This document discusses various techniques for superimposing cephalometric radiographs to assess dentofacial changes over time. It describes methods for evaluating overall facial changes, as well as changes specific to the maxilla, mandible, and individual teeth. Stable reference structures are identified for different regions. Ricketts' Eleven Factor Analysis and Four Position Analysis are also introduced as methods to differentiate skeletal growth changes from those resulting from orthodontic treatment.

1. SUPERIMPOSITION
TECHNIQUES
By
Dr Tony Pious

2. Introduction
• In 1931 Broadbent in USA and Hofrath in Germany
simultaneously presented a standardised cephalometric
technique using a high powered X-ray source and a head
holder called a cephalostat.
• Orthodontic diagnosis by enabling the study of skeletal, dental
and soft tissue structures of the craniofacial region
• Treatment planning.
• Evaluation of treatment results by quantifying the changes
brought about by treatment
• Predicting growth related changes

3. 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
• To evaluate changes in basal and dentoalveolar
relationships after treatment
• To quantify growth and treatment changes in
dentoalveolar and basal relationships.

4. Method of superimposing
radiographs
Superimposing on a stable plane
or structure
Registration on a stable
landmark

5. Validity and reproducibility
• 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.

6. Methods of assessing
Dentofacial changes
• Study of changes in dentofacial dimensions using
cephalometric superimposition have shown varying
results
• Brodie and broadbent have shown that dentofacial
growth patterns are established at a very early age and
thereafter are subject to proportional changes.
• Downs and Rickkets pointed out that 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.

7. Methods of assessing
Dentofacial changes
• Areas studied to assess changes due to growth or treatment
or both include:
• 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

8. • Color coding of consecutive cephalograms suggested by
ABO:
• Pretreatment – black
• Progress – blue
• End of treatment – red
• Retention - green

9. 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

10. • 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.

11. • Broadbent triangle
• Among the first structures used for
superimposition
• Broadbent based this method on
observations of dried skulls and a
comparative study of cranial base
planes (Bolton-nasion, porion-nasion,
sella-nasion) in persons 3 to 18 years
of age.
• Bolton point maybe obscured by
Mastoid
Superimposition at registration point R with Bolton-nasion planes parallel

12. Evaluation of overall changes
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
midsagittal plane and are displaced a
minimal degree by movement of the
head.
• Steiner used 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.
•

13. • Sella nasion plane:
• Unlike Steiner, Björk used sella
as registration point to assess
changes in position of both
jaws.
• Later, Björk reported that
errors of biologic origins of S
and N may weaken the SN
reference for estimation of
facial changes. He stated that
an upward or downward
displacement of nasion may
occur with growth at the
frontonasal suture. Likewise, a
posterior displacement of sella
may be induced by the
remodeling of dorsum sellae
connected with the increased
size of the pituitary gland.

14. • Basion horizontal
• Coben presented the Basion
horizontal concept.
• 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.

15. • 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.
• 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

16. • Basion - Nasion plane:
• one may doubt the reliability of this
axis because growth at nasion is
subjected to individual variations.
Moreover, the position of basion is
influenced by remodeling processes on
the clivus surface and on the anterior
border of the foramen magnum, and by
changes in the position of the pars
basilaris ossis occipitalis associated
with growth in the spheno-occipital
synchondrosis.

17. • De Coster line
• He advocated tracing
the inner contour of
the frontal bone
through the cerebral
aspect of the ethmoid ,
the planum
sphenoidale and the
anterior aspect of the
sella turcica.

19. • Viazis cranial base triangle
• The anterior wall of sella
turcica and the cribriform plate
(laminar cribrosa) remain
unchanged after age 5.
• 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.

20. • Viazis cranial base triangle
• 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.
• First priority should be given 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.

21. Evaluation of overall changes
in the face – Viazis Triangle

22. Frankl’s occipital reference
base
• 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).
• Phylogenetically and ontogenetically as the midbrain is
highly conserved minimal postnatal growth of this
structure and surrounding tissues is seen.
• It permits the study of craniofacial growth in relation to
an individual bone and its immediate structures

23. Frankl’s occipital reference
base
• Reference plane –
based on natural head
posture and parallel to
the ground

24. Frankl’s occipital reference
base

25. Evaluation of overall changes
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.
• 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

26. Growth changes in position of Nasion and sella

27. Reference structures for
overall face
superimpositions.• Nelson’s cephalometric study and Melsen’s
histological study on human autopsy materials
have reveled a few stable structures in the
anterior cranial base for use in superimposition.
• 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

28. Method of superimposition of
radiographs to assess overall
changes
Pretreatment tracing Progress tracing

29. Method of superimposition of
radiographs to assess overall
changes
Superimposition using ‘Best fit method’

30. Evaluation of changes in maxilla
and its dentition in relation to the
maxilla
• 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

31. Evaluation of changes in maxilla
and its dentition in relation to the
maxilla
• Superimposition on
the nasal floors with
films registered at the
anterior surface of the
maxilla
• Downs and Brodie.

32. Evaluation of changes in maxilla
and its dentition in relation to the
maxilla
• Superimposition
along the palatal
plane registered at the
pterygomaxillary
fissure
• Moore

33. Evaluation of changes in maxilla
and its dentition in relation to the
maxilla
• Superimposition on
the outline of the
infratemporal fossa
and the posterior
margin of the hard
palate.
• Reidel

34. Evaluation of changes in maxilla
and its dentition in relation to the
maxilla
• superimpostion
registered at the
common Ptm
cordinate maintaining
the basion horizontal
relationship.
• Coben

35. Evaluation of changes in maxilla
and its dentition in relation to the
maxilla
• superimposition on
the best fit of the
internal palatal
structures.
• McNamara

36. Evaluation of changes in maxilla
and its dentition in relation to the
maxilla
• superimposition on
metallic implants
• Bjork and skeiller

37. Evaluation of changes in maxilla
and its dentition in relation to the
maxilla
• the structural
superimposition on
the anterior surface of
the zygomatic process
of the maxilla
• Bjork and Skeiler

38. Evaluation of changes in maxilla
and its dentition in relation to the
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
• 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

39. Structural method of
superimposing maxillary
structures
Pretreatment tracing

40. Structural method of
superimposing maxillary
structures
superimposition

41. Mandibular superimposition
• Stable areas for
superimposition:
• 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

42. Mandibular superimposition
technique

43. Mandibular superimposition
technique

44. Methods to assess growth vs
treatment changes
• Though the techniques described till now will assess the
amount of growth changes in a given duration of time or
the overall changes of treatment and growth during a
given treatment period they do not however
differentiate between changes produced due to growth
and changes produced due to treatment.
• The following cephalometric analyses help us to assess
treatment changes against the background of natural
growth of the individual

45. 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.

46. 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.

47. Rickett’s Eleven factor
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
CONVEXITY
CON AT A 2+/-2 -1mm / 3 yrs
TEETH
L1 TO APO 1+/-2 No change
L1 INCL 22+/-4 No change
U6 TO PTV Age+3+2 1mm / year
PROFILE
L LIP TO E LINE -2+/-2 Less with age

48. Rickett’s Eleven factor
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 HALFBASION-NASION PLANE at CC

49. Rickett’s Eleven factor
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
BASION NASION PLANE AT
NASION

50. Rickett’s Eleven factor
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.
•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.
CORPUS AXIS AT PM

51. Rickett’s Eleven factor
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

52. Rickett’s Eleven factor
summary analysis
SUPERIMPOSITION AREA 5 – EVALUATION AREA 7
•
ESTHETIC PLANE AT INTERSECTION
OF OCCLUSAL PLANES

53. 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.

54. Rickett’s four position
analysis
• Position 1
• Mandible or chin

55. Rickett’s four position
analysis
• Position 2
• maxilla

56. Rickett’s four position
analysis
• Position 3
• Upper teeth

57. Rickett’s four position
analysis
• Position 4
• Lower teeth

58. Superimposition methods to assess
dentoalveolar and skeletal changes in
Class II treatment.
• Johnstons Pitchfork analysis

59. 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

60. Pitchfork analysis
• Superimposition on D
• Measurement of
molar and incisal
changes

61. Pitchfork analysis
• Measurement of
amount of molar
correction

62. Pitchfork analysis
• Measurement of
overjet correction

63. • For overall craniofacial growth/displacement and treatment
effect, superimpose on sella-nasion, registering at sella.
• For maxillary complex growth and treatment effect, superimpose
at the best fit on the palatal surface of the maxilla parallel to ANS-
PNS.
• For mandibular growth and treatment effect, superimpose on the
inferior cortical contour of the symphusis and on the inferior
alveolar canal. If the inferior alveolar canal is not clearly visible,
then align on the lower border of the mandible.