Department Of Orthodontics & Dentofacial Orthopedics Bapuji Dental COllege & Hospital Davangere 577004
Seminar on
ro!th "rediction & #$O "resented B% 'andan (ittur
CONTENTS
PAGE NO.
-INTRODUCTION
1
-GROWTH PATTERN, VARIABILITY, AND TIMING
2-6
-METHODS OF GROWTH PREDICTION
7-9
-WHAT ARE WE INTERSTED IN PREDICTING IN CRANIOFACIAL COMPLEX
1!-11
-INDICATORS OF S"ELETAL MATURITY -HAN -H AND D WRIS WRIST T RADI RADIOG OGRA RAPH PHS S AND AND
12-2 12-2# #
S"ELETAL MATURITY -CERVICAL VERTEBRAE AS
2$-27
MATURATIONAL INDICATORS -FRONTAL SINUS DEVELOPMENT AS
2%-29
INDICATOR OF PUBERTY -MANDIBULAR CANINE CALCIFICATION AND S"ELETAL MATURITY
&!-&1
-MANDIBULAR THIRD MOLAR DEVELOPMENT AND S"ELETAL
&2
MATURITY -PREDICTION OF MANDIBULAR ROTATION
&&-#!
-ARCIAL GROWTH OF THE MANDIBLE.
#1-#%
-VTO' VISUALI(ED TREATMENT OB)ECTIVE*
#9-$!
RIC"ETTS VTO
$1-7!
HOLDAWAY VTO
71-%9
-CONCLUSION
9!
CONTENTS
PAGE NO.
-INTRODUCTION
1
-GROWTH PATTERN, VARIABILITY, AND TIMING
2-6
-METHODS OF GROWTH PREDICTION
7-9
-WHAT ARE WE INTERSTED IN PREDICTING IN CRANIOFACIAL COMPLEX
1!-11
-INDICATORS OF S"ELETAL MATURITY -HAN -H AND D WRIS WRIST T RADI RADIOG OGRA RAPH PHS S AND AND
12-2 12-2# #
S"ELETAL MATURITY -CERVICAL VERTEBRAE AS
2$-27
MATURATIONAL INDICATORS -FRONTAL SINUS DEVELOPMENT AS
2%-29
INDICATOR OF PUBERTY -MANDIBULAR CANINE CALCIFICATION AND S"ELETAL MATURITY
&!-&1
-MANDIBULAR THIRD MOLAR DEVELOPMENT AND S"ELETAL
&2
MATURITY -PREDICTION OF MANDIBULAR ROTATION
&&-#!
-ARCIAL GROWTH OF THE MANDIBLE.
#1-#%
-VTO' VISUALI(ED TREATMENT OB)ECTIVE*
#9-$!
RIC"ETTS VTO
$1-7!
HOLDAWAY VTO
71-%9
-CONCLUSION
9!
-BIBLIOGRAPHY
91-9&
2
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
G+/ P0+, V0+304353, 0 T383
In studies of growth, the concept of pattern is an important one. Pattern represents proportionality. The C:/05;0<05 +03 = +/ 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 taes up almost !"# of total body length. $t the time of birth, the trun and limbs have grown faster so that only %"# of body length is the head. $t adulthood the head is only 12# the body length. $t birth legs are 1&% the body length, at adulthood they are about half the body length. This reflects the 'ephalocaudal gradient of growth. (ven 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. $lso mandible continues to grow more and later than the growth of ma)illa.
%
$nother aspect of normal growth pattern is that, not all tissues of the body grow at the same rate. This is graphically illustrated by the S;088> +/ ;<+?>.
*rowth does not tae place at a uniform rate, but there is acceleration and retardation in the rate of growth. The accelerative phases are called +/ >:<+>. There are % ma+or growth spurts recorded by oodside. They seemed to be se) lined. First peak occurred at %yrs of age. It is called 'hildhood growth spurt. Second peak at - to yrs in girls and to /yrs in boys. It is called 0uvenile growth spurt. Third peak was at 11 to 12yrs in girls and 1 to 1!yrs in boys. It is the prepubertal growth spurt.
The tendency is generally for boys to have 2 or % peas, while large numbers of girls show only 2 peas. ery few girls show the mi)ed dentition growth spurt. 3ut all show the pubertal growth spurt.
$nother important aspect of growth is ariability. 4bviously everyone is not alie 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 e)treme of the normal variation or falls outside the normal range. This is determined, using +/ ;/0+> for the particular population standards.
!
The final ma+or concept in Physical growth and development is T383.
ariation in Timing occurs because the same event happens in different individuals at different times. Therefore 'hronologic age often is not a good indicator of an individual5s growth status.
-
The effectiveness of a 3iologic or 6evelopmental ages in reducing timing. variability maes this approach useful in evaluating a child5s growth status.
METHODS OF GROWTH PREDICTION illiam 7irschfield and 8obert 9oyers :1/1; Several predictive methods are used in industry and science. e may group these under following headings. 1. Theoretical 2. Regression 3. Experimental 4. Time series
THEORETICAL METHODS OF PREDICTION:
$stronomers discovered earth si
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. 0ohnston has recently evaluated and reviewed regression methods of approach to craniofacial prediction. $mong his conclusions is that=
>
:1; The ultimate accuracy of cephalometric prediction may be limited to some e)tent by intrinsic errors with the cephalometric method itself. :2; 'ontemperory methods seem inadequate to provide an efficient estimate of individual changes attributed only to growth. 3urstone has reviewed some of the problems of attac and of selection of independent variables with regard to growth prediction.
EXPERIMENTAL
METHODS:
()perimental methods are based on the clinical e)perience 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 nown e)ample of the e)perimental method in craniofacial growth prediction is that of 8icetts, whose estimates of growth prediction for the individual utili
TIME SERIES METHOD@
3ecause of the great interest in prediction of craniofacial growth and the limitations of the methods thus far tried, it seems pertinent to as whether there might be some other method of prediction, as yet, untried on growth problems which /
would provide the desired accuracy, efficiency and individuality for the clinician. 4perations 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 e)tracts in a mathematical form the fundamental nature of the process as it relates to time. 2.smoothing methods, either moving averages or e)ponential, which operate to give representative or average values to the parameters of a previously derived time series equation .?or purpose of analysis a time series is considered to be composed of four parts. These are 1. Trend or long term movement 2. 4scillations about a trend %. 'yclic or periodic events . 8andom 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.
1"
WHAT
ARE
WE
PREDICTING
IN
INTERSTED
IN
CRANIOFACIAL
COMPLEX F<<+ >3 = :0+= the prediction of future si
3urstone, his primarily a problem of predicting future increments which are to be added to a si
R503>/3: = :0+>@ 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 si
T383 = +/ ?>@ 3ecause growth does not proceed
evenly, certain facial dimensions demonstrate maret changes in their velocity curve. These @spurtsA mae 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. V;+> = +/@ 9ost predictive methods thus far presume
a continuation of the pattern first seen thereforeB 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. 9andibles, which grow vertically for a period of time ine)plicably, start to grow hori
11
V5;3 V5;3 = +/ +/@@ It would be of use to now the future
e)pe e)pect cted ed rate rate of grow growth th.. Pred Predic icti tion on of velo veloci city ty is most most important during the pubescent spurt.
T/ == T/ ==; ; = +/ +/ 3 3;; / /+ +0: 0: 0 0 = / / 04? 04? :+3; :0+08+>@ 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.
12
I3;0+> = S505 M0<+3 HAND WRIST RADIOGRAPHS AND S"ELETAL MATURITY
The first recorded 7andCwrist radiograph film was published by Sydney 8owland of Dondon in 1>/-. This was +ust months after after the the anno announ unce ceme ment nt of the the disc discove overy ry of the the EC8a EC8ay y by 8oentgen. In 1/21/2- 'arter 'arter reporte reported d on a radiogra radiographi phicc study study of carpal carpal bones in children. 7oward :1/2>; using hand ECrays, reported on the physiologic changes of bone centers in a large group of male and female children from ages !to1-. In 1/2/ two comprehensive growth studies were begun, one at the the
3rus 3rush h
found oundat atio ion n
of
este estern rn
8eser eserve ve
Fnive nivers rsiity, ty,
'leveland, 4hio under the direction of T. ingate. Todd, and the the othe otherr at the the 7arva 7arvard rd Schoo Schooll of Publ Public ic 7eal 7ealth th,, 3ost 3oston on,, 9assachusetts under 7arold Stuart. Todd5s wor was continued 1%
after after his death by illiam illiam *reuli *reulich. ch. S. Idell Idell Pyle was also involved in the 'leveland pro+ect, and it was she who was instrumental in preparing the standards of growth in popular use today utili
pube puberal ral
stat statur ural al grow growth th,a ,and nd mena menarc rche he in girl girlss occu occurr rred ed afte afterr the the ma)imum puberal growth. 7elm et al :1/1; they found that one stage :PP2H; invariably occurred one to five years before ma)imum growth. The stage 1
9P% cap occurred close to the tome of the along with the ulnar sessamoid. The 6P% stage occurred from one to three years after the ma)imum. 3rown, 3arrett *rave :1/1; found that two other events occurred significantly at least one year prior to pea growth velocity. They were initial ossification of hoo of hamate as well as of pissiform. Pilesi et al :1/%; reported that 2"# females and 2!# males did not e)hibit appearance of sessamoid, until after ma)imum growth velocity was reached. *rave and 3rown :1/-; suggested that the epiphyseal union of radius could be used to assess the duration of retentive phase of treatment. 3owden :1/-; cautioned that strict reliance on 7and wrist indicators to determine the state of facial growth could not be guaranteed and that the relationship, although valid, was probably not absolute. *rave and 3rown :1//; described the use of hand wrist film in orthodontic treatment to tae advantage of the puberal growth spurt.
1!
G+0? 0 B+ have recorded 1ossification events
1.
PP2H
Pro)imal phalan) of second fingerB
epiphysis is as wide as diaphysis 2.
9P%H
9iddle phalan) of third fingerB
epiphysis is as wide as diaphysis %.
7C1
7ooing of 7amate JStage 1
.
Pisi
$ppearance of Pissiform
!.
8H
8adiusB epiphysis is as wide as
diaphysis -.
S
$ppearance of Flnar Sessamoid at
metacrpophalangeal +oint of first ?inger .
7C2
>.
9P%cap
7ooing of 7amate JStage 2 9iddle phalan) of third fingerB
epiphysis caps its diaphysis /.
PP1cap
Pro)imal phalan) of first fingerB
epiphysis caps its diaphysis 1".
8cap
11.
6P%µ
8adiusB epiphysis caps its diaphysis 6istal phalan) of third fingerB
complete epiphyseal union 12.
PP%µ
Pro)imal phalan) of third fingerB
complete epiphyseal union 1%.
9P%µ
9iddle phalan) of third fingerB
complete epiphyseal union 1.
8 µ
8adiusB complete epiphyseal union
1-
The events fell logically into % groups with respect to ossification times E?>, /3;/ ;;<++ 4=+ :0 +/ ?5;3
1.
PP2H
2.
9P%H
%.
7C1
.
Pisi
!.
8H
E?> /3;/ ;3;3 :0 +/ ?5;3
-.
S
.
7C2
>.
9P%cap
/.
PP1cap
1
1".
8cap
E?> /3;/ =55 :0 /3/ ?5;3 11.
6P%µ
12.
PP%µ
1%.
9P%µ
1.
8 µ
?usion 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.
1>
?ishman :1/; has given 11 Seletal 9aturity Indicators:S9I;
1/
Epiphysis as wide as Diaphysis 1.
Third finger J pro)imal phalan)
2.
Third finger Jmiddle phalan)
%. ?ifth fingerC middle phalan) 4ssification .
$dductor Sessamoid of thumb
apping o! Epiphysis !.
Third fingerC 6istal phalan)
-.
Third fingerC 9iddle phalan)
.
?ifth fingerC 9iddle phalan)
F"sion o! epiphsis and Diaphysis >.
Third fingerC 6istal phalan)
/.
Third finger JPro)imal phalan)
1".
Third fingerC 9iddle phalan)
11.
8adius
A;;5+03 +/ ?5;3 :+3. H3/ +/ ?5;3 :+3. D;5+03 +/ ?5;3 :+3.
SMI 1 - # SMI SMI
#-7 7 11
*irls generally reach point of pea growth velocity at S9I ! and boys at S9I -.
2"
3oys do not tae 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.
)<530 S3+ '19%!* has described - stages of development on
the hand wrist radiograph.
S0 1 'E0+5*@ 1. $bsence
of P3>3=+8
2. $bsence
of H = H080
%. (piphysis
of pro)imal phalan) of second digit 'PP2* narrower
than its shaft
S0 2 'P+:<4+05*@ 1. Pro)imal
phalan) of second digit and its epiphysis are equal in
width 'PP2*. 2. Initial
ossification of / = /080 .
%. Initial
ossification of :3>3=+8.
S0 & 'P<4+05 >*@ 1. 3eginning
calcification of U50+ >>>083.
2. Increased
width of :3:/>3> = PP2
%. Increased
calcification of /080 / and :3>3=+8.
S0 # 'P<4+05*@ 1.
C05;3=3 <50+ >>>083
2. 'apping
of shaft of middle phalan) of third digit by its
epiphysis'MP&;0:*
S0 $ 'P<4+05 D;5+03*@ 21
1.
U50+ >>>083 =<55 ;05;3=3
2. 'alcification
of the shaft of middle phalan) of third digit by
its epiphysis 'DP&<*. %.
$ll phalanges and carpals fully calcified.
.
(piphysis of radius and ulna not fully calcified with
respective shafts. S0 6 'G+/ ;8:53*@
Go remaining growth sites.
22
H0 0 T0+0+ '19%2*
investigated a prospective
longitudinal study in 212 Swedish children. 6ata comprised of Standing height, Tooth emergence, pubertal development and 7andwrist radiographs.
$dolescent growth was studied by graphical analysis of the unsmoothed incremental curves of standing height. The curves 2%
were based on the annual increments from % to 2" years. ?irst, the pea height velocity 'PHV* was located on incremental curves for each sub+ect. The growth curves were observed for reliable estimates of the beginning and end of the pubertal growth spurt. $ mared, continuous increase in growth rate up to P7 was found from one growth event, ONSET.
In all
sub+ects the increase in growth rate during puberty was more than 1"mmB that is , ONSET and PHV did not coincide. $ mared, continuous deceleration in growth occurred down to the first annual increment below 2"mm. 'END*.
6ental development was assessed by dental emergence stages. Seletal development was analy
yrs. Pubertal development was analy yrs of age by determining menarche in girls and change in voice in boys.
2
R><5>@ T/ :<4+05 +/ >:<+@
ONSET was at 1"."yrs in
girls and 12.1 yrs in boys. PHV was at 12." yrs in
girls and 1.1 yrs in boys. END was at 1.> yrs in
girls and 1.1 yrs in boys.
D05 ?5:8 0 :<4+05 +/ >:<+@
The dental emergence stages were not useful as indicators of pubertal growth spurt.
S505 ?5:8 0 / :<4+05 +/ >:<+ @
$t ONSET "# girls and 2!# boys had ossified ulnar sessamoid. 'S*. 2!
$t PHV /"# of the sub+ects were in either >0 MP&FG or >0 MP&-G.
$t END /!# boys and >"# girls were in one of the three radius >0>. 'R-I, R-I), R-)*
P<4+05 ?5:8 0 / :<4+05 +/ >:<+@
9enarche was reached 1.1 yrs after PHV. Pubertal voice was attained ".2 yrs before PHV. 9ale voice was attained "./ years after PHV.
2-
2
C+?3;05 V+4+0 0> M0<+0305 I3;0+>
Damparsi :1/2;
used cervial vertebrae morphology to
assess pubertal growth spurt. 7assel and ?arman :1//!; modified his criteria and gave - stages of cervical vertebrae development. *arcia J?ernande< :1//>; related these stages with the S9I given by ?ishman. The si) stages are as follows
I3303 'SMI 1 0 2*
the cervical vertebrae are wedge
shaped, with the superior vertebral borders tapering from posterior to anterior. #$to 1$$% growth can &e anticipated at this stage. A;;5+03 'SMI & 0 #* concavities develop along the
inferior borders of '2and '%. The bodies of '% and ' are nearly rectangular, and the inferior border of ' is flat. 'rowth acceleration &egins at this stage( when )*+#*% o! adolescent growth can &e anticipated. T+0>33 'SMI $ 0 6* distinct concavities develop on the
inferior borders of '2 and '%. $ concavity begins to develop at inferior border of ', and the bodies of '% and ' are rectangular. ,dolescent growth accelerates towards peak -elocity( with 2*+ )*% o! adolescent growth anticipated.
2>
D;5+03 'SMI 7 0 %* 'lear concavities are seen on the
inferior borders of '2, '%, and ' with the bodies of '% and ' nearly square. nly 1$+2*% o! adolescent growth remains. M0<+03 'SMI 9 0 1!* $ccentuated cavities are seen on
the inferior borders of '2, '%, and ', and the bodies of '% and ' are nearly square. Final mat"ration takes place at this stage when *+1$% adolescent growth can &e anticipated. C8:53 'SMI 11* 6eep concavities are seen on the inferior
borders of '2, '%, and ', and the vertebral bodies are more vertical than hori
2/
%"
%1
F+05 S3<> D?5:8 0> 33;0+ = :<4+
Sabine
8uf
and
7ans
Pancher<
:1//-;
evaluated
the
development of the frontal sinus to the longitudinal data of the sub+ect5s growth charts. 8esults showed that ?rontal sinus growth velocity at puberty is closely related to body height growth velocity. ?rontal sinus shows a well defined pubertal pea 'S:*, which on an average, occurs 1. years after the pubertal body height pea. 'B:*. If the only prediction was that whether pubertal growth ma)imum has passed the precision of this method was high :/" #;. 3ut if incidence of body pea was to be predicted the accuracy is only !!#. 9oreover, it is only possible if 2 cephalograms appro)imately 1C2 yrs spaced, of the same individual are available.
%2
%%
M034<50+ C03 ;05;3=3;03 0 >505 M0<+3
Sandra 'outinho et al in 1//% related canine calcification stages to >505 80<+3 33;0+> as shown in the figures. They concluded that the initiation of pubertal growth spurt relates with >0 F of canine calcification. S0 G occurs appro)imately around 1 yrs before PHV in
boys but only ! months before PHV in girls. The intermediate stage between >0 F and >0 G should be used to identify the early stages of pubertal growth spurt.
%
%!
M034<50+ /3+ M50+ ?5:8 0 S505 80<+3
(ngstorm :1/>%; compared lower third molar development stages with seletal maturity indicators.
Third molar stages were A@ Tooth germ visible as rounded radiolucency B@ cusp minerali
Seletal indicators used were
PP2@ pro)imal phalan) of second finger, epiphysis
as wide as diaphysis MP& ;0:@ middle phalan) third finger, epiphysis caps
the diaphysis DP& <@
distal phalan) of third finger, complete
epiphyseal union. R<@ 6istal epiphysis of radius, complete
epiphyseal union. $t stage PP2 third molar crown completion too place in ma+ority of sub+ects. $t stage MP& ;0: crown completion in all and root development had begun in few sub+ects. $t DP& < 8oot length was completed in some sub+ects. $t R < one third sub+ects crown was complete, half the root was complete in other one third, and in the remaining third root had reached full length.
%-
PREDICTION OF MANDIBULAR ROTATION In 1/-/ 3+or discussed three methods of growth prediction 1;
$ 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 e)tent mass the actual rotation. 2;
$ 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. %;
$ structural method is described by which it may be
possible to predict, from a single cephalogram, the course of rotation, where this feature is mared. This method is based on the information gained from implant studies of the remodeling process of the mandible during growth. The principle is to recogni
S+<;<+05 >3> = +/ +03@
?rom the clinical stand point, it is important to detect e)treme types of mandibular rotation occurring during growth. Seven structural signs of e)treme growth rotation are considered in relation to the condylar growth direction. Got all of them will be found in a particular individual, but the greater the number that %
are present, the more reliable the prediction will be. 7owever, it is evident that these signs are not so clearly developed before puberty.
%>
The seven signs are related to the following features 10 nclination o! the condylar head. 20 "r-at"re o! the mandi&"lar canal. %/
30 Shape o! the lower &order o! the mandi&le. 40 nclination o! symphisis( 0 nterincisal angle )0 nter premolar or inter molar angles 0 ,nterior lower !ace height.
I /+305 +3 33?3<05>@
1; The condyles are inclined forward. 2; The mandibular canal curvature tends to be greater than that of the mandibular contour. %; The lower border presents with pronounced apposition below the symphysis and the anterior part of the mandible produces an anterior rounding, with a thic cortical layer, while the resorption at the angle produces a typical concavity. ; The symphysis swings forwards in the face, and the chin is prominent. !; The difference in the inter incisal angle is evidentB in spite of the compensatory tipping of the lower incisors is more when compared to vertical growing individuals. -; The difference in the interpremolar and inter molar angles in the two growth types is also clear is more in hori@
1; the condyle is bacwardly inclined. 2; The mandibular canal is straight or in pathologic cases, it may even curve in the opposite direction. %; The lower border of the mandible anteriorly rounding is absent and the cortical layer is thin and lower contour at the +aw angle is conve). "
; The inclination of the symphysis is swung bac, with receding
chin.
The
evaluation
is
complicated
by
the
simultaneous remodelling of the alveolar process in the opposite direction, as is e)emplified by the cranium with openbite. !; The inter incisal angle is reduced in this case due to more proclination. -; The inter premolar and molar angles in this growth pattern is reduced. ; The over development of D.$.?.7 is seen in bacward rotating mandibles. Taing 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. ?rom 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. $ 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 +oints, as it usually imagined, although this is not readily evident from e)amination by conventional techniques. There follows schematic account of the various types of rotation of the mandible that may be recogni
3+or based on the location of '&8 classified =+0+ +03 % types= T: I@ There is a forward rotation about the centers in the
condyles which gives rise to a deep bite, in which the lower 1
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.
T: II@ ?orward growth rotation of the mandible about a
center located at the incisal edge of the lower anterior teeth is due to the combination of mared development of the posterior face height and normal increase in the anterior height. The posterior part of the mandible then rotates away from ma)illa. 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. 3ecause of the vertical direction of the condylar growth, the mandible is lowered more than it is carried forward. 3ecause of the muscular and ligamentous attachments, the lowering taes place as a forward rotation in relation to the ma)illa, with the center at the incisal edges of the lower incisors. The eruption of the molars eeps pace with the rotation. 3ecause of the simultaneous mared resorption below the gonial angle, the height in this region may not increase to a great e)tent and the lower border undergoes a characteristic remodelling. 2
T: III@ In anomalous occlusion of the anterior teeth the
forward rotation of the mandible with growth changes its character in the case of large ma)illary over+et or mandibular over+et, the center of rotation no longer lies at the incisors but is displaced bacward 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.
B0;0+ +03 is less frequent than forward rotation and
has been e)amined by the implant method in considerably fewer sub+ects two types have been recogni
T: I@ 7ere the center of the bacward rotation lies in the
temporomandibular +oints. 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.
3acward rotation of the mandible about a center in the +oints 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 bacward rotation of the mandible, with overdevelopment of the anterior face height and possibly openbite as a consequence.
T: II@ 3acward 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. $s 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 bacward. In this type of rotation the symphysis is swung bacward and the chin is drawn bac below the face. The soft tissue of the chin may not follow this movement, and a characteristic double chin can form. 3asal 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 lie 3+or, Davergne and *asson found an annual rotation of 1."" which ranges from " " to 2.1"" when compared to sells nasion line and found " during a period of si) years around the pubertal growth spurt in the forward rotation growth pattern individuals. In posterior rotation growth pattern the mean degree of rotation was J ".%"" with range from J "."-" to ".>!" when related to S.G. line.
!
ARCIAL GROWTH = / M0345@ 8.9.8icetts 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 foring of the stress lines at the terminus of the oblique ridge on the medial side of the ramus ::. E?0; 4n the basis of this, a primary method of prediction of development was devised. 3y plotting a line through the long a)is of the condyle and nec and e)tending it to the form during growth had been studied. 'onsequently, findings from this method suggested that the technique could serve as a woring hypothesis for growth prediction for the clinical problem of prognosis of growth. The
ne)t
move
was
to
identify
a
@central
coreA
cephalometrically. ()ternal mandibular form is sub+ect to remarable 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.
-
9ethod for determination of 3 point= R1H deepest point on the subcoronoid incisure R2Hpoint selected opposite 81 on the posterior border of
ramus. R&Hdepth of the sigmoid notch R#Hpoint selected directly inferiorly on the lower border of
ramus $ point at the superior aspect of the symphysis was selected as supra pogonion. It was labelled :.8. :Protuberance menti; This is substantiated as reference because :i; it is located at appro)imately a stress centerC8icetts. :ii; Its site of a reversal line J(nlow and :iii; it is consistent with the findings from implant studies 3+orB 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. 3y bisecting the height and width of the ramus at its narrowest dimension a geometric center was determined and labelled 3 point. Investigation of normal mandible from 2! dried sulls showed in every instance that this point fell in contract with the mandibular canal. 8icets used a point described previously with laminagraphs at the bisection of the condyle nec as high as visible in the cephalogram film below the fossa. This was labelled D; $ccordingly by connecting D; point with 3 a repeated condyle a)is was established. ?urther by connecting 3 to :.8. J a corpus a)is was erected.
It is an angle formed by the intersection of the condylar a)is :DC-3; and a bacward e)tension : 3-:.8.; from the center of ramus to suprapognion. The mean is 2- K . This angle has a tendency to increase with age :".!&yrs;. The first mandible is a reterognathic one with a steep mandible plane and grows vertically. The middle one is normal and the %rd mandible with an high angle is indicative of a forward growing mandible. 'onsequently 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 a)is and registered at 3 point were found to bend about L degree each year. It was recogni
>
8esults showed that the arc si!" years old mandible given to 8icetts by the late illiam downs revealed the secret. 4n 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 e)ternal cortical bone and clearly showed stress lines in the outer and inner plates. The lines thus e)hibited the design of the mandible /
for bracing e)ternally. :M1 foring of the stress lines at the base of the coronoid process;. ()perimentally 2 new points :E?0 and TR ; were located geometricallyB point E?0 is also a biologic line in the ramus. hen the si
point and R& the bisections of which locates point E?0. E?0 in turn is used to find a TR :true radius; measured from pm point. Gow using TR . as the center of a circle, an arc is drawn. M< 9urray point is the crossing of this arc on the sigmoid notch. 3y constructing the growth arc, growing the mandible on this arc, and e)tending the processing and drifting angular process a new forecasting technique is developed. 7aving become satisfied with this arc as a tool for prediction the ne)t 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 9u while others grew significantly. The short and small condyles were found not to grow and good wellCformed condylar heads were found to grow by ". mm and average !"
condyles ".2 mm&year. *rowth increment for coronoid J".> mm&year. SymphysisC1mm&year. $pposition of the lower border of the symphasis for males occurs at about 1mm each >yrs. ?rom point M< the mandible is grown out on the arc at the sigmoid notch about 2.!mm&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 ".2mm&year are given. The drift of the mandible occurs almost at a pace of !"# of the total mandible growth. In the series of the steps in forecasting of the mandible growth. $rt wor 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 ".mm&year. Implication of article growth prediction 1.;
It appears that the symphysis rotates essentially during
growth from a hori
This phenomenon e)plains why reversal lines are
observed at the area of pogonion and suprapogonion. %.;
It e)plains why the mandible plane changes e)tensively
in some individual and not in others.
!1
.;
It shows why anylosed teeth are observed to affect
occlusal plane development. !.;
It e)plains how the early anylosis 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 -.;
It suggests a reason why mandible anchorage is risy in
retrognathic faces because less space is available for molar eruption due to a more vertical eruption in that type than prognathic types. .;
It
e)plains
why
good
dentures
may
become
progressively more crowded in long tapered faces and sometimes even in normal faces. >.;
It suggests that abnormal growth or margins of the
mandible can be understood as a friction of relative contribution of the coronoid and process.
!2
DRAW BAC" OF ARCIAL GROWTH PREDICTIONS@
1.;
It relies heavily on the operator5s sill in tracing the
cephalogram. 9inor tracing errors could produce a wrong prediction. 2.;
9itchell and 0ordan :1/!; in their study to evaluate
8icetts prediction method concluded that 8icetts uses the patients chronologic age rather than the seletal age since he requests no hand Jwrist 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 resultsB
particularly if the time interval is short and the patients is near maturity. :8icetts presumes that girls are grown to 1.! years and boys to 1/ years; %.;
Since the growth increments constants are mainly
derived from western population it is to be found out if these constants are applicable to Indian sub+ects.
!%
VTO' V3><053 T+08 O4;3?* The term T4 which stands for isuali
the original tracing and the forecast goal, the orthodontist may evaluate progress along a definitely prescribed route. $ny deviation from e)pected progress will become apparent immediately and the need for midcourse corrections will be recogni
!!
R3;> VTO
$ stepCbyCstep procedure to construct a T4 for a in the following sequence :putting in average growth for an estimated twoCyear period of active treatment and the ob+ectives that we wish to achieve with our mechanics;= 1. the cranial base prediction 2. the mandibular growth prediction %. the ma)illary growth prediction . the occlusal plane position !. the location of the dentition -. the soft tissue of the face
!-
VTO C+0305 B0> P+3;3
Place the tracing paper over the original tracing and starting at '' point, follow these steps to construct the cranial base= 1. Trace the 3asionCGasion Plane. Put a mar at point ''. 2. *row Gasion 1mm&year :average normal growth; for 2 years :estimated treatment time;. %. *row 3asion 1mm&year :average normal growth; for 2 years :estimated treatment time;. . Slide tracing bac so Gasions coincide and trace Gasion area. !. Slide tracing forward so 3asions coincide and trace 3asion area.
!
VTO M034<50+ G+/ P+3;3 R03
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=
M;/03;>
1. 'onve)ity 8eduction ?acial $)is opens 1Q&!mm. !>
2. 9olar 'orrection ?acial $)is opens 1Q&%mm. %. 4verbite 'orrection ?acial $)is opens 1Q&mm. . 'rossbite 'orrection ?acial $)is opens 1QC1LQ. 8ecovers half the distance !. ?acial Pattern ?acial $)is opens 1Q&1 S.6. dolichofacialB 1Q closing effect against mechanics if brachyfacial. In constructing the T4, these factors must be taen into consideration in deciding what can be e)pected to happen to the facial a)is. Treatment may open the facial a)is as with 'lass II mechanics, or it may close the facial a)is as with the use of high pull headgear or due to e)traction. ?acial a)is opens 1Q for !mm of conve)ity reduction, for %mm of molar correction, and for mm of overbite correction. It opens 1Q to 1LQ in crossbite correction and recovers half that amount. ?or every standard deviation on the dolichofacial pattern side, it opens 1Q and for every standard deviation toward the brachyfacial side, it tends to close one degree. -. Superimpose at 3asion along the 3asionCGasion plane. 8otate NupN at Gasion to open the bite and NdownN at Gasion to close the bite using point 6' as the fulcrum. This rotation depends on anticipated treatment effects :whether treatment can be e)pected to open or close the facial a)is;. . Trace 'ondylar $)is, 'oronoid Process, and 'ondyle.
!/
T4 9andibular *rowth Prediction 'ondylar $)is *rowth 'orpus $)is *rowth 8eturn to tracing on page !. >. 4n condylar a)is, mae mar 1mm per year down from point 6'. /. Slide mar up to the 3asionCGasion plane along the condylar a)is. ()tend the condylar a)is to EI point, locating a new EI point. 1". ith old and new EI points coinciding, trace corpus a)is, e)tending it 2mm per year forward of old P9 point. :P9 moves forward 2mm&year in normal growth.; 11. 6raw posterior border of the ramus and lower border of the mandible.
-"
VTO M034<50+ G+/ P+3;3 S8:/>3> C>+<;3
12. Slide bac along the corpus a)is superimposing at new and old P9. Trace the symphysis and draw in mandibular plane. 1%. 'onstruct the facial plane from G$ to P4. 1. 'onstruct facial a)is from '' to *G :where facial plane and mandibular plane cross;.
-1
VTO M03550+ G+/ P+3;3
1!. To locate the NnewN ma)illa within the face, superimpose at Gasion along the facial plane and divide the distance between NoriginalN and NnewN 9entons into thirds by drawing two mars.
-2
1!.
To outline the body of the ma)illa, superimpose mar
R1 :superior mar; on the original 9enton along the facial plane. Trace the palate :with the e)ception of point $;.
-%
VTO M03550+ G+/ P+3;3 P3 A C/0 R50 BA-NA
These are the ma)imum ranges of Point $ change with various mechanics=
Point $ is altered as a result of growth and mechanics. Point $ and a new $P4 plane are drawn by the following steps= 1. Point $ can be altered distally with treatment. Place according to orthopedic problem and treatment ob+ectives. ?or each mm of distal movement, Point $ will drop Lmm.
-
1>. 'onstruct new $Po plane. VTO O;;5<>05 P50 P>33
1/. Superimpose mar R2 on original 9enton and facial plane, then parallel mandibular planes rotating at 9enton. 'onstruct occlusal plane :may tip % degrees either way depending on 'lass II or 'lass III treatment;.
-!
VTO D33 L+ I;3>+
The lower incisor is placed in relationship to the symphysis of the mandible, the occlusal plane and the $P4 plane. The arch length requirements and realistic results dictate its location. 2". ?or this e)ercise, superimpose on the corpus a)is at P9. 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 $P4 plane. 21. $ligning 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 22Q at K1mm to the $Po plane and K 1 mm to occlusal plane, but the angle increases 2Q with each mm of forward compromise.
--
VTO D33 L+ M50+
ithout treatment, the lower molar will erupt directly upward to the new occlusal plane. ith treatment, 1mm of molar movement equals 2mm of arch length. e moved the lower incisor forward 2mm in this case. There was also mm of leeway space. Therefore, the following calculation allows us to move the lower molar forward mm on each side= lower incisor forward 2mm H Kmm arch length leeway space H Kmm arch length K>mm arch length :lower molar forward mm on each side;
-
22. Superimpose the lower molar on the new occlusal plane at the molar :;, slide forward mm, upright molar and draw it in.
VTO D33 U::+ M50+
2%. Trace the upper molar in good 'lass I position to the lower molar. Fse the old molar as a template.
->
E08:5 = <>3 / <::+ 850+ 0> 0 8:50.
VTO D33 U::+ I;3>+
Place upper incisor in good overbiteCover+et position :2Lmm overbite, 2Lmm over+et; with an interincisal angle of 1%"Q 1"Q. 4pen bite patterns at a greater angle, deep bite patterns at a lesser angle. 2. Trace the upper incisor in its proper relationship, aligning over the original incisor or by use of a template.
-/
E08:5 = <>3 / <::+ 3;3>+ 0> 0 8:50
VTO S= T3>>< N>
2!. Superimpose at Gasion along the , facial plane. Trace bridge of nose.
"
2-. Superimpose at anterior nasal spine :$GS; along the palatal plane. 2. 9ove prediction NbacN 1mm per year :therefore, 2mm in this case; along the palatal plane. Trace tip of nose fading into bridge. VTO S= T3>>< P3 A 0 U::+ L3:
. 2>. Superimpose along the facial plane at the occlusal plane. Fsing the same technique as for maring the symphysis, divide the hori
1
2/. Soft tissue Point $ remains in the same relation to Point $ as in the original tracing. Superimpose new and old bony Point $, and mae a mar at soft tissue Point $. %". Ueeping the occlusal planes parallel, superimpose mar R 1 :posterior mar; on the tip of the original incisor :slide forward 2&%rds;. Trace upper lip connecting with soft tissue Point $. VTO S= T3>>< L+ L3:, P3 B, 0 S= T3>>< C/3
In constructing the lower lip, we bisect the over+et and overbite of the original tracing and mar the point. e then bisect the over+et and overbite of the T4 and mar the point. OVERBITE, ORIGINAL , VTO , OVER)ET
2
8eturn to tracing on page !. %1.Superimpose interincisal points, eeping occlusal planes parallel.Trace lower lip and soft tissue 3 point. The soft tissue below the lower lip remains in the same relation to point 3 as in the original tracing. Soft tissue point 3 drops down as the lower lip recontours. VTO C8:5 V3><05 T+08 O4;3?
%2. Superimpose on the symphyses,and arrange the soft tissue of the chin. It Ndrops downN and should I be evenly distributed over the symphysis taing into consideration reduction of strain and bite opening.
%
If you have completed the steps, you now have your isual Treatment 4b+ective. Tae your T4 and superimpose it in the
five superimposition areas to establish your individual ob+ectives for this case. In Superimposition $rea 1 :3asionCGasion at '';, (valuation 1 is chin change. In this case, our ob+ective is to allow 2Q of opening of the facial a)is, to e)pect the amount of chin growth shown, and to e)pect that the upper molar will grow down the facial a)is. In Superimposition $rea 2 :3asionCGasion at Gasion;, (valuation 2 is ma)illary change. 4ne of our ob+ectives is to reduce point $ only 2mm in this case. In Superimposition $rea % :'orpus $)is at P9;, (valuation % is the lower incisors. In this case, we are +ust tipping the lower incisors slightly. In Superimposition $rea % we also have (valuation , the lower molars. In this case, we are advancing the lower molars appro)imately mm. In Superimposition $rea :Palate at $GS;, we have (valuation !, the upper molars. In this case, all we have to do is hold the upper molars, even though this is a 'lass II division 1 malocclusion. Superimposition $rea also includes (valuation -, the upper incisors, and we see that we are going to have to distali
!
H500 VTO In using the 8icetts facial a)is to find the mandibular and softC tissue chin position, 0acobsen and Sadowsy 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 ".-to ".! mm per year occurs, whereas growth on the facial a)is is reasonably consistent at % mm per year e)cept during growth spurts, especially the pubertal growth spurt, when it may approach twice that amount in some boys. $nother variation from the article by 0acobsen and Sadowsy involves those cases which at the time of retention will not fall into the best range in the conve)ity 7 angle chart, on both the conve) and the concave sides. The use of the line to the vermilion border of the upper lip perpendicular to the ?ranfort plane plus the variable 7 angle as seletal conve)ity 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. 0acobsen and Sadowsy are correct in their statement= N*rowth responses are generally predictable within certain limits and can be measured. The T4 as described here is based on this philosophy. Gewer 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 recogni
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 nowledge of growth based on average increments.N 4rthodontic treatment is monitored with progress head films, usually at -Cmonth intervals. henever a case is encountered in which growth is occurring in a different direction than e)pected, a new midtreatment T4 is then constructed so that changes in treatment procedures can be made and any disfiguring lip responses can be avoided. henever possible, it is a good plan to tae 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 e)amine the patient that early. 6eveloping pretreatment growth profiles of our patients helps to overcome our inadequacies in growth forecasting. In addition to the si) reference lines for the actual T4 construction, three more shown in ?ig. 1, $ :dotted lines; are added to the tracing to facilitate rapid copying of portions of the pretreatment lateral cephalometric tracing.
?irst is the nasion to point $ line. In longitudinal growth studies of patients not undergoing orthodontic treatment, the constancy of the angle SG$ is e)tremely good only about 1Q
change in ! years on the average. ?or 1C or 2Cyear forecasts, we can disregard such a small amount. 8eference lines or angles that are very near to constants offer our best chance of constructing visual treatment ob+ectives that we can confidently use as treatment goals and guides during orthodontic treatment. Second is 8icettsO facial a)is :foramen rotundum to gnathion;. This is used as a guide to direction of mandibular growth. Third is the mandibular plane :6owns;. Some may prefer to use the *oC*n line as a lower border of the mandibular reference line. (ither is acceptable, but the 6owns mandibular plane line is preferred because of its nearness to the actual lower border. The headfilm should be taen with the patientOs lips lightly touching.
VTO >:> S: I 'F3. 1, B 0 C*
The first step is to place a clean sheet of tracing material over the original tracing, copying :1; the frontonasal area, both hardC and softCtissue, with the softCtissue nose carried down to near the point where the outline of the nose starts to change directionsB :2; the sellaCnasion lineB and :%; the nasionCpoint $ line.
>
S: II 'F3. 2*
?irst, superimpose on the SG line and move the tracing to show e)pected growth :".-- to ".! mm per year unless a pubertal growth
spurt
is
e)pected
from
wrist
plate
studies;.
Second, copy the outline of sella. Third, either copy or change the facial a)is :8icettsO foramen rotundum to gnathion; as you e)pect it to behave according to the facial type of the patient and the treatment mechanics that you customarily use in such cases. :The facial a)is line is usually opened about 1Q, but it may even be closed if one is confident that mandibular growth of the forward rotational type will occur during treatment.; Gote= It is important to understand that the prediction of growth at nasion, along the SG line, is actually an overall prediction for all midfacial structures, including the nasal bone, the ma)illa, and the soft tissues.
/
S: III 'F3. &, A 0 B*
?irst, superimpose the T4 facial a)is on the original and move the T4 up so that the T4 SG line is above the original SG. The amount of movement will usually be % mm per year of growth, e)cept in accelerated growthCspurt periods. :Gote= since the facial a)is may be opened or closed as +udged from the facial pattern, the SG lines will not be parallel if we have changed the facial a)is.;
Second, copy the anterior portion of the mandible, including the symphysis and anterior half of the lower border. $lso draw the softCtissue chin, eliminating any hypertonicity evident in the mentalis area. :Slightly round out this area.; Third, copy the 6owns mandibular plane. >"
S: IV 'F3. #, A 0 B*
?irst, superimpose on the mandibular plane and move the T4 forward until the original sella and the T4 sella are in a vertical relation.
Ge)t, with the tracing in this position, copy the gonial angle, the posterior border, and the ramus.
?inally, superimpose on sella to complete the condyle. >1
Gote= $t this point total vertical height has been forecast, as has ha s the forward location of the chin structures, both hard and soft, and consideration will have been given to effects of treatment mech mechan anic icss on vert vertic ical al dime dimens nsio ion. n. 4ne 4ne shou should ld not not open open the the facial a)is more than 1Q to 2Q because greater opening than this is usually inconsistent with good treatment mechanics. S: V 'F3. $, A 0 B*
?irst, superimpose the T4 G$ line on the original G$ line and and move ove the T4 up unti untill "# "# of the tota totall grow growth th is e)pre e)press ssed ed abov abovee the the SG line line and -"# -"# belo below w the the mand mandib ible le.. :Gote= This may be varied as you perceive the facial type to be short or long.;
Second, with the tracing in this position, copy the ma)illa to include the posterior two thirds of the hard palate, PGS to $GS to % mm below $GS. Third, also with the tracing tracing in this same position, complete complete the nose outline around the tip to the middle of the inferior surface.
>2
Gote= The vertical growth of the nose over the usual 1> to 2 months of estimated treatment time eeps pace with the growth from the ma)illa vertically to the anterior cranial base. Thus, its relationship to $GS is relatively constant. In some cases there may be an elevation elevation of the nasal bone and greater greater development development of the nasal bul, but this is difficult to predict and thus some noses will have changed form more than this T4 procedure suggests. S: VI 'F3. 6, A 0 B*
?irst, with the T4 still superimposed on the line G$, move the T4 so that vertical growth between the ma)illa and the mandible is e)pressed !"# above the ma)illa and !"# below the mandible.
Second, with the tracing in this position, copy the occlusal plan. >%
Gote= Ideally, the occlusal plane is located about % 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 then it can can be alte altere red d acco accord rdin ingl gly y at this this stag stage. e. In case casess involving short upper lips, it may not be practical to intrude the upper incisors to this e)tent, but the vertical relationship of the teeth and gingival tissue will be more esthetically pleasing if we can reach this goal. S: VII 'F3. 7, A 0 B*
Gote= hen 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 7 line is not adversely affected by e)cessive facial conv conve) e)it ity y or conc concav avit ity, y, the the dept depth h of the the supe superi rior or sulc sulcus us measured to the 7 line is most ideal at ! mm. $ range of % to mm allows one to maintain maintain type with short and&or thin lips and long and&or thic lips. $dditional refinement of the technique, which covers all of the above, is gained by use of the vertical line from ?ranfort plane to the vermilion border of the upper lip, which is ideal at % mm with a range from 1 to mm. To find the point along the lower border of the nose outline at
>
which the new 7 line will intersect it, both perspectives are used in the e)ceptional cases +ust mentioned. ?irst, line up a straightCedge tangent to the chin and angle it bac to a point where there is a % to %.! mm measurement to the superior sulcus outline of the original tracing and draw the 7 line to this. $s one redrapes the superior sulcus area to the new tip of the upper lip point, a ! mm superior sulcus depth develops almost automatically. If you have trouble with this, the use
of the 0acobsonCSadowsy
lipCcontour
template
is
recommended.
Second, with the tracing still superimposed on the ma)illa and line G$ and using the occlusal plane :?ig. >, $ and 3; 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 T4, >!
draw in the superior sulcus area. This is a gradual draping to the new vermilion border outline.
Third, superimpose on line G$ and the occlusal plane. ?orm the lower lip, remembering that from 1 mm behind the 7 line to 2 mm anterior can be e)cellent, depending on variations of thicness of the two lips. $gain, most cases will fall on the 7 line or within ".! mm of it. ?inally, complete the inferior sulcus drape from the lower lip to the chin in a form harmonious with the superior sulcus. :Gote= The lips are not e)pected to have fully adapted to this position in more than about one half of the cases at the time of retention.; S: VIII 'F3. 9, A 0 B*
>-
?irst, with the e)ceptions noted earlier, lip strain that shows up as e)cessive upper lip taper is our first consideration. In the case shown in ?ig. /, the basic lip thicness measurement was 1! mm and the thicness at the vermilion border was 1" mm. 4ne millimeter of taper is normal, leaving a lip strain factor of mm. Ge)t we are concerned with how many millimeters the upper lip is bac from its original position. This is measured with the tracings superimposed on line G$ and the ma)illa. In the present case this also amounts to mm.
The third consideration is ma)illary incisor Nrebound.N hen the ma)illary incisors have been retracted ! mm or more and the case has been slightly overtreated to a near edgeCtoCedge incisor overbite and over+et relationship, we can e)pect about 1.! mm relapse tendency. 4bviously, there will be no tendency >
to move labially in those cases in which the upper incisor is not retracted or in those cases, such as anterior crossbites and&or 'lass III cases, in which the ma)illary incisors have been e)panded labially. 7ere the incisor retraction is significant, and we will use 1.! mm for incisor rebound. In this particular patient, then, the calculations would be as follows= :1; (limination of lip strain, mm. :2; Fpper lip change, mm. :%; 9a)illary incisor rebound, 1.! mm. ?inally, with the tracing still superimposed on line G$ and the ma)illa, place the ma)illary incisor template, taing cogni
?irst, superimpose the T4 on the mandibular plane and symphysis. Fsing the template, reposition the lower incisor to be in ideal retention occlusion with the ma)illary incisor, using the occlusal plane as a guide and by tipping the tooth about the
>>
ape) 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 V H > mmB :2; model discrepancy, 2 mmB :%; total discrepancy, 1" mm. S: X 'F3. 11, A 0 B*
ith 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 if e)tractions must be part of the treatment plan. In the case shown in ?ig. 11, each lower molar must be moved forward 2.! mm. Gote= 3y using the T4 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. 6istal tipping of lower molars 2.! mm can allow none)traction treatment in cases of a model discrepancy of ! mm. In other cases, especially those having a history of thumbC or lipCsucing or in which serial e)traction is contraindicated, the T4 will show that the lower incisors need to be moved forward, thus also increasing arch length and reducing the need to e)tract. 4n 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 $Cpogonion line, as posttreatment stability and longCterm periodontal health are usually endangered by so doing.
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The use of the T4 at this point to study and evaluate anchorage and arch length is one of its great advantages. If the lower molar must be moved anteriorly as much as %.! mm, the lower second premolars will be removed. There are cases in which there is an e)tremely thin alveolar process, particularly those cases that have deficient lower face height where the lower molars seem to get loced up in cortical bone if the second premolars are e)tracted. ()traction of the second premolars instead of the first premolars actually increases the lower molar anchorage. hen these two factors combine as contraindications to forward lower molar movement, it is sometimes better to loo at +udicious narrowing of the teeth through stripping and polishing than to e)tract at all. S: XI 'F3. 12, A*
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?irst, using the occlusal plane and the lower first molar as a guide, with a tooth template, position the upper first molar in ideal 'lass I occlusion with the lower first molar. Second, superimposing tracings on the original G$ line and the outline of the ma)illa, evaluate the e)tent of upper molar movement. In cases that wored out as lower arch none)traction cases, one may still need to thin about other e)traction alternatives in the upper arch, such as upper second molars when good third molar buds are developing or upper first premolars.
S: XII 'F3. 12, B*
Gote= $s to how point $ changes with incisor retraction, it is imperative that the clinician study the before and after tracings of many cases superimposed on the original G$ line and best fit of the ma)illa to get the NfeelN for this step. 4bviously the change in point $ is greater when the upper incisor root apices are moved a considerable distance than when the upper incisors are tipped lingually. 9ore change in $ 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 mi)ed dentition;.
/2
hen completed, the T4 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. 9ention must also be made of the usefulness of T4s to monitor treatment from periodic head films. Fsing all that we thin we now 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 une)pected growth response. $s we loo at the retention tracing in ?ig. 1%, $, it is evident that the tooth movement ob+ectives of the T4 were accomplished. The softCtissue analysis measurements, while greatly improved, still fail to meet the T4 goals, even though the softCtissue chin position has improved 1Q. This is because the lips still have not completely adapted to the tooth movement. There is an increased measurement of the upper lip thicness at the vermilion border from 1" to 1- mm. The 7 angle has improved from 2%Q to 1Q. 7owever, with a 2 mm conve)ity, ideally it should be 12Q.
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In the Cyear followCup shown in ?ig. 1%, 3, the softCtissue facial angle is an ideal /"Q. The superior sulcus form is e)cellent to both reference lines. The upper lip has 1 mm of normal taper, with a slight decrease in basic thicness. Seletal conve)ity is down to ", and the 7 angle is ideal at 1"Q. The upper lip has completed its adaptive changes and has a 1 mm taper.
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$s we 4rthodontists nowadays deal with more and more of mi)ed dentition cases , many of whom may or may not present with a seletal 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 eeping 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. 7owever we should not forget that every individual is unique in his own aspect and therefore we should not +ump to conclusions but study our patients over time and treat them to their individual requirements.
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