic treatment.


Rickett ’s Eleven factor
summary analysis




Eleven factors of the basic facial and skeletal
structures are recorded from the cephalometric
tracing to describe the chin, maxilla, teeth and soft
tissue profile.
Five areas of superimposition within which are a
total of seven areas of evaluation are used to
evaluate in amount and direction, change in
normal growth and change due to treatment.

Rickett’s Eleven factor
summary analysis


summary analysis
CHIN IN SPACE

MEAN

CHANGE

FACIAL AXIS

90+/-3

No change

FACIAL DEPTH

87+/-3

+10 for 3 yrs

MAND PLANE

26+/-4

-1o for 3 yrs

FACIAL TAPER

68+/-3

No change

2+/-2

-1mm / 3 yrs

L1 TO APO

1+/-2

No change

L1 INCL

22+/-4

No change

U6 TO PTV

Age+3+2

1mm / year

-2+/-2

Less with age

CONVEXITY
CON AT A
TEETH

PROFILE
L LIP TO E LINE


summary analysis
SUPERIMPOSITION AREA 1 – EVALUATION
AREA 1
• FACIAL AXIS OPENS 1o FOR
DOLICOFACIAL PATTERN
•FACIAL AXIS CLOSES 1O FOR
BRACHYFACIAL PATTERNS
•FACIAL AXIS OPENS 1O FOR 5mm
CONVEXITY REDUCTION
•FACIAL AXIS OPENS 1O FOR 3mm
MOLAR CORRECTION
•FACIAL AXIS OPENS 1O OR 4mm
OVERBITE CORRECTION
•FACIAL AXIS OPENS 1 TO 1.5O FOR
CROSS BITE CORRECTION AND
RECOVERS ONE HALF

BASION-NASION PLANE at CC

summary analysis
SUPERIMPOSITION AREA 2 – EVALUATION
AREA 2
• THE BASION-NASION-POINT A
ANGLE OF 66O DOES NOT CHANGE
WITH GROWTH
•SO ANY CHANGES PRODUCED
MUST BE DUE TO TREATMENT
•HEADGEAR - -8mm
•CLASS II ELASTICS - -3mm
•ACTIVATOR - -2mm
•TORQUE- - 1 TO 2mm
•CLASS III ELASTICS 2 TO 3mm
•FACIAL MASK - 2 TO 4mm
BASION NASION PLANE AT
NASION

summary analysis
SUPERIMPOSITION AREA 3 – EVALUATION AREAS 3
AND 4
• LOWER DENTURE REMAINS
CONSTANT WITH THE A Pog LINE
•Without treatment, the lower molar will erupt
directly upward to the new occlusal plane.
•The LOWER INCISAL angle is 22° at +1mm
to the APo plane and + 1 mm to occlusal
plane, but the angle increases 2° with each mm
of forward compromise.

CORPUS AXIS AT PM

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OCCLUSAL PLANE TO
CORPUS AXIS DOES NOT
CHANGE
LOWER MOLAR ERUPTS IN A
DIRECTION PERPENDICULAR
TO THE FH PLANE
OCCLUSAL PLANE ERUPTS
0.8mm UPWARDS FROM THE
CORPUS AXIS.


summary analysis
SUPERIMPOSITION AREA 4 – EVALUATION AREAS 5
AND 6
• THE UPPER MOLAR AND INCISOR
FOLLOW THEIR POLAR AXIS WITH
GROWTH
•CHANGES IN POSITION OF THE
MOLAR OR INCISOR IS DUETO
TREATMENT.
•UPPER DENTAL ARCH ERUPTS
DOWNWARD AND FORWARD 0.2 TO
0.3mm PER YEAR

PALATE AT ANS

summary analysis
SUPERIMPOSITION AREA 5 – EVALUATION AREA 7
•

ESTHETIC PLANE AT INTERSECTION
OF OCCLUSAL PLANES


Rickett’s four position analysis


Takes into consideration two superimposition
areas to evaluate skeletal change and two
superimposition areas to evaluate dental change
against growth.


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Position 1
Mandible or chin





Position 2
Maxilla



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Position 3
Upper teeth



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Position 4
Lower teeth


Pitchfork analysis
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

Johnston in 1985
Used to describe
the treatment effects
of different
treatment strategies
used to correct
Class II patients
Data recorded in the
form of a pitch fork


Pitchfork analysis


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Reference planes – SE
perpendicular to MFOP
D perpendicular to
MFOP
Measurement of Max
change
Measurement of ABCH
Calculation of Mand


Pitchfork analysis


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Superimposition on
D
Measurement of
molar and incisal
changes


Pitchfork analysis


Measurement of
amount of molar
correction


Pitchfork analysis


Measurement of
overjet correction


References:




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

Orthodontic cephalometry Text book-Athanasios
E Athanasiou
Radiographic cephalometry second ed.,-Alexander
Jacobson(Text book)
Bioprogressive therapy-Robert M.Ricketts(Text
book)
A Four- step method to distinguish orthodontic
changes from natural growth:J.C.O,Vol 9,1975
pgs208-228

THANK YOU


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