skeletal growth prediction and Age estimation

Skeletal Growth
prediction&
Age Estimation
Proffit W, Fields H, Sarver D;Contemporary
Orthodontics 4 ed 2007; Elsevier

Contents
 Introduction
 Gnomic growth and logarithmic spiral
 Arcial growth
 Rickett’s cepahlometric prediction
 Prediction of mandibular growth rotations

 Mathematical model for prediction of
craniofacial growth
 VTO
 Tooth mineralization
 Skeletal maturity indicator

Introduction
 It is not possible to predict how a patient is
going to respond to a particular treatment.
 Variability is expected

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 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

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.

 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.

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.

 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
 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)

 Landmarks
 Xi point-
 The 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 formed is called Xi point.

 Supra pogonion- It is a point located at the superior
aspect of symphysis.
 It is labelled Pm
 This is substantiated as a reference point because-
 1. It is the site of a reversal line (Enlow)
 2. Stable unchanging bone in this area of bone (Bjork).
 Point Dc – It is a point at the bisection of condyle neck

 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.

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

 Steps in growth prediction
Step 1 amount of growth on arc- 2.5mm
From pt Mu the mandible is grown out on the arc at
the sigmoid notch about 2.5mm.
cutoff for males=19yrs
females= 14.5yrs

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

 Step 4 complete forcasting of the
mandibular form
Connections from coronoid process –RR –
0.4mm/yr
determine space available for 3rd molar

 By constructing the growth arc, growing the
mandible on the arc, extending and drifting the
angular process, this forecasting technique is
tested.

 Drawbacks 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
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
 Class II 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

 pubertal spurt – 1mm / yr
 Mixed dentition – 0.5 – 0.7 mm / yr.
 b) Expected changes between sella & Basion
change in length is 3/4th of S-N.
 c.) Establish Expected Ba-N
 Connect the new S & N & Ba –formation of new
basicranium.

 STEP 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 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.

 STEP 4:
 Construction of condylar axis
 From the centre of condyle to antegonial angle.

 STEP 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.

 STEP 6: assessment of remaining mandible
 Rotation of mandibular plane untill the change agrees with the
estimate of change for that case
 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
 Changes in the symphysis are
plotted

 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 Increase in face height( vertical changes)
 Facial plane is superimposed & registered on N
 40% above ANS
 60% of TFH increase is due to the denture area ie below
ANS.

 Step 2 Horizontal position of maxilla
 It is postulated from the tendency of S-Na to remain
constant to Ba-N
 Pt A is dropped parallel with line NA
 Great amt of bodily retraction- Pt. A will be moved back
as much as 3-5 degree.

 3. future facial convexity is determined by
predicted behavior of Pt. A

 4. Descent of the palate is forecast
 Post nasal spine drops parallel to ptm

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

 This constitutes the complete procedure
for estimating the changes that can be
expected in any given case prior to
treatment.

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
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

 Forward rotation may occur in 3 ways-
 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.

 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

 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.

 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.

 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.

 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

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. Matrix Rotation
2. Intramatrix rotation
3. Total rotation

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

 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.

 TOTAL ROTATION :
 Combination 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.

 Structural 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.

 2) CURVATURE OF MANDIBULAR CANAL:
Vertical condylar growth
– curvature of canal is more
Sagittal condylar growth
- straight mandibular canal
 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

 4. INCLINATION OF SYMPHYSIS
 Vertical type –
symphysis swings forward
 Sagittal type –
swings backward with receding chin.
 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.

 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.

 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
 There is no absolute correlation between structural growth
prediction and degree of growth rotation in cases showing
average changes.
 The method should be primarily used to determine whether
any typical signs of ant. or post. Growth rotations are
present.

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.

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

 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.

 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
 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.

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.

 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
 Mean Growth vector angle
Females – decreases 0.02/yr
Males – increases 0.14/yr
 Mean mandibular plane angle
Females –increases by 0.4/yr
Males – increases by 0.3/yrProffit W, Fields H, Sarver D;Contemporary

 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.

VTO
 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 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.

 Todd & mark conclude that the mathematical
transformation was shown to make reasonably
accurate prediction over a span of 10-15 yrs.
 REVISED CARDIOIDAL STRAIN
 R’ = R +bP

 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.

 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.

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

COMPUTERIZED GROWTH
FORECASTING

 Computerized growth predictions
 Cephalometric 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.
 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

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.

 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

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.
 Step 1. std normal reference is superimposed
on the patients tracings
 Size and shape difference is evaluated by
calculation of new relevant displacement vector
for each landmark

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….

Proffit W, Fields H, Sarver
D;Contemporary Orthodontics 4 ed
2007; Elsevier

skeletal growth prediction and Age estimation

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