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These sex hormones are released into the blood stream causing development of secondary sexual characteristics and accelerated growth of genitals. Also there is an increase in general body growth and decrease in lymphoid tissue.
The sex hormones stimulates cartilage to grow faster causing adolescent growth spurt, at the same time they also cause a increase in skeletal maturation this is the rate at which cartilage is transformed into bone. If the acceleration in maturation is faster then acceleration in growth it leads to cartilage getting used up faster then it is replaced, leading to growth completion.
80-100. 85-85, 25-65, 10-25, 5-10
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.
7. Growth rotations of mandible.
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.
d) F.F. Schudy.
7. Center of rotation of mandible- Isaacson.
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
–It is a gradual maturational process
involving a complex of different but
functionally interrelated organs and
–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.
PRINCIPLES OF GROWTH
Principles of growth and
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
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.
3. Bone has periosteal and endosteal layer
if one is resorbtive then other will be
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,
5. The various sites of growth do not show
a same rate of growth activity.
6. Remodeling is a basic part of growth
7. Growth process leads to primary or
AMOUNT AND TIMING OF
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.
1. Adolescent growth spurt.
• 11-13 yrs. in females.
• 14-16 yrs. in males.
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
– This activation is therefore also referred to as
– In girls more amount of hormones are
releases hence is more prominent then in
Adolescent Growth Spurt
• Initiation occurs in the brain.
Hypothalamus releases releasing factor
from neuroendocrine glands.
Base of the hypothalamus near pituitary
Via cytoplasmic transport
Ant pituitary releases
Stimulates endocrine cells in adrenal gland and
sex glands to produce sex hormones
• In males
– In testes
• Sertoli cells produce testosterone
• Leydig cells produce estrogen
– In adrenal cortex
• Male and female sex hormones are produced.
• In females
– In ovaries
• Estrogen is produced initially and then
– In adrenal cortex
• Male and female sex hormones are produced.
growth of genitals
• 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
cartilage to grow
adolescent growth spurt
increase in skeletal
Increases the rate at which
transformed into bone
This maturation occurs faster in females hence
they have a shorter stature.
ASSESSMENT OF AMOUNT
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.
• In our department we follow the hand
wrist x-ray method which was put
forward by Julian Singer (AO, Oct 1980),
and also the cervical vertebrae
assessment which was put forward by
Hassel and Farman (AJO, Jan 1995).
2 ½ years 6 ½ years 11 years 19 years
HAND WRIST RADIOGRAPH
GROWTH OF MANDIBLE
• Mandible is basically composed of two
– 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
• Ramus undergoes continuing remodeling
as a part of its growth process and several
basic functions are provided by these
– The entire ramus gets progressively relocated
posteriorly by combination of resorbtion and
– The ramus width increases to accommodate
the increase in middle cranial fossa and the
– 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.
• 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
• 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.
• 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
• 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.
• He refuted 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.
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
• 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
• 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.
• 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
– In horizontal growers the anterior rounding is
absent so the concavity of the lower border is
• INCLINATION OF THE SYMPHYSIS
– In horizontal growers chin swings forward to
– In vertical growers symphysis is swung
backward causing a receding chin.
• 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
• INTERMOLAR ANGLE
– In case of forward rotation the molars get
more upright increasing the intermolar and
– while in case of backward rotation the molars
become mesially tipped hence decreasing the
intermolar and interpremolar angle
• 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.
– 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
– 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
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
• The deposition at the lower border of the
symphysis continues to the anterior border of
mandible giving it the rounded appearance.
• Posterior border of the mandible shows
• 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
• 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.
• 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
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
Forward rotation type II
• Centre of rotation is at the incisal edges of the
• Increased posterior facial height normal lower
anterior facial height.
• Posterior facial height can increase due to
– Caudally placed glenoid fossa because in increase in
– Increased ramal height. As the mandible is held in its
place by muscles and the ramal height increases
there is swinging of mandible forward.
• 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
• Mandibular symphysis swings forward.
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.
• 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.
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.
Backward rotation type II
• Centre of resistance is at the most distally
• Growth at the condyles is in the sagital
• Mandible increases in length but is carried
forward more due to its muscles and
• 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
• Molars and premolars of mandible are
BJORK AND SKIELLER
• Divided the mandibular rotations into three
– Total rotation
– Matrix rotation
– Intramatrix 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
• If line anteriorly rotate towards the face
then is known as forward rotating and
signated as ‘-’
• 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
• 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
• 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
• 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.
• 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)
• 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)
• Rotation occurring due to rotation around
the condyle is called as TOTAL
ROTATION. (This is the rotation of the
mandible that is occurring around the
condyles or matrix rotation according to
BJORK SOLOW AND
relative to cranial
relative to cranial
relative to the core
of the mandible
• 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
• Growth increments causing downward
movement of chin is called as vertical growth,
while growth increments causing forward
movement of chin are called as horizontal
• If growth at the condyles is more than molar
eruption it causes horizontal growth deepening
• If growth at the condyles is less then molar
eruption is leads to vertical growth and a
• There are four vertical growth elements
which increase the facial height, these
– Anterior growth of nasion.
– Corpus of maxilla getting palatal plane down.
– Eruption of maxillary molars.
– Eruption of mandibular molars.
• 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
CENTER OF ROTATION
• Has devised a method for determining the
centre of rotation of the mandible.
STEPS IN FINDING CENTRE OF
ROTATION OF MANDIBLE
1. On pre-observation tracing reference
points are selected in the region of the
symphysis and the mandibular foramen.
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
The areas where the tracing do not coincide
shows the areas of external remodeling
and tooth movement.
3. A reference line is arbitrarily drawn in the
anterior cranial fossa region.
4. The two tracings are superimposed on
the anterior cranial structures. Lines are
drawn connecting the two pre and post
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.
GROWTH ROTATION OF
• Growth of maxilla occurs by two ways
– Passive displacement- in primary dentition
– Active growth is by surface remodeling
• The maxilla can be divided into
– It’s functional process
• Alveolar process
• Parts of bone surrounding the air passage
– Core of it’s bone
• 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 (implant line).
• TOTAL ROTATION, MATRIX ROTATION
not possible in a maxilla (condyle).
• 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.
• 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
• 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.
Displacement type Remodeling type
• Two cephalograms are taken at a gap of 12-18
• 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
– Type B
– Type C
• Middle and lower third grew forward and
downward in unison.
• The ANB value remained constant.
• If the ANB value does not exceed 4.5o
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
• 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
prognosis is fair while in cases with a
increased ANB of 7o
or beyond the
prognosis is poor.
• 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.
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.
• 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.
• 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.
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
– 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)
– Point at the bisection of the condyle neck as
high as visible in the cephalogram below the
• 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.
• 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.
• 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
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
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.
3. So it was thought that the actual arc
must lie in between these two.
– So a point in between Xi and R1 was
– A arc was made with a radius from this point
• Was found that it still causes increased
bending of the mandible, also the
mandible kept increasing in size causing
a spiral shaped arc.
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,
–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
• 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.
• Involves morphogenetic changes
(resorption and deposition) among various
regional parts as each grow in close
• Commonly seen is case of vertically long
Mandible rotates forward
And Class II
Widening of the ramus
Vertically long nasomaxillary complex
Mandibular comes forward
and Class I results
• The teeth can not move by its own
remodelling process, they need a extrinsic
force to move.
BETWEEN ROTATING JAW
• 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.
• 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.
1. Divergent jaw bases.
Severe open bite.
In severe cases orthognathic surgery is required.
3. Cranial rotation of both the bases.
Horizontal growth pattern.
Maxillary cranial rotation compensates for the
3. Caudal rotation of both bases.
Vertical growth pattern.
Maxillary caudal rotation compensates for the
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
– Backward rotation of maxilla causes incisors to tip
• 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.
4. Normally the forward rotation of the
maxilla is less then that of mandible
causing the mandibular arch length to
• Therefore in brachyfacial individuals the
mandibular incisors tend to retrocline
more, decreasing the arch length leading
• 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.
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
7. Functional appliances lead to opening of
mandibular plane angle hence are
contraindicated in cases of vertical
• 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.
• And with it’s knowledge therapy could be
truly tailored to the individual with the
possibility of obtaining optimal results in
shorter period of time.
1.Essentials of facial growth – D.H. Enlow.
2.Contemporary orthodontics – W.R. Proffit.
3.Handbook of orthodontics – R.E. Moyers.
4.Fundamentals of craniofacial growth –
5.Prediction of mandibular growth rotation –
A. Bjork, AJO, June 1969, pg. 585-599.
6.The puzzle of growth rotation – J.M.H.
Dibbets, AJO, June 1985, pg. 473-480.
7. Mandibular rotations : concepts and
terminology – B. Solow and W.J.B. Houston,
EJO, 1988, pg. 177-179.
8. Normal and abnormal growth of the mandible.
A synthesis of longitudnal cephalometric
implant studies over a period of 25 years –
Bjork and Skieller, EJO, 1983, pg. 1-46.
9. Prediction of mandibular growth rotation
evaluated from a longitudinal implant sample –
Bjork, Skieller and Hansen, AJO, Nov 1984,
10. Some effects of mandibular growth on the
dental occlusion and profile – R.J. Isaacson
et.al., AO, April 1977, pg. 97-106.
11. Growth pattern of mandible : some reflections
– B. G. Sarnat, AJO, Sept 1986, pg.221-231.
12. A principle of arcial growth of the mandible –
R.M. Ricketts, AO, 1972, pg. 368-386.
13. The Rotation Of The Mandible Resulting From
Growth: Its Implications In Orthodontic
Treatment - F. F. Schudy, AO, 1965, pg-36-50.
14. Skeletal maturation evaluation using cervical
vertebrae – Hassel and Farman, AJO, Jan
1995, pg. 58-66.
15. Physiologic timing of orthodontic treatment – J.
Singer, AO, Oct 1980, pg. 322-333.