Growth rotations 2 /certified fixed orthodontic courses by Indian dental academy

GROWTH
ROTATIONS

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INDIAN DENTAL ACADEMY
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CONTENTS
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Introduction
Implants
What is rotation
Different terminologies
Cause of rotation
Face types
Tooth eruption
Prediction of growth rotation
Clinical implications
conclusion


Introduction
The introduction of cephalometric
radiography in 1930’s initiated new
trends in orthodontics
It became a widely used tool in
orthodontic diagnosis and treatment
planning.


It facilitated the longitudinal study of
craniofacial growth by the method of
superimposition of radiographs on specific
landmarks.

Various angular and linear
measurements were used to determine &
predict the pattern of growth, and
 forward downward growth concept of the
face was accepted.





But growth in the craniofacial region is not
that simple or straight forward.



The concept of growth rotation helps us
to understand this complex process in a
better way.
With the use of metallic implants
inserted in bone, the understanding of
vertical jaw relation along with sagittal jaw
relation was made easier .




IMPLANTS






The technique where metal implants are
inserted in bone, has been used in animals for
more than a century but the application of the
method in growth studies of human is of more
recent date.
This method of study is used extensively by
Bjork and coworkers at Royal Dental College
copenhagen Denmark.
These implants were made up of Tantalum,
an inert material . This method is useful, as bone
does not grow interstitially and therefore once
placed inside the bone, the implants are stable.

The sites where implants are placed are-

Maxilla
1. Hard

palate behind the deciduous canines
(Prior to eruption of maxillary permanent incisors)
2. Below the anterior nasal spine
(after eruption of maxillary incisors)
3. Two implants on either side of the zygomatic process
of maxilla
4. Border between hard plate and alveolar process
medial to the first molars








Mandible
1. Anterior aspect of symphysis, in the midline
below the root tips
2. Two pins on the right side of the mandibular
body, one pin under the 1st premolar and other
below the 2nd premolar or first molar
3. One pin on the external aspect of the right
ramus in level with the occlusal surface of molars.


Rotations




The phrase “growth rotation” was introduced
in 1955 by Bjork who used it to describe a
particular phenomena occurring during the
growth of head.
reporting a case in which lowering of the
mandible during growth was different dorsally
than frontally








What is Rotation?
It is the angular movement of one rigid body
relative to another.
1. a wheel may rotate with reference to its
supporting framework.
2. A tooth may rotate as it is moved through its
supporting bone.
the displacement that satisfy, the concept of
“Rigid body model” should be termed
rotations.








Terminologies
.
. Angular Change:
When a single body changes in form due to
surface accretion and removal there may be
changes in orientation between reference lines
within that body, these changes are angular
changes not the rotations as in true sense.
. Forward rotation given by Bjork ( counter
clockwise rotation with the patients right in front)
. This is the rotation of the mandible in a direction
when posterior growth of mandible is more than
anterior growth


. Backward rotation ( or clockwise with
patients right in front)
 When anterior growth is more than
posterior growth.
 . Negative Rotation-By convention all
forward rotation are given a negative sign.
 . Positive Rotation- All backward
rotations are given a positive sign.





concept of forward and backward
rotation.



This was given by Bjork and Skeiller
based on their longitudinal implant
studies.


FORWARD ROTATION
Forward rotation can occur
in 3 ways.
 Type I- Forward rotation
about the centre in the
joints which gives rise to
deep bite.
 Results in the reduced
anterior facial height.



 Type

II- Forward growth rotation of
the mandible about a centre located
at the incisal edges of the anterior
teeth. This is due to the combination
of marked development of posterior
face height and normal increase in
anterior height

•Type III- This is the forward rotation of the
mandible with centre at the level of
premolars. So this is a combination of
decreased anterior facial height and
increased posterior facial height.


So in forward rotation the mandible symphysis
swings into a more forward direction & this is the
one of the reasons for the chin formation
characteristic of man


Backward Rotation
It can occur in 2 ways.
Type I-In this the
centre of rotation lies
in the
temporomandibular
joints. Results in an
increased anterior
facial height

Type II – Rotation occurs
about at the most distal
occluding molars. This is a
combination of increased
anterior facial height and
decreased posterior facial
height.




The concept of rotation was originated in relation
to mandible and then was studied for maxilla
also.

Maxillary Rotations
Rotation of maxilla during normal growth was not
suspected until the implant study of Bjork &
coworkers.

There seems to be an almost parallel lowering
of nasal floor( was shown by Brodie in 1941)

Why is it so?
It is because of the reasons that whatever
rotation that takes place in maxilla [ Whether it is
backward or forward] is masked by the process
of remodeling.






So, when metallic implants were placed above
the maxillary process usually rotation in a
forward direction were observed but in some
cases backward rotation was also seen.
But the angle between the s-n plane and nasal
floor didn’t show much variation this is because
of the compensatory remodeling that took place
on the nasal floor.


In cases of forward rotation; as the
anterior part of palate was tipped
upward resorption took place on the
anterior aspect of nasal floor and
deposition on the posterior aspect.

In cases of backward rotation of maxilla,
there is pronounced resorption posteriorly


The mean of forward rotation of 21 cases was -2.5 degrees.


Rotation of maxilla
Normal inclination = 850
 Ante inclination >850
 Retro inclination <850
 Inclination angle records rotation of
maxilla to the anterior cranial base i.e. to
the SN line as described by A.M. Schwarz



Maxillary anteinclination with reduced
overbite


Maxillary retroclination with increased
overbite







Transverse mutual rotation of two maxillae:
Since right and left maxillae are two separate
bones, joined along the median suture, there is
an anterior and a lateral implant in each maxilla,
so that distance between these implants is
constant throughout growth. In the transverse
plane, a triangle is constructed with sides of
constant length.
It was seen that the increase in width from
age 10 - 11yrs in 9 cases, measured between
lateral implants was 3 times as great as that
between anterior implants. From this it is inferred
that



1. Lateral implants separate more than anterior
during growth indicating that the two maxillae
rotate in relation to each other in transverse
plane.



2.
The length of maxilla is reduced in mid
saggital plane, due to this transverse rotation.
Lateral segments of dental arch also separate
more posteriorly than anteriorly due to transverse
rotation of the two maxillae.
Hence distance between molars increases
more than canines. Also the length of dental arch
becomes reduced in mid-sagital plane.






Mandibular Rotations as given by different
authors

Bjork /Skeiller
They used 3 terms to describe mandibular rotation

Total – Matrix – Intramatrix
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
anterior cranial base.

2. Matrix Rotation – This is the rotation of tangential
manibular line with respect to cranial base
Matrix Rotation has its centre at the condyles

3. Intramatarix Rotation : The difference between total and
matrix rotation and it is an expression of the remodeling at the
lower border of the mandible
It is identified by the change in inclination of an implant or
reference line in the manibular body relative to the tangential
mandibular line
This rotation has its centre somewhere in body of the mandible

According to Bjork and skeiller the position of
centre of rotation of “total rotation” is dependent
on the other two centres of rotation.
(Bjork & skiller case reports AJO Oct 72)
material – 21 subjects
9 girls
12 boys


Method – Metallic implants were inserted
in both jaws except for in 2 cases where
no implant was present in maxilla.
 The study was limited to 6 year period
around puberty
 Lateral cephs for all 3 periods were taken



Result
Mean forward rotation of the mandible for the
whole series was – 6 degrees.
For the maxilla the mean for the forward
rotations was -2.5 degrees .
Rotations were more than twice as great for the
mandible as for the maxilla


As observed in conventional cephalometry
ie. Between NS line and mandibular line
the forward rotation was –3.4 degrees.
 It is evident that about half the rotation
was masked by remodeling.
 Remodeling at the lower border of the
mandible was 2.6 degrees on an average.
.



•Inclination of the ramus in relation to nasion –
sella line, unlike that of the body of the mandible
was on an average practically unchanged over
the period. Mean change was -1 degree.
•This constancy in the ramus inclination is
because of remodeling of the ramus in order to
maintain its functional relation to the neck
muscles and the spinal column.

In maxilla
It was found that remodeling of the nasal floor
varied in the cases according to the difference in
direction of rotation of maxilla.
So, we see that inclination of the nasal floor
showed greater stability, irrespective of the
direction and magnitude of the rotation of the
maxilla .


.
Causes as mentioned by Bjork & skeiller were
1. Condylar growth
 2. Development of cranial base
 3. Instability of incisal occlusion
 4. Lip and tongue dysfunction
 5. Interaction of jaw and neck
musculature.



Importance of condylar growth

forward path – forward
rotation
backward path –
backward rotation.


Solow – Houston
Solow & Houston in EJO 1988 proposed their own
terminology
True rotation of the mandible term was
introduced by Solow Siersback- Nielsen (1986) This
is the rotation of the mandibular body as
represented by implants or stable trabecular
reference structures, relative to anterior cranial
base.
This is similar as total rotation of Bjork and Skeiller

Apparent Rotation of the mandible
Angular change in the orientation of
mandibular line relative to the cranial base
.
Lande(1952) observed that the lower border
of the mandible becomes less steeply
inclined with growth. The observation made
by him was the same as Solow Houston’s
Apparent rotation and also similar to Bjork &
Skeiller’s Matrix rotation.

This is what we see when superimposing
cephalograms conventionally
.
This apparent rotation is the result of true
mandibular rotation and remodeling at the
lower border
.


Angular remodeling of the mandibular
border
Angular change in the mandibular line when the
mandible is registered on implants or stable natural
structures
This is a measure of amount of remodelling at the
mandibular border


• This angular remodeling amounts to about 50
percent of the true mandibular rotation.
• when we see for the posterior border of the
mandible, Bjork & skeiller (1972) showed that
average angular remodeling (5degree) was almost
as large as the average true rotation (-6degree) over
the 6yr period.
• So the efficiency of the counter remodelling
process was around 80 percent.
• The apparent rotation of ramus line was only – 1
degree.



The same terminology can be applied to
remodeling of hard palate. When maxilla
rotates forward, counter remodeling of
nasal and palatal surfaces take place and
apparent rotation of palatal plane is much
less then the true rotation of maxilla.


Profitt
Internal rotation -rotation of
mandibular core relative to cranial base
implant.
 Total Rotation – Rotation of mandibular
plane relative to cranial base.
 External Rotation – Rotation of
mandibular plane.



INTERNAL AND EXTERNAL
ROTATION OF MAXILLA


Resorption on nasal floor and
deposition on palatal side plus
eruption of teeth corresponds to
external rotation of maxilla.



In total external and internal
rotations cancel each other leading to
zero effect or minimal forward
rotation of maxilla.

. Lavergne and Gasson (1976)
They defined rotation as Positional and

Morphogentic
Positional rotation deals with the position of
the mandible within the head.
Morphogenetic rotation concerns
with shape of the mandible.
They postulated that this is a compensating
mechanism which is capable of enlarging or
reducing mandibular length as measured along the
condylion pogonion diagonal.

. Enlow
Displacement
 Remodelling
 a) involves rotational positioning of jaws in
vertical and horizontal or antero –
posterior direction.
 b) Remodelling – involves resorptive and
despository growth process resulting in
angular as well as dimensional change.



. Dibbets
Dibbets in his article puzzle of growth
rotation ( Am J Orthod 1985) coined the
term counter balancing Rotation
counter balancing rotation pertains to
circular condylar growth, accompanied by
selective coordinated remodeling which
does not contribute to the incremental
growth of the mandible.









Dibbets made a hypothetical construction of the
two possible divergent patterns of mandibular
growth
A circular growth pattern, resulting only in
intramatrix rotation and marked by the absence
of actual enlargement of mandible.
A linear condylar growth pattern
characterized by the absence of intramatrix
rotation but evidencing mandibular enlargement


This counter balancing rotation is a
mechanism that
 1. neutralizes growth
 2. Results in selective enlargement of the
mandible



Mutual rotation of the jaws






Rotation of the jaws are a major contributing
factor in deciding the vertical proportions of face.
. convergent rotation of jaws
creates a severly deep overbite which is difficult
to manage using functional methods.
Divergent rotation of the jaw bases-- this
can cause marked open bite.


. Cranial rotation – In this there is
relatively harmonious rotation of both jaws
in an upward and forward direction.
 Caudal rotation
In relatively harmonious manner the
downward and backward maxillary
rotation offsets what could be an open bite
created by downward and backward
mandibular rotation.


CAUSE OF ROTATION
Houston Concept – EJO 1988
 According to him mandibular growth rotation is
merely a reflection of an imbalance of growth in
anterior and posterior facial heights.
Posterior facial height
 This is measured between the cranial base and
mandibular implant line .
 It is the sum of the Vertical components of –
 The descent of the middle cranial fossa
 growth of the mandibular condyle



Anterior facial height
Schudy (1965)
 Growth in anterior facial height is caused
by growth at maxillary sutures and at the
alveolar process together with eruption of
teeth
 But these all are secondary







Growth in the anterior facial height can be
understood only by examining the wider context
of the skeleton, muscles and fascia of neck and
head
Brodie (1950) stated that posture of the head
depends on the muscles of the neck and muscles
of mastication . Supra and infra hyoid muscles
act as link in a chain joining the cranium
,mandible, hyoid done and shoulder girdle.




Bench (1963) examined growth of the
upper cervical vertebrae and related this
to descent of the hyoid bone and chin,
relative to the Frankfort plane.


Solow and Krieborg (1977) suggested that
cranio cervical angulation might influence
facial growth direction through the
mechanism of soft tissue stretch
 Solow (1966) have found correlation
between facial height and stature in cross
section studies.



According to Houston growth in cervical
column is the primary factor determining
growth in anterior face height.
 Acts through differential growth in muscles
and fascia that are attached to the
mandible and to the cranium above and to
the hyoid bone and shoulder girdle below.







In the normally growing child, the head is carried
upwards relative to the shoulder girdle due to
growth of cervical vertebrae.
Decent of hyoid bone and mandibular symphysis
relative to the cranial base is largely the result of
the differential growth and strength of the
musculature, fascia and other soft tissues that
pass between the cranium, mandible , hyoid bone
and shoulder girdle. Thus growth in anterior facial
height is paced.

.


Rotation--- Any discrepancy in the relative
growth of the anterior and posterior face
heights will be manifested as true rotation
of mandible.
 According to Ballard growth of the alveolar
process and eruption of the teeth adapt to
the growth in height of the intermaxillary
spaces so that in most cases normal
occlusion is established



In cases- anterior face height is greatly
increased.inadequate vertical dentoalveolar compensation
skeletal anterior open bite.


Solow and Tallgren (1976) found that
posture of head in relation to the cervical
column was related to craniofacial
morphology.
Where the head was tilted back, the face
was retrognathic and the mandible plane
angle as well as the total and anterior face
height was large

Solow Kreiborg (1977)
 Factors effecting the adequacy of nasal
airway can result in a posterior tilt of the
head, and these factors are-:
1 Nasal obstruction due to adenoids( Linder
Aronson 1979)
2 Experimental nasal obstruction( Vig et al
1980)
3 Allergic rhinitis( Wenzel etal 1983)



According to Schudy






He postulated that growth
rotation of the mandible
results from an inharmony
between vertical growth and
anteroposterior or horizontal
growth.
Clockwise rotation (as from
patients right) is a result of
excessive vertical growth as
it relates to horizontal
growth and causes reduction
of overbite.
Counter clockwise rotation is
a result of deficiency in
vertical growth as relates to
horizontal growth and causes
deep bite.







What is vertical and horizontal growth ?
Increments of growth which cause the chin to
move vertically are called vertical growth.
Increments which cause the chin to move
forward i e condylar growth are termed –
horizontal growth.




Condylar growth is pitted against
combined vertical elements of growth and
the final position of chin will be resultant
of the horizontal and vertical growth.




What are these vertical elements ?

1) Growth of nasion and in the corpus of the maxilla
which produces an increase in the distance from
nasion to anterior nasal spine and cause the
maxillary molars and posterior nasal spine to more
away from the sella-nasion plane.
2) Growth of maxillary posterior alveolar processes
causing the molar teeth to move away from the
palatal plane.
3) Growth at the mandibular posterior alveolar
process causing the molar teeth to move occlusally.








Clockwise Rotation
Result of more posterior vertical growth than
condylar growth,
Centre of rotation is at condyles.
Pogonion cannot keep pace with the forward
growth of the upper face and mandibular plane
becomes steeper.








Counter clockwise Rotation- is a result of
more condylar growth than combined vertical
growth . There is forward movement of pogonion
and an increase in overbite.
Flattening of mandible plane renders vertical
overbite correction and retention more difficult.
The ratio between horizontal and vertical growth
increment is called the posterior growth

analysis.




The size of the gonion angle has an important
influence upon the number of degrees of
resultant counter clockwise rotation.



The smaller the gonion angle the greater rotation
is produced for each millimeter of forward
movement of pogonion.



The degree of facial divergence ie SN –MP has an
effect on rotation. The longer the SN-MP angle
more the mandible tends to become steeper and
more the chin moves backward
Smaller the angle mandible becomes flatter and
chin grows forward.




FACE TYPES





1.
2.

Why do we need to study face types?
Because certain types of facial
morphology are identified with specific
type of malocclusion
Schudy selected angle SN-MP for
identifying face types
He classified face type as
Hyper divergent
Hypodiverent



Schendel described hyper divergent as long face syndrome
and hypo divergent as short face syndrome



Long face
Horizontal facial planes
tend to be steeper
Tendency for open bite
Associated with backward
rotational growth

Short face
Less steeper

Obtuse gonial angle
Palatal plane
tipped down posteriorly

Small gonial angle
Flatter palatal plane








For deep bite
Associated with forward
rotational growth


• Nanda in his study (AJO 1990)
• 32 subjects were selected with extremes
of facial heights and various relationships
between horizontal planes was given.


.
Inclination of palatal plane is significantly
different between two extreme type of
faces
 Mandibular plane, Occlusal plane and
gonial angle steadily decreased in both
open and deep bite cases.





Interaction between Jaw Rotation and
Tooth eruption



It is essential to take into consideration that the
rotation of the jaws during growth exerts an
influence on the path of eruption of the teeth and
hence on the occlusion .




Results



1. Eruption of lower molars was greater than that
of the incisors.
2. Eruption of upper molars was greater than that
of the incisors.
3. Lower incisor were inclined backward in
relation to NS line, but only to the extent of two
thirds of the mandibular rotation, and thus were
tipped forward on the mandibular base.
4. upper incisors proclined in relation to the NS
line but followed maxilla in its forward rotation.







5.Molars followed mandible in its rotation.
 6. Intermolar angle remained unchanged
 7. Lower incisors compensated by forward
tipping.
 8. Lower molars had a compensatory
forward tipping on the jaw base



Backward Rotation of the face
 Centre of rotation at molars
 1. Incisors erupted further than molars
 2. Incisors tipped backward









Path of eruption of the maxillary teeth is
downward. When maxilla rotates forward this will
tip incisors forward but backward rotation directs
anterior teeth posteriorly. The molars migrate
further mesially during growth than incisors so,
there is decrease in arch length.
As forward rotation of mandible is greater than
maxilla, there is more decrease in mandibular
arch length.
places greater importance on lingual movement
of the incisors as for the cause of decrease in
arch length

DEEP BITE


BACKWARD rotation of
maxilla






BACKWARDS
ROTATION OF
MAXILLA
FORWARD ROTATION
OF MANDIBLE




FORWARD rotation of
mandible


Open Bite


FORWARD ROTATION
OF MAXILLA






FORWARD rotation of
Maxilla
backward rotation of
Mandible


GROWTH PREDICTION
Methods of growth prediction
 1.Longtudinal
 2.Metric
 3.Structural
.













Longitudinal Method
It is commonly used and consists of following the
course of development in annual X-Ray cephalometric
films.
Limitation
1. The pattern of growth is not constant and the pattern
recorded at a juvenile age may well have changed by
adoloscence.
2. Particular limitation of this method is that it permits the
observation of changes in the sagittal jaw relation but
those occuring the vertical direction are masked.
This method can be made more useful by superimposition
on natural reference structures









Metric Method
Aims at a Prediction of facial development on the
basis of facial morphology, determined metrically
from a single X-Ray film.
But there is only weak correlation between
the dimensions of face at the age of 12 years and
the residual growth ( as was shown by Bjork by
his study on Swedish boys in 1954.)
So, we can say that length of the mandible
during adoloscence can’t be judged from it size
before puberty.


Structural Method

This is based on information concerning
the remodeling processes of the mandible
during growth, gained from implant
studies



PREDICTION OF GROWTH
ROTATION









Bjork in 1969 gave 7 structural signs to predict
future growth rotation.
1. Inclination of condylar head
2. Curvature of mandibular canal
3. Shape of Lower border of Mandible
4. Inclination of symphysis
5. Interincisal Angle
6. Inter premolar or intermolar angles
7. Anterior Lower facial Height


Leslie et al ( 1998 AJO)
Reviewed this method










Obtained result that –
Out of the four individual independent
variable ie
i) Mandibular inclination
ii) Intermolar angle
iii) Shape of the lower border of the mandible
iv) Inclination of symphysis
Minimal ability of any of the four individual
independent variables to predict mandibular
growth rotation.
Highest predictive value was of intermolar angle.


Brema and Pancherz (angle 2005)
 Again reviewed Bjork’s method and found
that
 symphysial inclination is a reliable sign.
 Lower border is less reliable
 And also found that hypodivergent
patterns can be easily recognised .



Clinical Implications
1. It has been agreed that orthodontic
treatment does not stimulate growth at
mandibular condyles. So, we have got
only vertical increments that can be
possibly changed to serve our purpose.
inhibiting vertical growth is equivalent to
stimulating condylar growth eg- high pull
head gear , face bow.

. •2. When we see deep bite cases because of
deficient vertical growth,.
we should stimulate vertical growth of alveolar
process with class II elastics and /or
conventional face bow head gear with cervical
traction.
•.

•3 Predominance of vertical growth of the face
facilitates correction and retention of vertical
overbite.



4 Too much vertical growth of the molar
teeth would prevent forward positioning of
the chin and render class II correction
very difficult



5 Forward rotation pattern renders vertical
overbite correction and retention difficult.




6 When at the completion of orthodontic
treatment mandibular plane is increased,
most commonly it will return to normal ,
as condyles will grow and horizontal
growth will compensate

.


7. Posterior rotations induced by
orthodontic treatment, ie by the use of
class II elastics, anchorage bends and
anterior bite planes are often transient as
posterior facial height will catch up.



Conclusion



The ability of an orthodontist to
understand and predict future mandibular
growth rotation would greatly aid in
diagnosis and treatment planning



Better therapeutic decisions could be
made regarding timing and length of
treatment, appliance selection ,extraction
pattern and possible need for surgery

.


Treatment planning can be customized
with the possibility of optimal results in a
shorter period of time.

Thank you
Leader in continuing dental education


Growth rotations 2 /certified fixed orthodontic courses by Indian dental academy

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Growth rotations 2 /certified fixed orthodontic courses by Indian dental academy