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GROWTH
ROTATIONS

www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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CONTENTS











Introduction
Implants
What is rotation
Different terminologies
Cause of rotation
Face types
...
Introduction
The introduction of cephalometric
radiography in 1930’s initiated new
trends in orthodontics
It became a wide...
It facilitated the longitudinal study of
craniofacial growth by the method of
superimposition of radiographs on specific
l...


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



The concept of growth rotation helps ...
IMPLANTS






The technique where metal implants are
inserted in bone, has been used in animals for
more than a centur...
The sites where implants are placed are-

Maxilla
1. Hard

palate behind the deciduous canines
(Prior to eruption of maxil...
www.indiandentalacademy.com







Mandible
1. Anterior aspect of symphysis, in the midline
below the root tips
2. Two pins on the right side of t...
www.indiandentalacademy.com
Rotations




The phrase “growth rotation” was introduced
in 1955 by Bjork who used it to describe a
particular phenomen...
www.indiandentalacademy.com






What is Rotation?
It is the angular movement of one rigid body
relative to another.
1. a wheel may rotate with ...






Terminologies
.
. Angular Change:
When a single body changes in form due to
surface accretion and removal there ...
. Backward rotation ( or clockwise with
patients right in front)
 When anterior growth is more than
posterior growth.
 ....
www.indiandentalacademy.com


concept of forward and backward
rotation.



This was given by Bjork and Skeiller
based on their longitudinal implant
...
FORWARD ROTATION
Forward rotation can occur
in 3 ways.
 Type I- Forward rotation
about the centre in the
joints which giv...
 Type

II- Forward growth rotation of
the mandible about a centre located
at the incisal edges of the anterior
teeth. Thi...
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•Type III- This is the forward rotation of the
mandible with centre at the level of
premolars. So this is a combination of...
www.indiandentalacademy.com
So in forward rotation the mandible symphysis
swings into a more forward direction & this is the
one of the reasons for th...
Backward Rotation
It can occur in 2 ways.
Type I-In this the
centre of rotation lies
in the
temporomandibular
joints. Resu...
Type II – Rotation occurs
about at the most distal
occluding molars. This is a
combination of increased
anterior facial he...


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

Maxillary Rotati...
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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...
www.indiandentalacademy.com




So, when metallic implants were placed above
the maxillary process usually rotation in a
forward direction were obse...
In cases of forward rotation; as the
anterior part of palate was tipped
upward resorption took place on the
anterior aspec...
www.indiandentalacademy.com
The mean of forward rotation of 21 cases was -2.5 degrees.

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Rotation of maxilla
Normal inclination = 850
 Ante inclination >850
 Retro inclination <850
 Inclination angle records ...
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Maxillary anteinclination with reduced
overbite

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Maxillary retroclination with increased
overbite

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




Transverse mutual rotation of two maxillae:
Since right and left maxillae are two separate
bones, joined along the...


1. Lateral implants separate more than anterior
during growth indicating that the two maxillae
rotate in relation to ea...
Mandibular Rotations as given by different
authors

Bjork /Skeiller
They used 3 terms to describe mandibular rotation

Tot...
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2. Matrix Rotation – This is the rotation of tangential
manibular line with respect to cranial base
Matrix Rotation has it...
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According to Bjork and skeiller the position of
centre of rotation of “total rotation” is dependent
on the other two centr...
Method – Metallic implants were inserted
in both jaws except for in 2 cases where
no implant was present in maxilla.
 The...
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Result
Mean forward rotation of the mandible for the
whole series was – 6 degrees.
For the maxilla the mean for the forwar...
As observed in conventional cephalometry
ie. Between NS line and mandibular line
the forward rotation was –3.4 degrees.
 ...
•Inclination of the ramus in relation to nasion –
sella line, unlike that of the body of the mandible
was on an average pr...
In maxilla
It was found that remodeling of the nasal floor
varied in the cases according to the difference in
direction of...
.
Causes as mentioned by Bjork & skeiller were
1. Condylar growth
 2. Development of cranial base
 3. Instability of inc...
Importance of condylar growth

forward path – forward
rotation
backward path –
backward rotation.

www.indiandentalacademy...
Solow – Houston
Solow & Houston in EJO 1988 proposed their own
terminology
True rotation of the mandible term was
introduc...
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Apparent Rotation of the mandible
Angular change in the orientation of
mandibular line relative to the cranial base
.
Land...
This is what we see when superimposing
cephalograms conventionally
.
This apparent rotation is the result of true
mandibul...
Angular remodeling of the mandibular
border
Angular change in the mandibular line when the
mandible is registered on impla...
• This angular remodeling amounts to about 50
percent of the true mandibular rotation.
• when we see for the posterior bor...


The same terminology can be applied to
remodeling of hard palate. When maxilla
rotates forward, counter remodeling of
n...
Profitt
Internal rotation -rotation of
mandibular core relative to cranial base
implant.
 Total Rotation – Rotation of ma...
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INTERNAL AND EXTERNAL
ROTATION OF MAXILLA


Resorption on nasal floor and
deposition on palatal side plus
eruption of tee...
. Lavergne and Gasson (1976)
They defined rotation as Positional and

Morphogentic
Positional rotation deals with the posi...
. Enlow
Displacement
 Remodelling
 a) involves rotational positioning of jaws in
vertical and horizontal or antero –
pos...
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. Dibbets
Dibbets in his article puzzle of growth
rotation ( Am J Orthod 1985) coined the
term counter balancing Rotation
...






Dibbets made a hypothetical construction of the
two possible divergent patterns of mandibular
growth
A circular g...
This counter balancing rotation is a
mechanism that
 1. neutralizes growth
 2. Results in selective enlargement of the
m...
Mutual rotation of the jaws






Rotation of the jaws are a major contributing
factor in deciding the vertical proport...
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. Cranial rotation – In this there is
relatively harmonious rotation of both jaws
in an upward and forward direction.
 Ca...
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CAUSE OF ROTATION
Houston Concept – EJO 1988
 According to him mandibular growth rotation is
merely a reflection of an im...
Anterior facial height
Schudy (1965)
 Growth in anterior facial height is caused
by growth at maxillary sutures and at th...




Growth in the anterior facial height can be
understood only by examining the wider context
of the skeleton, muscles ...


Bench (1963) examined growth of the
upper cervical vertebrae and related this
to descent of the hyoid bone and chin,
re...
Solow and Krieborg (1977) suggested that
cranio cervical angulation might influence
facial growth direction through the
me...
According to Houston growth in cervical
column is the primary factor determining
growth in anterior face height.
 Acts th...
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



In the normally growing child, the head is carried
upwards relative to the shoulder girdle due to
growth of cervical...
Rotation--- Any discrepancy in the relative
growth of the anterior and posterior face
heights will be manifested as true r...
In cases- anterior face height is greatly
increased.inadequate vertical dentoalveolar compensation
skeletal anterior open ...
Solow and Tallgren (1976) found that
posture of head in relation to the cervical
column was related to craniofacial
morpho...
Solow Kreiborg (1977)
 Factors effecting the adequacy of nasal
airway can result in a posterior tilt of the
head, and the...
According to Schudy






He postulated that growth
rotation of the mandible
results from an inharmony
between vertical...





What is vertical and horizontal growth ?
Increments of growth which cause the chin to
move vertically are called v...


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

What are these vertical elements ?

1) Growth of nasion and in the corpus of the maxilla
which produces an increase in ...
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





Clockwise Rotation
Result of more posterior vertical growth than
condylar growth,
Centre of rotation is at condy...






Counter clockwise Rotation- is a result of
more condylar growth than combined vertical
growth . There is forward ...


The size of the gonion angle has an important
influence upon the number of degrees of
resultant counter clockwise rotat...
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FACE TYPES





1.
2.

Why do we need to study face types?
Because certain types of facial
morphology are identified w...


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



Long face
Horizo...
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• Nanda in his study (AJO 1990)
• 32 subjects were selected with extremes
of facial heights and various relationships
betw...
.
Inclination of palatal plane is significantly
different between two extreme type of
faces
 Mandibular plane, Occlusal p...
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

Interaction between Jaw Rotation and
Tooth eruption



It is essential to take into consideration that the
rotation of...


Results



1. Eruption of lower molars was greater than that
of the incisors.
2. Eruption of upper molars was greater ...
5.Molars followed mandible in its rotation.
 6. Intermolar angle remained unchanged
 7. Lower incisors compensated by fo...
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Backward Rotation of the face
 Centre of rotation at molars
 1. Incisors erupted further than molars
 2. Incisors tippe...
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





Path of eruption of the maxillary teeth is
downward. When maxilla rotates forward this will
tip incisors forward ...
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DEEP BITE


BACKWARD rotation of
maxilla

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



BACKWARDS
ROTATION OF
MAXILLA
FORWARD ROTATION
OF MANDIBLE

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

FORWARD rotation of
mandible

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Open Bite


FORWARD ROTATION
OF MAXILLA

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



FORWARD rotation of
Maxilla
backward rotation of
Mandible

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

www.indiandentalacademy.com










Longitudinal Method
It is commonly used and consists of following the
course of development in annual X-Ra...







Metric Method
Aims at a Prediction of facial development on the
basis of facial morphology, determined metrical...
Structural Method

This is based on information concerning
the remodeling processes of the mandible
during growth, gained...
PREDICTION OF GROWTH
ROTATION









Bjork in 1969 gave 7 structural signs to predict
future growth rotation.
1....
Leslie et al ( 1998 AJO)
Reviewed this method










Obtained result that –
Out of the four individual independ...
Brema and Pancherz (angle 2005)
 Again reviewed Bjork’s method and found
that
 symphysial inclination is a reliable sign...
Clinical Implications
1. It has been agreed that orthodontic
treatment does not stimulate growth at
mandibular condyles. S...
. •2. When we see deep bite cases because of
deficient vertical growth,.
we should stimulate vertical growth of alveolar
p...


4 Too much vertical growth of the molar
teeth would prevent forward positioning of
the chin and render class II correct...


6 When at the completion of orthodontic
treatment mandibular plane is increased,
most commonly it will return to normal...


Conclusion



The ability of an orthodontist to
understand and predict future mandibular
growth rotation would greatly...
Thank you
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Leader in continuing dental education

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

  1. 1. GROWTH ROTATIONS www.indiandentalacademy.com
  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  3. 3. CONTENTS           Introduction Implants What is rotation Different terminologies Cause of rotation Face types Tooth eruption Prediction of growth rotation Clinical implications conclusion www.indiandentalacademy.com
  4. 4. 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. www.indiandentalacademy.com
  5. 5. 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.  www.indiandentalacademy.com
  6. 6.  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 .  www.indiandentalacademy.com
  7. 7. 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. www.indiandentalacademy.com
  8. 8. 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 www.indiandentalacademy.com
  9. 9. www.indiandentalacademy.com
  10. 10.     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. www.indiandentalacademy.com
  11. 11. www.indiandentalacademy.com
  12. 12. 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 www.indiandentalacademy.com
  13. 13. www.indiandentalacademy.com
  14. 14.      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. www.indiandentalacademy.com
  15. 15.     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 www.indiandentalacademy.com
  16. 16. . 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.  www.indiandentalacademy.com
  17. 17. www.indiandentalacademy.com
  18. 18.  concept of forward and backward rotation.  This was given by Bjork and Skeiller based on their longitudinal implant studies. www.indiandentalacademy.com
  19. 19. 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.  www.indiandentalacademy.com
  20. 20.  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 www.indiandentalacademy.com
  21. 21. www.indiandentalacademy.com
  22. 22. •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. www.indiandentalacademy.com
  23. 23. www.indiandentalacademy.com
  24. 24. 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 www.indiandentalacademy.com
  25. 25. 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 www.indiandentalacademy.com
  26. 26. 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. www.indiandentalacademy.com
  27. 27.  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. www.indiandentalacademy.com
  28. 28. www.indiandentalacademy.com
  29. 29. 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. www.indiandentalacademy.com
  30. 30. www.indiandentalacademy.com
  31. 31.   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. www.indiandentalacademy.com
  32. 32. 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 www.indiandentalacademy.com
  33. 33. www.indiandentalacademy.com
  34. 34. The mean of forward rotation of 21 cases was -2.5 degrees. www.indiandentalacademy.com
  35. 35. 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  www.indiandentalacademy.com
  36. 36. www.indiandentalacademy.com
  37. 37. Maxillary anteinclination with reduced overbite www.indiandentalacademy.com
  38. 38. Maxillary retroclination with increased overbite www.indiandentalacademy.com
  39. 39.    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 www.indiandentalacademy.com
  40. 40.  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.   www.indiandentalacademy.com
  41. 41. 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. www.indiandentalacademy.com
  42. 42. www.indiandentalacademy.com
  43. 43. 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 www.indiandentalacademy.com
  44. 44. www.indiandentalacademy.com
  45. 45. www.indiandentalacademy.com
  46. 46. 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 www.indiandentalacademy.com
  47. 47. 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  www.indiandentalacademy.com
  48. 48. www.indiandentalacademy.com
  49. 49. www.indiandentalacademy.com
  50. 50. www.indiandentalacademy.com
  51. 51. www.indiandentalacademy.com
  52. 52. www.indiandentalacademy.com
  53. 53. 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 www.indiandentalacademy.com
  54. 54. 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. .  www.indiandentalacademy.com
  55. 55. •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. www.indiandentalacademy.com
  56. 56. 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 . www.indiandentalacademy.com
  57. 57. . 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.  www.indiandentalacademy.com
  58. 58. Importance of condylar growth forward path – forward rotation backward path – backward rotation. www.indiandentalacademy.com
  59. 59. 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 www.indiandentalacademy.com
  60. 60. www.indiandentalacademy.com
  61. 61. www.indiandentalacademy.com
  62. 62. 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. www.indiandentalacademy.com
  63. 63. 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 . www.indiandentalacademy.com
  64. 64. 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 www.indiandentalacademy.com
  65. 65. • 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. www.indiandentalacademy.com
  66. 66.  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. www.indiandentalacademy.com
  67. 67. 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.  www.indiandentalacademy.com
  68. 68. www.indiandentalacademy.com
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  70. 70. 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. www.indiandentalacademy.com
  71. 71. . 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. www.indiandentalacademy.com
  72. 72. . 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.  www.indiandentalacademy.com
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  74. 74. . 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.  www.indiandentalacademy.com
  75. 75.    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 www.indiandentalacademy.com
  76. 76. This counter balancing rotation is a mechanism that  1. neutralizes growth  2. Results in selective enlargement of the mandible  www.indiandentalacademy.com
  77. 77. 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. www.indiandentalacademy.com
  78. 78. www.indiandentalacademy.com
  79. 79. . 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. www.indiandentalacademy.com
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  82. 82. 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  www.indiandentalacademy.com
  83. 83. 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  www.indiandentalacademy.com
  84. 84.   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. www.indiandentalacademy.com
  85. 85.  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. www.indiandentalacademy.com
  86. 86. 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.  www.indiandentalacademy.com
  87. 87. 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.  www.indiandentalacademy.com
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  89. 89.   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. . www.indiandentalacademy.com
  90. 90. 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  www.indiandentalacademy.com
  91. 91. In cases- anterior face height is greatly increased.inadequate vertical dentoalveolar compensation skeletal anterior open bite. www.indiandentalacademy.com
  92. 92. 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 www.indiandentalacademy.com
  93. 93. 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)  www.indiandentalacademy.com
  94. 94. 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. www.indiandentalacademy.com
  95. 95.    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. www.indiandentalacademy.com
  96. 96.  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. www.indiandentalacademy.com
  97. 97.  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. www.indiandentalacademy.com
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  99. 99.     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. www.indiandentalacademy.com
  100. 100.    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. www.indiandentalacademy.com
  101. 101.  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.  www.indiandentalacademy.com
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  103. 103. 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 www.indiandentalacademy.com
  104. 104.  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 www.indiandentalacademy.com
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  106. 106. • Nanda in his study (AJO 1990) • 32 subjects were selected with extremes of facial heights and various relationships between horizontal planes was given. www.indiandentalacademy.com
  107. 107. . 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.  www.indiandentalacademy.com
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  110. 110.  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 . www.indiandentalacademy.com
  111. 111.  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.    www.indiandentalacademy.com
  112. 112. 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  www.indiandentalacademy.com
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  114. 114. Backward Rotation of the face  Centre of rotation at molars  1. Incisors erupted further than molars  2. Incisors tipped backward  www.indiandentalacademy.com
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  117. 117.    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 www.indiandentalacademy.com
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  120. 120. DEEP BITE  BACKWARD rotation of maxilla www.indiandentalacademy.com
  121. 121.   BACKWARDS ROTATION OF MAXILLA FORWARD ROTATION OF MANDIBLE www.indiandentalacademy.com
  122. 122.  FORWARD rotation of mandible www.indiandentalacademy.com
  123. 123. Open Bite  FORWARD ROTATION OF MAXILLA www.indiandentalacademy.com
  124. 124.   FORWARD rotation of Maxilla backward rotation of Mandible www.indiandentalacademy.com
  125. 125. GROWTH PREDICTION Methods of growth prediction  1.Longtudinal  2.Metric  3.Structural .  www.indiandentalacademy.com
  126. 126.       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 www.indiandentalacademy.com
  127. 127.     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. www.indiandentalacademy.com
  128. 128. Structural Method  This is based on information concerning the remodeling processes of the mandible during growth, gained from implant studies  www.indiandentalacademy.com
  129. 129. 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 www.indiandentalacademy.com
  130. 130. 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. www.indiandentalacademy.com
  131. 131. 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 .  www.indiandentalacademy.com
  132. 132. 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. www.indiandentalacademy.com
  133. 133. . •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. www.indiandentalacademy.com
  134. 134.  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. www.indiandentalacademy.com
  135. 135.  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. www.indiandentalacademy.com
  136. 136.  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. www.indiandentalacademy.com
  137. 137. Thank you www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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