Growth prediction & age estimation /fixed orthodontic courses

Growth
Prediction & Age
Estimation

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Contents
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Introduction
Methods of growth prediction
Gnomic growth and logarithmic spiral
Arcial growth
Rickett’s cepahlometric prediction
Parental data to predict craniofacial growth
Johnston method
FEM
Prediction of mandibular growth rotations
Mathematical model for prediction of craniofacial
growth

 Holdaway

soft tissue cepahlometric analysis
 Tooth mineralization
 Skeletal maturity indicator
 Symphysis morphology
 Pubertal growth spurt
 Third molar prediction


Patient’s growth pattern
Variability
Effect of treatment on
growth


In the absence of growth, treatment
responses are reasonably predictable
GROWTH IS NOT…….


 The

goal of growth prediction is to reduce the
clinician’s ignorance of the future…


What are we interested in predicting in
the craniofacial complex?
 1.

Future size of a part -The prediction of
future size is primarily a problem of predicting
future increments which are to be added to a
size that is already known.
 Eg: prediction of length of the mandible


 2.

Relationship of parts - The most
important prediction for the clinician is the
future relationship of parts, that is the future
facial pattern.


 3.

Timing of growth events – Because
growth does not proceed evenly, certain
facial dimensions demonstrate marked
change in their velocity curves. These spurts
make predictions much more difficult.
 If one were to predict a “spurt”, we might
want to predict the a) time of onset. b)
duration of increased rate of growth c) rate
of growth during the spurt.

 4.

Vectors of growth- Most predictive
method presume a continuation of the pattern
first seen.The presumption is made that the
vectors of the growth present at the time of
prediction will remain.
However this is not true…..
Mandible which grow vertically for a period
of time can start to grow horizontally!!!
Can such changes in growth direction be
predicted???

5. Velocity of growth- It would be of use to know
the future expected rate of growth especially during
pubescent spurt.
6.Effect of orthodontic therapy on any of the
above predicted parameters
What effect therapy is having on the predicted
and actual growth of one specific face

 How

well can we predict these
parameters???

 Future

Size

Complex craniofacial growth
Any simple series of size prediction is not clinically
useful.


 Relationship

of parts

Harvold, Johnston, Ballach –
predicted maxillo mandibular relationship.
None were accurate…
 Timing
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and growth events

Hunter & Miller reported the shape of the face as
roughly related to the timing of the pubuscent spurt.
Frisancho- predict the individual spurt in stature
from noting the time of calcification of the sesamoid
bone

Vectors of growth
There is no means of anticipating change in the
direction of growth
Predicting vector is not same as predicting
changes in the vector….

Velocity
Not much attention is given to this


 The

effect of orthodontic therapy on
growth
Ricketts’ method- sets the prediction and
then works to make them come true


Methods of prediction of
craniofacial growth
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

William J Hirschfeld AJO Vol 60 no 5 1971
Several predictive methods that are used
can be grouped as followsA) Theoretical B) Regression
C) Experiential D) Time Series


 1.Theoretical

methods of prediction-

A theoretical model is constructed mathematically,
and a test for hypothesis is devised.
 Theoretical models of craniofacial growth have not yet
been defined mathematically in terms precise enough
to permit the application of the method to prediction
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Regression methods- These methods serve to
calculate a value for one variable, called dependent,
on the basis of its initial state and degree of its
correlation with one or more independent variables
 However Johnston evaluated and revised this method
and concluded1.The ultimate accuracy of cephalometric prediction
may be limited by intrinsic error within the
cephalometric method itself.
2. These methods seem inadequate to provide an
efficient estimate of individual change attributable to
growth only.
 2.


Experiential method- These methods are based on
the clinical experience of a single investigator who
attempts to quantify his observations of practice in such
a way that they can be modified for use by others.

 3.

Time series methods- 2 types
A) Time series analysis- it extracts in a mathematical
form the fundamental nature of the process as it relates
to time.
B) Smoothing methods –it gives representative or
average values to the parameters of a previously
derived time series equation.

 4.


Gnomic growth and logrithmic
spiral
 What

is gnomic growth?

The process where upon the addition to a body
leaves the resultant body similar to the original is called
gnomic growth.
 D’Arcy Thompson classified the sea shells in
accordance to their pattern of enlargement and
developed an equation.


 The

Nautilus offers 2 fundamental characterstics 1. The shell grows in size but does not change its
shape
new growth

 2.

Its gnomic growth can be described by a particular
kind of curve- the logarithmic or equiangular spiral.


 The

spiral is characterized by the movement of a point
away from the pole along the radius vector with a
velocity increasing as its distance from the pole


Logarithmic growth of human
mandible
 There

are several functional conditions which are not
violated during orofacial growth- one of these is neural
innervations which must never be subjected to external
loading.
 Craniometric studies were performed on American
Indian skull .they are representative of mandible with
fetal, deciduous, mixed and adult dentition.
 Small lead shots were fixed to foramen ovale.
Mandibular foramen.& foramen mental

 Lateral

x-rays effectively outlined the pathway
of the Inf. Alveolar nerve.
 All the 3 neural foramina at all ages fit
precisely upon a single mathematically
defined, logarithmic spiral.


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Another longitudinal and cross sectional clinical
growth data showed that these foramina moved
along the same logarithmic spiral in geometric
fashion, with the gradient of motion directly
increasing with the distance of the foramina from the
cranial base. ie mental foramen moves most and the
foramen ovale least.


The shape of the anatomic course of the inf alv nerve
depends 1) position of 3 foramina
2) distance between same foramina
In the fetal period the 3 foramina are relatively near the
origin of the spiral and at the same time they are
placed nearer to each other than at later stage. This
produces a flatter curvatre hence gonial angle is
relatively flat
With growth due to increase in distance ramus
becomes straight relative to corpus and gonial angle
acute.

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During all stages of development the corpus stays in
essentially a horizontal position. At the same time
the mandible curves down the logarithmic spiral
course of the inferior alveolar nerve.


Arcial growth
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Ricketts in 1972 developed a method to determine
the arc of growth of the mandible.
PRINCIPLE:
A normal human mandible grows by superior
anterior apposition at the ramus on a curve or arc
which is a segment formed from a circle. The radius
of this circle is determined by using the distance
from mental protrubence (Pm) to a point at the
forking of the stress lines at the terminus of the
oblique ridge on the medial side of the ramus( point
Eva)

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Landmarks
Xi pointThe deepest point on the subcoronoid is selected as R1.
R2 is selected directly opposite to it on post border of ramus.
R3 is selected at the depth of the sigmoid notch.
R4 is directly on the lower border of ramus.
The centroid of the rectangle foremd is called Xi point.


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Supra pogonion- It is a point located at the superior aspect of
symphysis.
It is labelled Pm
This is substantiated as a reference point because1. It is the site of a reversal line (Enlow)
2. Stable unchanging bone in this area of bone (Bjork).

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Point Dc – It is a point at the bisection of condyle neck

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Point Eva- it is a biologic point as it is located over
the point of forking of the stress line in the ramus.
Ramus reference point (RR) is the point halfway
between Xi point and R3 on the anterior border of
ramus.


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1

2

3
4

Construction of growth
arc:
Point RR and R3 are
connected.
Mid point of RR and R3 is pt Eva
Take pt Eva –Pm as radiuscircle is drawn
1. taking eva as a centre
2. taking Pm as a centre.
The point of intersection is TR
(True radius) taking this as a
centre an arc is drawn.
Where this arc crosses sigmoid
notch is called Murray point.


 Steps

in growth prediction

Step 1 Apposition of the lower border of the symphysis
Males- 1mm/ 8 yrs
From pt Mu the mandible is grown out on the arc at the
sigmoid notch about 2.5mm.


Step 2
Coronoid –
upwards &outwards – 0.8mm/ yr
Condyle upward & backward - 0.2 mm / yr

Step 3 - Drift of gonial angle
Females- no addition
Males - 0.2 mm / yr


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Step 4 Apposition on the oblique ridge
Connections from coronoid process –RR –
0.4mm/yr


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Implications of arcial growth prediction
1.

It appears that the symphysis rotates essentially from
horizontal to a more vertical inclination which explains
the major part of the form characterstic of the
symphysis.

2. This phenomenon explains why reversal line are
observed at the areas of Pg & Pm.
3. It explains why mandible plane changes extensively.
.
4. It suggests that abnormal growth or margins of the
mandible can be understood as a friction of relative
contribution of the coronoid and condyloid process.

 Drawbacks
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of arcial growth prediction

1. It relies heavily on the operators skill in tracing the
cephalogram.
2. Mitchell & Jordan (1975) concluded Ricketts uses
chronological age rather than the skeletal age. If the
patient is in a growth spurt or lag phase it will alter the
result.
3. The growth increments constants are for a fixed
population.


Ricketts cephalometric or short
term prediction
Ricketts 1957
The changes in the face during treatment
were thought to be influenced by a
phenomenon within TMJ complex.
1. The changes in the angle of cranial base to
a more acute or obtuse relationship.
2. Forward or backward movement of the
condyle that influenced the chin behavior.

Procedure for growth
estimation
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ClassII Div 1 case was selected to demonstrate the
procedure.
For growth estimation work, the cranial plane
basion-nasion (Ba-Na) plane is employed.
It can be studied in following steps:
STEP 1:
1. Projection of probable changes in the basi
cranium
It includes Points N, S, & Ba.
a.) Sella – starting point.
Average expectancy for increase along SN

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pubertal spurt – 1mm / yr
Mixed dentition – 0.5 – 0.7 mm / yr.

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b) Expected changes between sella & Basion
change in length is 3/4th of S-N.

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c.) Establish Expected Ba-N
Connect the new S & N & Ba –formation of new basicranium.

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 STEP
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2:

Predeterming the behaviour of condyle
Condyle position remained same in 60% of cases
Downward & forward movement of Ar & Ba –similar after the age of 6
Superimposing Ba- N and registering Ba will reveal the future condylar
position..


 STEP
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3:

Ptm is outlined-evaluation of maxillary growth, coronoid pr.
Superimposing of SN and registering at S shows
Downward dropping of this fissure.
Tip of the coronoid process is located 3mm forward to ptm at
both start and completion of Treatment.


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STEP 4:

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Construction of condylar axis
From the centre of condyle to antegonial angle.

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 STEP
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5:

Contemplation of growth of condyle
Estimated on the condyle axis .
During Rx 2mm of growth / yr upto 9yrs
During puberty = 3 or 4 mm / yr may be expected
The assessment of condylar growth permits the construction of the post.
Border, gonial angle, sigmoid notch,& ant. Border of ramus.


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STEP 6:
Rotation of mandibular plane..
Forward direction of condyle – lower mandibular plane angle
Backward condylar growth - higher mandible plane angle.
STEP 7:
Lengthening of body of mandible
It is slightly greater than S-N plane
1.5 mm / yr


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STEP 8:
Facial plane and Y axis is constructed
Superimposition on the BA-N plane will indicate the direction of growth of
mandible.


Position of Maxilla
 Step1
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Increase in face height

40% above ANS
60% of TFH is credited to the denture area ie below
ANS.


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Step 2 Horizontal position of maxilla

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It is postulated from the tendency of S-Na to remain constant to
Ba-N
Pt A is dropped parallel with line NA

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Great amt of bodily retraction- Pt. A will be moved back as much
as 3-5 degree.


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Soft tissue behavior
Nose – superimposing of the palatal bone and registering on
ANS
2mm of growth of nose
Profile outlined is then constructed to the area below nose.
Upper Lip- severely protruding cases- 2-4 mm increase in
thickness
Moderate protrusion 1-2mm increase in thickness.


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Lower lip- bisecting the overbite& overjet change
and drawing sup portion of the lower lip at this level.


Planning the arrangement of teeth
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During normal growth, cant of occlusal plane
decreases. Ie it ll drop faster in the back than in
front.
The application of intermaxillary Cl II elastics work in
a reverse direction & rotate the plane on average of
3 degree from the mandibular plane.
This action elevates mandibular 1st molar- 2.5mm
Ant teeth elevate slowly and are held in place
vertically


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After construction of new occlusal plane new Pt.APg is constructed.
Lower incisors = 1mm forward to it & 220 inclination
Upper incisors =1300 to lower incisors


Prediction of mandible growth
Rotations
Bjork 1969 gave 3 methods to predict growth.
1.Longitudnal – following the course of development in annual x –ray
pattern of growth is not constant
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2.Metric- prediction of the facial development on the basis of facial morphology
from a single x ray film.
3.Structural- based on the information concerning the remodelling process of the
mandible during growth gained from implant studies.
Principle- to recognize specific structural feature that develop as a result of
remodelling in a paricular type of mandibular rotation. A prediction of the
subsequent course is then made on assumption that the trend will continue.

 Mandible

may be regarded as an unconstrained bone.
 The site of the center of rotation may be located at:
Anterior ends
Posterior ends
Between the ends
Thus center may not necessarily lie at TMJ


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Forward rotation may occur in 3 ways-

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Type I: Forward rotation centre in TMJ
It gives rise to deep bite resulting in under development of anterior face height
Cause may be occlusal imbalance
powerful muscular pressure.

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TYPE 2: Rotation centre at the incisal edges
Marked Development of Post. Facial height + normal increase in Ant. Facial
height. The post part of mandible rotates away from maxilla.
Increase in post facial height : lowering of middle cranial fossa
increase height of ramus.
Vertical direction of condylar growth
Mandilble is lowered more than it is carried forward
Muscle and ligamnetous attachment
lowering takes place as a forward rotation in relation to maxilla


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Type 3: centre at pre molar
In case of large maxillary overjet the center of rotation is displaced backward in
the arch.to the level of premolars
AFH – under developed
PFH - increases.
Dental arches are pressed into each other and basal deep bite develops.
In Type II & III the mandibular symphysis swings forward to a marked degree
and the chin becomes prominent.


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BACKWARD ROTATION OF THE MANDIBLE
2 types.

TYPE 1: centre of rotation in TMJ
Backward rotation of the mandible about a center in the
joints also occurs in connection with growth of the cranial
base.
In the case of flattening of the cranial base, the middle
cranial fossae are raised in relation to the anterior one, and
then the mandible is also raised.

There may be other causes also, such as an incomplete
development in height of the middle cranial fossae.


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This underdevelopment of the posterior face height
leads to a backward rotation of the mandible, with
overdevelopment of the anterior face height and
possibly open-bite as a consequence. The mandible
is, in principle, normal.


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TYPE 2: Centre at distal occluding molars

. This occurs in connection with growth in the sagittal direction
at the mandibular condyles.
As the mandible grows in the direction of its length it is carried
forward more than it is lowered in the face, and because of its
attachment to muscles and ligaments it is rotated backward.


The symphysis is swung backward and the chin
is drawn back below the face. The soft tissues of
the chin may not follow this movement, and a
characteristic double chin can form.
 Basal open-bite may develop,
 Difficulty in closing the lips without tension.
 Lower incisors, functionally related to the upper
incisors, become retroclined in the mandible and
the alveolar prognathism is reduced
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BJORK & RUNE found a contrast between the positioning of
mandible in a longitudnal series when superimposed on the
cranial base and positioning contours resulting from
superimposition on metallic implants. They divided rotations
into 3 components.
1.
2.
3.

Matrix Rotation
Intramatrix rotation
Total rotation


Matrix Rotation: centre in the condyle
 Rotation of bone with its matrix or periosteal capsule in
its articulation with surrounding bone


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INTRAMATRIX ROTATION : centre in corpus
Rotation of the mineralized corpus inside the matrix periosteum.
Periosteal cellular activity
rotation of the bony corpus
Surface of bone are remodeled in compensatory fashion
Matrix retains its stable inclination.


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TOTAL ROTATION :

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Cobination of the 2 types
It is rotation of the mandibular corpus measured as a change in
the inclination of an implant line in the mandibular corpus
relative to anterior cranial base.
The position of center of rotation of total rotation is dependent
on the other 2 centers of rotation.

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 Structural

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method of growth prediction

STRUCTURAL SIGNS OF GROWTH ROTATION
7 structural signs of extreme growth rotation
The greater in number that are present, the more reliable the
prediction.
1) INCLINATION OF CONDYLE HEAD:
Forward or backward inclination
of the condylar head
May not be easy to identify
on the cephalograms.

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2) CURVATURE OF CONDYLAR HEAD:
Vertical condylar growth
– curvature of canal is more
Sagittal condylar growth
- straight mandibular canal

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3) SHAPE OF THE LOWER BORDER OF MANDIBLE
Vertical condylar growth –
apposition below the symphysis
and anterior part of mandible
Sagittal growth –
ant rounding absent
thin cortical layer
jaw angle is convex

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4. INCLINATION OF SYMPHYSIS
 Vertical type –
symphysis swings forward
 Sagittal type –
swings backward with receding chin.
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5.Position of the lower incisor seems to be functionally related to the upper
incisors
Inter incisal angle undergoes a smaller change than the rotation of the jaws.


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6. INTERMOLAR & PREMOLAR ANGLE:
Forward growth rotation - mandibular post. More upright
increase in inter molar/ premolar angle
Backward rotation - mandibular molar and premolars inclined forward
small inter molar / premolar angle.


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7. LOWER ANT. FACIAL HEIGHT
Forward growth rotation- decrease in lower AFH
Backward rotation
- over development of AFH


 Thus,

from structural method for prediction of
rotation B’jork concluded:
 Forward inclination of condyle- ant rotation of
the mandible
 Backward inclination- post rotation of the
mandible.


 Drawbacks

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There is no absolute correlation between structural growth
prediction and degree of growth rotation in cases showing
average changes.

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The method should be primarily used to determine whether any
typical signs of ant. or post. Growth rotations are present.


Johnston method of growth
prediction
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This is a simple method based on the addition of
mean increment by direct superimposing on a
printed grid
In this regular angular changes in average direction
was shown ie each point advanced 1grid/yr using
standard SN orientation registered at S


Forecast grid


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This method by using the grid produces a moderate
flattening of the profile and occlusal plane as well as
a slight mesial drift of M.
This method do not fit a random series of patients
It is not easy to evaluate the significance of the
forecasting error.


Mesh analysis
 Coenrad.

F.A moorrees et al

 The

mesh diagram is composed of a grid of rectangular
scaled on the pt’s upper facial height and depth.


 The

face is inscribed in a coordinate system consisting
of 24 rectangles.


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The length and height of mesh rectangle differs
among individuals.
The size increases from 8-16yrs.
Boys-4.5mm- ht
Girls- 3.5mm-ht
Length- 3.2mm in boys
Length 2.4mm in girls
Shape of mesh rectangle is determined by shape
of the core rectangle- represents the ratio between
face depth and upper facial height.


 In

the original proposal, the grid was distorted
to fit the proportionate location of pt’s
cephalometric landmark as compared to the
norm, thereby graphically representing how
the patient face deviated from the norm.
 Disadv- complex and laborious method


 Modification

– a norm is superimposed on
the pt’s grid in order to reveal difference from
a normalized mesh diagram
 Advantages graphically display pt’s deviation
 Normal mesh diag is readily understood by
patient

Growth vectors
C- Axis : A growth vector for maxilla
Stanley Braun et al, Angle Orthodontist Vol 69,
No6 1999
G –Axis : A growth vector for mandible
Stanley Braun et al , Angle orthodontist, Vol 74 No3
,2004


C- AXIS
M point- by Nanda & Meritt (AJO 1994)


It is a constructed point representing the
center of the largest circle that is tangent to
the superior, anterior & palatal surfaces of
maxilla as seen in the sagital plane.


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C-Axis: The line from the sella (S) to M- point is
defined as C- axis.


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It permits the quantification of a complex maxillary
growth process
Age group -7.4-18.75yrs
The regression formula is independent of gender
within the chronological age studied.
Upto age 14, both male and females show- growth
increment of 1.41mm &1.31mm/yr.


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The mean growth axis angle (C-axis- SN)
Increased for both males and females.
Males = 3.98
Females = 2.25


Palatal plane to C-Axis
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Palatal plane is geometrically related to C-axis.
Females= increases from 35.4 – 37.4
Males =increases from 39.3- 41.6
These changes tend to flatten the palatal plane.


A

single M point cannot by itself summarize
the growth of dentomaxillary complex in
sagital plane.
 However, when associated with the palatal
plane the downward & forward migration is
more accurately decsribed.


 Quantification

of the displacement of the

mandible???


Y axis !!!

 What

about remodeling of external
symphyseal area….???


G Axis
G –Axis : A growth vector for mandible
Stanley Braun et al , Angle orthodontist, Vol 74 No3
,2004
G point : it is a point representing the centre of largest
circle that is tangent to the internal inf, anterior, and
post surfaces of the mandibular symphyseal region
as seen on lat cephalograms.


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Length of this axis is determined by Sella & G- point.
Direction is determined by alpha angle
-Mean growth axis vector angle
Theta angle- Mandibular plane & G-axis.
- Mean mandibular plane angle


Age group- 6- 19.25yrs.
 G-axis length
Females – 1.6mm/yr
Males – 2.3mm/yr
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Mean Growth vector angle
Females – decreases 0.02/yr
Males – increases 0.14/yr

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Mean mandibular plane angle
Females –increases by 0.4/yr
Males – increases by 0.3/yr

 Thus,

G-axis allow for the quantification of
the complex mandibular growth process in
cephalometric terms relative to various
craniofacial structure in the sagittal plane.


Holdaway’s VTO
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It is completely practical as a treatment planning
procedure to approach the proposed orthodontic
changes from a soft tissue analysis perspective
Possible soft tissue profile is established--- compute
the tooth movements.
It can be done manually or cephalometric tracings.
Tracing represents the expected growth or any
growth changes induced during treatment.
This is especially noticeable when growth over a
period of 5yrs or longer was forecast

Mathematical Model for prediction
of craniofacial growth


Presented by James. T. Todd & Leonard Mark



The model is derived from the basic assumptions
about the long range effects of gravitational
pressure on the remodelling of bone and is
expressed formally on a single geometric
transformation.


 The

validity of the model is examined
empirically using data for 20 individuals from
the Denver Child research Council,
longitudnal growth study.
 It is based on the following hypothesis “The overall pattern of craniofacial growth is
primarily controlled by biomechanical
influences.” This is known as Wolf ‘s law.
 The wolf law’s states- The bone elements
place themselves in the direction of
functional pressure and increase or
decrease their mass to reflect the amount
of functional pressure.



Gravity influences the biomechanics of growth which is exerted
on every point with in the craniofacial complex and it also
provides a counter force for the action of muscles.


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Heads are not perfectly spherical
There are other sources of stress operating on
craniofacial complex besides the force gravity
The orientation of the head with respect to the
gravity does not remain fixed.




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Todd & mark conclude that the mathematical
transformation was shown to make reasonably
accurate prediction over a span of 10-15 yrs
This finding is important as the transformation
changes both shape and size of the profile and the
transformed profile does not have to be normalized
for size with respect to the actual profile.


 The

predictions that were made were not
accurate because of mechanical errors
 Oral habits
Nevertheless they very closely predict the
actual outcome of growth……


FEM method of craniofacial
growth
Finite element modeling is able to provide
absolute quantitive description of cranial
skeletal size and shape change with local
growth significance, independent of any
external frame of references.


Finite element fundamental attribute its ability to
dicretize or subdivide structures or bodies into
2-3 dimensional elements by a series of
imaginary lines, called as finite element.
Each line is connected at one end to at least one
other line. The point of connection is termed as
nodes

 Growth

strains –
It is the measurable deformation of a
biologic body resulting from its growth. The
quantitative description of the values of the
growth strain as well as the determination of
the principal direction of these extensions
can be computed and graphically displayed.
Finer the discretization of the body , the
more closely the resulting numerical resulting
numerical result will approximate the reality of
growth behavior at each point.

 Growth

tensors- This is independent of the
body registration methods and define growth
changes locally
The growth tensor describes the relative
displacement of all points in the
neighborhood of the given point.
It may be regarded as specifying
transformation of coordinates from one stage
of growth to another.

Growth tensor and growth prediction
If growth process is prescribed by specifying growth
tensors at every point of the body, then assuming the
growth strains are compatible, initial shape of the body
is given, the fem is capable of predicting the shape of
the body at any subsequent stage during its growth.




Advantage over roentgenographic cephalometry
1. Growth prediction is independent of any external
frame of reference thus eliminating the principal
source of methodological error in RCM
2. It describes growth locally



Limitations
1.The errors of anatomic or material point imaging,
detection and representations.
2. This does not correspond closely to biologic reality
because tissues of different histologic type and
growth process are present, including the air fluid.

Parental data to predict growth
of craniofacial form


Akira Suzuki & Yashuhide Takahama
Am J Orthod Dentofac Orthop 1991;99 107-121

 In

a family study of craniofacial dimension the most
striking feature is the high level of significant correlation
between parents and off springs and between siblings
especially when they are contrasted with the co-relation
of fathers to mothers


Twin studies:
- genetic analysis of craniofacial morphology was of
prime concern
 Family studies:

the statistically significant correlations between
parents and their children have been reported.
1)
The cranio facial forms of children with a certain
degree of bone maturity were significantly co rrelated
with those of their parents



2) The genetic influence of parents on their children
appear to be equal
3)Coefficient of correlation of craniofacial forms between
children and their parents increased from childhood to
adulthood
4) The heritabilities of variables associated with
craniofacial form ranged from 0.5-0.9 except respiratory
and masticatory system.


 The

following hypothesis formed the basis of parental
data to predict growth 1. The face of off spring often resemble that of at least
one of his parents
 2. if the face of a young offspring resembles the face of
either parent, it will continue to resemble that parent
when the off spring becomes an adult .
 3. if the cranio facial type of an off spring resembles
that of the father or of the mother in the early growing
stage , its adult craniofacial type will be nearly like that
of the same parent.

 Equation

of the individual growth
prediction

Y(t) = C1X(s)+ C2X(d) + C3
1+exp(C4(t-C5)

+ C6)

)

Here, C1X(s) similiar parents
C2X(d) dissimiliar parents


 There

is a high correlation between the craniofacial
form of an off spring and that of his or her parents.
 The relationship become closer with growth, so its
better to use the parental information than to use
average growth curves when the individual growth of a
child is to be determined.


 Computerized

growth predictions

software (quickceph image,
dentofacial planner) have replaced manual acetate
tracings with computer generated tracings derived from
digitized head film. During the process of digitization,
the x-y coordinates of cephalometrics landmarks are
recorded and stored in data set from which various
cephalometric measurements are made.

 Cephalometric

 Growth

and treatment response can be displayed and
measured by longitudnal superimposition of serial
datasets on stable cranial base or regional landmarks

 Rickett’s

technique- It is the most widely

used and the first technique that is
implemented in software.
 It assigns mean increments of growth to a
series of landmarks along reference lines
determined by the use of growth increments
that are sensitive to the skeletal age.


 Computerized








VTO-

The manual method of prediction gives a
reasonable good graphic representation of growth
changes to create a VTO
Computer offers the added advantage
quicker access to information
greater accuracy in producing the tracing
useful in pt education
Software used are. Rocky Mountain Data System,
Quickceph II


Computerized mesh analysis




It is a quantitative assessment of the direction and
amount of deviation of each facial landmark of the
patient.
A modified 3 dimensional mesh analysis could then
be used to compare patients values to reference
soft tissue data collected on normal standard.


Construction of the reference
grid






Normal reference have been constructed on the
basis of the data bank available at LAFAS, Milan
with the use of 3D facial morphometry, which
detects 3 dimensional coordinates.
The digitized landmarks described the head, the
face, the orbits, the nose lips&mouth. Mean values
were computed within genders.
A standard lattice of equidistant horizontal, vertical,&
A-P line was constructed comprising 84
parallelopipeds (28 frontal , 21 sagital 12 horizontal
tracings)

Comparison of the patient to
the norm.








3 dimensional coordinates of the facial landmarks of
each pt were obtained, oriented on x-y-z axis & a
grid is constructed.
The modified analysis quantifies the shape and size
discrepancies that occurs in 2 steps.
Step 1. std normal reference is superimposed on
the patients tracings at mid tragus and on camper
plane.
The xyz projection of the pt’s landmark relative to
the reference



A mean difference factor is computed as MDF=
GDF/N



Consequently a size normalization that quantified
the size difference by producing 3 size coefficient is
perfromed, the vol of pt’s parallelopied is reduced/
enlarged to match the reference.



Step2 the std normal reference is then
superimposed on the size normalized pt’s tracing
and the shape difference is evaluated by calculation
of new relevant displacement vector for each
landmark.

Roengten sterophotogrammetry
for analysis of cranial growth








Goran Selvik et al AJO’86: 89:315-26
It is a superior means to obtain bimetric information
on cranial growth with the aid of metallic implants.
Tantalum is used as bone marker
2 roengten tubes simultaneously expose the object
placed in predetermined positions or co-ordinates.
Cartographic instrument is used to obtain 2
dimension image






By computer reconstruction of the X- ray beams
through the markers a 3 D object coordinates are
calculated.
Extensive software is required for subsequent
analysis of growth.

Advantage
1. Technical accuracy is high
2. Complications are few.



Conclusion
 Burstone

has pointed out “ the knowledge
of prediction might best proceed by
learning to predict untreated growing
faces.”
 The clinician must always wonder what effect
his therapy is having on the patient and
actual growth of one specific face.


 Research

work may develop mathematical
models, devise predictive procedures and
test them statistically but the practicing
orthodontist treating one child at a time
will prove the ultimate worth of any
suggested method….


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