The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
2. INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indiandentalacademy.com
3. DOWNS ANALYSIS
DOWNS ANALYSIS WAS INTRODUCED BY W.B. DOWNS IN 1948.
This analysis was one of the first to be introduced
DOWNS SAMPLE
The control material studied by downs was derived form 20 white
subjects, who ranged in age from 12 to 17 years.
All individuals possessed clinically excellent occlusions.
www.indiandentalacademy.com
4. VARIOUS LANDMARKS USED IN DOWNS ANALYSIS
Nasion
Sella
Porion
Point A (Subspinale)
Point B (Supramentale)
Gnathion
Pogonion
Orbitale
Bolton point - The highest point on the concavity behind
the
occipital condyles
www.indiandentalacademy.com
5. VARIOUS PLANES USED IN THIS ANALYSIS
Most important reference plane (FRANK FORT HORIZONTAL
PLANE)
OCCLUSAL PLANE
N
MANDIBULAR PLANE
FACIAL PLANE
Pog
www.indiandentalacademy.com
6. Downs anaylsis describes the
skeletal pattern and dental pattern
Skeletal pattern
Facial angle
Angle of convexity
A-B plane
Mandibular plane angle
Y (Growth) Axis
Dental pattern
Cant of occlusal plane
Inter incisal angle
Incisor occlusal plane
angle
Incisor mandibular plane
angle
Protrusion of maxillary
incisors.
www.indiandentalacademy.com
7. Downs Facial Types
WB downs noted the position of
the mandible could be used in
determining the facial types.
Downs four basic facial types
Retrognathic facial type
Orthognathic facial type
www.indiandentalacademy.com
Prognathic facial type
True prognathism
8. FACIAL ANGLE
This is the inferior inside angle in which
the facial line (nasion-pogonion)
intersects Frankfort horizontal plane.
The mean reading for this angle is 87.8
degrees (SD, 3.6) range varies from 82
to 95 degrees.
The facial angle is used to measure the
degree of retrusion or protrusion of the
lower jaw.
www.indiandentalacademy.com
N
FH Plane
Pog
9. ANGLE OF CONVEXITY
The angle of convexity is formed by the
intersection of line N-point A and point
A-pogonion.
This angle measures the degree of the
maxillary basal arch at its anterior limit
(point A) relative to the total facial
profile (nasion-pogonion)
This angle measures the convexity or
concavity of skeletal profiles.
The range extends from a minimal of –
8.5 degrees to a maximal of +10 degrees,
with a mean reading of 0 degree.
www.indiandentalacademy.com
10. A-B PLANE
This angle is formed between a line
connecting point A and point B and line
Joining nasion to pogonion (facial
plane) .
The A-B plane is a measure of the
relation of the anterior limit of the apical
bases to each other relative to the facial
plane.
The readings extend from a maximal of
0 degree to a minimal of –9 degrees with
a mean reading of –4.6 degrees.
www.indiandentalacademy.com
11. MANDIBULAR PLANE PLANE
Mandibular plane according to
downs, is tangent to the gonial
angle and the lowest point of the
symphysis.
The mandibular plane angle is
established by relating the MP
to the Frank fort horizontal
plane.
The range of readings extends
from a minimal of 17 degrees to
a maximal of 28 degrees with
mean reading of 21.9 degrees.
www.indiandentalacademy.com
12. Y – (GROWTH) AXIS
The y-axis is measured as the acute
angle formed by the intersection of a
line from the sella turcica to
gnathion with the Frankfort
horizontal plane
The y-axis indicates the degree of
the downward, rearward, or forward
position of the chin in relation to the
upper face.
The range extends from a minimal
of 53 degrees to a maximal of 66
degrees with a mean reading of 59.4
degrees.
www.indiandentalacademy.com
13. CANT OF OCCLUSAL PLANE
Downs
occlusal
originally
plane
defined
as
that
the
line
bisecting the overlapping cusps of
the first molars and the incisal
overbite
The cant of the occlusal plane is a
measure of the slope of the
occlusal plane to the Frankfort
horizontal .
The minimal angular measurement
is +1.5 degrees; the maximal +14
degrees;
and
the
mean
+9.3
www.indiandentalacademy.com
14. INTERINCISAL ANGLE
The interincisal angle is established
by passing a line through the incisal
edge and the apex of the root of the
maxillary and mandibular central
incisors.
The minimal angular reading is 130
degrees; the maximal 150 degrees;
and the mean 135.4 degrees.
This angle is decreased in class I
bimaxillary protrusion and Class II
div1 cases. Increased in Class II div 2
cases.
www.indiandentalacademy.com
15. INCISOR – OCCLUSAL
PLANE ANGLE
The incisor – occlusal plane angle
relates the lower incisors to their
functioning surface at the occlusal
plane .
The inferior inside angle is read as a
positive or negative deviation from a
right angle. The positive angle
increases as the teeth incline forward.
The minimal angle is +3.5 degrees;
the maximal +20 degrees; and the
mean 14.5 degrees (SD, 3.5)
www.indiandentalacademy.com
16. INCISOR – MANDIBULAR PLANE
ANGLE
The incisor mandibular plane angle
is formed by the intersection of the
mandibular plane with a line
passing through the incisal edge
and the apex of the root of the
mandibular central incisor
The minimal angular reading is –
8.5 degrees; the maximal, +7
degrees; and the mean 1.4 degrees.
www.indiandentalacademy.com
17. PROTRUSION OF MAXILLARY
INCISORS
The protrusion of the maxillary
incisors is measured as the distance
between the incisal edge of the
maxillary central incisor to the line
from point A-pogonion
The distance is positive if the incisal
edge is ahead of the point Apogonion line and indicates the
amount
of
maxillary
dental
protrusion.
The minimal reading is –1.0 mm; the
maximal +5 mm, and the mean +2.7
www.indiandentalacademy.com
mm
18. Parameter
Minimal
(degrees)
Maximal
(degrees)
Mean
(degrees)
SD
Skeletal pattern
Facial angle
82
95
87.8
3.6
Angle of
convexity
-8.5
+10
0
5.1
A-B plane angle
-9
0
-4.6
3.7
Mandibular plane 17
angle
28
21.9
3.2
Y- axis
66
59.4
3.8
53
Dental pattern
Cant of occlusal
plane
+1.5
+14
+9.3
3.8
⊥to 1
130
150.5
135.4
5.8
+20
+14.5
3.5
+7
+1.43
3.8
+2.7 mm
1.8
+3.5
⊥ To occlusal
plane
1 To mandibular -8.5
plane
⊥ To A-P plane
-1.0 mm
www.indiandentalacademy.com
+5 mm
19. Vorhies and Adams, 1951
Polygonic interpretation of
Downs analysis
www.indiandentalacademy.com
20. RICKETT’S ANALYSIS
This analysis was introduced by Robert Murray Ricketts
in the year 1960
Material for this study was collected form 1000 white
subjects in the age group of 3-44 yrs
www.indiandentalacademy.com
21. Various land marks in this analysis
A6 - point on the occlusal plane located
perpendicular to the distal surface of the
crown of the upper first molar.
B6 - Point on the occlusal plane located
PT
CC
perpendicular to distal surface of the crown
of the lower first molar.
C1 - Point on the condyle head in contact
with and tangent to ramus plane.
DT - Point on the anterior curve of the soft tissue chin tangent to the
esthetic plane or E-line.
CC - Point of intersection of the basion – nasion plane and the faical
www.indiandentalacademy.com
22. Other land marks
DC - Point in the center of the condyle
neck along the Ba-N plane
PT -Point
at
junction
of
the
pterygomaxillary fissure and the foramen
rotundum
PT
CC
En - Point on the soft tissue nose tangent
to the esthetic plane or E-line.
Gn - Point at the intersection of the facial
and the mandibular planes
Go - Point at the intersection of the ramus and the mandibular planes.
TI - Point of intersection of the occlusal and the facial planes
www.indiandentalacademy.com
23. PM - Point at which the shape of the symphysis
mentalis changes from convex to concave- also
known as protuberance menti.
Pog - Point on the bony symphysis tangent to the
facial plane.
PO - Intersection of the facial plane and the corpus
axis.
www.indiandentalacademy.com
24. LOCATION OF Xi POINT
Xi - Point located at the centre of the ramus.
Locate FH and draw PtV plane
perpendicular to the FH plane
Construct four planes tangent to
points R-1, R-2, R-3 and R-4 on the
borders of the ramus.
The constructed planes form a
rectangle enclosing the ramus
Xi point is located in the center of
the rectangle at the intersection of
the diagonals.
www.indiandentalacademy.com
27. Various measurements used in this analysis
To locate the position of chin
Facial axis
Facial angle
Mandibular plane angle
Convexity of the face
Convexity at point A
Position of upper & lower teeth
Lower incisor to APog line
Upper molar to Ptv plane
Lower incisor to Apog plane
Evaluate the facial profile
Lower lip to E-plane
www.indiandentalacademy.com
28. Facial
Angle
Facial axis
FACIAL ANGLE (Depth)
The angle formed between the facial plane (N-pog) and the frank fort
horizontal plane.
Mean values for 9 year old is 87o ± 3 and increases 1o every 3 years
FACIAL AXIS
The angle formed between the Basion -Nasion plane and the plane
from foramen rotandum (PT) to gnathion.
On the a average this angle is 90o ± 3.5 degrees and there is no age
changes.
www.indiandentalacademy.com
29. Go
MANDIBULAR PLANE ANGLE
Measures an angle formed by the mandibular plane
(Gonion – Gnathion) with Frankfort horizontal plane
On the average this angle is 26o at 9 yrs of age and
decreases 1o every 3 years
www.indiandentalacademy.com
30. Facial contour indicator
Convexity at point A
The convexity of the middle face is measured form (point A –
N- pog).
Normal value on the average is 2 mm at 9 years of age and
decreases approximately 1mm every 3 years
According to AJO 1960
Faces displaying 2mm convexity or concavity straight
faces.
Faces with 5 to 6 mm of convexity or concavity
moderately convex or concave.
If it is more than 10 mm or more severely convex or
www.indiandentalacademy.com
concave.
31. INDICATOR OF LOWER DENTURE
POSITION
Lower incisor to A-pog
Dentureplane (A-Pog) plane
The incisal tips of lower incisors are
measured to A- Pog plane and position
of lower anterior teeth determined.
Indicates protrusion of lower anteriors
Ideally the lower incisor is 1 mm
ahead of A-Pog line.
Lower incisor Inclinations
The angle between the long axis of the lower
incisor and the A- pog plane (1 to A-Po) is
measured
On the average this angle is 28 degrees
Mean values for 9 years old is 22o±4 and there
is no changes with age. www.indiandentalacademy.com
32. Upper molar to PtV Plane
This measurement is the distance from the
ptery goid vertical plane to the distal of
upper molar.
Mean value in a 9 year old patient is (age
+3 mm) and 1 mm is added per year.
Evaluation of the profile
The distance between the lower lip and
esthetic plane is an indication of soft tissue
balance between the lips and profile.
www.indiandentalacademy.com
34. A
CEPHALOMETRIC
SUPERIMPOSITION
IS
AN
ANALYSIS OF LATERAL CEPHALOGRAMS OF THE
SAME PATIENT TAKEN AT DIFFERENT TIMES
CEPHALOMETRIC SUPER IMPOSITIONS INVOLVE
THE EVALUATION OF:
♦ Changes in the overall face
♦ Changes in the maxilla and its dentition
♦ Changes in the mandible and its dentition
♦ Amount and direction of condylar growth
Mandibular rotation
www.indiandentalacademy.com
35. TO PERFORM ACCURATE SUPER
IMPOSITION
Consecutive cepholograms should be taken under identical condition
of magnification head position, and radiological exposure
The tracing of the superimpositions must be accurate
It is of great importance that exactly the same structures and their
corresponding radiographic shadows be traced in the consecutive
cepholograms
One should have the thorough knowledge of anatomy of dentofacial &
cranial structures as well as radiographic interpretation
They have to be registered on stable reference areas in the face.
www.indiandentalacademy.com
36. SUPERIMPOSITION OF THE
Evaluates
MAXILLA
1. Movement of maxillary teeth
2. Rotation of maxilla
Two method for superimposing the maxillary structutres are
recommended- the structural method and a modified best fit
method.
Structural Method : - Suggested by Bjork & Skieller in 1976. is
recommended if the details of the zygomatic process of the
maxilla are clearly identified in both cephalograms.
Modified best fit method : - If the details of zygomatic process of
maxilla are not identified in both cephalograms.
www.indiandentalacademy.com
37. Structural method of superimposition of maxilla
Pre treatment
Tracing
Post treatment
Tracing
Super imposition of
pre & post treatment tracing
On each cephologram, trace the contours of palate, maxillary 1st molar,
central incisors, zygomatic process of maxilla, floor of the orbit N-S line
and the construction line.
www.indiandentalacademy.com
38. Modified best fit method
Pre treatment
Tracing
Progress treatment
tracing
Super imposition of
pre & progress treatment
tracing
On each cephologram trace the outline of the palate 1st permanent
molars and central incisors.
Following structures are in a best fit alignment.
Contour of the oral part of the palate
Contour of the nasal floor
www.indiandentalacademy.com
39. MANDIBULAR SUPERIMPOSITIONS
Evaluates
Movement of the mandibular teeth
Mandibular rotation
Amount & direction of condylar growth
Stable structures for superimposition on the mandible:According to Bjork and Skieller (1983).
The anterior contour of the chin (area 1)
The inner contour of the cortical plates at the inferior border of
the symphysis. (area 2)
Posteriorly, the contours of the mandibular canal (area 3)
Lower contour of a mineralized molar germ. (area 4) before root
www.indiandentalacademy.com
formation.
40. Step – by – step approach for mandibular superimpositions
Pre treatment
Tracing
Progress treatment
tracing
Super imposition of
pre & progress treatment
tracing
On each cephologram trace the following
The symphysis with inner cortical bone
The inferior and posterior contour of the mandible
The anterior contour of the ramus
The most labially positioned lower incisor, and
The first molar.
www.indiandentalacademy.com
41. Evaluation of the overall changes in the face
Nelson’s (1960) and Melsen (1974)
identified certain stable
structures for superimposition.
1. The anterior wall of sella turcica;
2. The contour of the cribiform plate of the ethmoid
bone (lamina cribrosa);
3. Details in the trabecular system in the ethmoid
cells;
4. The median border of the orbital roof; and
5. The plane of the sphenoid bone (planum
sphenoidale)
www.indiandentalacademy.com
42. What can we learn from cranial base
superimpositions ?
1. Cranial base superimpositions provide an over all assessment
of the growth and treatment changes of the facial structures.
2. Amount and direction of maxillary and mandibular growth or
displacement
3. Changes in maxillary – mandibular relationships
4. Relative changes in the soft tissue (specifically the nose, lips,
and chin)
5. Information on the overall displacement of the teeth.
www.indiandentalacademy.com
43. RICKETTS SUPER IMPOSITION
TECHNIQUE
It is one of the most important superimposition technique used.
Ricketts super imposition is used to differentiate the changes in
normal growth and those due to treatment mechanics.
This techniques involves five super imposition areas to evaluate
1. The chin
2. The maxilla
3. The teeth in the mandible
4. The teeth in the maxilla
5. The facial profile
www.indiandentalacademy.com
44. Superimposition area 1 (Basion – Nasion at CC point
(Evaluation area 1)
Evaluates:- growth of the chin
Position of upper molar
In normal growth chin grows
down the facial axis at 2.8mm per year
Mean change = 0o SD± 3.3o/year
www.indiandentalacademy.com
45. Super imposition area 2 (Basion – Nasion at Nasion)
Evaluation area 2
Skeletal behaviour of maxilla
Evaluates:- Any change in position
Maxilla
In normal growth:- Basion Nasion
point A angle does not change
Maxilla drops in a parallel fashion with
point A straight down Nasion A line.
Mean change = 0o SD± 2o/year
www.indiandentalacademy.com
46. Super imposition area 3 (Corpus axis at PM)
Evaluation area 3 & 4
Relation of mandibular teeth to
mandible
Evaluates:- Position of lower central
incisors & lower molar
www.indiandentalacademy.com
47. Super imposition area 4 (Palate at ANS)
Evaluation area 5 & 6
Relation of maxillary teeth to
maxilla
Evaluates:- Any changes in the upper
central incisors and upper molars
www.indiandentalacademy.com
48. Super imposition area 5
(Esthetic plane at the crossing of the occlusal plane)
Evaluation area 7
Evaluate the soft tissue
profile
www.indiandentalacademy.com
49. Other Super Imposition Methods to Evaluate
over all changes in the face
The broadbent triangle (Na-S-Bo)
and its registration point R were
among the first structures used for
superimpositions to determine overall
changes
Sella – nasion line
Broadbent triangle
(Na-S-Bo)
In this method two tracings on the Sella
– nasion line with registration at sella
www.indiandentalacademy.com
50. CONCLUSION
Rickett’s, Down’s & Cephalometric superimposition are a valuable
tool in treatment planning.
These analysis help in orthodontic diagnosis by enabling the study
of skeletal, dental and soft tissue structures of the cranio facial region.
These analysis also classify the skeletal and dental abnormalities
and establish the facial type.
www.indiandentalacademy.com
51. BIBLIOGRAPHY
Orthodontic cephalometry
-
By E. Athanasiou
Radiographic cephalometry
-
By Alexander Jacobson
Contemporary orthodontics
-
By R. Proffitt
American journal of orthodontics, 1960 May (Ricketts)
www.indiandentalacademy.com