Growth prediction1 /certified fixed orthodontic courses by Indian dental academy

GROWTH PREDICTIONS

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

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Growth and Development is a remarkable tale
of an orderly sequence by which each human
being blossoms out from a minute cell to an
adult man


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Growth is defined as :
Multiplication of living substance (J.S. Huxley)
increase n size, proportion and progressive
complexity (Krogman)
an increase in size (Todd)


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Growth has some characteristics like :

 Pattern
 Variability
 Timing


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Why is understanding growth so important?
Growing
Non-Growing
Brodie in 1938 said “There seems to be a
definite correlation between success of
treatment and growth. Apparently growth
and development accounts for a
considerable part of change which takes
place during orthodontic treatment”


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Correction of dentofacial malocclusions
would be helped immeasurably if he could
predict with a degree of certainty the adult
features of his patient
If the dentist could forecast the child’s adult
appearance with or without therapeutic
intervention, decisions could be made about
the timing, type, and length of treatment
In borderline cases, decisions on whether to
treat at all could be better weighed


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For growth prediction to be feasible at all,
craniofacial growth must be orderly


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What is Fibonacci series ?
0+ 1
+

+
=

1

+
=

2

=

3

5


8

13

21

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It would appear that the principle of the golden
section and Fibonacci numbers are basic to this
orderly arrangement and growth of the human
face
Mandible grows on the logarithmic spiral
which has a basis the golden triangle, in turn,
related to the golden section which is related to
the Fibonacci series


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According to Kendall and Buckland “ The
process of forecasting the magnitude of
statistical variations, at some future point of
time”
“Specifying the amount and direction of future
growth in the context of a base line or reference
point”


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Is a change in the vertical or horizontal
relationship of the upper to the lower jaw
indicated?
Should the lower incisor be repositioned both
horizontally and vertically?
What movement of the upper incisor is
required?
Should anchorage be prepared or preserved in
the lower arch?
Is movement or stabilization required for the
upper molars?

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Will the tooth movement bring about a desired
esthetic result which will still be acceptable at
maturity?
Will post-treatment growth affect retention?
Will there be space for the third molars given a
specific treatment?


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The principal proponents of growth prediction
Ricketts and Holdaway have suggested that the
major value of the technique is the compilation
of all the treatment factors (mechanics, growth,
skeletal and soft tissue) together on paper to
see how they inter-relate


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According to Hirschfield and Moyers :
Future size of a part
Relationship of parts
Timing of growth events
Vectors of growth
Velocity of growth
The effects of orthodontic therapy on any of
the above predicted parameters

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Future size of a part
The prediction of future size, as Burstone
has pointed out, is primarily a problem of
predicting future increments which are to be
added to a size that is already known
Relationship of parts
perhaps the most important prediction for
the clinician is the future relationship of
parts, i.e. the future facial pattern. Johnson
found measures of relationship and
proportion to be of greater predictive
significance than the linear size of anatomic
parts.

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Timing of growth events
Growth spurts
Vectors of growth
Most predictive methods thus far
presume a continuation of the pattern first
seen
Therefore, the presumption is made that
the vectors of growth present at the time of
prediction will remain


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Velocity of growth
It would be of use to know the future
expected rate of growth
Prediction of velocity is most important
during the pubescent spurt


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The effects of orthodontic therapy on any of
the above predicted parameters
Our knowledge of prediction might best
proceed by learning to predict untreated
growing faces
The clinician must always wonder what
effects his therapy have on the predicted
and actual growth of one specific face


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Theoretical
Regression
Experiential
Time series


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Collection of series of relevant, random data
Mathematical construction of a theoretical
model
Theoretical development of a hypothesis
from the model
Proving the hypothesis practically
The model began theoretically and was
proved practically
Implication in orthodontics :
 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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These methods serve to calculate a value for
one variable, called dependent, on the basis of its
initial state and the degree of its correlations
with one or more independent variables. E.g.
Johnston grid


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Ultimate accuracy of cephalometric prediction
may be limited to some extent by intrinsic
errors within the cephalometric method itself
Contemporary methods seem inadequate to
provide an efficient estimate of individual
changes attributable only to growth


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The assumption within the method that the
coefficients remain constant over thw whole
time period.
An individual whose growth is to be predicted
in clinical practice may not even be a member
of the population upon which the regression
equation was based


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They 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 used by others. E.g. Ricketts


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Theoretical basis is shaky on two counts:
The assumption must be made that the individual
being predicted will behave as the mean of a
population of which he is a not a member
 The morphology of the mandible and other parts is a
clue to the future growth of the face



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Accuracy, efficiency and individuality for
clinical application
“Random walk” type or process
These methods consists of two types:
time-series analysis
smoothing methods


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1.
2.
3.
4.

Time-series is considered to be composed of
four parts :
Trend or long-term movement
Oscillations about a trend
Cyclic or periodic events
Random (unsystematic) components


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Exponential smoothing is a way of
estimating the current value of a parameter
by means of some sort of average of past
values of that parameter
Prediction is then based on coefficients
derived from the smoothed parameters.
Since the coefficients will change in accord
with changes in parameter, the predicted
coefficients will change in accord with
changes in the parameter


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Based on average values
individualized prediction
manual
computerized
short range
long range


Most predictions of growth are based on some
mathematical model of the growth process, two
kinds of which can be distinguished:
(1) the transformed coordinate method of D’Arcy
Thompson
(2) Equations producing curves descriptive of
processes


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The numeric standards from which the present
specific templates were drafted are derived
from 3 major studies reports. They are:
Michigan Growth study
Bolton-Brush Growth study
Burlington Growth study


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Existing data sets are too small to allow
subdivision in different categories :
Bolton’s data is age specific only
 michigan has subdivision on the basis of sex
 Burlington has subdivision on the basis of facial
types



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All data sets are derived from whites of
Northern European descent
sample mostly consists of normal children.
The patient to be predicted for growth may not
have the average amount or direction of
growth


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Johnston forecast Grid
template methods

 schematic template
 anatomically complete template
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Ricketts prediction

 short range
 long range
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Holdaway soft tissue VTO

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Based on the addition of mean increments of
growth by direct superimposition on a printed
grid
The land marks used are :
Sella
Nasion
Tip of nose
Point M
Point A
Point B
Posterior Nasal Spine

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Tracing of landmarks is superimposed along
S-N and registered at S
The points are then advanced downward
and forward one unit per year
Vectors for A, B and M were inferred from
descriptive templates prepared by Hries and
associates and the behavior of N and P was
patterned after reports by Ricketts


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When an average cephalometric tracing is
made of a group by connecting the average
values of each landmark, the composite tracing
thus prepared is called a Template
There are 2 types of templates :
Schematic template
 Anatomically complete template



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Schematic template
The schematic templates show the changing
position of selected landmarks with age on a
single template
Michigan and Burlington growth studies have
developed this type of templates
Michigan templates have sub-divisions on the
basis of sex
Burlington templates have subdivision on the
basis of facial pattern


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anatomically complete template
Based on Bolton growth study data.
Age-specific
A reference template is selected so that the
lengths of anterior cranial base are same
The growth is predicted by advancing the
template ages from the reference templates


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The term VTO is used in two different
contexts :
VTO as a diagnostic test for functional
appliances
Growth prediction VTO
Holdaway’s VTO
 Ricketts’ VTO



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Soft-tissue facial
angle


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Nose prominence


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Superior sulcus depth measured to a
perpendicular to Frankfort and tangent to the
vermilion border to the upper lip


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Soft-tissue subnasale to H line


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Skeletal profile convexity


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Basic upper-lip
thickness


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Upper lip strain measurement


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H angle


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Lower lip to H line, Inferior sulcus
to H line, soft tissue chin thickness


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In the case of Steiner Analysis, it can be
demonstrated with geometric principles that
the sum of the following 4 angles is equal to
180 degrees
ANB
 Mandibular incisor to the NB plane
 Maxillary incisor to the NA plane
 Interincisal angle



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The first treatment in obtaining the visual
treatment objective involves a clinical
judgment - determination of the desired
angulation of the mandibular incisor to the
NB plane
In actual planning of treatment, the desired
angulation of the lower incisor to the NB
plane must be left to the judgment of the
individual clinician


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Downs - Interincisal angle 131 degrees
Reidel - suggested that the relationship
between maxillary and mandibular incisors is
best determined by functional and esthetic
considerations


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From a functional standpoint the relationship
of maxillary lingual crown contour to
mandibular incisal edge position is more
important than the interincisal angle
Considering esthetics, he suggested that the
upper and lower incisor facial crown angle
should approach 0 degrees or a straight line


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Because of variations in crown axis/root
axis angulation ass seen in dilaceration, an
optimal facial crown angle of 0 degrees does
not always correlate to any single “ideal”
interincisal angle
The interincisal angle most appropriate to a
particular case must be determined by
drawing a cephalometric incisor “setup”
with a facial crown angle of 0 degrees


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Determine the angulation of lower incisor to
NB plane
Set upper and lower incisors at a facial
crown angle of 0 degrees
Measure the resulting interincisal angle
Estimate the expected ANB angle following
treatment
Calculate the required upper incisor to NA
angulation


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Growth Estimation - 1957
Cephalometric Analysis and Synthesis-1961
Short-range VTO Long-range VTO - 1972


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The Static Synthesis
Estimation is made almost entirely for the movement
of the teeth and changes in lips
 the lower incisor is positioned with one SD of the
normal to the APo
 the upper incisor is then adjusted to it with normal
overbite and overjet
 the necessary anchorage can be envisioned by
movement of the posterior teeth



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The Dynamic Synthesis
Growth of the chin - foremost consideration
 Cranial areas are employed for basal refernces



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Cranial Behavior
Maxilla seemed to grow forward at almost an
identical rate with nasion
 SNA angle changed very little
 1 mm per year of growth on the SN plane can be
expected and Sella-Basion is usually about twothirds of that amount



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Mandibular Behavior
estimating the change in the chin by the direction of
the Y axis or growth axis of the face
 in the ave. Class II case the Y axis tended to open
about one degree during a two year period during
treatment
 In Class III cases, the Y axis closed one degree or
more during orthodontic treatment



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So the final consideration for estimation of
change in the direction of the Y axis revolves
around the original facial pattern
the amount of growth of the mandible
knowledge of average case is the starting point
 average yearly expectancy is about 2.5 to 3 mm of
growth on the Y axis



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Change the Y axis and lengthen it for estimated
growth, draw the symphysis and establish the
mandibular plane backward from the
symphysis consistent with the tilt of the
mandible


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Maxilla Behavior
Behavior of Point A from a vertical and horizontal
standpoint is estimated
 Point A and the anterior nasal spine usually drop
vertically about one-third the total facial height
increase during treatment
 about two-thirds height increase is measured in the
denture area or lower face



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Cephalometric Tooth Set Up
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Lower incisor is related to the A-Pog line depending
on the environmental forces operating on the
denture and the age of the patient


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Analysis - “where he was”
Synthesis - “where to go”


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“The radius of this circle is determined by
using the distance from mental protuberance
(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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By plotting a line through the long axis of the
condyle and neck and extending it to the lower
mandible, the bending of the mandibular form
during growth had been studied


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Bjork’s implant studies had revealed that the
lower border of the mandible was resorbing
and that the mandibular plane was not
acceptable as a reference base for growth
analysis
The next move toward improving the method
was to identify a “central core”
cephalometrically
External form of mandible

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First, a point (Xi) in
the center of the
ramus was located


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Occlusal plane holds a strong tendency to pass
through Xi point
Xi also represents the entrance of the
neurotrophic bundle into the mandible


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Second, a point at the superior aspect of the
symphysis was selected as suprapogonion (Pm)
Stress-center acc. to Ricketts
 Site of a reversal line acc. to Enlow
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Third, point Dc as
located
Corpus axis
Condyle axis


Bending occurred in an orderly manner and therefore the
greater the magnitude of growth, the greater the bending
Mandible was found to bend about half degree each year

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Constructed an experimental arc bisecting the
two previous arcs
The use of this arc still bent the mandible a
fraction too much
Stress lines


Apposition of the lower
border of the symphysis
for males occurs at about
1 mm each 8 years
From the point Mu the
mandible is grown on the
arc at the sigmoid notch
about 2.5 mm each year


K factor
Coronoid is extended
upward and outward at a
rate of 0.8 mm per year
Condyle in this average
individual is extended
upward and backward
0.2 mm per year

Drift of the mandible
occurs almost precisely
at a pace of 50% of the
total mandibular growth


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Oblique ridge of the
mandible shows
apposition of about
0.4 mm each year
This is a critical point
because it helps to
determine the space
available for the
developing
mandibular third
molar

Thank you
Leader in continuing dental education


Growth prediction1 /certified fixed orthodontic courses by Indian dental academy

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