Growth Rotations.ppt

GROWTH
ROTATION
1
PRESENTED BY: Dr Rana
Chikhale

Contents
Introduction
Concepts related to rotation
Enlow’s counterpart principle
Rotational terminology
- Matrix rotation
- Intramatrix rotation
- Total rotation
Types of rotation
Rotation of maxilla
2

Methods of prediction of growth rotation
Structural sign as prediction of growth rotation
Implication of mandibular rotation in orthodontic treatment
Association between facial height development and mandibular
growth rotation
Variations in treatment plan
Conclusion
3

INTRODUCTION
ROTATION
 The angular movement of one rigid body relative to the other
 Ex; a wheel may rotate with reference to its supporting structures and
frame work.
 Odegard (1970) described the rotation as a change in the orientation
that can occur between the implant line and the lower border of the
mandible
4

 This concept was elaborated by Lavergne & Gasson in 1970 as
‘positional rotation’ changes in the orientation of the mandible relative
to the cranial base and ‘morphologic rotation’ changes in the shape of
the mandible.
5

6
• GROWTH ROTATION -- BJORK (1955)
• CONCEPT -- Early studies of facial growth
indicated that during childhood
the face enlarges progressively
and consistently growing.
DOWNWARD and FORWARD away
from the cranial base.

LATER BJORK (1950) HAS SHOWN
THAT THE DIRECTION OF FACIAL
GROWTH IS CURVED, GIVING A
ROTATIONAL EFFECT.
7

 GROWTH ROTATION is most obvious in
MANDIBLE
 IN MAXILLA -- small and completely masked by
surface remodeling.
8

Why RAMUS-CORPUS rotation occurs?
9

1.To compensate the
normal growth process
of other structures like
middle cranial fossa,
spheno-occipital
synchondrosis, midface
region.
MANDIBLE has to grow,
as well rotate according
to the structures.
10

 2. To prevent the change in
occlusal relationship or to
maintain the occlusal relationship.
11

DUE TO REMODELLING AND DISPLACEMENT
 Changes in midface region or nasomaxillary complex (forward and
downward)
 vertical length of ramus increases
 antero-posterior length of ramus also increases, helps in 3rd molar
eruption.
13

 Rotation in corpus.
 Gonial angle must change in order to prevent in occlusal relationship.
14

ENLOW’S COUNTERPART
PRINCIPLE
GROWTH OF ANY GIVEN FACIAL OR
CRANIAL PART RELATES SPECIFICALLY TO OTHER
STRUCTURAL AND GEOMETRIC COUNTERPARTS IN THE
FACE AND CRANIUM.
17

DIFFERENT PARTS &THEIR COUNTERPARTS
ARE:-
1.Nasomaxillary complex relates to the anterior
cranial fossa.
2.Horizontal dimension of the pharyngeal space
relates to the middle cranial fossa.
3.Middle cranial fossa and ramus are counterpart.
4.Maxillary and mandibular arches are mutual
counterparts.
5.Bony maxilla and corpus of mandible are
counterparts.
6.Maxilary tuberosity and lingual tuberosity are
counterparts. 18

 These structures develop MORPHOLOGIC COMPENSATION.
 Facial development is a basic and important biologic concept.
 Functional and structural balance
(equilibrium or homeostasis)
19

21
Björk and Skieller (1983)
 They stated that the various patterns resulting from different
registrations can be expressed in a rotational terminology if the
phenomenon is divided into three components:

22
1. Matrix Rotation
2. Intramatrix Rotation
3. Total rotation

24
1. Total rotation:
 The rotation of the mandibular corpus
measured as a change in inclination of
an implant line in the mandibular
corpus relative to the anterior cranial
base.
 Designated negative when
reference line in corpus rotates forward in
relation to SN line.

25
With superimposition on a
reference line in the mandibular
corpus, the direction & the
amount of the total rotation are
manifested by the converging NS
lines representing different age
stages.

26
Matrix Rotation:
Schudy(1965), Jarabak & Fizzell(1972)
were pioneers in this aspect of rotation

27
2. Matrix rotation. Metrically
defined as a change in
inclination of the
tangential mandibular line
(ML1) in relation to the SN
line.
The tangential mandibular
line represents the soft
tissue matrix.
The matrix rotation has its
center at the condyles.
Designated negatively
when ML1 rotates forward.

28
The matrix sometimes rotates forwards
& sometimes backwards in the same
subject during the growth period.
This can be described as Pendulum
movement.

29
Intramatrix rotation:
Contributions have been made by
Bjork & Skieller1980,1983
Lavergne & Gasson 1976,1982
Dibbets 1977,1980

30
3. Intramatrix rotation..
. The difference between the total rotation and the matrix rotation is
an expression of the remodeling at the lower border of the mandible.

31
It is identified by the change in
inclination of an implant or reference line
in the mandibular corpus relative to the
tangential mandibular line ML1.
There is usually considerable intramatrix
rotation, while the matrix rotation is
moderate and may even be in the opposite
direction to the total rotation.

32
Forward intramatrix rotation
lifts up the anterior part of
the corpus from the soft
tissue matrix and the
stretching leads to apposition
below the symphysis and
anteriorly at the lower
margin.
The posterior part of the
corpus is simultaneously
pressed down into the
matrix, resulting in
resorption at the lower
border in the region of angle
of the mandible.

33
The intramatrix rotation has its center somewhere in the corpus &
not at condyles.
The location of center of rotation also depends on the growth rotation
of maxilla & occlusion of teeth.

34
A, Two mandibles superimposed on their external
contours. shows divergence of the implant lines
indicative of "intramatrix rotation" not reflected in
dimensional change or alteration of mandibular
contours.
B, The same two mandibles superimposed on the
implant markers shows lack of concordance of
mandibular contours, indicating extensive
remodeling during development.

35
Lavergne and Gasson, define rotation as:
"positional" and ''morphogenetic.“
morphogenetic rotation of the mandible concerns the shape of the
mandible itself, while
positional rotation deals with the position of the mandible within the
head.
They found the working mechanism in the forward or backward
inclination of the ramus, thereby elongating or shortening the
mandible.

36
An operational definition may now be suggested 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.

37
.
Thus, counterbalancing rotation is a mechanism that:
(1) neutralizes growth and
(2) results in selective enlargement of the mandible.

TYPES OF ROTATIONS
As recognised with implant method:
Forward rotation Backward Rotation
Type I Type I
Type II Type II
Type III
38

BACKWARD ROTATION OF
MANDIBLE
I. Center at the joints.
II. Center at the last occluding molars.
40

FORWARD ROTATION
In such cases, Intramatrix rotation
accounts for the preponderance of the total
rotation ,quite the reverse of backward
rotation.
41

Of this, about 25 % results from matrix
rotation ,and 75% results from intramatrix rotation.
42

BACKWARD GROWTH ROTATION
Of the total rotation ,
71% is accounted for
by “Matrix rotation” &
29% by “intramatrix
rotation”.
43

ROTATION OF MAXILLA
It is less easy to divide the maxilla into
 a core of bone and
 a series of functional processes.
The alveolar process is certainly a functional process.
44

INTERNAL ROTATION
OF MAXILLA
45
This internal rotation is analogous to the intramatrix rotation of the
mandible.
Matrix Rotation ,as defined for mandible is not possible for maxilla.

EXTERNAL ROTATION
OF MAXILLA
At the same time that internal rotation is occurring ,there also are varying
degrees of resorption of bone on the nasal side & apposition on palatal side in
anterior and posterior regions.
These changes amount to external rotation.
46

47
For most patients ,the external rotation is opposite in direction &
equal in magnitude to the internal rotation ,so that the two equal
rotations cancel & the net change in jaw orientation as evaluated by
the palatal plane is zero..

48
Methods of Prediction of
Growth Rotations

IMPLANTS
The use of Implants to study bone growth was first introduced by Bjork in 1969.
inert Tantalum alloy
These are around 1.5mm in length ,and 0.5mm in diameter.
49

SITES FOR IMPLANT PLACEMENT
Maxilla:
Hard Palate behind deciduous canines.
Below the anterior nasal spine.
2 implants on either side of zygomatic process of maxilla.
Border between hard palate & alveolar process medial to the first
molar.
50

51
Mandible:
Anterior aspect of symphysis, in the midline below the root tips.
2 pins on the right side of the mandibular body. One under the first
premolar & the other below the second premolar or first molar.
One pin on the external aspect of right ramus in level with the occlusal
surface of molars.

52
Bjork 1969 presented a survey of experience with the implant
method in the study of facial growth ,with particular emphasis on
prediction of mandibular growth rotation.
The three methods discussed were:
Longitudinal Method
Metric Method
Structural Method

LONGITUDINAL METHOD
It consists of following the course of development by annual X-ray cephalograms.
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.
53

METRIC METHOD
Aims at prediction based on a metric description of the facial
morphology at a single stage .
Predicting the intensity or direction of subsequent development from
size or shape at childhood was not feasible with any cephalometric
analysis.
54

STRUCTURAL METHOD
This method is based on information gained from implant studies of
the remodeling process of the mandible during growth.
55

56
Structural Signs as predictor
of
Growth Rotations

STRUCTURAL SIGNS AS GIVEN
BY BJORK (1969
57
Bjork gave 7 structural signs of extreme growth rotation in relation to
condylar growth direction.

58
The signs are related to following features:
Inclination of the condylar head
Curvature of the mandibular canal.
Shape of the lower border of the mandible
Inclination of the symphysis.
Interincisal angle
Interpremolar or Intermolar angles.
Anterior lower facial height

INCLINATION OF THE CONDYLAR HEAD
A forward inclination of the condylar head denotes forward rotation,
characterized by deep bite.
A backward inclination of the condylar head denotes backward
rotation ,characterized by open bite.
59

CURVATURE OF THE
MANDIBULAR CANAL
In the vertical type of condylar growth, the
curvature of the canal tends to be greater than that of the mandibular contour,
including the angle of the jaw.
In the sagittal type, the canal may be straight or, in pathologic cases, it may even
curve in the opposite direction.
60

SHAPE OF THE LOWER BORDER OF THE
MANDIBLE
In vertical condylar growth, the pronounced apposition below the
symphysis & the anterior part of the mandible produces an anterior
rounding, with a thick cortical layer, while resorption at the angle
produces a typical concavity.
In sagittal growth, the anterior rounding is absent & the cortical
layer is thin ,while the lower contour at the jaw angle is convex.
61

SHAPE OF LOWER BORDER, ML1-ML2
62

INCLINATION OF SYMPHYSIS, CTL-NSL
 It is measured as the angle
between the tangent to the
anterior surface of the mandible
and the anterior cranial base ,
63

INTERINCISAL ANGLE &
INTERMOLAR ANGLE
In forward rotators ,it is vertical or obtuse.
In backward rotators, it is acute.
64

65
 Molar inclination. Change in inclination of the
lower first molar in forward rotation (a) and in
backward rotation (b) of the mandible.

66
►Cephalometric evaluation of skeletal open
and deep bite tendencies
(ANTHONY D.VIAZIS)

69
 1. Width of symphysis (PgTH):
Greater ----- forward growth rotation
Narrow ------ backward growth rotation
 2. Angle of the symphysis (BPg-MeTH):
Acute angle ------ forward growth rotation
Obtuse angle ----- backward growth rotation

70
3.Mandibular plane angle(GoMe-TH):
High value ------- backward rotator
Low value ------- forward rotato
4.Sum of the posterior angles
(SNa-SAr + SAr-ArGo +ArGo-GoMe)
High values ------vertical growth pattern
low values --------horizontal growth pattern

71
5. Gonial angle (ArGoMe):
Increased gonial angle----- backward growth
rotator
Decreased angle ------ forward growth
rotator
6. Gonial angle ratio(ArGoNa:NaGoMe):
>75 % , high upper angle--- Horizontal growth
pattern high lower angle ------
- Vt. pattern

72
7.Posterior cranial base to Ramus ht. ratio(SAr:ArGo)
Short ramus ht. & short post. Cranial base ----
backward growrh rotation.
8. post. to ant. Face ht.(SGo:NaMe)
>65%---- forward growth pattern
<65%----- backward growth rotation

73
9. Post to ant.maxillary ht.ratio(EPNS:NaANS):
>90%------vt.growth pattern
< 90%------ Hz.growth pattern
10. Lower to Total Ant. Face Ht.
Ratio(ANSMe:NaMe):
>60%-------backward growth rotator
<60%------- forward growth rotation

74
Implications of mandibular
rotations in orthodontic
treatment
Schudy: AO 1965

76
If vertical growth in the 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.
Extremes of this condition cause open
bites.

77
WHAT ARE THESE VERTICAL
“ELEMENTS” OF GROWTH?

78
 In harmonious facial growth there is
balance between increment A and
increments I, II, III, and IV.
Growth at the condyles is trying to
carry the chin forward & combined
vertical growth in the molar area is
trying to carry the chin downward &
backward.

EFFECTS ON
TREATMENT
(COUNTERCLOCKWISE
)
 This “flattening” of the mandibular plane tends to increase the
vertical overbite and renders vertical overbite correction and
retention more difficult .
79

EFFECTS ON
TREATMENT
(CLOCKWISE)
Too much vertical growth of the molars would prevent forward
positioning of the chin rendering Class II correction difficult.
 However, it would tend to help correct the vertical overbite of the
incisors.
80

FACTORS AFFECTING
ROTATION
 Gonial angle
 Facial Divergence (SN-MP)
81

VARIABLES AFFECTED BY
GROWTH ROTATIONS
The Y axis
The Freeway space
The Occlusal plane
82

83
The more vertical growth
exceeds horizontal growth,
the more the Y axis must drop
posteriorly.
If during treatment vertical
growth far exceeds horizontal
growth, the Y-axis must move
backward just as it would do
if the individual were not
being treated orthodontically
Pogonion went downward
& backward and the MP
became steeper. The cause
was a marked deficiency of
condylar growth.
The Y axis

84
This illustrates that
condylar growth (as related
to vertical growth) is the
key to changes of the
occlusal plane.
The posterior growth
analysis shows that the
condyles grew 23 mm and
the vertical growth in the
molar area was 18 mm
(9+6+3). The result was an
8° change of the occlusal
plane.
Some Examples:

ASSOCIATION BETWEEN FACIAL HEIGHT
DEVELOPMENT AND MANDIBULAR
GROWTH ROTATION (Alf tor karlson, Bjork )
 Post facial ht. (snp) :
 S - go  post. Facial ht
 s - pm  upper post. Facial height
 pm - go  lower post facial height
PFH > AFH (FORWARD ROTATION)
85

 determined by factors including the direction
of growth at the condyles and vertical growth
at the spheno-occipital synchondrosis
86

Anterior facial height
n – gn : anterior facial height
n – sp : upper facial height
sp – gn : lower ant facial height.
In mandible their effect is significant in vertical
dimension
-- is affected by eruption of teeth and vertical
growth of the soft tissues, including masticatory
musculature and the suprahyoid musculature and
fascia, which are in turn influenced by growth of the
spinal column.
AFH > PFH (BACKWARD ROTATION)
87

 Average being a mild forward growth rotation well balanced facial
appearance. Forward growth rotation are more common than backward
rotation.
 Reduced ant. vertical facial height ----- an increased overbite.
Backward growth rotation
 Increased ant. vt. Facial proportion
 Reduced overbite or anterior open bite.
 Vt. Dimension , antero-posterior
 Ex. Class ІІ
90

VARIATIONS IN TREATMENT PLAN
Forward rotators Backward rotators
Cervical headgears are
ideal for deep overbites as
high outer bows produce
distal root movement &
vertical extrusion.
Leveling of occlusal
curves desirable.
All teeth including 2nd
molars should be banded.
High pull headgears are
more suited that exert a
vertical intrusive force to
the maxillary molars with a
short outer bow.
Leveling would cause
frank open bite.
Only necessary teeth
banded, preferably not 2nd
molars.
92

93
► Intermaxillary elastics
will produce posterior
extrusion ,helping deep
bites.
► Extractions are harmful
since molars can come
forward & incisors can be
uprighted to increase
overbite.
Intermaxillary
elastics are not
indicated.
Extractions are desirable
as molars can come forward
& incisors can be uprighted
to increase overbite.

94
Deep bite patients
experience later pubertal
growth spurts, can be
treated later, & often
require prolonged retention
to ride the wave of
continued post adolescent
growth.
Use of an anterior bite
plate during retention may
add to the stability of deep
bite correction.
Open bite individuals
mature earlier & benefit
from early treatment and
force distributions
designed to hold, restrict
or redirect vertical
growth.

Correlation between masticatory muscles orientation and dento-skeletal
morphology
Muscles
Masseter temporalis
..Early studies removal and repositioning pf the masticatory muscles and
destruction of trigeminal nucleus produce alteration in growth pattern in
animals.
..Later in humans geometric arrangement of the superficial masseter
affects on the occlusal plane. (insertion)
95

Three canonical correlation
1  growth ( occlusal plane) -- masseter muscle insertion &
temporalis muscle.
2 fluctuation of occlusal plane position by positively loading of these
muscles.
98

3. (a) LONG FACIAL HT.
.. Masseter is superior in position.
.. Steep mandibular angle
.. Large gonial angle
(b) SHORT FACIAL TYPE
.. Maximum jaw closing force, positively correlated
.. MP angle & gonial angle are negatively correlated
99

CONCLUSION
Substantial evidence exists today that the simplicity or complexity of the force
system is not the deciding factor in producing the best treatment.
In average skeletal patterns much leeway exists & the undesirable side effects of
inappropriate mechanotherapy will not be so obvious.
100

101
Severe skeletal pattern discrepancies, however, represent at least
one third of a typical practice & are the major source of problem
cases. These must be managed carefully & appropriately with full
knowledge of what has happened & what can happen in extreme
variations of facial growth.

 Bjork : Prediction of mandibular growth rotation
 Dibbets J.M.H : Puzzle of growth rotation
 Foster T.D : Textbook of orthodontics
 Karlson Alf Tor : Association b/w facial height development & mandibular
growth rotation in low & high MP –SN angle faces
 Kenji, Takada : Gonial correlation b/w masticatory muscles and
dentoskeletal morphology
 Rakosi : An atlas & manual of cephalometric radiography
102

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