This document provides an overview of principles of facial growth and development, with a focus on mandibular growth rotations. It discusses key concepts such as the amount and timing of growth, assessment of growth, growth of the mandible, and mechanisms of mandibular rotation. Several studies on mandibular growth rotations are summarized, including the seminal work by Bjork in the 1950s using metal implants to track growth sites and directions. Bjork identified seven structural signs that can indicate the direction of mandibular growth. The document also briefly discusses the work of Bjork and Skieller, Proffit, Schudy, and Isaacson related to mandibular growth rotations.

1. Presented by
Dr mohammed aslam
2nd year pg student
Department of orthodontics
1

2. CONTENTS
1. Introduction.
2. Principles of growth and development.
3. Amount and timing of growth.
4. Assessment of amount of growth.
5. Growth of mandible.
6. Mechanism of rotation.
2

3. 7. Growth rotations of mandible.
a) Bjork.
i. Direction of growth.
ii. Structural signs.
a) According to Bjork.
b) According to Petrovic.
iii. Results of implants studies.
iv. Type of rotations.
b) Bjork and Skieller.
c) Proffit.
d) F.F. Schudy.
8. Center of rotation of mandible- Isaacson.
3

4. 9. Growth rotations of maxilla.
10. Tweed’s facial growth trends.
11. Rickets growth prediction.
12. Compensatory growth.
13. Clinical aspects.
14. Conclusion.
15. References.
4

5. INTRODUCTION
 Growth and development
 Frequently heard together.
 Why both the terms?
 As growth is not merely a process of increase in size,
rather is a progressive facial enlargement with
differential growth processes in which the various parts
develop earlier or later then other parts in different
facial region, in a multitude directions and different
rates.
5

6.  It is a gradual maturational process involving
a complex of different but functionally
interrelated organs and tissues.
 The growth process also involves a
bewildering succession of regional changes
of great proportions and it requires countless
localized ‘adjustments’ to achieve proper
fitting and function among all the parts.
6

7. PRINCIPLES OF GROWTH AND
DEVELOPMENT
1. Bone grows by adding new bone on one side of bony
cortex and taking it away from the other side, due to
which bone drift occurs.
2. The inner and outer surface of the bone are covered
with mosaic type appearance of growth fields, which
can be resorbtive or depository. If it is resorbtive on
one side it will be depository on other.
7

8. 3. Bone has periosteal and endosteal layer if one is
resorbtive then other will be depository.
4. The control of growth is done by the soft tissue
matrix present around the bone. The blueprint of
the design construction and growth of the bone lies
in the composite of muscles, tongue, lips,
connective tissue, nerves, blood vessels, airways etc.
8

9. 5. The various sites of growth do not show a same rate
of growth activity.
6. Remodeling is a basic part of growth process.
7. Growth process leads to primary or secondary
displacement.
9

10. AMOUNT AND TIMING OF
GROWTH
 There are four growth spurts :
1. On birth.
2. 1 yr. after birth.
3. Pre pubertal growth spurt.
 6-7 yrs. in females.
 7-9 yrs. in males.
4. Adolescent growth spurt.
 11-13 yrs. in females.
 14-16 yrs. in males.
10

11. Prepuberal Growth Spurt
 Occurs due to production of sex hormones from adrenal
gland at the age of around 6 yrs. In the form of a weak
androgen (Dihydroepiendosterone).
 This activation is therefore also referred to as
adrenarche.
 In girls more amount of hormones are releases hence is
more prominent than in boys.
11

12. 12
Adolescent Growth Spurt
• Initiation occurs in the brain.
Hypothalamus releases releasing factor
from neuroendocrine glands.
Base of the hypothalamus near pituitary
Via cytoplasmic transport
pituitary
Via capillaries
Ant pituitary releases
pituitary gonadotropins
Stimulates endocrine cells in adrenal gland and
sex glands to produce sex hormones

13.  In males
 In testes
 Sertoli cells produce testosterone
 Leydig cells produce estrogen
 In adrenal cortex
 Male and female sex hormones are produced.
13

14.  In females
 In ovaries
 Estrogen is produced initially and then progesterone.
 In adrenal cortex
 Male and female sex hormones are produced.
14

15. sex hormones
blood stream
development of
secondary
sexual characteristics
growth of genitals
GENERAL BODY
GROWTH
decrease in
lymphoid
tissue

16.  Timing of puberty makes a difference in ultimate body
size. The earlier the puberty the smaller will be the
body size.
 Height depends on endochondral bone formation.
16

17. sex hormones
sex hormones
cartilage to grow
adolescent growth spurt
increase in skeletal
maturation
Increases the rate at which
cartilage is
transformed into bone
Growth complete
This maturation occurs faster in females hence
they have a shorter stature.

18. ASSESSMENT OF AMOUNT OF
GROWTH
 Various skeletal maturity indicators are
 Hand wrist radiograph.
 Cervical vertebrae.
 Canine calcification.
 Corpus index.
 Hyoid bone position.
 Third molar level.
 Frontal sinus.
 Antigonial notch.
18

19. GROWTH OF MANDIBLE
 Mandible is basically composed of two structures
 The corpus
 The ramus
 Corpus of the mandible is a direct structural
counterpart to the maxillary corpus
 Ramus is related to the pharyngeal space and
middle cranial fossa, with the function being to
bridge the middle cranial fossa and place the
corpus in proper relation with the cranial floor
articulation on one side and maxillary corpus on
other side.
19

20.  Ramus undergoes continuing remodeling as a part of
its growth process and several basic functions are
provided by these changes
 The entire ramus gets progressively relocated posteriorly
by combination of resorbtion and deposition.
 The ramus width increases to accommodate the increase
in middle cranial fossa and the pharynx.
20

21.  The length of the ramus increases to accommodate the
increased size of nasomaxillary complex and erupting
teeth.
 Progressive remodeling changes occur in the ramus to
place the mandibular corpus in proper relation with the
maxillary corpus.
21

22.  These changes lead to change in orientation of the
mandible leading to ROTATION OF THE MANDIBLE.
(Rotation literally means to move round a axis or a
centre.)
 Rotation can be
 Forward and upward
 Downward and backward
22

23.  Since classic description of mandibular growth by
John Hunter in 1771 there has been various studies
and reports on it.
 He had applied anthropometry (aligned human
skulls along symphyseal and lower border of
mandible) to find out how mandible increased in
size.
23

24.  He said mandible size increased by
1. Apposition at posterior border,
2. Increase at coronoid and condyloid process above the
line of teeth
3. The increase in height was mainly due to increase in
alveolar bone.
 Later in 1955 Bjork coined the term growth rotations.
24

25. 25
GROWTH ROTATIONS.

26. Bjork study
 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.
26

27.  He disagreed with the concept that the given
intermaxillary relation remained static through out
life. Considerable variation in the development of
facial form and intermaxillary relation was seen.
27

28. Direction of Growth
 Mandible can have a forward direction of growth
(good growing) or backward direction of growth (bad
growing).
 Bjork gave seven structural signs to find the
direction of mandibular growth.
 These signs are not clearly developed before puberty.
28

29. Structural Signs
1. Condylar inclination.
2. Mandibular canal inclination.
3. Lower border of mandible (Antigonial notch).
4. Symphysis inclination.
5. Interincisal inclination.
6. Intermolar angle.
7. Lower face height.
29

30.  CONDYLAR INCLINATION
 Forward or backward inclination of the condylar head is
characteristic sign
 In forward growing mandible condyle is upright
compared to a backward growing mandible in which it is
inclined backward
 Is difficult to identify on the lateral cephalogram.
30

31. 31

32.  MANDIBULAR CANAL
 The mandibular canal curvature remains the same
throughout the life.
 In vertical growing mandible the curvature of the canal
is more than that of the mandibular contour. Where as
in case of horizontal growers the canal may be flat or
may even be curved in opposite direction.
32

33. 33

34.  Shape of the lower border of mandible.
 In vertical growers there is an increased deposition
below the symphysis, anterior part of the mandible
becomes thick along with this there is resorption at the
angle producing a characteristic concavity.
 In horizontal growers the anterior rounding is absent so
the concavity of the lower border is absent.
34

35. 35

36.  INCLINATION OF THE SYMPHYSIS
 In horizontal growers chin swings forward to become
prominent.
 In vertical growers symphysis is swung backward
causing a receding chin.
36

37. 37

38.  INTERINCISAL ANGLE
 Interincisal angle is almost constant showing that the
lower incisors is related functionally to the upper
incisors
 In vertical growers angle in less
 In horizontal growers there is an increased interincisal
angle.
38

39. 39

40.  INTERMOLAR ANGLE
 In case of forward rotation the molars get more upright
increasing the intermolar and interpremolar angle
 while in case of backward rotation the molars become
mesially tipped hence decreasing the intermolar and
interpremolar angle
40

41. 41

42.  LOWER FACE HEIGHT
 is increased in case of vertical growth pattern while is
less in case of a horizontal growth pattern
42

43. 43

44.  According to Petrovic
In orthognathic type of face the ramus and the body of
the mandible are fully developed, and the width of the
ascending ramus is equal to the height of the body of the
mandible, including height of the alveolar process and
the incisors. The condyle and coronoid process are
almost in the same plane and symphysis is well
developed.
44

45.  In case of a retrognathic mandible corpus is narrow in
molar region. Symphysis is narrow and long, ramus is
narrow and short and the gonial angle is obtuse and the
coronoid process is relatively smaller than the condylar
process..
45

46.  In prognathic type the corpus is well developed and
wide in molar region. Symphysis is wider in sagital
plane, ramus is wide and long and the gonial angle is
acute or small.
46

47. Results of the implants studies
 Increase in length of the mandible mainly due to
deposition at the condyles.
 Anterior border of the symphysis is stable. Increased
thickness of the chin was due to deposition at the
posterior border and the increase in length was due to
deposition at the lower border.
 The deposition at the lower border of the symphysis
continues to the anterior border of mandible giving it
the rounded appearance.
47

48.  Posterior border of the mandible shows resorption.
 Growth at the condyles is not in the direction of the
ramus but slightly forward.
 Mandibular canal is not remodeled to the extent of the
mandible. Trabaculae of the canal remains stable and
the shape of the canal reflects the earlier shape of the
mandible.
48

49.  The lower border of the developing tooth germ of
lower molar is relatively stable till the root formation.
 Mandible can be considered as a unconstrained bone,
it can change its inclination in several ways. One
critical factor for this is the centre of rotation.
49

50.  According to the type of rotation and the centre of
rotation the growth of the mandible can be divided
into
 Forward rotation
 Type I
 Type II
 Type III
 Backward rotation (less common)
 Type I
 Type II
50

51. Forward rotation type I
 Centre of rotation is in the joint.
 Deep bite is seen.
 Decreased lower anterior facial height.
 Powerful musculature is usually seen
 May lead to occlusal imbalance loss of teeth.
51

52. Forward rotation type II
 Centre of rotation is at the incisal edges of the
lower incisors.
 Increased posterior facial height normal lower
anterior facial height.
 Posterior facial height can increase due to
 Caudally placed glenoid fossa because in increase in
cranial flexure.
 Increased ramal height. As the mandible is held in its
place by muscles and the ramal height increases there is
swinging of mandible forward.
52

53.  Anterior facial height does not change as
 The eruption of molars occurs in the pace with
increased ramal height.
 Lower border of the mandible undergoes remodeling.
 Mandibular symphysis swings forward.
53

54. Forward rotation type III
 In cases of increased overjet the centre of rotation is
displaced to the premolars.
 There is decreased lower facial height.
 Increased posterior facial height.
 Skeletal deep bite is seen.
 Mandibular symphysis swings forward.
54

55.  Rotation of the mandible effects the inclination of the
teeth. The interincisal angle is almost constant
(showing the lower incisors are functionally related to
upper incisors). Hence their eruption is guided
forward and there is increase in alveolar prognathisim.
 Rotation also influences the posterior teeth incase of
forward rotation the posterior teeth become more
upright, increasing the intermolar and interpremolar
angles.
55

56. Backward rotation type I
 Centre of rotation at the joint.
 Seen in cases of
 Bite is raised by orthodontic treatment increasing the
lower anterior facial height.
 Growth of cranial base occurs such that the cranial base
flexure flattens leading to the mandible being raised
posteriorly.
56

57. Backward rotation type II
 Centre of resistance is at the most distally occluding
molar.
 Growth at the condyles is in the sagital direction.
 Mandible increases in length but is carried forward
more due to its muscles and ligaments attachments.
57

58.  Symphysis is swung backward, chin goes below the
face. The soft tissues may not follow this leading to a
double chin.
 Skeletal open bite is seen.
 Incompetent lips.
 Lower incisors retrocline and meet the upper incisors.
 Molars and premolars of mandible are inclined
forward.
58

59. BJORK AND SKIELLER
 Divided the mandibular rotations into three
components
 Total rotation
 Matrix rotation
 Intramatrix rotation
59

60. Total Rotation
 Is the 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,
 If line anteriorly rotate towards the face then is known
as forward rotating and signated as ‘-’
60

61. 61

62. Matrix rotation
 Was called as apparent rotation by Lande.
 Is rotation of soft tissue matrix of the mandible
relative to the cranial base.
 Is shown by a tangential mandibular line.
 It can rotate forward and backward in the same patient
with condyles as the centre of rotation and is described
by the term pendulum movement.
62

63. 63

64. Intramatrix rotation
 Is the difference between total rotation and the matrix
rotation.
 It is an expression of remodeling of the lower border of
the mandible.
 It is found out by the change in inclination of an
implant line or reference line in the mandibular corpus
to the tangential mandibular line.
64

65.  Rotation of the corpus relative to the tangential line
such that it faces front is called as forward rotation.
 Centre of rotation is somewhere in corpus and
depends on rotation of corpus, growth rotation of the
maxilla and occlusion of the teeth.
65

66. 12/18/2015
GROWTH ROTATIONS 6666

67.  Bjork and Skieller said that three changes occur in
Intramatrix rotation
 The mandible “wiggles” in in its matrix
 This wiggling is associated with the corpus and is caused
by growing condyle.
 The rotation results from or compensates for genetically
predetermined program.
67

68. PROFFIT
 Rotation occurring in the core of the jaw were called as
INTERNAL ROTATION. Hence is the rotation which is
visualized by the implant line. (This is the rotation in
the mandibular core proper or total rotation according
to Bjork)
68

69.  Rotation caused by the surface changes and the
alteration in the rate of tooth eruption is called as
EXTERNAL ROTATION. (this is the remodeling that is
occurring of the mandible or intramatrix rotation
according to Bjork)
69

70.  Rotation occurring due to rotation around the condyle
is called as TOTAL ROTATION. (This is the rotation of
the mandible that is occurring arounda the condyles or
matrix rotation according to Bjork)
70

71. BJORK SOLOW AND
HOUSTON
PROFITT
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 core of
the mandible
Intra matrix
rotation
Angular
remodelling of
lower border
External rotation
71

72. F.F. SCHUDY
 Rotation of the mandible is a result of in-harmony
between vertical growth, antero-posterior growth and
horizontal growth.
 Clockwise rotation is a result of increased vertical
growth causing a decrease in bite.
 Counter-clockwise rotation is a result of decreased
vertical growth causing a deep bite.
72

73.  Growth increments causing downward movement of
chin is called as vertical growth, while growth
increments causing forward movement of chin are
called as horizontal growth.
 If growth at the condyles is more than molar eruption
it causes horizontal growth deepening the bite.
 If growth at the condyles is less then molar eruption is
leads to vertical growth and a decreased bite.
73

74.  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.
74

75.  The migration of glenoid fossa is cancelled by growth
of condyles.
 Clockwise rotation is when there is an increased
growth at the condyles than the vertical growth of the
mandible. It can increase ANB angle and can correct
deep bite if present.
 Counterclockwise rotation is when there is decreased
condylar growth then the vertical growth.
75

76. CENTER OF ROTATION
Isaacson has devised a method for determining the
centre of rotation of the mandible.
7676

77. STEPS IN FINDING CENTRE OF
ROTATION OF MANDIBLE
 On pre-observation tracing reference points are
selected in the region of the symphysis and the
mandibular foramen.
77

78. 2. The post observation tracing is super-imposed on
the previous tracing on the mandibular canal, third
molar follicle and symphysis internal border. The
two reference points are transferred to this tracing.
The areas where the tracing do not coincide shows the
areas of external remodeling and tooth movement.
78

79.  A reference line is arbitrarily drawn in the anterior
cranial fossa region.
79

80.  The two tracings are superimposed on the anterior
cranial structures. Lines are drawn connecting the two
pre and post reference points.
80

81. 5. Perpendicular bisector of these two lines are made.
The intersection of these two perpendicular bisector
gives us the center of rotation of the mandible.
81

82. GROWTH ROTATION OF MAXILLA
82

83.  Growth of maxilla occurs by two ways
 Passive displacement- in primary dentition
period
 Active growth is by surface remodeling
83

84.  The maxilla can be divided into
 It’s functional process
 Alveolar process
 Parts of bone surrounding the air passage
 Core of it’s bone
84

85.  Implants placed on maxillary alveolar process show
that the core of the maxilla undergoes a small and
variable degree of rotation- forward and backward –
INTERNAL ROTATION
 TOTAL ROTATION, MATRIX ROTATION not possible
in a maxilla (condyle).
85

86.  Varying degree of resorption on nasal side and deposition on
palatal side, also varying amount of eruption of incisors and
molars lead to EXTERNAL ROTATION, INTRAMATRIX
ROTATION (lower border).
 In most individuals the external and internal rotations cancel
each other.
86

87. MECHANISM OF ROTATIONS
87

88. Mechanism of rotations
 Displacement type.
 Remodeling type.
88

89. Displacement type of rotation
 Mandible rotates on the condylar pivot.
 The primary reason for this is to adjust to the
vertical size of midface and alignment of
middle cranial fossa
 Rotates forward to meet short mid face or closed
bicranial flexure.
 Rotates backward to meet vertically increased
mid face or open bicranial flexure.
89

90.  Remodeling type
 Occurs at angle between corpus and ramus
 Occurs due to resorbtive and depository changes
occurring at this junction.
 It basically leads to
 More upright ramus alignment relative to corpus
accommodating a vertically lengthened mid face.
90

91. TWEED’S GROWTH TRENDS
91

92.  Two cephalograms are taken at a gap of 12-18
months.
 They are then superimposed on S-N keeping S as
the reference point.
 Three types of growth was seen.
 Tweed classified it into
 Type A
 Subdivision
 Type B
 Type C
92

93. Type A
 Middle and lower third grew forward and downward
 The ANB value remained constant.
 If the ANB value does not exceed 4.5o and case is
having a molar relation of Class I then is type A
 If molar relation is of Class II and ANB is more then
4.5o then is called as Type A subdivision.
93

94. Type B
 There is an change in ANB reading in Pre and Post
radiographs.
 The growth trend is in downward and forward
direction with middle face growing more rapidly then
the lower face.
 In cases of ANB of less then 4o the prognosis is fair
while in cases with a increased ANB of 7o or beyond
the prognosis is poor.
94

95. Type C
 In case the lower face is growing downward and
forward more rapidly then the middle face.
 The ANB decreases.
 The mandibular incisors usually get tipped lingually
and get crowded or the max incisors get tipped labially.
95

96. RICKETTS GROWTH PREDICTION
96

97. Ricketts Growth Prediction
 According to Ricketts a normal human mandible grows by
superior-anterior (vertical) apposition at the ramus on a
curve or a arc which is a segment formed from a circle.
 Then radius of the circle is described by using the distance
from the mental protuberance to a point at forking of the
stress lines at the terminus of oblique ridge on the medial
side of the ramus.
97

98.  On basis of studies a primary method of growth
prediction was devised.
 A line was plotted through the long axis of the condyles
extending it through the line making the lower border
of the mandible.
 Keeping these lines as reference line a bending of the
mandibular form was studied.
98

99.  Later use of mandibular plane as the reference plane
was refuted as its lower border showed resorbtion.
 Also the ramus as reference area was disapproved as it
also showed remodeling as shown by Enlow’s studies.
99

100. So new reference points were taken
 Xi point
 Centre of the ramus
 Contacts the mandibular canal
 Suprapogonion (Po, Pm)
 Bone crest on the superior aspect of the compact bone
and anterior contour of the symphysis.
 Was taken as was located at the stress centre (ricketts),
is the site of reversal lines (Enlow), and is a stable
unchanging point as seen by implant studies (Bjork)
100

101.  Dc
 Point at the bisection of the condyle neck as high as
visible in the cephalogram below the fossa.
 Now by joining Dc to Xi and Xi to Po a repeatable
condyle and corpus axis could be made. And by
studying the changes in the mandible in relation to
these axis the growth could be predicted.
101

102.  By studying the mandibular growth on these axis it
was found that the bending of the mandible occurred
in an orderly fashion, with greater the magnitude of
growth greater was the bending.
 Now the next task was to make a arc to predict this
growth.
102

103.  Point Pm, Xi, Dc were used to depict the mandibular
core, and the prediction of the mandibular size and
shape at five years interval was done.
 The current arcial prediction of ricketts was reached in
three steps
103

104. 1. A arc was made passing through these three points. But
it was found that the increase in size could be produced
but not increase in curvature. The Pm point was taken as
constant.
2. A second arc was made using tip of coronoid process,
anterior border of ramus at the deepest point R1 and Pm.
Using this was found that the mandible would bend too
much.
104

105. 3. So it was thought that the actual arc must lie in
between these two.
 So a point in between Xi and R1 was selected.
 A arc was made with a radius from this point to Pm.
 Was found that it still causes increased bending of
the mandible, also the mandible kept increasing in
size causing a spiral shaped arc.
105

106. A mandible 850 yrs old was taken. In it the stress lines
were visible.
 The stress lines were seen to converge at the tubercle
menti, from there they swung downward then
upward and backward and outward through the
oblique ridge.
 In the medial aspect a Y shaped bony prominence was
seen at the superior aspect of the mylohyoid ridge,
also above this point a small nutritive canal was seen,
106

107.  Experimentally two points were found
 Pt. Eva
 just over the forking of the stress lines
 Is made by bisecting Xi to R3 point and
make a line
 Pt. Mu
107

108. 108
Xi
R3
RR
EVA
Pm
TR
Mu

109.  Now the arc that the mandible will follow to grow is
found out, next part was to find the amount of growth
that will take place.
 It was found that the mandible increased by 2.5mm
per year.
 Coronoid process shows an increment of 0.8mm per
year.
109

110. COMPENSATORY GROWTH
110

111.  Involves morphogenetic changes (resorption and
deposition) among various regional parts as each grow
in close relation.
111

112. 112
Commonly seen is case of vertically long naso-maxilary
complex.
Mandible rotates forward
and downward
Retruded mandible
And Class II
Widening of the ramus
Vertically long nasomaxillary complex
Mandibular comes forward
and Class I results

113. CLINICAL ASPECTS
113

114. MUTUAL RELATIONSHIP BETWEEN ROTATING JAW BASES
 Rotation of mandible decides the vertical proportions
of the face.
 Horizontal growers have a
 Short lower anterior facial height.
 Predisposed to having a deep bite.
 Opposite of above for the vertical growers.
114

115.  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.
115

116. 3. Cranial rotation of both the bases.
 Horizontal growth pattern.
 Maxillary cranial rotation compensates for the mandibular
rotation.
 Normal overbite.
4. Caudal rotation of both bases.
 Vertical growth pattern.
 Maxillary caudal rotation compensates for the mandibular
rotation.
 Normal overbite.
116

117. CLINICAL ASPECTS
1. Growth rotation of mandible influence the
amount the teeth can erupt.
2. Also it influences the direction of eruption and
ultimate position of teeth.
 Eruption of maxillary teeth is in a downward
and forward direction.
 Forward rotation of maxilla causes incisors to tip
forward.
 Backward rotation of maxilla causes incisors to tip
palatally.
117

118.  Eruption of mandibular teeth is in a upward and
forward direction.
 Forward rotation of mandible causes incisors to tip
lingually.
 Backward rotation of maxilla causes incisors to tip
labially.
3. Normal internal rotation rotates mandible forward
uprighting the incisors and allowing the molars to
mesialize.
118

119. 4. Normally the forward rotation of the maxilla is less
then that of mandible causing the mandibular arch
length to decrease.
 Therefore in brachyfacial individuals the
mandibular incisors tend to retrocline more,
decreasing the arch length leading to crowding.
119

120.  In dolicofacial individuals there is usually a anterior open
bite, unless the incisors over erupt, also the incisors tend
to flare out.
5. In case of vertical growers the ANB, or the Class II does
not improve, but the correction and retention of the deep
bite is facilitated, visa-versa for horizontal growers.
120

121. 6. In case of vertical growers the occlusal forces on the
molars are less hence is more easy to loose
anchorage, while in horizontal growers it is difficult
to loose anchorage.
7. Functional appliances lead to opening of
mandibular plane angle hence are contraindicated
in cases of vertical growers.
121

122. ENLOW’S CONCEPT
Maxillary Rotations
Displacement Remodeling
122

123. Displacement
 Primary displacement occurs-antroinferior direction.
 Sutures are tension adapted-cannot grow by pushing-apart.
 Stimulus for sutural remodeling is due to the displacement.
123

124. Secondary displacement
124

125. Drift of the teeth
125
 As the maxilla and mandible enlarge, dentition drifts-
horizontally and vertically.
 The whole tooth and its socket move.

126. Nasal and palatal remodeling
126

127.  The balance between greater and lesser amounts of
remodeling in the posterior & anterior parts of the maxilla
is the response to clockwise/ counterclockwise rotatory
displacement of middle cranial fossa.
 Compensatory remodeling rotation of the nasomaxillary
complex-sustains its proper position relative to the neutral
orbital axis.
 Remodeling also occurs as bones assume new positions
with expansion of the soft tissue matrix.
127

128. BJORK’S CONCEPT
 Longitudinal study done by implant method.
 Lateral implants:4yrs of age
-inserted laterally in the zygomatic
process of the maxilla (2 on each side).
-increase in distance between the
implants on the frontal film - increase in the
width in the median suture at the level of the
1st molars.
128

129.  Anterior implants:10-11yrs of age
-inserted below the anterior nasal spine.
-one on each side of the median suture at level with
the apices of the central incisors.
- increased distance bw the implants measured on
frontal film - growth in the width in the median
suture at the level of the incisors.
129

130.  Implant line-
-Tip of 1 anterior implant to midpoint of 2 lateral
implants.
-Change in the inclination of implant line to the S-N
line-vertical rotation of maxilla in relation to cranial
base.
130

131. MAXILLARY GROWTH-LATERAL
IMPLANTS [4YRS]
 Height
-growth at frontal and zygomatic process.
-apposition at lower alveolar process and eruption of
teeth.
-apposition at floor of the orbit.
-nasal floor lowered down.
131

132.  Lateral implants-vertical component calculated at right
angles to S-N.
 Sutural lowering -11.2mm
 Apposition at the floor of the orbit-6.4mm.
 Lowering of nasal floor-4.6mm
 Appositional growth in height of alveolar process-14.6.mm
132

133.  Width
-growth in the median suture.
-appositional remodeling in the outer aspects.
-Enlow-widening of hard palate mainly result of
remodeling.
-Persson, Melsen-growth in median suture upto
adolescence.
133

134.  Implants study show
-median suture growth-6.7mm
-outer aspect of maxilla-9.5mm
-growth in the median suture follow the same curve as their
growth in body height.
134

135. Growth of maxilla in 3-d - anterior and
lateral implants(10-11 yrs)
 Length-
-sutural growth towards palatine bone by apposition on
tuberosities.
-anterior surface was thought to be resorptive; unchanged
when studied using implants.
135

136.  Sagittal growth studied in relation to infrazygomatic crest.
136

137. ROTATIONS
 Transverse plane
 Vertical plane.
137

138.  Joining anterior and lateral implants on each side a triangle
is constructed with sides of constant length.
138

139.  Lateral implants increased 3mm against 0.9mm of the
anterior implants.
 Thus, the lateral implants separate more.
 This reduces length of maxilla in mid sagittal plane.
 The distance between 1st molars increases more than
canines
139

140. VERTICAL ROTATIONS
 Superimposition shows parallel lowering of nasal
floor.
140

141.  Implant studies-
-maxilla undergoes vertical rotation.
-inclination of anterior cranial base to nasal floor is
maintained by compensatory remodeling.
-forward rotation-anterior resorption & deposition
posteriorly.
141

142.  Backward rotation-
-Rotates down anteriorly.
-posterior resorption more than anterior.
142

143. 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.
143

144. references
 Essentials of facial growth-D.H.Enlow
 Contemporary orthodontics-W.R.Proffit
 Handbook of orthodontics-R.E.Moyers
 Dentofacial orthopaedics with functional appliance-M
Graber,Thomas Rakosi,G.Petrovic
 Prediction of mandibular growth rotation-A.Bjork,Am
J Orthod june 1969;585-599
144