Growth rotations

CONTENTS
1.INTRODUCTION
2.IMPLANT RADIOGRAPHY
3.MANDIBULAR GROWTH ROTATIONS
4.MAXILLARY GROWTH ROTATION
5.JAW ROTATIONS AND TOOTH ERUPTION
6.MUTUAL RELATIONSHIP OF ROTATING
JAW BASES
7.ROLE OF GROWTH ROTATIO1
NS IN
ORTHODONTIC TREATMENT PLAN
8.CONCLUSION
9.BIBILOGRAPHY
SEMINAR ON GROWTH ROTATIONS1

INTRODUCTION
The phrase growth rotation was introduced in 1955 by Bjork, who
used it to describe a particular phenomenon occurring during the
growth of the head. The technique whereby metal implants are
inserted in bone has been used in animals for more than a century, but
the application of the method in craniometrics studies of growth in
man is of a more recent date. Professor Bjork is considered the father
of implant radiography. Cephalometric implant radiography has
revolutionized the growth studies in the field of orthodontics. Of all
the pattern of growth, growth rotations assume an important role in
orthodontics because of its major impact on treatment strategies. The
rotation of maxillary and mandibular jaw bases is a major factor in
etiological assessment, determining the nature of anomaly, the
prognostic evaluation, determining the possible forms of treatment in
choosing the principles of treatment and also in assessing the stability
of treatment results. Certain rotational patterns of jaw bases can be
manipulated quite effectively by means of functional and orthopaedic
devices. Extreme rotations are very difficult to treat and surgical
correction has to be performed at a later stage.
IMPLANT RADIOGRAPHY4
The first implant radiographic study was initiated in the 2year 1951 by
Bjork. The implant radiography, metallic implants have been inserted
in the jaws to serve a fixed reference points. By means of the implant
SEMINAR ON GROWTH ROTATIONS 2

method, it is possible to locate sites of growth and resorption in the
individual jaws and to examine individual variations in direction and
intensity.
Technique for implant radiography
Rotation of jaw bases was estimated using implant radiography only.
In this procedure, inert metal pins are placed in the mandible and
maxilla. Tantalum inert pins which are 1.5cm long and have 0.5mm
diameter are used. Osseo integrated implants have serve as reference
points and serial cephalometric radiographs are taken repeatedly over
a period of time and compared.
Site of implants
Mandible :
Symphysis in the midline below roots.Right side body of mandible
one below first premolar second below first molar.Outer surface of
ramus on the right side in level with occlusal plane3
Maxilla :

Inferior to anterior nasal spine.Bilaterally in the zygomatic
process.Hard palate behind canines, front of first molar in the junction
between alveolar process and palate
4
MANDIBULAR GROWTH ROTATIONS1,2,3,5,10
Mandibular rotations assume an important role in orthodontic
treatment planning because mandibular growth rotations are more
common than maxillary rotations. It drastically affects facial
morphology, and treatment planning and treatment outcome. Implants
were placed on the indicated site of mandible. By superimposing two
consecutive tracings of child mandible registered on implants. Bjork
SEMINAR ON GROWTH ROTATIONS4

found that the image of the older mandible had appeared to have
rotated slightly forward during the intervening period.
BJORKS CLASSIFICATION 5,4
In the year 1969, Bjork has classified ro5tation of mandible into
forward and backward rotations.
Forward rotation has three types

Type A – in this type there is forward rotation about centres in the
joints which give rise to deep bite, in which the lower dental arch is
pressed into the upper, resulting in underdevelopment of the anterior
facial height. The cause may be occlusal imbalance due to loss of
teeth or powerful muscular pressure.
6
Type B – forward growth rotation of mandible about a centre located
at the incisal edges of the lower anterior teeth due to combination of
marked development of posterior face height and normal increase in
anterior height. The posterior part of the mandible then rotates away
from the maxilla.

Type C – the anomalous occlusion of the anterior teeth, the forward
rotations of the mandible with growth changes its character. In case of
large maxillary overjet or mandibular overjet, the centre of rotation no
longer lies at the incisors but is displaced backward in the dental
arc7h, to the level of premolars. In this type of rotation, the anterior

facial height becomes underdeveloped when the posterior face height
increases.
In the growth rotation type 2 and 3 the mandibular sym8physis swings
forward to a marked degree and thechin becomes prominent. The
inclination of the teeth is also greatly influenced by the rotation of the
jaw. The interincisal angle undergoes a smaller change than the
rotation of the jaw. The incisors in their eruption are guided forward
and there is an increase in the alveolar prognathism right down to
apical zone. This is contrary to the impression given by the jaw
profile. Rotation, also displaces the path of eruption of all the teeth in
the mesial direction, thereby tending to create crowding in the anterior
segment through what may be referred to as packing. The rotation
also effects the position of the lower posterior teeth in relation to the
upper teeth. Forward growth rotation thus causes the lower posterior
teeth to be more uprightthan the usual in relation to upper posterior

9teeth, with an increase in what may be called interpremolar and
intermolar angles.
Backward rotation of the mandible is less frequent than the forward
rotation. Two types have been recognized.
Type A – herethe centre of the backward rotation lies in the TMJ.
This is case when the bite is raised by orthodontic means, by a change
in the intercuspation or by a bite raising aplliance, and results in an
increase in anterior face height.
Type B – backward rotation occurs about a centre situated at the most
distal occluding molars. This occurs in connection with growth in the
saggital direction at the mandibular condyles. As the mandible grows
in the direction of its length, it is carried forward more than it is
lowered in the face, and because of its attachment to muscles and
ligaments it is rotated backward

BJORK AND SKEILLER’S METHOD2,3,4,8
Bjork and skeillerin the year 1972 subsequently together carried out
extensive implant studies and introduced various terminologies to
understand the rotational pattern of mandible.T10hey divided the
rotation into three components
Matrix rotation : this is the rotation of the soft tissue matrix of the
mandible relative to the cranial base. The soft tissue matrix is defined
by the tangential mandibular line. The matrix rotation has its centre at
the condyles
Intramatrixrotation: the difference between the total rotation and the
matrix rotation is an expression of the remodelling at the lower border
of the mandible.itis identified by the change in inclination of an
implant reference line in the mandibular corpus relative to tangential
mandibular line. The intramatrix rotation has its centre somewhere in
corpus.
Total rotation : therotation of the mandibular corpus meas11ured as a
change in inclination of an implant line in the mandibular corpus
relative to the anterior cranial base.
12Bjork also makes a clear distinction between what he terms matrix
rotation and intramatrix rotation. Matrix rotation often goes in the
form of a pendulum movement with the rotation point in the
condyle.Intramatrix rotation is the rotation of the mandibular corpus
inner half of its matrix within the mandibular corpus and not in the
condyle. It is imporatant to note that skeiller, Bjork et al showthat
total so called rotation is made up of sum of both matrix and

intramatrix rotation.According to ENLOW anatomic function of the
mandibular ramus, in addition to providing insertion for masticatory
muscles is to properly position the lower dental arch in occlusion with
upper. It is primarily remodelling of the ramus not the corpus, that is
responsible and it is a combination of remodelling fields that carries
out the remodelling rotation of the ramus. As the growth change
proceeds, the entire mandible can also become rotated more
downward and backward or upward and forward. This is a
displacement rotation of the mandible as a whole as its ramus
simultaneously rotates to a usually more closed position by
anadjustive remodelling rotation.13
SCHUDY’S CONCEPT6,4
Schudy in 1965 considers the rotation of the mandible is the result of
disharmony between vertical growth and anteroposterior or horizontal
growth of jaws.
Schudys concept of growth rotations14

The clockwise rotation:
Clockwise rotation of the mandible is a result of more posterior
vertical growth than the condylar growth, the point of rotation being
the condyles. If the vertical growth in molar region is greater than that
at the condyles, the mandible rotates clockwise resulting in more
anterior facial height and less horizontal change of the chin. Extreme
of this condition causes open bite.

Counterclockwise rotation:
It ia a result of more condylar growth than combined vertical growth.
15This type of rotation is nearly always accompanied by a forward
movement of pogonion and an increase in the facial angle. The point
of rotation is the most distal mandibular molar in occlusal contact.
This flattening of the mandibular plane tends to increase the vertical
overbite and render vertical overbite correction and retention more
difficult.The size of the gonionnagle has an important influence upon
the number of degrees of resultant counterclockwise rotation. The
smaller the gonion angle, the greater is rotation which is produced for
each millimetre of forward movement of pogonion. When this angle
is extremely small, it results in extreme flattening of the mandibular
angle together growth of pogonion.
DIBBETS CONCEPT9

Dibbets re-examined the concept of intramatrix rotation as defined by
Bjork and skeiller in 1983. Lavergne and Gasson on the other hand ,
contended that the rotation affected the ramus and the gonial angle
and consequently the length of the condylion – pogoniondiagnol. An
alternative interpretation of the mandibular rotation was presented by
dibbets in order to overcome the controversies of intramatrix rotation.
Dibbets hypothetically constructed two possible divergent patterns
of16 mandibular growth.
1. Circular growth pattern : which postulates condylar growth as
a segment of a circle with its centre at the chin. The whole
mandible would then rotate around itself within its periosteal
countours, resulting in intramatrix rotation without enlargement
of mandible.
2. Linear growth pattern : without any intramatrix rotation and
maximum enlargement of the mandible
This mechanism for selective enlargement of the mandible in
response to condylar growth increments may be termed
counterbalancing rotation. An operational definition is presented as
follows: counterbalancing rotation pertains to circular condylar
growth, accompanied by selective coordinated remodeling, which
does not contribute to the incremental growth of the mandible.
PROFFITS DESCRIPTION ON ROTATION 1
Profit carried different terminologies to explain growth rotation of
mandible, namely internal rotation, external rotation and total
rotation. The core of the mandible that surrounds the inferior alveolar
nerve. The rest of the mandible consists of its several functional
processes. These are the alveolar process, muscular process and the
condylar process. If implants are placed in areas of stable bone away

from the functional processes it can be observed in most individuals,
the core of the mandible rotates during growth in a way that wou17ld
tent to decrease the mandibular plane angle.
Internal rotation :
It is the rotation that occurs in the core of the18 jaw. The internal
rotation is marked by surface changes and alterations in the rate of
eruption of teeth. There are two contributions to internal rotations,
namely MATRIX ROTATION (A) and INTRAMATRIX
ROTATION (B). Matrix rotation occurs around the condyle while
Intramatrix rotation is centred within the body of mandible.

External rotation :
It is the result of surface changes. These surface changes include
resorption in the posterior part of the lower border of the mandible,

while the anterior aspect of the lower border is unchanged or
undergoes slight apposition. The external compensation in an19
average growing adult is about 11 to 12 degree.
In short face type there is excessive forward rotation of mandible due
to increase in internal rotation and decrease in external rotation. A
high angle case shows backward rotation due to lack of
normalinternal rotation
MAXILLARY GROWTH ROTATIONS1,10

It is less easy to divide the maxilla into core of bone and a series of
functional processes. The alveolar process is certainly a functional
process, but there are no areas of muscle attachment analogous to
those of the mandible. If implants are placed above the maxillary
alveolar process, one can observe the core of the maxilla that
undergoes a small and a variable degree of rotation. Bjork and
Skeiller in 1972 studied rotational growth of maxilla with thehelp of
implants. Indicated sites of implants were placed. The lateral implant
placed on the anterior and posterior countours of zygomatic process
seems to give best results when compared to other sites. Seri20al
superimposition of the lateral cephalogram at these revealed varying
degree of rotation of the jaw bases. Based on these studies Bjork and
skeiller introduced terminologies to describe maxillary growth
rotations.
Internal rotation :This internal rotation is analogous to the rotation
within the body of the mandible. It occurs in the core of the maxilla. It
is also called intramatrix rotation
External rotation :At the sametime that internal rotation of the
maxilla is occurring, there also are varying degree of remodelling of
the palate. Similar variations in the amount of eruptions of incisors
and molar occurs. These changes amount to an external rotation. The
external rotation is opposite in direction and equal in magnitude to the
internal rotation, so that the two rotations cancel and the net change in
jaw orientation is zero.Depending upon the different degree s of
combination of internal and external rotations, Bjork and skeiller
observed two types of rotational growth. The terminologies they used
are forward and backward rotations
Forward growth rotation : this condition occurs either due to
excessive internal rotation or lack of normal compensatory external
rotation or both. The maxilla is inclined upward and forward i.e

anterior end is tipped up. This is called ante inclination coined by
Schwarz. He also named this condition as pseudotrusio21n. This
actually aggrevates maxillary protrusion, tends to tip the
incisorsforward increasing their prominence. The extent of forward
tipping in relation to anterior cranial base is given in degrees by
Schwarz. It is defined as the angle between the Pn-perpendicular and
the palatal plane (j angle). The normal angulation is 85 degrees but in
ante inclination it is greter than 85 degrees.
Backward rotation : it is exactly opposite to that of forward rotation
where there downward and backward tipping of the anterior end of
the palatal plane and the maxillary base. This is otherwise called
retroinclination a term coined by Schwarz. In this type the jaw bases
are translated posteriorly and the upper incisors appear to tip
lingually. The angle between palatal plane and the anterior cranial
base is lesser than the normalvalue. It is less than 85 degree.

JAW ROTATION AND TOOTH ERUPTION 1,8
Growth of the mandible away from the maxilla creates a space into22
which teeth erupt. The rotational pattern of jaw growth obviously
influences the magnitude of tooth eruption, direction of eruption and
the ultimate anterioposterior position of the incisor teeth. The path of
eruption of the maxillary teeth in downward and somewhat forward.
In normal growth the maxilla usually rotates a few degree forward but
frequently rotates slightly backward. Forward rotation would tend to
tip the incisors forward, increasing their prominence while backward
rotation directs the anterior teeth more posteriorly than would have
been the case without rotation, relatively uprighting them and
decreasing their prominence. The eruption path of the mandibular
teeth is upward and somewhat forward. The normal internal rotation
of the mandibular caries the jaw upward infront. This rotation alters
the eruption path of the incisors tending to direct them more
posteriorly. Because the internal jaw rotation tends to upright the
incisors, the molars migrate further mesially during growth than do
the incisors and this migration is reflected in the decrease in arch
length. Since the forward internal rotation of the mandible is greater
than that of the maxilla it is not surprising that the normal decrease in
mandibular arch length is somewhat greater than the decrease in
maxillary arch length. Implant studies that revealed the internal jaw
rotation also confirmed that changes in the anteroposterior position of
the incisors teeth are a major influence on arch length changes. When
excessive rotation occurs in short face type of development, the
incisors tend to be carried into an overlapping position even if they
erupt very little, thus the tendency for deep bite malocclusion in short
face individuals. The rotation also progressively uprights the incisors,
displacing them lingually and causing a tendency towards crowding.
In the long face pattern, on the other hand, an anterior openbit23e will

develop as anterior face height increases unless the incisors erupt for
an extreme distance. The rotation of the jaws also carries the
incisorforward, creatind dental protrusion.
MUTUAL RELATIONSHIP OF ROTATING JAW
BASES 10
When Bjork introduced the concept of rotation to orthodontics after
using metallic implants, the concept was widely extended and
misused. In an attempt to clarify this situation a classification was
proposed whereby a clear cut distinction between morphogenetic and
positional rotations were presented. Morphogenetic rotation of the
mandible concerns with the shape of the mandible itself, while the
positional rotation deals with the position of the mandible. Four types
of mutual rotation of jaw bases were proposed by Lavergne and
Gasson after extensive implant studies in 1982. This is important
clinically because dentoalveolar malocclusion depend24 on the
combination of these rotations.
1. Convergent rotation of jaw bases : this rotation results with
closing of maxilla mandibular plane angles creating a severe

true deep bite that is difficult to manage. Both maxilla and
mandible converge towards each other.
2. Divergent rotation of jaw bases : the maxilla and mandible move
away or diverge from each other. This rotation leads to the
opening of the basal angle and can result in open bite. Ex25treme
cases require surgical correction.

3. Cranial rotation of maxilla and mandible : both maxilla and
mandible rotates upwards and forwards.this horizontal growth
pattern occurs in a relatively harmonious manner wherein
rotation of maxilla occurs upwards and forwards and
compensates for cranially rotating mandible.
4. Caudal rotation of maxilla and mandible : both maxilla nad
mandible rotates downward and backward s26imilar to cranial
rotation wherein the downward and backward maxillary rotation
causes open bite.

ROLE OF GROWTH ROTATIONS IN
ORTHODONTIC TREATMENT PLAN
Mandibular rotation is a major factor in the development of
malocclusion. Posterior rotation is frequently seen with retrognathia,
anterior rotation with prognathia. Skeletal open bite is concomitant
with posterior rotation, skeletal deep bite with forward rotation. The
variations in direction of growth giving rise to the above rotations are
not only a factor in development of malocclusions, but also play an
important role in the treatment planning. With forward rotation,
treatment of class III and deep bite is difficult, with the backward
rotation that of class II and open bite. It is therefore important to
determine the growth type before orthodontic treatment is initi27ated.
CONCLUSION
Growth rotations play a major role in orthodontic treatment planning
and outcome. Though various diagnostic methods were evolved to

predict growth rotations, none seems to be fulfilling and newer
diagnostic methods have to be used in future. Better therapeutic
decisions should be made regarding timing and length of treatment,
appliance selection, extraction patter and possible need for surgery
BIBILOGRAPHY :
1. CONTEMPORARY ORTHODONTICS – PROFFIT W R 5th
EDITION
2. HAND BOOK OF ORTHODONTICS – ROBERT E MOYERS
3. ESSENTIALS OF FACIAL GROWTH – ENLOW D. H
4. TEXT BOOK OF CRANIOFACIAL GROWTH – SRIDHAR
PREMKUMAR
5. Bjork A. Prediction of mandibular growth rotation AJO-DO
1969;55:585- 599
6. F Schudy. The rotation of the mandibleresulting from growth: its
implications in orthodontic treatment. Angle orthod 1965;1:36-50
7. Julian von Bremen, Hans Pancherz. Association between bjork’s
structural signs of mandibular growth rotation and skeletofacial
morphology. Angle orthod 2005;75:506-509
8. A Bjork, V Skeiller. Facial development and tooth eruption. An
implant study at the age of puberty AJO DO 1972;62(4):339-83
9. Dibbets JMH. Puzzle of growth rotation, AJO-DO 1985;473-80
10. ORTHODONTIC DIAGNOSIS – THOMAS RAKOSI,
IRMTRUD JONAS, THOMAS M. GRABER

11. AN ATLAS AND MANUAL OF C28EPHALOMETRIC
RADIOGRAPHY – THOMAS RAKOSI

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