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Page  1
GROWTH
ROTATIONS
Dr MOHAMMED BASHEER
Page  2
Page  3
Introduction
The phrase growth rotation was introduced in 1955 by Dr ARNE BJORK
He described it a particular ph...
Page  4
Of all the patterns of growth , growth rotations assume an important role in
orthodontics because of its major i...
Page  5
ENLOWS CONCEPT
basic categories of rotations:
remodelling rotations displacement rotations
FUNDAMENTAL PRINCIPLE ...
Page  6
remodelling rotations
• Surface towards the directions
is depository +
• Surface away from the growth
direction i...
Page  7
Schema of “skeletal units” of the mandible.
Page  8
Schematic representation of mandibular growth, showing
the fetal mandible superimposed
upon the adult mandible.
Page  9
Displacement rotations
The whole bone is carried by mechanical force as it simultaneously enlarges .
Page  10
2 types of displacements
Primary displacement
Takes place with a bones own enlargement
The whole bone displace...
Page  11
Secondary displacement
• The movement of a bone is not related
to its own enlargement
• the anterior direction o...
Page  12
A Bjork Started his study in 1951
Had a sample size of 100 children between the age group of 4 – 24 yrs.
Used me...
Page  13
Mandibular growth rotations assume an important role because they are
common than maxillary rotations.
Mandibu...
Page  14
BJORKS CLASSIFICATION OF MANDIBULAR ROTATIONS
(1969)
Arne Bjork (1911–1996) was a Swedish
dentist
Dr. Bjork wa...
Page  15
AJO JUNE 1969 , VOL 55 , ISSUE 6 , P 585-599
Page  16
Rotations of mandible
forward rotations backward rotation
-Type 1 -Type 1
-Type 2 -Type 2
-Type 3
AJO JUNE 1969 ...
Page  17
Type 1 forward rotations
Center- TMJ
Lower dental arch
compressed in to the
upper arch
Deep bite ↓ Ant facial he...
Page  18
6/26/2016
Page  19
Type II
Center- incisal edges
of lower ant teeth
It is due to Marked
development of post
facial height & normal ...
Page  20
6/26/2016
Page  21
Type III
Center of rotation -
premolars
The dental arches
compressed in to
each other , & basal
deep bite develo...
Page  22
• Chin becomes prominent
• Mandibular symphysis
swings forward
Page  23
Backward Rotation Type I
Center – TMJ
Bite raised by
orthodontic means 
AFH increases
Causes- the middle
Crania...
Page  24
6/26/2016
Page  25
Type II
Center – Most distal occluding molars
Cause - Sagittal growth direction of condyle , as
mandible grows i...
Page  26
Finally he also concluded that
Mandibular growth Rotation is closely associated with both the direction & the
a...
Page  27
Structural Signs given by DR A . Bjork
Condylar inclination.
Mandibular canal inclination.
Lower border of mandi...
Page  28 GROWTH ROTATIONS
28
Condylar inclination
Page  29
Mandibular canal inclination.
Page  30
GROWTH ROTATIONS
30
Lower border of mandible
(Antigonial notch).
Page  31
GROWTH ROTATIONS
31
Symphysis inclination.
Page  32
32
Interincisal inclination.
Intermolar angle.
Page  33
33
LOWER ANTERIOR FACIAL HEIGHT
Page  34
Page  35
He concluded on the structural signs
It is important to detect extreme types of mandibular rotation occurring d...
Page  36
Clinical implications !!
Both forward & Backward rotation greatly influences paths of eruption
Serious risk of...
Page  37
BJORK AND SKIELLER
Page  38
After conducted the implant study they concluded that
Divided the
mandibular rotations
into three
components
• T...
Page  39
Total rotation
rotation of the
mandibular
corpus
Is measured as
change in
inclination of a
reference line or
a i...
Page  40
MATRIX ROTATION
Rotation of the soft tissue
matrix of the mandible
relative to the Anterior
cranial base
The sof...
Page  41
Defined as the change in inclination
of an implant line in the mandibular
corpus relative to the tangential
mand...
Page  42
The diff b/n Total Rotation & Matrix Rotation is
intramatrix Rotation
Page  43
Fred F SCHUDY
• Fred was born on a small farm in south Missouri
• he entered Washington University Dental School...
Page  44
SCHUDYS CONCEPT
Angle orthod 1965 ; 1; 36-50
Page  45
According to F F SCHUDY
Rotation of the mandible is a result of disharmony between vertical growth, antero-poste...
Page  46
Basic idea ???
IF horizontal growth >> vertical growth == counter clock wise rotation
in the molar area
If ver...
Page  47
Clock wise rotation
As a result of more vertical growth in the molar region than at
the condyles
Point of rotati...
Page  48
There are four vertical
growth elements which
increase the facial height,
these are:-
• Anterior growth of nasio...
Page  49
Counter clock wise rotation
It due to more condylar growth than vertical growth
Point of rotation being == most ...
Page  50
Clinical implications !!!
If vertical growth is deficient , simulation of
vertical growth can be done , vice ver...
Page  51
DIBBETS CONCEPT
AJO 1985 volume 87 issue 6
Page  52
He re examined Bjork & Skeiller method
Diagrammatic illustration of the concept of “intramatrix rotation.” The
m...
Page  53
Bjork and skeiller stated that “ intramatrix rotation “ is an expression of the
remodeling at the lower border ...
Page  54
An alternative interpretation was given by DIBBETS
He hypothetically
constructed Two
divergent patterns of
mandi...
Page  55
Counterbalancing Rotation
 Defined as the percentage of condylar incremental growth, detected by
implants that ...
Page  56 AM J
ORTHOO DENTOFAC ORTHOP 1990;98:29-32.)
Page  57
Counterbalancing =
proportion
Growth of articulare to pogonion
Condylar incremental growth
×100
Mandibular growt...
Page  58
• Average counterbalancing proportion for Angle classes
Class III – 85%
Class I – 76%
Class II Div 2 – 59%
Class...
Page  59
PROFFIT S CLASSIFICATION
rotation depending location of growth
Internal external
rotation rotation
Total rotation
Page  60
Rotation occurring in the core of the jaw were called as INTERNAL ROTATION
The core is the bone that surrounds...
Page  61
Matrix rotation
It occurs around the condyle
Termed as hinge rotation
Rotation of the mandibular plane relate...
Page  62
Intra matrix rotation
It is the rotation of bony element within its periosteal matrix which occurs in the
corpu...
Page  63
Rotation caused by the surface changes and the alteration in the rate of tooth eruption
is called as EXTERNAL R...
Page  64
Clinical importance
Short face type
 Low mandibular plane angle
 Skeletal anterior deep bite
 Crowding of ant...
Page  65
BJORK SOLOW AND
HOUSTON
PROFFIT
Rotation of
mandibular core
relative to cranial
base
Total
rotation
True rotatio...
Page  66
Growth rotation of maxilla
Maxilla undergoes extensive remodeling and displacements when subjected
to various f...
Page  67
Growth of maxilla occurs by two ways
– Passive displacement- in primary dentition
period
– Active growth is by ...
Page  68
Enlow’s
Maxillary Rotations
Displacement Remodeling
Page  69
Displacement Rotations
Primary displacement
The whole nasomaxillary
complex is displaced in
conjunction with its...
Page  70
Secondary Displacement
- Results from growth of other bones & their soft tissues
Page  71
In 1972 Bjork and skeiller studied rotational growth of
maxilla with the help of implants
3 sites of implant pla...
Page  72
Based on this they gave the various terminologies
Internal rotation
External rotation
Forward growth
rotation
Ba...
Page  73
Internal rotation
A rotational pattern that
occurs in the core of the
maxilla
Also known as intra matrix
rotatio...
Page  74
External rotation
Simultaneous to the internal rotation of maxilla , various degrees of
resorption of bone occur...
Page  75
Combination of IR and ER
•Forward rotation
•Backward rotation
Bjork and
skeiller
observed 2
types of
rotational
...
Page  76
Forward growth rotation
Due to excessive internal
rotation or lack of normal
external rotation or
combination of...
Page  77
Backward rotation
Downward and
backward
tipping of the
anterior end of
the palatal
plane and the
maxillary base
...
Page  78
Clinical importance
An upward and forward tipping of the anterior part of maxilla often
seen in mouth breathers ...
Page  79
MUTUAL REALTIONSHIP OF ROTATING JAW BASES
It was an attempt to clarify weather there was a difference between t...
Page  80
 According to Lavergne and Gasson the mutual rotation of the upper
and lower jaw can be of following 4 types
1....
Page  81
3. Cranial rotation of both the bases.
 Horizontal growth pattern.
 Maxillary cranial rotation compensates
for...
Page  82
Studies on growth rotation
Various studies have been conducted , notable among them are Bjork ,
skeiller , lave...
Page  83
AJODO 1994 ;106 : 60-9
Page  84
Page  85
Inferences
Mandible with anterior growth rotation was associated with small height ,large
depth ,small ratio an...
Page  86
Mandibular auto rotation after surgery (lefort 1 )
Page  87
Conclusion
The ability of an orthodontist to predict future mandibular growth would greatly aid in
the diagnosi...
Page  88
References
Contemporary orthodontics- William.R.Proffit 5th and 4th edition
Essentials of of facial growth - D...
Page  89
Facial Growth in Man, Studied With the Aid of Metallic Implants. By Arne Bjork,
Acta odontol. scandinav 13: 9-3...
Page  90
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Growth rotations in orthodontics

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The various types of growth rotations in orthodontics and its implications

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Growth rotations in orthodontics

  1. 1. Page  1 GROWTH ROTATIONS Dr MOHAMMED BASHEER
  2. 2. Page  2
  3. 3. Page  3 Introduction The phrase growth rotation was introduced in 1955 by Dr ARNE BJORK He described it a particular phenomenon occurring during the growth of the head
  4. 4. Page  4 Of all the patterns of growth , growth rotations assume an important role in orthodontics because of its major impact on treatment strategies. It is a major factor in etiological assessment , determining the nature of anomaly , the prognostic evaluation , determining the possible forms of treatment and also in assessing the stability of treatment results .
  5. 5. Page  5 ENLOWS CONCEPT basic categories of rotations: remodelling rotations displacement rotations FUNDAMENTAL PRINCIPLE OF GROWTH
  6. 6. Page  6 remodelling rotations • Surface towards the directions is depository + • Surface away from the growth direction is resorptive (-) • If deposition > resoprtion then cortical thickness increases • This pattern causes a rotation
  7. 7. Page  7 Schema of “skeletal units” of the mandible.
  8. 8. Page  8 Schematic representation of mandibular growth, showing the fetal mandible superimposed upon the adult mandible.
  9. 9. Page  9 Displacement rotations The whole bone is carried by mechanical force as it simultaneously enlarges .
  10. 10. Page  10 2 types of displacements Primary displacement Takes place with a bones own enlargement The whole bone displaced in anterior and inferior directions The amount of primary displacement produces space within the bone continues to enlarge
  11. 11. Page  11 Secondary displacement • The movement of a bone is not related to its own enlargement • the anterior direction of growth by the middle cranial fossae and the temporal lobes of the cerebrum secondarily displaces the entire nasomaxillary complex anteriorly and inferiorly
  12. 12. Page  12 A Bjork Started his study in 1951 Had a sample size of 100 children between the age group of 4 – 24 yrs. Used metal implants to find the sites of growth and resorption in individual jaws. Also examined individual variation in direction and intensity. Analyzed mechanics of changes in intermaxillary relations during growth. Implant radiography
  13. 13. Page  13 Mandibular growth rotations assume an important role because they are common than maxillary rotations. Mandibular inclinations drastically affects facial morphology , and treatment planning , treatment outcome Implants were placed in the anterior aspect of symphysis 2 pins on the right side of the mandibular body One pin on the external surface of the ramus
  14. 14. Page  14 BJORKS CLASSIFICATION OF MANDIBULAR ROTATIONS (1969) Arne Bjork (1911–1996) was a Swedish dentist Dr. Bjork was born in Darlane, Sweden. He served as chairman of orthodontics in Malmo, Sweden from 1940-1950. Professor of Orthodontics in Royal Dental College, Denmark. Eventually he became the head of Department of Orthodontics and head of Craniofacial Growth Center at the Royal Dental College for 30 years. He was nominated as member of World Federations of Orthodontists in 1995.
  15. 15. Page  15 AJO JUNE 1969 , VOL 55 , ISSUE 6 , P 585-599
  16. 16. Page  16 Rotations of mandible forward rotations backward rotation -Type 1 -Type 1 -Type 2 -Type 2 -Type 3 AJO JUNE 1969 , VOL 55 , ISSUE 6 , P 585-599
  17. 17. Page  17 Type 1 forward rotations Center- TMJ Lower dental arch compressed in to the upper arch Deep bite ↓ Ant facial height Cause-occlusal imbalance due to loss of teeth/powerful musculature AJO JUNE 1969 , VOL 55 , ISSUE 6 , P 585-599
  18. 18. Page  18 6/26/2016
  19. 19. Page  19 Type II Center- incisal edges of lower ant teeth It is due to Marked development of post facial height & normal ↑ ant facial height Lowering of the mandible occurs which happens as forward rotation Muscular & ligamentus attachments Carries the lowered mandible forward • Lowering of middle cranial fossae • increase in height of ramus in case of vertical growth Post facial height:::2 components
  20. 20. Page  20 6/26/2016
  21. 21. Page  21 Type III Center of rotation - premolars The dental arches compressed in to each other , & basal deep bite develops in case of large overjets the COR shifts to the LEVEL of premolars The AFH when the PFH Cause – unbalanced occlusions
  22. 22. Page  22 • Chin becomes prominent • Mandibular symphysis swings forward
  23. 23. Page  23 Backward Rotation Type I Center – TMJ Bite raised by orthodontic means  AFH increases Causes- the middle Cranial fossae is raised Incomplete development in height of middle cranial fossae  underveloped of PFH underdevelopment of post facial height leads to Backward Rotation
  24. 24. Page  24 6/26/2016
  25. 25. Page  25 Type II Center – Most distal occluding molars Cause - Sagittal growth direction of condyle , as mandible grows in direction of length because it is attached to ligament , it is rotated backwards The symphysis is swung backwards & chin drawn back Double chin Basal open bite develops Lower ant teeth retroclined & alveolar prognathism is reduced This type of rotation is characteristic in condylar hypoplasia & In condylar aplasia AJO JUNE 1969 , VOL 55 , ISSUE 6 , P 585-599
  26. 26. Page  26 Finally he also concluded that Mandibular growth Rotation is closely associated with both the direction & the amount of growth at the condyles
  27. 27. Page  27 Structural Signs given by DR A . Bjork Condylar inclination. Mandibular canal inclination. Lower border of mandible (Antigonial notch). Symphysis inclination. Interincisal inclination. Intermolar angle. Lower face height. Bjork gave seven structural signs to find the direction of mandibular growth. These signs are not clearly developed before puberty.
  28. 28. Page  28 GROWTH ROTATIONS 28 Condylar inclination
  29. 29. Page  29 Mandibular canal inclination.
  30. 30. Page  30 GROWTH ROTATIONS 30 Lower border of mandible (Antigonial notch).
  31. 31. Page  31 GROWTH ROTATIONS 31 Symphysis inclination.
  32. 32. Page  32 32 Interincisal inclination. Intermolar angle.
  33. 33. Page  33 33 LOWER ANTERIOR FACIAL HEIGHT
  34. 34. Page  34
  35. 35. Page  35 He concluded on the structural signs It is important to detect extreme types of mandibular rotation occurring during growth Not all of them will be found in a particular individual , but the greater the number which is present the more reliable the prediction will be .
  36. 36. Page  36 Clinical implications !! Both forward & Backward rotation greatly influences paths of eruption Serious risk of extreme migration after extractions Extractions should be avoided until the beginning of pubertal growth spurt
  37. 37. Page  37 BJORK AND SKIELLER
  38. 38. Page  38 After conducted the implant study they concluded that Divided the mandibular rotations into three components • Total rotation • Matrix rotation • Intramatrix rotation
  39. 39. Page  39 Total rotation rotation of the mandibular corpus Is measured as change in inclination of a reference line or a implant line in the mandibular corpus relative to the anterior cranial base,‘-’
  40. 40. Page  40 MATRIX ROTATION Rotation of the soft tissue matrix of the mandible relative to the Anterior cranial base The soft tissue matrix is defined by the Tangential mandibular line(ML1) The matrix rotates forwards & backwards in same individual during the growth period – PENDULUM MOVEMENT Center of Rotation – Condyles
  41. 41. Page  41 Defined as the change in inclination of an implant line in the mandibular corpus relative to the tangential mandibular line Intramatrix Rotation is an expression of remodeling at the lower border of the mandible Is the difference between total rotation and the matrix rotation. Centre of rotation is somewhere in corpus and depends on rotation of corpus, growth rotation of the maxilla and occlusion of the teeth.
  42. 42. Page  42 The diff b/n Total Rotation & Matrix Rotation is intramatrix Rotation
  43. 43. Page  43 Fred F SCHUDY • Fred was born on a small farm in south Missouri • he entered Washington University Dental School in St Lou- is, • Fred was a member of the AAO, the American Dental Association, The Edward H. Angle Society, and the Charles Tweed Foundation.
  44. 44. Page  44 SCHUDYS CONCEPT Angle orthod 1965 ; 1; 36-50
  45. 45. Page  45 According to F F SCHUDY Rotation of the mandible is a result of disharmony between vertical growth, antero-posterior growth and horizontal growth. Clockwise rotation Counter- clockwise rotation
  46. 46. Page  46 Basic idea ??? IF horizontal growth >> vertical growth == counter clock wise rotation in the molar area If vertical growth >> horizontal growth == clockwise movement rotation To those increments which move the chin vertically = we apply vertical growth The condyles which causes the chin to move forward we apply the term horizontal growth
  47. 47. Page  47 Clock wise rotation As a result of more vertical growth in the molar region than at the condyles Point of rotation == condyles Results in ++ AFH , this can cause open bites Growth at condyle == forward component  chin When the vertical aspects are applied through occlusal contact == downward +backward direction chin === clockwise rotation
  48. 48. Page  48 There are four vertical growth elements which increase the facial height, these are:- • Anterior growth of nasion. • Corpus of maxilla getting palatal plane down. • Eruption of maxillary molars. • Eruption of mandibular molars.
  49. 49. Page  49 Counter clock wise rotation It due to more condylar growth than vertical growth Point of rotation being == most distal aspect mandibular molar Forward movement of the pogonion FACIAL ANGLE The flattening of the occlusal plane causes more vertical bite The smaller the gonial angle the greater the rotation is produced for each mm of forward movement
  50. 50. Page  50 Clinical implications !!! If vertical growth is deficient , simulation of vertical growth can be done , vice versa The mandible should not be considered as a single entity , He concluded that mandibular growth is the principal determining factor of facial morphology .
  51. 51. Page  51 DIBBETS CONCEPT AJO 1985 volume 87 issue 6
  52. 52. Page  52 He re examined Bjork & Skeiller method Diagrammatic illustration of the concept of “intramatrix rotation.” The mandibular periosteal contours may be likened to a frame bordering a painting. The painting may be rotated within the frame, but the external outline, configuration, and dimensions do not change. AJO 1985 volume 87 issue 6
  53. 53. Page  53 Bjork and skeiller stated that “ intramatrix rotation “ is an expression of the remodeling at the lower border of the mandible & rotation occurs at the corpus of the mandible A third option was given by dibbets after evaluation of bjorks technique
  54. 54. Page  54 An alternative interpretation was given by DIBBETS He hypothetically constructed Two divergent patterns of mandibular growth 1)Circular growth pattern of condyle, resulting in Intramatrix Rotation without any enlargement of mandible 2)linear growth pattern of the condyle, characterized by the absence of intramatrix rotation but evidencing mandibular enlargement.
  55. 55. Page  55 Counterbalancing Rotation  Defined as the percentage of condylar incremental growth, detected by implants that has contributed to the enlargement of the condylion- pogonion dimension Counterbalancing Rotation pertains to circular condylar growth, accompanied by selective coordinated remodeling, which does not contribute to the incremental growth of the mandible. The actual path of the condyle is accompanied by selective remodeling & thus neutralizes the growth
  56. 56. Page  56 AM J ORTHOO DENTOFAC ORTHOP 1990;98:29-32.)
  57. 57. Page  57 Counterbalancing = proportion Growth of articulare to pogonion Condylar incremental growth ×100 Mandibular growth =pg-Ar2 – Pg-Ar1 Condylar growth – Ar1 – Ar2
  58. 58. Page  58 • Average counterbalancing proportion for Angle classes Class III – 85% Class I – 76% Class II Div 2 – 59% Class II Div 1– 65.5% • proportion ranges from 50% to 97%. • It is apparent that an incongruity often exists between the condylar growth direction and the direction of enlargement of the anatomic mandible. • Two mandibular tracings of the same individual at age 11 years 7 months and 17 years 7 months,
  59. 59. Page  59 PROFFIT S CLASSIFICATION rotation depending location of growth Internal external rotation rotation Total rotation
  60. 60. Page  60 Rotation occurring in the core of the jaw were called as INTERNAL ROTATION The core is the bone that surrounds the inferior alveolar nerve  internal rotation of the mandible 10-15 degrees internal rotation matrix rotation intramatrix rotation
  61. 61. Page  61 Matrix rotation It occurs around the condyle Termed as hinge rotation Rotation of the mandibular plane related to cranial base Opening and closing of bite will change the inclination of mandibular plane relative to S-N
  62. 62. Page  62 Intra matrix rotation It is the rotation of bony element within its periosteal matrix which occurs in the corpus of the core of the mandible . If there is no hinge movement then the total rotation and intra matrix will be identical On an average there is about 15 degrees of total for age 4 to adult life
  63. 63. Page  63 Rotation caused by the surface changes and the alteration in the rate of tooth eruption is called as EXTERNAL ROTATION The external compensation in an average growing adult is 11-12 degrees The difference between the internal and external rotation accounts for 3-4 degrees reduction in mandibular plane angle during growth in adolescence.
  64. 64. Page  64 Clinical importance Short face type  Low mandibular plane angle  Skeletal anterior deep bite  Crowding of anterior teeth  --LAFH Long face  Skeletal anterior open bite  Dental protrusion  ++LAFH
  65. 65. Page  65 BJORK SOLOW AND HOUSTON PROFFIT Rotation of mandibular core relative to cranial base Total rotation True rotation Internal rotation Mandibular plane relative to cranial base Matrix rotation Apparent rotation Total rotation Mandibular plane relative to the core of the mandible Intra matrix rotation Angular remodeling of lower border External rotation
  66. 66. Page  66 Growth rotation of maxilla Maxilla undergoes extensive remodeling and displacements when subjected to various functional demands . Due to the varying growth activities of middle cranial fossa , the sutural attachments of midface and surface remodeling , the maxilla tends to get rotated by displacement .
  67. 67. Page  67 Growth of maxilla occurs by two ways – Passive displacement- in primary dentition period – Active growth is by surface remodeling
  68. 68. Page  68 Enlow’s Maxillary Rotations Displacement Remodeling
  69. 69. Page  69 Displacement Rotations Primary displacement The whole nasomaxillary complex is displaced in conjunction with its own growth
  70. 70. Page  70 Secondary Displacement - Results from growth of other bones & their soft tissues
  71. 71. Page  71 In 1972 Bjork and skeiller studied rotational growth of maxilla with the help of implants 3 sites of implant placement were as follows Inferior to nasal spine Zygomatic process of maxilla ( lateral implant) At the border between the hard palate and the alveolar process medial to first molar
  72. 72. Page  72 Based on this they gave the various terminologies Internal rotation External rotation Forward growth rotation Backward rotation
  73. 73. Page  73 Internal rotation A rotational pattern that occurs in the core of the maxilla Also known as intra matrix rotation It is similar to the intra matrix rotation of mandible In most individuals the external and internal rotations cancel each other.
  74. 74. Page  74 External rotation Simultaneous to the internal rotation of maxilla , various degrees of resorption of bone occur on the nasal side and deposition of bone on the palatal side , Similarly ,variations in the amount of eruption of incisors and molars . All these contribute to external rotation
  75. 75. Page  75 Combination of IR and ER •Forward rotation •Backward rotation Bjork and skeiller observed 2 types of rotational growth
  76. 76. Page  76 Forward growth rotation Due to excessive internal rotation or lack of normal external rotation or combination of both Maxilla inclined upward and forward This rotation tips incisors forward
  77. 77. Page  77 Backward rotation Downward and backward tipping of the anterior end of the palatal plane and the maxillary base The jaw bases are translated posteriorly ,Incisors appear to tip lingually
  78. 78. Page  78 Clinical importance An upward and forward tipping of the anterior part of maxilla often seen in mouth breathers . Downward and backward tipping of anterior part of maxilla is observed as a natural compensation in patients with vertically growing faces The inclination of maxilla can be influenced by fixed mechancho therapy and orthopedic treatment .
  79. 79. Page  79 MUTUAL REALTIONSHIP OF ROTATING JAW BASES It was an attempt to clarify weather there was a difference between the morph ogenic and positional rotations Morphogenic rotation concerns with the shape Positional rotation concerns with the position of the mandible They have a major role in the mutual adjustment of both the jaws .
  80. 80. Page  80  According to Lavergne and Gasson the mutual rotation of the upper and lower jaw can be of following 4 types 1. Convergent rotation.  Severe deep bite.  Difficult to treat with a functional therapy. 2. Divergent jaw bases.  Severe open bite.  In severe cases orthognathic surgery is required.
  81. 81. Page  81 3. Cranial rotation of both the bases.  Horizontal growth pattern.  Maxillary cranial rotation compensates for the mandibular rotation.  Normal bite.  Bot maxilla and mandible rotates upward and forward 4. Caudal rotation of both bases.  Vertical growth pattern.  Maxillary caudal rotation compensates for the mandibular rotation.  Normal bite.
  82. 82. Page  82 Studies on growth rotation Various studies have been conducted , notable among them are Bjork , skeiller , lavenrgne and gasson , schudy , profit All these studies have been conducted to predict the mandibular growth
  83. 83. Page  83 AJODO 1994 ;106 : 60-9
  84. 84. Page  84
  85. 85. Page  85 Inferences Mandible with anterior growth rotation was associated with small height ,large depth ,small ratio and large angle of the symphysis Men posses a stronger relationship between symphyseal growth and and direction of mandibular growth Women also showed the same relationship as men between symphysis height ,depth ,ratio and angle to the direction of growth The symphyseal depth , height , ratio ,increased while symphyseal angle decreased with age .
  86. 86. Page  86 Mandibular auto rotation after surgery (lefort 1 )
  87. 87. Page  87 Conclusion The ability of an orthodontist to predict future mandibular growth would greatly aid in the diagnosis and treatment planning. Better therapeutic decisions could be made regarding timing and length of the treatment, appliance selection, extraction pattern and possible need for surgery.
  88. 88. Page  88 References Contemporary orthodontics- William.R.Proffit 5th and 4th edition Essentials of of facial growth - Donald.H.Enlow. CRANIOFACIALDEVELOPMENT- Geoffrey H. Sperber Text book of craniofacial growth – Sridhar premkumar Prediction of growth rotation - A.Bjork-AJO-DO-1969,jun 39-53. Facial development and tooth eruption :an implant study at the age of puberty- A.Bjork,V.Skieller AJO-DO 1972,62,4;339-383. The rotation of mandible resulting from growth;Its implications in orthodontic treament -F.F.Schudy-AO 1965.no.1,36-50. The puzzle of growth rotation. J.M.H.Dibbets –AJO-DO June 1985 ,87,6;473- 480. Mandibular rotation and enlargement. J.M.H.Dibbets.AJO-DO July 1990,29- 32.
  89. 89. Page  89 Facial Growth in Man, Studied With the Aid of Metallic Implants. By Arne Bjork, Acta odontol. scandinav 13: 9-34, June, 1955 Prediction of mandibular growth rotation evaluated from a longitudinal implant sample – Bjork, Skieller and Hansen, AJO, Nov 1984, pg. 359-370. Assessment of symphysis morphology as a predictor of the direction of mandibular growth Todd Aki, DDS, MS," Ram S. Nanda, DDS, MS, PhD, b G. Frans Currier, DDS, MDS, MED, = and Surender K. Nanda, DMD, MS d
  90. 90. Page  90 Thank you

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