Department Of Orthodontics &

Dentofacial Orthopedics

Bapuji Dental COllege &

Hospital Davangere 577004

Seminar on

Growth

Prediction &

VTOPresented By-

Nandan Kittur

CONTENTS PAGE NO.

-INTRODUCTION 1

-GROWTH PATTERN,

VARIABILITY, AND TIMING 2-6

-METHODS OF GROWTH PREDICTION 7-9

-WHAT ARE WE INTERSTED IN PREDICTING

IN CRANIOFACIAL COMPLEX? 10-11

-INDICATORS OF SKELETAL MATURITY

-HAND WRIST RADIOGRAPHS AND 12-24

SKELETAL MATURITY

-CERVICAL VERTEBRAE AS 25-27

MATURATIONAL INDICATORS

-FRONTAL SINUS DEVELOPMENT AS 28-29

INDICATOR OF PUBERTY

-MANDIBULAR CANINE CALCIFICATION

AND SKELETAL MATURITY 30-31

-MANDIBULAR THIRD MOLAR

DEVELOPMENT AND SKELETAL 32

MATURITY

-PREDICTION OF MANDIBULAR

ROTATION 33-40

-ARCIAL GROWTH OF THE MANDIBLE. 41-48

-VTO( VISUALIZED TREATMENT OBJECTIVE) 49-50

RICKETTS VTO 51-70

HOLDAWAY VTO 71-89

-CONCLUSION 90

-BIBLIOGRAPHY 91-93

INTRODUCTION

The growth and development of the human face provides a

fascinating interplay of form and function. The mosaic of the

morphogenetic pattern, as it is influenced by epigenetic and

environmental forces, requires an understanding of many

factors if we are to fully appreciate the phenomenon. This has

more artistic value as far as orthodontist is concerned.

Surveys have shown that two thirds of the cases seen for

orthodontic therapy involve types of malocclusion in which

growth and development play a significant role in the success or

failure of mechanotherapy.

1

Growth Pattern, Variability, and Timing

In studies of growth, the concept of pattern is an important one.

Pattern represents proportionality. The Cephalocaudal

gradient of growth strongly affects proportions and leads to

changes in proportion with growth.

2

In fetal life, at about the third month of intrauterine

development, the head takes up almost 50% of total body

length.

At the time of birth, the trunk and limbs have grown faster so

that only 30% of body length is the head.

At adulthood the head is only 12% the body length.

At birth legs are 1/3 the body length, at adulthood they are

about half the body length.

This reflects the Cephalocaudal gradient of growth.

Even within the head and face, the cephalocaudal gradient of

growth strongly affects the proportions.

In new born, the cranium is larger and face is much smaller,

when compared to an adult.

Also mandible continues to grow more and later than the

growth of maxilla.

Another aspect of normal growth pattern is that, not all

tissues of the body grow at the same rate. This is graphically

illustrated by the Scammons growth curves.

3

Growth does not take place at a uniform rate, but there is

acceleration and retardation in the rate of growth. The

accelerative phases are called growth spurts.

There are 3 major growth spurts recorded by Woodside.

They seemed to be sex linked.

First peak occurred at 3yrs of age. It is called Childhood growth

spurt.

Second peak at 6 to 7yrs in girls and 7 to 9yrs in boys. It is

called Juvenile growth spurt.

Third peak was at 11 to 12yrs in girls and 14 to 15yrs in boys. It

is the prepubertal growth spurt.

The tendency is generally for boys to have 2 or 3 peaks, while

large numbers of girls show only 2 peaks. Very few girls show

the mixed dentition growth spurt. But all show the pubertal

growth spurt.

4

Another important aspect of growth is Variability. Obviously

everyone is not alike in the way that they grow, as in everything

else. It can be difficult, but it is important to decide whether the

individual is merely an extreme of the normal variation or falls

outside the normal range. This is determined, using growth

charts for the particular population standards.

5

The final major concept in Physical growth and development is

Timing.

Variation in Timing occurs because the same event happens in

different individuals at different times. Therefore Chronologic

age often is not a good indicator of an individual’s growth

status.

The effectiveness of a Biologic or Developmental ages in

reducing timing. variability makes this approach useful in

evaluating a child’s growth status.

6

METHODS OF GROWTH PREDICTION

William Hirschfield and Robert Moyers (1971)

Several predictive methods are used in industry and science. We

may group these under following headings.

1. Theoretical

2. Regression

3. Experimental

4. Time series

THEORETICAL METHODS OF PREDICTION:

Astronomers discovered earth size planet several thousand light

years away from us by collecting a series of inexplicable

apparently random data on the behavior of celestial bodies until

a theoretical model could be constructed mathematically which

might explain all the unusual activity observed, and a test for

the hypothesis was devised.

Theoretical models of cranio facial growth have not yet been

defined mathematically in terms precise enough to permit the

application of the method to prediction.

REGRESSION METHODS:

These methods serve to calculate a value for one variable called

dependent, on the basis of its initial states and the degree of its

correlation with one or more independent variables.

Johnston has recently evaluated and reviewed regression

methods of approach to craniofacial prediction. Among his

conclusions is that:

7

(1) The ultimate accuracy of cephalometric prediction may be

limited to some extent by intrinsic errors with the cephalometric

method itself.

(2) Contemperory methods seem inadequate to provide an

efficient estimate of individual changes attributed only to

growth. Burstone has reviewed some of the problems of attack

and of selection of independent variables with regard to growth

prediction.

EXPERIMENTAL METHODS:

Experimental 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 codified for use by

others. The best known example of the experimental method in

craniofacial growth prediction is that of Ricketts, whose

estimates of growth prediction for the individual utilize means

derived from a large sample of treated orthodontic patients. The

method is popular and widely used, but its theoretical base is

shaky on two counts. First the assumption must be made that

the individual being predicted will behave as the mean of a

population of which he is not a member. Second, the

morphology of the mandible and the other parts is a clue to the

future growth of the face, appoint disputed by Horowitz and

Hixon, Balbach and Woodside.

TIME SERIES METHOD:

Because of the great interest in prediction of craniofacial

growth and the limitations of the methods thus far tried, it

seems pertinent to ask whether there might be some other

method of prediction, as yet, untried on growth problems which

8

would provide the desired accuracy, efficiency and individuality

for the clinician.

Operations research has been concerned with the development

of methods which are based on individual not population

behaviour.

The methods are essentially two types

1. Time series analysis which extracts in a mathematical form

the fundamental nature of the process as it relates to time.

2.smoothing methods, either moving averages or exponential,

which operate to give representative or average values to the

parameters of a previously derived time series equation .For

purpose of analysis a time series is considered to be composed

of four parts. These are

1. Trend or long term movement

2. Oscillations about a trend

3. Cyclic or periodic events

4. Random compliments

The analysis consists of assessment of each of these parts by

means of specific statistical tests. Time series method offers

more promise for craniofacial growth than any of the methods

thus far used.

9

WHAT ARE WE INTERSTED IN

PREDICTING IN CRANIOFACIAL

COMPLEX?

Future size of part: the prediction of future size, according to

Burstone, his primarily a problem of predicting future

increments which are to be added to a size that is already

known. Most of the size dimension of interest to the

orthodontist displays a combination growth curve through time.

Relationship of parts: The most important prediction for the

clinician is the future relationship of parts, that is, future facial

patterns. Pattern, however represented, is a summation of the

growth and size in several component regions.

Timing of growth events: Because growth does not proceed

evenly, certain facial dimensions demonstrate market changes

in their velocity curve. These “spurts” make prediction much

more difficult. If one were to predict a spurt, he might want to

predict the time of its onset, the duration of the increased rate of

growth, and the rate of growth during the spurt.

Vectors of growth: Most predictive methods thus far presume

a continuation of the pattern first seen therefore; the

presumption is made that the vectors of growth presents at the

time of prediction will remain. There is much documentation

that this presumption is not true. Mandibles, which grow

vertically for a period of time inexplicably, start to grow

horizontally.

10

Velocity of growth: It would be of use to know the future

expected rate of growth. Prediction of velocity is most

important during the pubescent spurt.

The effect of orthodontic therapy on any of the above

predicted parameters: It is not unreasonable for clinician to be

interested in predicting what effect the treatment will have on

the predicted and actual growth of one specific face.

11

Indicators of Skeletal MaturityHAND WRIST RADIOGRAPHS AND SKELETAL

MATURITY

The first recorded Hand-wrist radiograph film was published by

Sydney Rowland of London in 1896. This was just 4 months

after the announcement of the discovery of the X-Ray by

Roentgen.

In 1926 Carter reported on a radiographic study of carpal

bones in children.

Howard (1928) using hand X-rays, reported on the physiologic

changes of bone centers in a large group of male and female

children from ages 5to16.

In 1929 two comprehensive growth studies were begun, one at

the Brush foundation of Western Reserve University,

Cleveland, Ohio under the direction of T. Wingate. Todd, and

the other at the Harvard School of Public Health, Boston,

Massachusetts under Harold Stuart. Todd’s work was continued

12

after his death by William Greulich. S. Idell Pyle was also

involved in the Cleveland project, and it was she who was

instrumental in preparing the standards of growth in popular use

today utilizing the hand-wrist film.

The concept that facial growth was in some way related to

general body growth was reported by Nanda(1955) . He stated

that facial growth tended to lag slightly behind general body

growth in height during the pubertal growth spurt period.

Rose (1960) cited a cross sectional study of 125 individuals and

determined that carpal ranking was an ineffective guide to facial

development. Stature and body weight were thought to be the

best indicators.

Bhamba(1961) stated that the face showed the characteristic

skeletal growth pattern with the time of maximal spurt

occurring a little after the spurt in body height.

Johnston(1965)demonstrated a relationship between skeletal

and facial growth and emphasized that there were, in addition to

normal growth patterns, retarded as well as accelerated types

which required special attention.

Hunter (1966) reported that the carpal bones as well as adjacent

skeletal structures had proven to be the most satisfactory sites

for determining skeletal maturation.

Bjork and Helm(1967) stated that the appearance of the ulnar

sessamoid on the Hand-wrist radiograph was significantly

related to the onset of maximum puberal statural growth in

height. The sessamoid appeared before maximal puberal

statural growth,and menarche in girls occurred after the

maximum puberal growth.

Helm et al (1971) they found that one stage (PP2=) invariably

occurred one to five years before maximum growth. The stage

13

MP3 cap occurred close to the tome of the along with the ulnar

sessamoid. The DP3 stage occurred from one to three years

after the maximum.

Brown, Barrett &Grave (1971) found that two other events

occurred significantly at least one year prior to peak growth

velocity. They were initial ossification of hook of hamate as

well as of pissiform.

Pileski et al (1973) reported that 20% females and 25% males

did not exhibit appearance of sessamoid, until after maximum

growth velocity was reached.

Grave and Brown (1976) suggested that the epiphyseal union of

radius could be used to assess the duration of retentive phase of

treatment.

Bowden (1976) cautioned that strict reliance on Hand wrist

indicators to determine the state of facial growth could not be

guaranteed and that the relationship, although valid, was

probably not absolute.

Grave and Brown (1979) described the use of hand wrist film in

orthodontic treatment to take advantage of the puberal growth

spurt.

14

Grave and Brown have recorded 14ossification events

1. PP2= Proximal phalanx of second finger;

epiphysis is as wide as diaphysis

2. MP3= Middle phalanx of third finger;

epiphysis is as wide as diaphysis

3. H-1 Hooking of Hamate –Stage 1

4. Pisi Appearance of Pissiform

5. R= Radius; epiphysis is as wide as

diaphysis

6. S Appearance of Ulnar Sessamoid at

metacrpophalangeal joint of first

Finger

7. H-2 Hooking of Hamate –Stage 2

8. MP3cap Middle phalanx of third finger;

epiphysis caps its diaphysis

9. PP1cap Proximal phalanx of first finger;

epiphysis caps its diaphysis

10. Rcap Radius; epiphysis caps its diaphysis

11. DP3 Distal phalanx of third finger; complete

epiphyseal union

12. PP3 Proximal phalanx of third finger;

complete epiphyseal union

13. MP3 Middle phalanx of third finger;

complete epiphyseal union

14. R Radius; complete epiphyseal union

15

The events fell logically into 3 groups with respect to

ossification times

Events, which occurred before peak growth velocity

1. PP2=

2. MP3=

3. H-1

4. Pisi

5. R=

Events which coincided peak growth velocity

6. S

7. H-2

8. MP3cap

9. PP1cap

16

10. Rcap

Events which followed peak height velocity

11. DP3

12. PP3

13. MP3

14. R

Fusion of distal phalanges occurs about the time of menarche

and it is suggested that epiphyseal union of radius can be used

to assess the duration of retention phase of treatment.

Fishman (1974) has given 11 Skeletal Maturity Indicators(SMI)

17

Epiphysis as wide as Diaphysis

1. Third finger – proximal phalanx

2. Third finger –middle phalanx

3. Fifth finger- middle phalanx

Ossification

4. Adductor Sessamoid of thumb

Capping of Epiphysis

5. Third finger- Distal phalanx

6. Third finger- Middle phalanx

7. Fifth finger- Middle phalanx

Fusion of epiphsis and Diaphysis

8. Third finger- Distal phalanx

9. Third finger –Proximal phalanx

10. Third finger- Middle phalanx

11. Radius

Accelerating growth velocity period. SMI 1 - 4

High growth velocity period. SMI 4 - 7

Decelerating growth velocity period. SMI 7 – 11

Girls generally reach point of peak growth velocity at SMI 5

and boys at SMI 6.

18

Boys do not take a longer time to mature. They simply do it at a

later chronologic age. The period of male adolescence generally

lasts no longer than female adolescence.

Julian Singer (1980) has described 6 stages of development on

the hand wrist radiograph.

Stage 1 (Early):

1. Absence of Pisiform

2. Absence of Hook of Hamate

3. Epiphysis of proximal phalanx of second digit (PP2)

narrower than its shaft

Stage 2 (Prepuberal):

1. Proximal phalanx of second digit and its epiphysis are

equal in width (PP2).

2. Initial ossification of hook of hamate .

3. Initial ossification of pisiform.

Stage 3 (Puberal onset):

1. Beginning calcification of Ulnar sessamoid.

2. Increased width of epiphysis of PP2

3. Increased calcification of hamate hook and pisiform.

Stage 4 (Puberal):

1. Calcified ulnar sessamoid

2. Capping of shaft of middle phalanx of third digit by its

epiphysis(MP3cap)

Stage 5 (Puberal Deceleration):

19

1. Ulnar sessamoid fully calcified

2. Calcification of the shaft of middle phalanx of third

digit by its epiphysis (DP3u).

3. All phalanges and carpals fully calcified.

4. Epiphysis of radius and ulna not fully calcified with

respective shafts.

Stage 6 (Growth completion):

No remaining growth sites.

20

Hagg and Taranger (1982) investigated a prospective

longitudinal study in 212

Swedish children. Data comprised of Standing height, Tooth

emergence, pubertal development and Handwrist radiographs.

Adolescent growth was studied by graphical analysis of the

unsmoothed incremental curves of standing height. The curves

were based on the annual increments from 3 to 20 years. First,

the peak height velocity (PHV) was located on incremental

curves for each subject. The growth curves were observed for

reliable estimates of the beginning and end of the pubertal

growth spurt. A marked, continuous increase in growth rate up

to PHV was found from one growth event, ONSET. In all

subjects the increase in growth rate during puberty was more

21

than 10mm; that is, ONSET and PHV did not coincide. A

marked, continuous deceleration in growth occurred down to

the first annual increment below 20mm. (END).

Dental development was assessed by dental emergence

stages.

Skeletal development was analyzed using hand wrist

radiographs taken annually from 6 to 18 yrs.

Pubertal development was analyzed from 10 to 18 yrs of

age by determining menarche in girls and change in voice in

boys.

Results:

The pubertal growth spurt: ONSET was at 10.0yrs in

girls and 12.1 yrs in boys.

PHV was at 12.0 yrs in

girls and 14.1 yrs in boys.

END was at 14.8 yrs in

girls and 17.1 yrs in boys.

22

Dental development and pubertal growth spurt:

The dental emergence stages were not useful as

indicators of pubertal growth spurt.

Skeletal development and the pubertal growth spurt :

At ONSET 40% girls and 25% boys had ossified ulnar

sessamoid. (S).

At PHV 90% of the subjects were in either stage MP3-

FG or stage MP3-G.

At END 95% boys and 80% girls were in one of the

three radius stages. (R-I, R-IJ, R-J)

23

Pubertal development and the pubertal growth spurt:

Menarche was reached 1.1 yrs after PHV.

Pubertal voice was attained 0.2 yrs before PHV.

Male voice was attained 0.9 years after PHV.

24

Cervical Vertebrae as Maturational Indicators

Lamparski (1972) used cervial vertebrae morphology to

assess pubertal growth spurt. Hassel and Farman (1995)

modified his criteria and gave 6 stages of cervical vertebrae

development. Garcia –Fernandez (1998) related these stages

with the SMI given by Fishman.

The six stages are as follows

Initiation (SMI 1 and 2) the cervical vertebrae are wedge

shaped, with the superior vertebral borders tapering from

posterior to anterior.

80to 100% growth can be anticipated at this stage.

Acceleration (SMI 3 and 4) concavities develop along the

inferior borders of C2and C3. The bodies of C3 and C4 are

nearly rectangular, and the inferior border of C4 is flat.

Growth acceleration begins at this stage, when 65-85% of

adolescent growth can be anticipated.

Transition (SMI 5 and 6) distinct concavities develop on the

inferior borders of C2 and C3. A concavity begins to develop at

inferior border of C4, and the bodies of C3 and C4 are

rectangular.

Adolescent growth accelerates towards peak velocity, with 25-

65% of adolescent growth anticipated.

25

Deceleration (SMI 7 and 8) Clear concavities are seen on the

inferior borders of C2, C3, and C4 with the bodies of C3 and C4

nearly square.

Only 10-25% of adolescent growth remains.

Maturation (SMI 9 and 10) Accentuated cavities are seen on

the inferior borders of C2, C3, and C4, and the bodies of C3 and

C4 are nearly square.

Final maturation takes place at this stage when 5-10%

adolescent growth can be anticipated.

Completion (SMI 11) Deep concavities are seen on the inferior

borders of C2, C3, and C4, and the vertebral bodies are more

vertical than horizontal.

Little to no adolescent growth is expected at this stage.

26

27

Frontal Sinus Development as indicator of puberty

Sabine Ruf and Hans Pancherz (1996) evaluated the

development of the frontal sinus to the longitudinal data of the

subject’s growth charts.

Results showed that Frontal sinus growth velocity at puberty is

closely related to body height growth velocity.

Frontal sinus shows a well defined pubertal peak (Sp),

which on an average, occurs 1.4 years after the pubertal body

height peak. (Bp).

If the only prediction was that whether pubertal growth

maximum has passed the precision of this method was high (90

%).

But if incidence of body peak was to be predicted the accuracy

is only 55%.

Moreover, it is only possible if 2 cephalograms approximately

1-2 yrs spaced, of the same individual are available.

28

29

Mandibular Canine calcification and skeletal Maturity

Sandra Coutinho et al in 1993 related canine calcification stages

to skeletal maturity indicators as shown in the figures.

They concluded that the initiation of pubertal growth

spurt relates with stage F of canine calcification.

Stage G occurs approximately around 1 yrs before PHV in

boys but only 5 months before PHV in girls.

The intermediate stage between stage F and stage G should be

used to identify the early stages of pubertal growth spurt.

30

31

Mandibular third Molar development and Skeletal maturity

Engstorm (1983) compared lower third molar development

stages with skeletal maturity indicators.

Third molar stages were

A: Tooth germ visible as rounded radiolucency

B: cusp mineralization complete.

C: Cown formation complete.

D: Root half formed.

E: Root formation complete but apex not closed.

Skeletal indicators used were

PP2: proximal phalanx of second finger, epiphysis

as wide as diaphysis

MP3 cap: middle phalanx third finger, epiphysis caps

the diaphysis

DP3 u: distal phalanx of third finger, complete

epiphyseal union.

Ru: Distal epiphysis of radius, complete

epiphyseal union.

At stage PP2 third molar crown completion took place in

majority of subjects.

At stage MP3 cap crown completion in all and root

development had begun in few subjects.

At DP3 u Root length was completed in some subjects.

At R u one third subjects crown was complete, half the root was

complete in other one third, and in the remaining third root had

reached full length.

32

PREDICTION OF MANDIBULAR

ROTATION

In 1969 Bjork discussed three methods of growth prediction

1) A longitudinal method, which consists of following the

course of development by annual cepholograms, is shown to be

of limited use for this purpose, as the remodeling process at the

lower border of the mandible to a large extent masks the actual

rotation.

2) A metric method, which aims at prediction based on a

metric description of the facial morphology at a single stage of

development, has for not proved of value.

3) A structural method is described by which it may be

possible to predict, from a single cephalogram, the course of

rotation, where this feature is marked. This method is based on

the information gained from implant studies of the remodeling

process of the mandible during growth. The principle is to

recognize specific structural features that develop as a result of

the remodeling in a particular type of mandibular rotation. A

prediction of the subsequent course is then made on the

assumption that the trend will continue. Such structural signs

are detailed as follows.

Structural signs of growth rotation:

From the clinical stand point, it is important to detect extreme

types of mandibular rotation occurring during growth. Seven

structural signs of extreme growth rotation are considered in

relation to the condylar growth direction. Not all of them will be

found in a particular individual, but the greater the number that

33

are present, the more reliable the prediction will be. However, it

is evident that these signs are not so clearly developed before

puberty.

The seven signs are related to the following features

1) Inclination of the condylar head.

2) Curvature of the mandibular canal.

3) Shape of the lower border of the mandible.

34

4) Inclination of symphisis,

) Interincisal angle

6) Inter premolar or inter molar angles

7) Anterior lower face height.

In horizontal growing individuals:

1) The condyles are inclined forward.

2) The mandibular canal curvature tends to be greater than that

of the mandibular contour.

3) The lower border presents with pronounced apposition below

the symphysis and the anterior part of the mandible produces an

anterior rounding, with a thick cortical layer, while the

resorption at the angle produces a typical concavity.

4) The symphysis swings forwards in the face, and the chin is

prominent.

5) The difference in the inter incisal angle is evident; in spite of

the compensatory tipping of the lower incisors is more when

compared to vertical growing individuals.

6) The difference in the interpremolar and inter molar angles in

the two growth types is also clear is more in horizontal growth

than vertical type growth pattern. 7) A compression or reduced

lower anterior face height.

In vertical growing individuals:

1) the condyle is backwardly inclined.

2) The mandibular canal is straight or in pathologic cases, it

may even curve in the opposite direction.

3) The lower border of the mandible anteriorly rounding is

absent and the cortical layer is thin and lower contour at the jaw

angle is convex.

35

4) The inclination of the symphysis is swung back, with

receding chin. The evaluation is complicated by the

simultaneous remodelling of the alveolar process in the opposite

direction, as is exemplified by the cranium with openbite.

5) The inter incisal angle is reduced in this case due to more

proclination.

6) The inter premolar and molar angles in this growth pattern is

reduced.

7) The over development of L.A.F.H is seen in backward

rotating mandibles.

Taking the consideration of these structural signs the growth

trend is predicted. The mechanism underlying the mandibular

rotation and the centers of rotation will be considered.

From the start point of growth, the mandible may be regarded

as a more or less unconstrained bone it may change its

inclination in several ways. A critical factor in this respect is the

site of the center of rotation, which may be located at the

posterior or anterior ends of the bone or somewhere in between,

in which case the ends of the mandible swing in different

directions, thus the center may not necessarily lie at the

temporomandibular joints, as it usually imagined, although this

is not readily evident from examination by conventional

techniques. There follows schematic account of the various

types of rotation of the mandible that may be recognized with

the implant method are as follows.

Bjork based on the location of C/R classified forward rotation

3 types:

Type – I: There is a forward rotation about the centers in the

condyles which gives rise to a deep bite, in which the lower

36

dental arch is pressed into the upper, resulting in

underdevelopment of the anterior face height. The cause may be

occlusal imbalance due to loss of teeth or powerful muscular

pressure. This deep bite of the bite may occur at nay age during

active growth process.

Type – II: Forward growth rotation of the mandible about a

center located at the incisal edge of the lower anterior teeth is

due to the combination of marked development of the posterior

face height and normal increase in the anterior height. The

posterior part of the mandible then rotates away from maxilla.

The increase in the posterior face height has two components.

The first is the lowering of the middle cranial fossa in relation

to anterior one as the cranial base bends, the condylar fossa then

being lowered. The second component is the increase in the

height of the ramus, which is pronounced in the case of vertical

growth at the mandibular condyles. Because of the vertical

direction of the condylar growth, the mandible is lowered more

than it is carried forward. Because of the muscular and

ligamentous attachments, the lowering takes place as a forward

rotation in relation to the maxilla, with the center at the incisal

edges of the lower incisors. The eruption of the molars keeps

pace with the rotation. Because of the simultaneous marked

resorption below the gonial angle, the height in this region may

not increase to a great extent and the lower border undergoes a

characteristic remodelling.

37

Type – III: In anomalous occlusion of the anterior teeth the

forward rotation of the mandible with growth changes its

character in the case of large maxillary overjet or mandibular

overjet, the center of rotation no longer lies at the incisors but is

displaced backward in the dental arch, to the level of the

premolars. In this type of rotation the anterior face height

becomes underdeveloped when the posterior face height

increases. The dental arches are pressed into each other and

basal deep bite develops.

Backward rotation is less frequent than forward rotation and

has been examined by the implant method in considerably

fewer subjects two types have been recognized.

38

Type – I: Here the center of the backward rotation lies in the

temporomandibular joints. This is the case when the bite is

raised by orthodontic means, by a change in the intercuspation

or by a bite raising appliance and results in an increase in the

anterior face height.

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 fossa is

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 fossa.

This underdevelopment in the posterior face height leads to a

backward rotation of the mandible, with overdevelopment of

the anterior face height and possibly openbite as a consequence.

Type – II: Backward rotation here occurs about a center

situated at the most distal occluding molars. This occurs in

connection with the 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

39

face, and because of its attachment to muscles and ligaments it

is rotated backward. In this type of rotation the symphysis is

swung backward and the chin is drawn back below the face.

The soft tissue of the chin may not follow this movement, and a

characteristic double chin can form. Basal openbite may

develop, and there is difficulty in closing the lips with out

tension. Since the position of the lower incisors, are related

functionally to the upper incisors, they become retroclined in

the mandible and the alveolar prognathism is reduced.

In regarding to the degree of rotation of the mandible,

investigators like Bjork, Lavergne and Gasson found an annual

rotation of 1.070 which ranges from 00 to 2.100 when compared

to sells nasion line and found 70 during a period of six years

around the pubertal growth spurt in the forward rotation growth

pattern individuals.

In posterior rotation growth pattern the mean degree of

rotation was – 0.300 with range from – 0.060 to 0.850 when

related to S.N. line.

40

ARCIAL GROWTH of the Mandible:

R.M.Ricketts using trial and error procedure with longitudinal

cephalomatric records and computers has developed a method

to determine the arc of growth of the mandible.

The principle is “a normal human mandible grows by superior

anterior (vertical) apposition at the ramus or the curve or arc

which is a segment formed from a circle. The radius of this

circle is determined by using the distance from mental

protuberance to a point at the forking of the stress lines at the

terminus of the oblique ridge on the medial side of the ramus

(pt. Eva)

On the basis of this, a primary method of prediction of

development was devised. By plotting a line through the long

axis of the condyle and neck and extending it to the form during

growth had been studied.

Consequently, findings from this method suggested that the

technique could serve as a working hypothesis for growth

prediction for the clinical problem of prognosis of growth.

The next move was to identify a “central core”

cephalometrically. External mandibular form is subject to

remarkable remodeling and therefore not reliable as a reference.

The attempt to surface variation and to determine central or

internal structure resulted in the center of the ramus.

41

Method for determination of xi point:

R1= deepest point on the subcoronoid incisure

R2=point selected opposite R1 on the posterior border of ramus.

R3=depth of the sigmoid notch

R4=point selected directly inferiorly on the lower border of

ramus

A point at the superior aspect of the symphysis was selected as

supra pogonion. It was labelled p.m. (Protuberance menti)

This is substantiated as reference because (i) it is located at

approximately a stress center-Ricketts. (ii) Its site of a reversal

line –Enlow and (iii) it is consistent with the findings from

implant studies Bjork; which indicated stable unchanging bone

in this area of the chin. There fore, a bone crest located at the

superior aspect of the compact bone on the anterior contour of

the symphysis was accepted as the most stable and useful

reference for out most basal bone in the mandible. By bisecting

the height and width of the ramus at its narrowest dimension a

geometric center was determined and labelled xi point.

Investigation of normal mandible from 25 dried skulls showed

in every instance that this point fell in contract with the

mandibular canal.

Rickets used a point described previously with laminagraphs at

the bisection of the condyle neck as high as visible in the

cephalogram film below the fossa. This was labelled “Dc”

Accordingly by connecting Dc point with xi a repeated condyle

axis was established. Further by connecting xi to p.m. – a

corpus axis was erected.

It is an angle formed by the intersection of the condylar axis

(DC-xi) and a backward extension (xi-p.m.) from the center

42

of ramus to suprapognion. The mean is 26 + 4. This angle has a

tendency to increase with age (0.5/yrs).

The first mandible is a reterognathic one with a steep mandible

plane and grows vertically. The middle one is normal and the 3rd

mandible with an high angle is indicative of a forward growing

mandible.

Consequently by studying linear growth on these planes and the

form change as a change in a angulation between the two an

interpretation could be gained regarding the characteristics of

mandible growth in a given patients. Samples that were

superimposed on the corpus axis and registered at xi point were

found to bend about ½ degree each year.

It was recognized that a bending was occuring in an orderly

manner and therefore the greater the magnitude of growth,

greater the bending. It was apparent that a growth arc was

operative. It was of interest to see if this arc could be reduced to

a segment of a circle an ellipse or a spiral curve. The mandible

became more obtuse than was the actual behavior of the sample.

This shows the method used to determine the true arc of

mandible po,xi, and c2 (center of condyle head) were

connected and increments added.

After using pm, xi and dc points as a method of depicting the

cortical core of the mandible, experiments were undertaken to

determine a method by which the form and size of the

mandible; often at 5 years interval could be predicted with the

use of only the first x-ray as reference.

Results showed that the arc size increase was seen, but not

enough bending occurred. Pm was then retained as a stable and

reliable reference for further study.

43

A second arc was explored by using the tip of the coronoid

process, the anterior border of the ramus at its deepest curve

(R1) and the same pm point. The extension of this curve

exhibited the segment of a circle too small in radius and

resulted in excessive bending of the mandible when the same

gradient of growth was employed for a project.

These 2 unsuccessful arcs obviously bracketed the true arc,

which must be somewhere in the mandible between the

condyloid and coronoid process and between xi and the anterior

border of the ramus. Hence Ricketts decided to construct an

experimental arc bisecting the 2 previous arcs. By establishing a

halfway point between xi and Ri points (the center and anterior

border of ramus) and using the distance from this points to pm

as radius of a circle an arc could be producer.

The use of this arc still bent the mandible a fraction too much.

In addition a radius selected from this point would increase or a

changing arc or ultimate spiral shape would result. Growth

therefore could not be represented as a simple segment of a

circle if these dimensions were employed.

It was though that perhaps the stress lines of the mandible

would reveal its hidden secrets. An 850 years old mandible

given to Ricketts by the late William downs revealed the secret.

On close investigation of the mandible the true arc was

determined. This mandible had been weathered to a state of

disintegration of the interprismatic substance of the external

cortical bone and clearly showed stress lines in the outer and

inner plates. The lines thus exhibited the design of the mandible

for bracing externally. (Y1 forking of the stress lines at the base

of the coronoid process).

44

Experimentally 2 new points (Eva and TR) were located

geometrically; point Eva is also a biologic line in the ramus.

When the size increase of the mandible as determined in the

computer study was incrementally added to the arc at the

sigmoid notch it was found that the predicted mandible was

almost absolutely correct in size and form when compared with

the final composite.

The growth increase for the condylar and coronoid processes

were different when measured from a point at the point crossing

of the arc of the sigmoid notch. The point of crossing was

labelled as Mu (Murray point which is named after Ricketts

father).

RR (Ramus reference) point is the point halfway between xi

point and R3 the bisections of which locates point Eva. Eva in

turn is used to find a TR (true radius) measured from pm point.

Now using TR. as the center of a circle, an arc is drawn. Mu

Murray point is the crossing of this arc on the sigmoid notch.

By constructing the growth arc, growing the mandible on this

arc, and extending the processing and drifting angular process a

new forecasting technique is developed.

Having become satisfied with this arc as a tool for prediction

the next problem lay in the amount of growth on forecast on the

arc. The coronoid and condylar process grow upward and

outward in a direction essentially as a function of the curve of

an original arc. Some condyles did not grow at all from the

original point Mu while others grew significantly. The short and

small condyles were found not to grow and good well-formed

condylar heads were found to grow by 0.4 mm and average

condyles 0.2 mm/year. Growth increment for coronoid –0.8

mm/year. Symphysis-1mm/year.

45

Apposition of the lower border of the symphasis for males

occurs at about 1mm each 8yrs. From point Mu the mandible is

grown out on the arc at the sigmoid notch about 2.5mm/yr.

The method to determine the drift of the gonial angle on the arc

in females no further addition are given on the border of

mandible from the arc, in males 0.2mm/year are given. The drift

of the mandible occurs almost at a pace of 50% of the total

mandible growth.

In the series of the steps in forecasting of the mandible growth.

Art work for normal contours is employed as connections are

made from the coronoid process to point RR on the coronoid

crest. The oblique ridge shows opposition of about 0.4mm/year.

Implication of article growth prediction

1.) It appears that the symphysis rotates essentially during

growth from a horizontal to a more vertical inclination and the

suggestion is presented that the genial tubercles and the lingual

plate drop downward in the process. This explains the major

part of the form characteristics of the symphysis, in the

cephalogram film (chin button development). Implant studies

have shown that greatest apposition takes place at the inferior

margin of symphysis (and perhaps the posterior side) in the

preschool years. The growth by apposition may appear lateral to

the midline on the symphysis as bulk is needed for bracing.

2.) This phenomenon explains why reversal lines are

observed at the area of pogonion and suprapogonion.

3.) It explains why the mandible plane changes extensively

in some individual and not in others.

4.) It shows why ankylosed teeth are observed to affect

occlusal plane development.

46

5.) It explains how the early ankylosis of a lower molar

tooth terminates with the tooth located at the lower border of

mandible,the mandibular arc simply continues and this tooth

becomes trapped with in the cortical bone and the lower border

resorbs point up to it

6.) It suggests a reason why mandible anchorage is risky in

retrognathic faces because less space is available for molar

eruption due to a more vertical eruption in that type than

prognathic types.

7.) It explains why good dentures may become

progressively more crowded in long tapered faces and

sometimes even in normal faces.

8.) It suggests that abnormal growth or margins of the

mandible can be understood as a friction of relative contribution

of the coronoid and process.

47

DRAW BACK OF ARCIAL GROWTH PREDICTIONS:

1.) It relies heavily on the operator’s skill in tracing the

cephalogram. Minor tracing errors could produce a wrong

prediction.

2.) Mitchell and Jordan (1975) in their study to evaluate

Ricketts prediction method concluded that Ricketts uses the

patients chronologic age rather than the skeletal age since he

requests no hand –wrist film. Since average growth increments

are added to the age, if the patients has completed growth or if

he is a growth spurt or lag phase, it will alter the results;

particularly if the time interval is short and the patients is near

maturity. (Ricketts presumes that girls are grown to 14.5 years

and boys to 19 years)

3.) Since the growth increments constants are mainly

derived from western population it is to be found out if these

constants are applicable to Indian subjects.

48

VTO( Visualized Treatment Objective)

The term VTO which stands for Visualized Treatment

Objective was first coined by Holdaway but used extensively by

Dr. Ricketts.

The term visual (or visualized ) treatment objective (VTO) was

coined to communicate the planning of treatment for any

orthodontic problem.

A Visual Treatment Objective (VTO) is like a blueprint used in

building a house. It is a visual plan to forecast the normal

growth of the patient and the anticipated influences of

treatment, to establish the individual objectives we want to

achieve for that patient. Treatment for a growing patient must

be planned and directed to the face and structure that can be

anticipated in the future, not to the skeletal structure that the

patient presents initially. The treatment plan should take

advantage of the beneficial aspects of growth and minimize any

undesirable effects of growth, if possible.

The Visual Treatment Objective permits the development of

alternative treatment plans. After setting up the teeth ideally

within the anticipated or "grown" facial pattern, the orthodontist

must decide how far he must go with mechanics and

orthopedics to achieve his goals, whether it is possible to

achieve them, and what the alternatives are.

Once treatment has begun, there is a continuing need for a

visual goal against which treatment progress can be measured

and monitored. By superimposing a progress tracing between

49

the original tracing and the forecast goal, the orthodontist may

evaluate progress along a definitely prescribed route. Any

deviation from expected progress will become apparent

immediately and the need for midcourse corrections will be

recognized and can be instituted early. Although the majority of

individuals react predictably to treatment, particular individuals

may deviate from the usual pattern and require alterations in

strategy. Differences in response to treatment may result from

lack of patient cooperation, variations in growth patterns, or

from ineffective orthodontic mechanics. The necessity for this

type of monitoring is important in accommodating treatment to

individual variability.

The VTO forecast is valuable for the orthodontist's self-

improvement in that it permits him to set his goals in advance

and compare them with the results at the end of treatment.

Identification of the discrepancies between goals and results

provide him with an objective picture of the areas in which his

treatment could be improved.

50

Ricketts VTO

A step-by-step procedure to construct a VTO for a in the

following sequence (putting in average growth for an estimated

two-year period of active treatment and the objectives that we

wish to achieve with our mechanics):

1. the cranial base prediction

2. the mandibular growth prediction

3. the maxillary growth prediction

4. the occlusal plane position

5. the location of the dentition

6. the soft tissue of the face

51

VTO — Cranial Base Prediction

Place the tracing paper over the original tracing and starting at

CC point, follow these steps to construct the cranial base:

1. Trace the Basion-Nasion Plane. Put a mark at point CC.

2. Grow Nasion 1mm/year (average normal growth) for 2 years

(estimated treatment time).

3. Grow Basion 1mm/year (average normal growth) for 2 years

(estimated treatment time).

4. Slide tracing back so Nasions coincide and trace Nasion area.

5. Slide tracing forward so Basions coincide and trace Basion

area.

52

VTO — Mandibular Growth Prediction — Rotation

The construction of the mandible and its new position start with

the rotation of the mandible. The mandible rotates open or

closed from the effects of the mechanics used and the facial

pattern present. The average such effect on mandibular rotation

is as follows:

Mechanics

1. Convexity Reduction— Facial Axis opens 1°/5mm.

53

2. Molar Correction — Facial Axis opens 1°/3mm.

3. Overbite Correction — Facial Axis opens 1°/4mm.

4. Crossbite Correction— Facial Axis opens 1°-1½°. Recovers

half the distance

5. Facial Pattern— Facial Axis opens 1°/1 S.D. dolichofacial;

1° closing effect against mechanics if brachyfacial.

In constructing the VTO, these factors must be taken into

consideration in deciding what can be expected to happen to the

facial axis. Treatment may open the facial axis as with Class II

mechanics, or it may close the facial axis as with the use of high

pull headgear or due to extraction. Facial axis opens 1° for 5mm

of convexity reduction, for 3mm of molar correction, and for

4mm of overbite correction. It opens 1° to 1½° in crossbite

correction and recovers half that amount. For every standard

deviation on the dolichofacial pattern side, it opens 1° and for

every standard deviation toward the brachyfacial side, it tends

to close one degree.

6. Superimpose at Basion along the Basion-Nasion plane.

Rotate "up" at Nasion to open the bite and "down" at Nasion to

close the bite using point DC as the fulcrum. This rotation

depends on anticipated treatment effects (whether treatment can

be expected to open or close the facial axis).

7. Trace Condylar Axis, Coronoid Process, and Condyle.

54

VTO — Mandibular Growth Prediction — Condylar Axis

Growth & Corpus Axis Growth

Return to tracing on page 745.

8. On condylar axis, make mark 1mm per year down from point

DC.

9. Slide mark up to the Basion-Nasion plane along the condylar

axis. Extend the condylar axis to XI point, locating a new XI

point.

10. With old and new XI points coinciding, trace corpus axis,

extending it 2mm per year forward of old PM point. (PM moves

forward 2mm/year in normal growth.)

11. Draw posterior border of the ramus and lower border of the

mandible.

55

VTO — Mandibular Growth Prediction — Symphysis

Construction

12. Slide back along the corpus axis superimposing at new and

old PM. Trace the symphysis and draw in mandibular plane.

13. Construct the facial plane from NA to PO.

14. Construct facial axis from CC to GN (where facial plane

and mandibular plane cross).

56

VTO — Maxillary Growth Prediction

15. To locate the "new" maxilla within the face, superimpose at

Nasion along the facial plane and divide the distance between

"original" and "new" Mentons into thirds by drawing two

marks.

57

15. To outline the body of the maxilla, superimpose mark

#1 (superior mark) on the original Menton along the facial

plane. Trace the palate (with the exception of point A).

58

VTO — Maxillary Growth Prediction — Point A Change

Related to BA-NA

These are the maximum ranges of Point A change with various

mechanics:

Point A is altered as a result of growth and mechanics. Point A

and a new APO plane are drawn by the following steps:

17. Point A can be altered distally with treatment. Place

according to orthopedic problem and treatment objectives. For

each mm of distal movement, Point A will drop ½mm.

59

18. Construct new APo plane.

VTO — Occlusal Plane Position

19. Superimpose mark #2 on original Menton and facial plane,

then parallel mandibular planes rotating at Menton. Construct

occlusal plane (may tip 3 degrees either way depending on

Class II or Class III treatment).

60

VTO — Dentition — Lower Incisor

The lower incisor is placed in relationship to the symphysis of

the mandible, the occlusal plane and the APO plane. The arch

length requirements and realistic results dictate its location.

20. For this exercise, superimpose on the corpus axis at PM.

Place a dot representing the tip of the lower incisor in the ideal

position to the new occlusal plane, which is 1 mm above the

occlusal plane and 1 mm ahead of the APO plane.

21. Aligning over the original incisor outline or using a

template, draw in the lower incisor in the final position as

required by arch length. The angle is 22° at +1mm to the APo

plane and + 1 mm to occlusal plane, but the angle increases 2°

with each mm of forward compromise.

61

VTO — Dentition — Lower Molar

Without treatment, the lower molar will erupt directly upward

to the new occlusal plane. With treatment, 1mm of molar

movement equals 2mm of arch length. We moved the lower

incisor forward 2mm in this case. There was also 4mm of

leeway space. Therefore, the following calculation allows us to

move the lower molar forward 4mm on each side:

lower incisor

forward 2mm = +4mm arch length

leeway space = +4mm arch length

+8mm arch length

(lower molar forward 4mm on each side)

62

22. Superimpose the lower molar on the new occlusal plane at

the molar (*), slide forward 4mm, upright molar and draw it in.

VTO — Dentition — Upper Molar

23. Trace the upper molar in good Class I position to the lower

molar. Use the old molar as a template.

63

Example of using the upper molar as a template.

VTO — Dentition — Upper Incisor

Place upper incisor in good overbite-overjet position (2½mm

overbite, 2½mm overjet) with an interincisal angle of 130° ±

10°. Open bite patterns at a greater angle, deep bite patterns at a

lesser angle.

24. Trace the upper incisor in its proper relationship, aligning

over the original incisor or by use of a template.

64

Example of using the upper incisor as a template

VTO — Soft Tissue — Nose

25. Superimpose at Nasion along the , facial plane. Trace bridge

of nose.

65

26. Superimpose at anterior nasal spine (ANS) along the palatal

plane.

27. Move prediction "back" 1mm per year (therefore, 2mm in

this case) along the palatal plane. Trace tip of nose fading into

bridge.

VTO — Soft Tissue — Point A and Upper Lip

.

28. Superimpose along the facial plane at the occlusal plane.

Using the same technique as for marking the symphysis, divide

the horizontal distance between the "original" and "new" upper

incisor tips into thirds by using two marks.

66

29. Soft tissue Point A remains in the same relation to Point A

as in the original tracing. Superimpose new and old bony Point

A, and make a mark at soft tissue Point A.

30. Keeping the occlusal planes parallel, superimpose mark # 1

(posterior mark) on the tip of the original incisor (slide forward

2/3rds).

Trace upper lip connecting with soft tissue Point A.

VTO — Soft Tissue — Lower Lip, Point B, and Soft Tissue

Chin

In constructing the lower lip, we bisect the overjet and overbite

of the original tracing and mark the point. We then bisect the

overjet and overbite of the VTO and mark the point.

OVERBITE, ORIGINAL , VTO , OVERJET

67

Return to tracing on page 745.

31.Superimpose interincisal points, keeping occlusal planes

parallel.Trace lower lip and soft tissue B point. The soft tissue

below the lower lip remains in the same relation to point B as in

the original tracing. Soft tissue point B drops down as the lower

lip recontours.

VTO — Completed Visual Treatment Objective

32. Superimpose on the symphyses,and arrange the soft tissue

of the chin. It "drops down" and should I be evenly distributed

over the symphysis taking into consideration reduction of strain

and bite opening.

68

If you have completed the steps, you now have your Visual

Treatment Objective. Take your VTO and superimpose it in the

69

five superimposition areas to establish your individual

objectives for this case.

In Superimposition Area 1 (Basion-Nasion at CC), Evaluation 1

is chin change. In this case, our objective is to allow 2° of

opening of the facial axis, to expect the amount of chin growth

shown, and to expect that the upper molar will grow down the

facial axis.

In Superimposition Area 2 (Basion-Nasion at Nasion),

Evaluation 2 is maxillary change. One of our objectives is to

reduce point A only 2mm in this case.

In Superimposition Area 3 (Corpus Axis at PM), Evaluation 3 is

the lower incisors. In this case, we are just tipping the lower

incisors slightly. In Superimposition Area 3 we also have

Evaluation 4, the lower molars. In this case, we are advancing

the lower molars approximately 4mm.

In Superimposition Area 4 (Palate at ANS), we have Evaluation

5, the upper molars. In this case, all we have to do is hold the

upper molars, even though this is a Class II division 1

malocclusion. Superimposition Area 4 also includes Evaluation

6, the upper incisors, and we see that we are going to have to

distalize the upper incisors.

In Superimposition Area 5 (Esthetic Plane at the intersection

with Occlusal Plane), we have Evaluation 7, the soft tissue, and

we see that we are going to have a great amount of soft tissue

reduction in this case.

70

Holdaway VTO

In using the Ricketts facial axis to find the mandibular and soft-

tissue chin position, Jacobsen and Sadowsky report three times

the growth of that at nasion, which is nearly always less than 1

mm per year. If my observations are correct, usually only 0.66

to 0.75 mm per year occurs, whereas growth on the facial axis is

reasonably consistent at 3 mm per year except during growth

spurts, especially the pubertal growth spurt, when it may

approach twice that amount in some boys. Another variation

from the article by Jacobsen and Sadowsky involves those cases

which at the time of retention will not fall into the best range in

the convexity H angle chart, on both the convex and the

concave sides. The use of the line to the vermilion border of the

upper lip perpendicular to the Frankfort plane plus the variable

H angle as skeletal convexity varies should be substituted

whenever upper lip curl or overall lip support appears

questionable by the usual method.

The overall effects of growth and treatment appear more

accurate with this simplified technique for growth forecasting

when used along with our own understanding of the treatment

responses of my own patients. Jacobsen and Sadowsky are

correct in their statement: "Growth responses are generally

predictable within certain limits and can be measured. The VTO

as described here is based on this philosophy. Newer studies,

however, have indicated quite clearly that one cannot rely

completely on the constancy of the growth pattern, since

increments of facial growth are not necessarily uniform in either

direction or rate. It is recognized that precise prediction of

skeletal or soft-tissue growth in amount or direction is beyond

our present knowledge. However, until the stage is reached

71

whereby orthodontists and/or scientific investigators are able to

accurately predict or determine direction and rates of growth,

we have no alternative but to avail ourselves of our present

knowledge of growth based on average increments."

Orthodontic treatment is monitored with progress head films,

usually at 6-month intervals. Whenever a case is encountered in

which growth is occurring in a different direction than expected,

a new midtreatment VTO is then constructed so that changes in

treatment procedures can be made and any disfiguring lip

responses can be avoided.

Whenever possible, it is a good plan to take head films for a

year or two prior to beginning treatment and thus develop a

growth profile for the case, assuming that there is an

opportunity to examine the patient that early. Developing

pretreatment growth profiles of our patients helps to overcome

our inadequacies in growth forecasting.

In addition to the six reference lines for the actual VTO

construction, three more shown in Fig. 1, A (dotted lines) are

added to the tracing to facilitate rapid copying of portions of the

pretreatment lateral cephalometric tracing.

First is the nasion to point A line. In longitudinal growth

studies of patients not undergoing orthodontic treatment, the

constancy of the angle SNA is extremely good— only about 1°

72

change in 5 years on the average. For 1- or 2-year forecasts, we

can disregard such a small amount. Reference lines or angles

that are very near to constants offer our best chance of

constructing visual treatment objectives that we can confidently

use as treatment goals and guides during orthodontic treatment.

Second is Ricketts' facial axis (foramen rotundum to gnathion).

This is used as a guide to direction of mandibular growth. Third

is the mandibular plane (Downs). Some may prefer to use the

Go-Gn line as a lower border of the mandibular reference line.

Either is acceptable, but the Downs mandibular plane line is

preferred because of its nearness to the actual lower border.

The headfilm should be taken with the patient's lips lightly

touching.

VTO steps

Step I (Fig. 1, B and C)

The first step is to place a clean sheet of tracing material over

the original tracing, copying (1) the frontonasal area, both hard-

and soft-tissue, with the soft-tissue nose carried down to near

the point where the outline of the nose starts to change

directions; (2) the sella-nasion line; and (3) the nasion-point A

line.

73

Step II (Fig. 2)

First, superimpose on the SN line and move the tracing to show

expected growth (0.66 to 0.75 mm per year unless a pubertal

growth spurt is expected from wrist plate studies).

Second, copy the outline of sella.

Third, either copy or change the facial axis (Ricketts' foramen

rotundum to gnathion) as you expect it to behave according to

the facial type of the patient and the treatment mechanics that

you customarily use in such cases. (The facial axis line is

usually opened about 1°, but it may even be closed if one is

confident that mandibular growth of the forward rotational type

will occur during treatment.)

Note: It is important to understand that the prediction of growth

at nasion, along the SN line, is actually an overall prediction for

all midfacial structures, including the nasal bone, the maxilla,

and the soft tissues.

74

Step III (Fig. 3, A and B)

First, superimpose the VTO facial axis on the original and move

the VTO up so that the VTO SN line is above the original SN.

The amount of movement will usually be 3 mm per year of

growth, except in accelerated growth-spurt periods. (Note: since

the facial axis may be opened or closed as judged from the

facial pattern, the SN lines will not be parallel if we have

changed the facial axis.)

Second, copy the anterior portion of the mandible, including the

symphysis and anterior half of the lower border. Also draw the

soft-tissue chin, eliminating any hypertonicity evident in the

mentalis area. (Slightly round out this area.)

Third, copy the Downs mandibular plane.

75

Step IV (Fig. 4, A and B)

First, superimpose on the mandibular plane and move the VTO

forward until the original sella and the VTO sella are in a

vertical relation.

Next, with the tracing in this position, copy the gonial angle, the

posterior border, and the ramus.

Finally, superimpose on sella to complete the condyle.

76

Note: At this point total vertical height has been forecast, as has

the forward location of the chin structures, both hard and soft,

and consideration will have been given to effects of treatment

mechanics on vertical dimension. One should not open the

facial axis more than 1° to 2° because greater opening than this

is usually inconsistent with good treatment mechanics.

Step V (Fig. 5, A and B)

First, superimpose the VTO NA line on the original NA line

and move the VTO up until 40% of the total growth is

expressed above the SN line and 60% below the mandible.

(Note: This may be varied as you perceive the facial type to be

short or long.)

Second, with the tracing in this position, copy the maxilla to

include the posterior two thirds of the hard palate, PNS to ANS

to 3 mm below ANS.

Third, also with the tracing in this same position, complete the

nose outline around the tip to the middle of the inferior surface.

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Note: The vertical growth of the nose over the usual 18 to 24

months of estimated treatment time keeps pace with the growth

from the maxilla vertically to the anterior cranial base. Thus, its

relationship to ANS is relatively constant. In some cases there

may be an elevation of the nasal bone and greater development

of the nasal bulk, but this is difficult to predict and thus some

noses will have changed form more than this VTO procedure

suggests.

Step VI (Fig. 6, A and B)

First, with the VTO still superimposed on the line NA, move

the VTO so that vertical growth between the maxilla and the

mandible is expressed 50% above the maxilla and 50% below

the mandible.

Second, with the tracing in this position, copy the occlusal plan.

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Note: Ideally, the occlusal plane is located about 3 mm below

the lip embrasure. This permits the lower lip to envelop the

lower third of the crowns of the upper incisor teeth. If the cant

of the occlusal plane is correct, it should be maintained. If not,

then it can be altered accordingly at this stage. In cases

involving short upper lips, it may not be practical to intrude the

upper incisors to this extent, but the vertical relationship of the

teeth and gingival tissue will be more esthetically pleasing if we

can reach this goal.

Step VII (Fig. 7, A and B)

Note: When there is a uniform distribution of the soft tissues in

the profile and the upper lip is of average length, and where the

cant of the H line is not adversely affected by excessive facial

convexity or concavity, the depth of the superior sulcus

measured to the H line is most ideal at 5 mm. A range of 3 to 7

mm allows one to maintain type with short and/or thin lips and

long and/or thick lips. Additional refinement of the technique,

which covers all of the above, is gained by use of the vertical

line from Frankfort plane to the vermilion border of the upper

lip, which is ideal at 3 mm with a range from 1 to 4 mm. To

find the point along the lower border of the nose outline at

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which the new H line will intersect it, both perspectives are

used in the exceptional cases just mentioned.

First, line up a straight-edge tangent to the chin and angle it

back to a point where there is a 3 to 3.5 mm measurement to the

superior sulcus outline of the original tracing and draw the H

line to this. As one redrapes the superior sulcus area to the new

tip of the upper lip point, a 5 mm superior sulcus depth

develops almost automatically. If you have trouble with this, the

use of the Jacobson-Sadowsky lip-contour template is

recommended.

Second, with the tracing still superimposed on the maxilla and

line NA and using the occlusal plane (Fig. 8, A and B) as a

guide for the lip embrasure, draw the upper lip from the

vermilion border to the embrasure. Then from the point on the

lower border of the nose where its outline stopped on the VTO,

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draw in the superior sulcus area. This is a gradual draping to the

new vermilion border outline.

Third, superimpose on line NA and the occlusal plane. Form the

lower lip, remembering that from 1 mm behind the H line to 2

mm anterior can be excellent, depending on variations of

thickness of the two lips. Again, most cases will fall on the H

line or within 0.5 mm of it.

Finally, complete the inferior sulcus drape from the lower lip to

the chin in a form harmonious with the superior sulcus. (Note:

The lips are not expected to have fully adapted to this position

in more than about one half of the cases at the time of

retention.)

Step VIII (Fig. 9, A and B)

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First, with the exceptions noted earlier, lip strain that shows up

as excessive upper lip taper is our first consideration. In the case

shown in Fig. 9, the basic lip thickness measurement was 15

mm and the thickness at the vermilion border was 10 mm. One

millimeter of taper is normal, leaving a lip strain factor of 4

mm.

Next we are concerned with how many millimeters the upper lip

is back from its original position. This is measured with the

tracings superimposed on line NA and the maxilla. In the

present case this also amounts to 4 mm.

The third consideration is maxillary incisor "rebound." When

the maxillary incisors have been retracted 5 mm or more and

the case has been slightly overtreated to a near edge-to-edge

incisor overbite and overjet relationship, we can expect about

1.5 mm relapse tendency. Obviously, there will be no tendency

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to move labially in those cases in which the upper incisor is not

retracted or in those cases, such as anterior crossbites and/or

Class III cases, in which the maxillary incisors have been

expanded labially. Here the incisor retraction is significant, and

we will use 1.5 mm for incisor rebound. In this particular

patient, then, the calculations would be as follows: (1)

Elimination of lip strain, 4 mm. (2) Upper lip change, 4 mm. (3)

Maxillary incisor rebound, 1.5 mm.

Finally, with the tracing still superimposed on line NA and the

maxilla, place the maxillary incisor template, taking cognizance

of the amount that it is to be repositioned (9.5 mm in this case),

its axial inclination, and the relationship of the incisal edge to

the occlusal plane, and draw the tooth.

Step IX (Fig. 10, A and B)

First, superimpose the VTO on the mandibular plane and

symphysis. Using the template, reposition the lower incisor to

be in ideal retention occlusion with the maxillary incisor, using

the occlusal plane as a guide and by tipping the tooth about the

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apex unless bodily movement is needed to improve the form of

the inferior sulcus area.

Second, with the tracing in this same position, measure the

amount of lingual movement of the lower incisors. Twice this

amount is the arch length loss due to lower incisor (uprighting)

lingual tipping or gain from labial tipping when indicated. This

loss of arch length is now combined with the arch length

discrepancy determined from the model to obtain the total arch

length discrepancy. In this case, the calculations would be (1)

arch length loss from reposition, 2 ´ 4 = 8 mm; (2) model

discrepancy, 2 mm; (3) total discrepancy, 10 mm.

Step X (Fig. 11, A and B)

With the tracing superimposed on the mandibular plane and

symphysis and using the occlusal plane as a vertical guide, draw

the lower molar where it must be to eliminate remaining space

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if extractions must be part of the treatment plan. In the case

shown in Fig. 11, each lower molar must be moved forward 2.5

mm.

Note: By using the VTO approach, you will come upon many

cases where mesially tipped lower molars can be uprighted to

gain all of the model arch length discrepancy when the incisor

position is adequate. Distal tipping of lower molars 2.5 mm can

allow nonextraction treatment in cases of a model discrepancy

of 5 mm. In other cases, especially those having a history of

thumb- or lip-sucking or in which serial extraction is

contraindicated, the VTO will show that the lower incisors need

to be moved forward, thus also increasing arch length and

reducing the need to extract. On occasion both approaches can

be used. In my opinion, lower incisors should not be moved

forward to a point more than 1 mm anterior to the A-pogonion

line, as posttreatment stability and long-term periodontal health

are usually endangered by so doing.

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The use of the VTO at this point to study and evaluate

anchorage and arch length is one of its great advantages. If the

lower molar must be moved anteriorly as much as 3.5 mm, the

lower second premolars will be removed. There are cases in

which there is an extremely thin alveolar process, particularly

those cases that have deficient lower face height where the

lower molars seem to get locked up in cortical bone if the

second premolars are extracted. Extraction of the second

premolars instead of the first premolars actually increases the

lower molar anchorage. When these two factors combine as

contraindications to forward lower molar movement, it is

sometimes better to look at judicious narrowing of the teeth

through stripping and polishing than to extract at all.

Step XI (Fig. 12, A)

86

First, using the occlusal plane and the lower first molar as a

guide, with a tooth template, position the upper first molar in

ideal Class I occlusion with the lower first molar.

Second, superimposing tracings on the original NA line and the

outline of the maxilla, evaluate the extent of upper molar

movement. In cases that worked out as lower arch nonextraction

cases, one may still need to think about other extraction

alternatives in the upper arch, such as upper second molars

when good third molar buds are developing or upper first

premolars.

Step XII (Fig. 12, B)

Note: As to how point A changes with incisor retraction, it is

imperative that the clinician study the before and after tracings

of many cases superimposed on the original NA line and best fit

of the maxilla to get the "feel" for this step. Obviously the

change in point A is greater when the upper incisor root apices

are moved a considerable distance than when the upper incisors

are tipped lingually. More change in A point is also evident

when the tracing is superimposed in this manner if we are going

to use heavier orthopedic forces, especially in younger patients

(in the mixed dentition).

87

When completed, the VTO can be used not only in case analysis

and treatment planning, but as we consider movement of the

various groups of teeth to correct a malocclusion the

mechanical procedures that will be most direct and efficient

practially suggest themselves. Mention must also be made of

the usefulness of VTOs to monitor treatment from periodic head

films. Using all that we think we know about growth and facial

types, on occasion we discover that nature has something else in

mind and we may need to change the course of our treatment

because of an unexpected growth response.

As we look at the retention tracing in Fig. 13, A, it is evident

that the tooth movement objectives of the VTO were

accomplished. The soft-tissue analysis measurements, while

greatly improved, still fail to meet the VTO goals, even though

the soft-tissue chin position has improved 1°. This is because

the lips still have not completely adapted to the tooth

movement. There is an increased measurement of the upper lip

thickness at the vermilion border from 10 to 16 mm. The H

angle has improved from 23° to 14°. However, with a 2 mm

convexity, ideally it should be 12°.

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In the 7-year follow-up shown in Fig. 13, B, the soft-tissue

facial angle is an ideal 90°. The superior sulcus form is

excellent to both reference lines. The upper lip has 1 mm of

normal taper, with a slight decrease in basic thickness. Skeletal

convexity is down to 0, and the H angle is ideal at 10°. The

upper lip has completed its adaptive changes and has a 1 mm

taper.

89

Conclusion

As we Orthodontists nowadays deal with more and more of

mixed dentition cases , many of whom may or may not present

with a skeletal malocclusion.

It is very important for us to determine the magnitude and

direction of growth if we are to treat these cases with a fair

amount of success.

It is a great challenge therefore to diagnose and to plan an ideal

treatment for these cases keeping in mind their growth potential.

The above mentioned studies were attempts made by various

people in order to ascertain the type of growth in their patients

and set forth guidelines for us to follow.

However we should not forget that every individual is unique in

his own aspect and therefore we should not jump to conclusions

but study our patients over time and treat them to their

individual requirements.

90

Bibliography

1) Bergersen, E.: The male adolescent growth spurt: Its

prediction and relation to skeletal maturation, Angle

Orthod. 42:319-338, 1972.

2) Bjork, A. and Helm, S.: Prediction of the age of

maximum pubertal growth in body height, Angle

Orthod. 37:134-143, 1967.

3) Chapman, S.: Ossification of the adductor sesamoid

and the adolescent growth spurt, Angle Orthod.

42:236-244, 1972.

4) Chertkow, S. and Fatti, P.: The relationship between

tooth mineralization and early radiographic evidence

of the ulnar sesamoid, Angle Orthod. 49:282-288,

1979.

5) Demirjian, A.; Buschang, R.; Tanguay, R.; and

Patterson, K.: Interrelationships among measures of

somatic, skeletal, dental and sexual maturity, Am. J.

Orthod. 88:433-438, 1985.

6) Fishman, L.: Radiographic evaluation of skeletal

maturation, a clinically oriented study based on hand-

wrist films, Angle Orthod. 52:88-112, 1982.

7) Grave, K. and Brown, T.: Skeletal ossification and the

adolescent growth spurt, Am. J. Orthod. 69:611-619,

1976.

8) Hassel, B. and Farman, A.: Skeletal maturation

evaluation using cervical vertebrae, Am. J. Orthod.

107:58-66, 1995.

91

9) Moore, R.; Moyer, B.; and Dubois, L.: Skeletal

maturation and craniofacial growth, Am. J. Orthod.

98:33-40, 1990.

10) Graber T.M. Orthodontics PPrinciples and

Practice. Saunders WB 1995.

11) Greulich, W. and Pyle, S.: Radiographic ossification

and the adolescent growth spurt, Am. J. Orthod.

69:611-619, 1959.

12) Hägg, U. and Taranger, J.: Maturation indicators

and the pubertal growth spurt, Am. J. Orthod.

82:299-308, 1982.

13) Holdaway RA. A soft tissue cephalometric analysis

and its u e in orthodontic treatment planning. Am J

Orthod 1983;84:1-28

14) Holdaway RA. A soft tissue cephalometric analysis

and its u e in orthodontic treatment planning. Am J

Orthod 1984;87:279-293

15) Jacobson A. Radiographic Cephalometery.

Quintessence 1995.

16) Johnston, F. and Hufham, H.: Skeletal maturation

and cephalofacial development, Angle Orthod. 35:1-

11, 1965.

17) Nanda, R.: The rates of growth of several facial

components measured from serial cephalometric

roentgenograms, Am. J. Orthod. 41:658-673, 1955.

18) O’Reilly, M. and Yanniello, G.: Mandibular growth

changes and maturation of cervical vertebrae, Angle

Orthod. 58:179-184, 1988.

92

19) Pileski, R.: Relationship of the ulnar sesamoid and

maximum mandibular growth velocity, Angle Orthod.

43:162-170, 1973.

20) Proffit W.R. Contemperory Orthodontics 3rd Ed.

Mosby 2000.

21) Sierra, A.: Assessment of dental and skeletal

maturity: A new approach, Angle Orthod. 57:194-208,

1987.

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