Growth prediction& Age Estimation
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
www.indiandentalacademy.com
Contents
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 www.indiandentalacademy.com
VTO Tooth mineralization Skeletal maturity indicator Symphysis morphology Pubertal growth spurt Third molar prediction
www.indiandentalacademy.com
Introduction
It is not possible to predict how a patient is going to respond to a particular treatment. ď Ź Variability is expected ď Ź
www.indiandentalacademy.com
Patient’s growth pattern Variability Effect of treatment on growth www.indiandentalacademy.com
In the absence of growth, treatment responses are reasonably predictable GROWTH IS NOT…….
www.indiandentalacademy.com
The goal of growth prediction is to reduce the clinician’s ignorance of the future…
www.indiandentalacademy.com
What are we interested in predicting in the craniofacial complex? ď Ź
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.
ď Ź
Eg: prediction of length of the mandible
www.indiandentalacademy.com
2. Relationship of parts – ď Ź The most important prediction for the clinician is the future relationship of parts, that is the future facial pattern.
www.indiandentalacademy.com
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. www.indiandentalacademy.com
ď Ź
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??? www.indiandentalacademy.com
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
www.indiandentalacademy.com
ď Ź How
well can we predict these parameters???
ď Ź
Future Size Complex craniofacial growth Any simple series of size prediction is not clinically useful.
www.indiandentalacademy.com
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
www.indiandentalacademy.com
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
www.indiandentalacademy.com
ď Ź
The effect of orthodontic therapy on growth Ricketts’ method- sets the prediction and then works to make them come true
www.indiandentalacademy.com
Methods of prediction of craniofacial growth ď Ź ď Ź
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
www.indiandentalacademy.com
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
www.indiandentalacademy.com
2. 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 ď Ź 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. ď Ź
www.indiandentalacademy.com
ď Ź
3. 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.
ď Ź
4. 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. www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź
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
www.indiandentalacademy.com
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
www.indiandentalacademy.com
Lateral x-rays effectively outlined the pathway of the Inf. Alveolar nerve. ď Ź All the 3 neural foramina at all ages fit precisely upon a single mathematically defined, logarithmic spiral. ď Ź
www.indiandentalacademy.com
ď Ź
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź
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.
www.indiandentalacademy.com
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) www.indiandentalacademy.com
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 formed is called Xi point.
www.indiandentalacademy.com
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).
Point Dc – It is a point at the bisection of condyle neck
www.indiandentalacademy.com
ď Ź
ď Ź
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.
www.indiandentalacademy.com
ď Ź
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.
www.indiandentalacademy.com
ď Ź
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
www.indiandentalacademy.com
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 www.indiandentalacademy.com
Step 4 complete forcasting of the mandibular form Connections from coronoid process –RR – 0.4mm/yr determine space available for 3rd molar
www.indiandentalacademy.com
ď Ź
By constructing the growth arc, growing the mandible on the arc, extending and drifting the angular process, this forecasting technique is tested.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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. www.indiandentalacademy.com
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 www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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..
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
STEP 4:
Construction of condylar axis From the centre of condyle to antegonial angle.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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 www.indiandentalacademy.com
STEP 8: Facial plane and Y axis is constructed Superimposition on the BA-N plane will indicate the direction of growth of mandible.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź
3. future facial convexity is determined by predicted behavior of Pt. A
www.indiandentalacademy.com
4. Descent of the palate is forecast ď Ź Post nasal spine drops parallel to ptm ď Ź
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź
This constitutes the complete procedure for estimating the changes that can be expected in any given case prior to treatment.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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. www.indiandentalacademy.com
Mandible may be regarded as an unconstrained bone. ď Ź 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 ď Ź
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź ď Ź
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
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź ď Ź
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. www.indiandentalacademy.com
ď Ź
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.
www.indiandentalacademy.com
ď Ź
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.
www.indiandentalacademy.com
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
www.indiandentalacademy.com
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
www.indiandentalacademy.com
Matrix Rotation: centre in the condyle ď Ź Rotation of bone with its matrix or periosteal capsule in its articulation with surrounding bone
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź
7. LOWER ANT. FACIAL HEIGHT Forward growth rotation- decrease in lower AFH Backward rotation - over development of AFH
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
Johnston method of growth prediction ď Ź
ď Ź
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
www.indiandentalacademy.com
Forecast grid
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź
The face is inscribed in a coordinate system consisting of 24 rectangles.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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. ď Ź Disadv- complex and laborious method ď Ź
www.indiandentalacademy.com
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
www.indiandentalacademy.com
C- AXIS M point- by Nanda & Meritt (AJO 1994) ď Ź
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 .
www.indiandentalacademy.com
ď Ź
C-Axis: The line from the sella (S) to M- point is defined as C- axis.
www.indiandentalacademy.com
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 showgrowth increment of 1.41mm &1.31mm/yr.
www.indiandentalacademy.com
The mean growth axis angle (C-axis- SN) Increased for both males and females. Males = 3.98 Females = 2.25
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
A single M point cannot by itself summarize the growth of dentomaxillary complex in sagital plane. ď Ź However, when associated with the palatal plane the downward & forward migration is more accurately decsribed. ď Ź
www.indiandentalacademy.com
Quantification of the displacement of the mandible??? Y axis !!! What about remodeling of external symphyseal area….??? www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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
www.indiandentalacademy.com
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/yr www.indiandentalacademy.com
ď Ź
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.
www.indiandentalacademy.com
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 www.indiandentalacademy.com
Mathematical Model for prediction of craniofacial growth ď Ź
Presented by James. T. Todd & Leonard Mark
ď Ź
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź
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.
www.indiandentalacademy.com
www.indiandentalacademy.com
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
www.indiandentalacademy.com
ď Ź
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.
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
The predictions that were made were not accurate because of mechanical errors Oral habits Nevertheless they very closely predict the actual outcome of growth……
www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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
www.indiandentalacademy.com
ď Ź
Growth strains – It is the measurable deformation of a biologic body resulting from its growth. The direction and quantification of growth tensor 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.
www.indiandentalacademy.com
Growth tensorsď Ź define growth changes locally independent of the body registration methods ď Ź
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. www.indiandentalacademy.com
Growth tensor and growth prediction If growth process is prescribed by -specifying growth tensors at every point of the body, -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. www.indiandentalacademy.com
ď Ź 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 www.indiandentalacademy.com
ď Ź
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.
www.indiandentalacademy.com
Parental data to predict growth of craniofacial form ď Ź
Akira Suzuki & Yashuhide Takahama Am J Orthod Dentofac Orthop 1991;99 107-121
ď Ź
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 www.indiandentalacademy.com
Twin studies: - genetic analysis of craniofacial morphology was of prime concern ď Ź Family studies: ď Ź 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 ď Ź
www.indiandentalacademy.com
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. www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź
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
www.indiandentalacademy.com
ď Ź ď Ź
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.
www.indiandentalacademy.com
ď Ź Computerized ď Ź
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 xy coordinates of cephalometrics landmarks are recorded and stored in data set from which various cephalometric measurements are made. ď Ź
Growth and treatment response can be displayed and measured by longitudnal superimposition of serial datasets on stable cranial base or regional landmarks www.indiandentalacademy.com
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.
www.indiandentalacademy.com
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 www.indiandentalacademy.com
Computerized mesh analysis ď Ź
ď Ź
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.
www.indiandentalacademy.com
Construction of the reference grid ď Ź
ď Ź
ď Ź
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) www.indiandentalacademy.com
www.indiandentalacademy.com
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 www.indiandentalacademy.com
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.
www.indiandentalacademy.com
ď Ź
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.
www.indiandentalacademy.com
www.indiandentalacademy.com Leader in continuing dental education
www.indiandentalacademy.com