Cephalometric superimposition methods

Chepalometric
superimposition
methods
www.indiandentalacademy.com

What is cephalometric
superimposition ?
 A cephalometric superimposition is an
analysis of lateral cephalograms of the
same patient taken at different times.

Need for Cephalometric
superimposition
Evaluate a patient’s growth pattern at different
ages
To evaluate changes in basal and
dentoalveolar relationships after treatment
To quantify growth and treatment changes in
dento-alveolar and basal relationships.

Reliability of superimposition
 Stable reference landmarks are needed.
 Cranial base superimpositions are subject to error due to the continued
growth of the sphenoccipital synchondrosis (Knott).
 Bone remodelling at sella and Nasion can cause errors.
 Nasion position can change in a vertical direction (Nelson and Knott).
 Melsen’s study’s showed that the position of sella may change in a
downward or a downward and backward direction.
 The Bolton point could be difficult to locate in children due to the shadow of
the mastoid process.

Reference planes for
superimposition-a review
 Bolton-nasion plane - Broadbent
 Basion nasion plane –Ricketts
 Anterior cranial base –De coster
 Sella nasion line- ABO1990
 Basion horizontal- Coben

Bolton-nasion plane –by Broadbent
shows the downward and forward growth of the face from
beneath the cranium.
Reference plane : Bolton –Nasion plane
Registration point: perpendicular drawn from ‘S’ to the bolton
nasion plane.

Basion nasion plane –by Rickett’s
-forms baseline for growth analysis
Reference plane-basion nasion plane
Reference point- ‘cc’ -point of intersection between the
basion nasion plane and the Rickett’s facial axis

Anterior cranial base –De-coster
It is the sella tursica – ethmoid line.
It is drawn along the inner contour of the frontal bone through the
cerebral aspect of the ethmoid, the planum sphenoidale and the
anterior aspect of the sella tursica.
Ant. wall of sella Cribriform plate
of ethmoid
Planum sphenoidale

 Sella nasion line- ABO 1990
Reference plane- sella nasion line
Registration point-sella
-Shows the amount of growth
change between two serial
radiographs.
-accurate as long as the growth at
the nasion is a linear extension
of the sella nasion line.

 Basion horizontal-
Coben
Reference plane-plane
constructed at the basion
parallel to the foramen
magnum.
Registration point-basion

Superimposition methods to study
growth

Maxillary superimposition
 1937,Broadbent superimposing palatal plane at ANS ,the
anterior surface of maxilla and point A moved posteriorly.
 Down’s superimposed the nasal floor at the anterior surface
of maxilla to eliminate appositional changes at ANS.
 Moore superimposed palatal plane registered at the
pterygomaxillary fissure.
 Reidel superimposed the infra-temporal fossa at the posterior
portion of the hard palate.
 Bjork and Skieller applied implant studies to assess growth

Broadbent-Palatal plane registered at ANS for maxillary superimposition

Down - Superimposition at the nasal floor registered at the
anterior surface of maxilla

Moore – superimposition of palatal plane registered at the
pterygomaxillary fissure

Reidel –superimposition at the infra-temporal fossa

The basion horizontal registered at Ptm.

Maxillary superimposition on the best fit of the internal
palatal structures

Bjork and Skieller - implant studies to assess growth

Maxillary superimposition…
 According to Bjork and Skieller
 Remodelling involves resorptive lowering of the
nasal floor which is greater anteriorly than
posteriorly.
 Zygomatic process underwent remodelling in
the superior part of the orbital floor and the most
inferior part of the key ridge.

Maxillary superimposition…
 Hard palate undergoes continuous resorption on its
nasal floor and apposition on the oral side.-
superimpositions are unsatisfactory
 ANS and PNS undergo significant remodelling.
 The best fit method provides a higher degree of validity
compared to ANS -PNS.

Two methods of maxillary
superimposition
1.Structural method
2.Best fit method

Structural method
Superimposition on the anterior contour of the zygomatic process
of maxilla.
This area is relatively stable after 8 yrs.
On both the pretreatment and post-treatment
cephalogram
1.Trace anterior contour of the zygomatic process
2.Draw a line tangent to it –construction line
3.Trace the orbit, palate, N-S line

Assessing maxillary rotation
The pretreatment and post-treatment chepalograms are superimposed
on the construction line.
The amount of apposition at the orbital floor is obtained.
The superimposition is moved so that the amount of resorption is equal
to the amount of apposition at the nasal floor.
The two tracing are stabilised.
The angle formed by the two S-N line gives the amount of maxillary
rotation.

Best fit method of superimposing
maxillary structures.
 If the zygomatic process of maxilla is not
clearly defined then the best fit method is
used.
 The superimpositions are made on the
nasal and palatal surfaces of the hard
palate that is not influenced by tooth
movement.
 On the pretreatment and post-treatment
cephalogram maxillary structures are
traced.
 The 2nd
tracing is placed over the 1st
tracing
for best fit alignment of
-the contour of the oral part of the palate
-the contour of the nasal floor.
-the entrance of the incisal canal.
The best fit method has low degree of validity
and minimum degree of reproducibility.

Mandibular superimposition
 Reference plane for mandibular
superimposition –Salzmann1972
 The mandibular plane between
menton and gonion.
 Tangent to the lower border.
 The Mandibular outline
 Bjork’s reference planes are
1.Anterior contour of the bony chin
2.Inner contour of the cortical plate at the
lower border of the symphysis.
3.The contour of the mandibular canal.
4.The lower contour of the mineralised 3rd
molar tooth germ prior to root
formation.

Mandibular superimposition…
 Bjork’s four stable landmarks are
marked on the pretreatment and
post-treatment chephalogram.
 The two cephalograms are
superimposed .
 This method gives a medium to
high degree of validity and
reproducibility
 Mandibular rotations are evaluated
by changes in N-S lines.the angle
between the two line gives the
amount of mandibular rotation.

Superimposition methods to study
treatment changes

Various superimposition methods
 Rickett’s eleven factor analysis
 Pithfork analysis
 Pancherz analysis
 Modified pancherz analysis

Eleven factor analysis
 The eleven factor’s are
Chin in space
 Facial axis
 Facial angle
 Mandibular plane
 Facial taper
 Mandibular arc
Convexity
 Convexity of point A
Teeth
 Lower incisor to APog
 Mandibular incisor inclination
 Upper molar to Ptv
 Profile
 Lower lip to E line.

Eleven factor analysis…
 Five superimposition areas and seven evaluation areas
 Each superimposition are evaluates a particular area of
the face.
Superimposition areas
1.The chin
2.The maxilla
3.The teeth in the mandible
4.The teeth in the maxilla
5.The facial profile
Evaluation areas
1.Amount of growth of the chin
2.Changes in maxilla
3.Need for intrusion, extrusion, retraction and
advancement of the lower incisor .
4.Need to advance ,upright and hold the lower
molars for anchorage.
5.Need to intrude, extrude, distalize or bring them
forward.
6.Need to intrude, extrude, retract, advance,
torque or tip the upper incisors.
7.Evaluation of soft tissue profile.www.indiandentalacademy.com

Superimposition area 1
 Reference plane-basion
nasion plane
 Registration point-cc
point
 Evaluates growth of the
chin in mm.

The facial axis open or closed
from the effect of mechanics
Facial axis opens
• 1˚for 5mm of convexity
reduction.
• 1˚ for 3mm of molar correction.
• 1˚ for 4mm of overbite
correction.
• 1˚-1.5˚ with cross-bite
correction.
Facial axis closes with extraction

Superimposition area2
 The superimposition area
2 shows any change in
maxilla (point A).
 Reference plane –Basion
nasion plane
 Registration point-Nasion
 The basion nasion point
A angle does not change
with normal growth

 Any change is due to the effect
of mechanics.
 The maximum range to which
point A can be changed by
mechanics are
• Headgear -8mm
• Class II elastics -3mm
• Activator -2mm
• Torque -1-2mm
• Class III elastics 2-3mm
• Facial mask 2-4mm

 Evaluates changes in
the mandibular
dentition, the lower
molars and incisors.
 Reference plane-
corpus axis
 Registration point-PM

 This evaluates the
maxillary dentition, the
maxillary molars and
incisors.
 Reference plane-palate
 Registration point-ANS

 This evaluates soft tissue
profile.
 Reference plane is the E
line.
 Evaluates effects of
mechanics on the soft
tissue of the face.
 In normal growth the face
becomes less protrusive
with reference to the
E line.

Rickett’s four position analysis
 Takes into consideration two superimposition
areas to evaluate orthopedic change and two
superimposition areas to evaluate orthodontic
change against growth.

Position 1

position2

position3

position4

Pitchfork analysis
 The pitchfork analysis was developed
by Johnston.
 Growth and displacement of the
maxilla and mandible are measured
relative to the cranial base
(SE).
The change in the position of the upper
and lower molars and incisors are
measured relative to the basal bone.
All measurements are made parallel to a
mean functional occlusal plane.
The algebric sum of various skeletal and
dental changes = to the treatment
change in the molar relationship and
incisal overjet.

Pitchfork analysis
 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
 Reference planes – SE
perpendicular to MFOP
 D perpendicular to MFOP
 Measurement of Max.
change
 Measurement of
ABCH(shows differential
jaw growth)
 Calculation of Mand.
change

Pitchfork analysis
 Superimposition on D
 Measurement of
molar and incisal
changes

Pitchfork analysis
 Measurement of
amount of molar
correction

Pitchfork analysis
 Measurement of
overjet correction

Pancherz analysis

Pancherz analysis
 is/OLp minus ii/OLp— Overjet.
 ms/OLp minus mi/OLp— Molar
relation (a positive value indicates a
distal relation; a negative value
indicates a normal relation).
 Skeletal measuring points
 ss/OLp— Position of the maxillary
base.
 pg/OLp— Position of the mandibular
base.
 co/OLp— Position of the condylar
head.
 pg/OLp + co/OLp— Mandibular
length.

Pancherz analysis
 Dental measuring points
 is/OLp— Position of the maxillary
central incisor.
 ii/OLp— Position of the mandibular
central incisor.
 ms/OLp— Position of the maxillary
permanent first molar.
 mi/OLp— Position of the mandibular
permanent first molar

Pancherz analysis
 11. is/OLp (d) minus ss/OLp (d)
— Change in position of the
maxillary central incisor within
the maxilla.
 12. ii/OLp (d) minus pg/OLp (d)
mandibular central incisor within
the mandible.
 13. ms/OLp (d) minus ss/OLp
(d)— Change in position of the
maxillary permanent first molar
within the maxilla.
 14. mi/OLp(d) minus pg/OLp(d)
mandibular permanent first
molar within the mandible.

Modified Pancherz Analysis
The original analysis The modified Analysis

LINEAR
MEASUREMENTS
Co-pg
Co-go
Go-pg

ANGULAR
MEASUREMENTS
FMN-T-ba
FMN-T-ar
Cl_ml
Ar-goi-me
Nl-T-FMN
Ml-T-FMN
Nl-ml

VERTICAL DENTAL
T-FMN/is
T-FMN/ii
T-FMN/ms
T-FMN/mi

Regional superimpositions
 Regional superimpositions can be
used to analyse growth changes
and growth vectors.
 Cephalometric studies done at the
Forsyth dental center-1948
 Lateral cephalograms were
obtained at 8 and 16yrs.
 The tracing were superimposed
for best fit.
 The tracing gave the expected
downward and forward growth of
the maxilla and mandible, the
incisors and the chin.
 Three growth vectors were
obtained to illustrate growth along
the three co-ordinate axis.

The reliability of mandibular radiographic
superimposition. BJO1988
 The three outlines commonly used were investigated.
-the mandibular plane
-the mandibular outline
-Bjork’s mandibular structures.
It was found that the use mandibular outline was more
reliable when the time interval between radiographs was
short or the patient has passed maturity.

Maxillary superimposition:A comparison of 3 methods of
cephalometric evaluation of growth and treatment change.
AJO1989
 The implant method, the best fit method method and the
structural method were compared.
 The best fit method under-estimates the eruption of the
teeth by 30-50%
 The structural method showed no significant difference
when compared to the implant method.

References
 Radiographic cephalometry - Alexander Jacobson
 Orthodontic cephalometry – athanasios
 Bioprogressive therapy-Rickett’s
 Maxillary superimposition: superimposition:A comparison of 3
methods of cephalometric evaluation of growth and treatment
change. AJO1989
 The reliability of mandibular radiographic superimposition. BJO1988
 Pitchfork analysis-

Cephalometric superimposition methods

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