Growth Prediction & Age Estimation
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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
Holdaway soft tissue cepahlometric analysis Tooth mineralization Skeletal maturity indicator Symphysis morphology Pubertal growth spurt Third molar prediction
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Patient’s growth pattern Variability Effect of treatment on growth
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In the absence of growth, treatment responses are reasonably predictable GROWTH IS NOT…….
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The goal of growth prediction is to reduce the clinician’s ignorance of the future…
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What are we interested in predicting in the craniofacial complex? ď Ź
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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
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2. Relationship of parts - The most important prediction for the clinician is the future relationship of parts, that is the future facial pattern.
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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
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??? ď Ź
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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
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How well can we predict these parameters???
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Future Size Complex craniofacial growth Any simple series of size prediction is not clinically useful.
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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
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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
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The effect of orthodontic therapy on growth Ricketts’ method- sets the prediction and then works to make them come true
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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
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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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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
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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.
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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.
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The Nautilus offers 2 fundamental characterstics1. 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.
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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
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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
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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.
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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. www.indiandentalacademy.com
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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.
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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 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).
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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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.
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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.
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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. 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.
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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. www.indiandentalacademy.com
Procedure for growth estimation
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 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.
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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..
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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.
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STEP 4:
Construction of condylar axis From the centre of condyle to antegonial angle.
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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.
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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.
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Position of Maxilla
Step1 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
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.
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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.
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Planning the arrangement of teeth
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
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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 ď Ź
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. 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
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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.
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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.
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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
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Matrix Rotation: centre in the condyle ď Ź 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 :
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 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
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.
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
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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.
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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.
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Johnston method of growth prediction ď Ź
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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
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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.
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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.
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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.
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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
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Modification – a norm is superimposed on the pt’s grid in order to reveal difference from a normalized mesh diagram Advantagesgraphically display pt’s deviation Normal mesh diag is readily understood by patient www.indiandentalacademy.com
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
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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.
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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
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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.
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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.
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Quantification of the displacement of the mandible??? Y axis !!! What about remodeling of external symphyseal area….???
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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
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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
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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.
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Holdaway’s 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
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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.
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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. www.indiandentalacademy.com
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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.
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The predictions that were made were not accurate because of mechanical errors Oral habits Nevertheless they very closely predict the actual outcome of growth……
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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.
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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
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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. www.indiandentalacademy.com
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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. www.indiandentalacademy.com
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.
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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
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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
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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
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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
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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.
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The following hypothesis formed the basis of parental data to predict growth1. 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
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Equation of the individual growth prediction
Y(t) = C1X(s)+ C2X(d) + C3 1+exp(C4(t-C5)
+ C6)
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Here, C1X(s) similiar parents C2X(d) dissimiliar parents
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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.
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Computerized growth predictions
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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.
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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.
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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
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Computerized mesh analysis ď Ź
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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.
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Construction of the reference grid ď Ź
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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
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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 www.indiandentalacademy.com
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. www.indiandentalacademy.com
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
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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.
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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.
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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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