Post on 26-Nov-2014
GOOD MORNING…
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GROWTH ROTATIONS
DR. DIVYA SWARUP1st YEAR
CONTENTS• Introduction • Terminologies• Concepts of Mandibular Rotations • Concepts of Maxillary Rotations• Tooth eruption and facial development• Prediction of growth rotations• Clinical implications of Rotations• Conclusion
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INTRODUCTION• First publication on the growth of the face-
18th century
• Hunter suggested that mandible lengthens due to resorption of the anterior surface of ramus and deposition posteriorly
• Growth was studied using stains and inserting metal wires
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• Cephalometrics introduced in 1930s
• Originally used to reveal the anatomy of head
• Since longitudinal study is possible it was used to test various concepts concerning the mechanisms of postnatal enlargement of head
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• Measurements and tracings showed little changes in the facial form
• The development in the form of the face was considered static
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• With the use of metallic implants as markers it was seen that mandibular corpus rotates during growth but the shape is kept stable by surface remodeling
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• Lande in 1952 observed that the lower border becomes less steeply inclined with growth
• The phrase ‘growth rotation’ was introduced by Bjork in 1955
• Metallic implants were precise markers from which sites and amount of growth and resorption could be found
• Superimposing two consecutive tracings showed that the older mandible had rotated
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• Study began in 1951
• It comprised of a study of about 100 children of each sex covering the age period from 4 to 24 years
• The sample consisted of normal children with and without malocclusion and also children with pathologic conditions
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The mandible can be visualized as consisting of a core of bone surrounding the inferior alveolar neurovascular bundle,
and a series of functional processes: the alveolar process, serving the function of mastication; the muscular processes, serving for muscle attachments; and the condylar process,
serving to articulate the bone with the rest of the skull
terminologies
• 1965-Schudy introduced clockwise and
counterclockwise rotation
• 1969-Bjork discussed different directions of
rotation of the mandibular implant line and
the relation of these to mandibular form-
forward & backward12
• Counterclockwise (Schudy) 1965 /
Forward rotation (Bjork) 1969
• Clockwise (Schudy)1965 /
Backward rotation (Bjork) 1969
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• 1970-Odegard described rotation as the change in the orientation that can occur between implant line and lower border of the mandible
• 1977-Lavergne and Gasson described the terms Positional and Morphogenetic rotations
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• 1983-Bjork and Skieller gave the terms-
Total rotation
Matrix rotation
Intramatrix rotation
• 1985-Dibbets introduced the term
Counterbalancing rotation
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• 1988-Solow,Houston True rotation Apparent rotation Angular remodeling of the lower border• Proffit- used the terms Internal rotation Total rotation External rotation
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Total Rotation
True Rotation
Internal Rotation
Matrix Rotation
Apparent Rotation
Total Rotation
Intramatrix Rotation
Angular Remodeling
of lower border
External Rotation
BJORK SOLOW,HOUSTON PROFFIT
Rotation of the mandibular core relative to cranial base
Rotation of mandibular plane relative to cranial base
Rotation of mandibular plane relative to core of the mandible
Total / True / Internal• Is the rotation of the mandibular corpus
• Is measured as a change in inclination of a reference line or an implant line in the mandibular corpus relative to the anterior cranial base
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• If line anteriorly rotate towards the face then is known as forward rotating and signated as ‘-’
i.e. posterior growth > anterior growth
• If line anteriorly rotate away from the face then is known as backward rotating and signated as ‘+’
i.e. anterior growth > posterior growth
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Matrix / Apparent /Total• Rotation of the soft tissue matrix of the
mandible relative to the anterior 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
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Centre of rotation at the condyle
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Intramatrix / Angular remodeling of lower
border / External rotation• Rotation of mandibular plane relative to
core of mandible
• 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
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Schematic illustration of "intramatrix rotation." A, Two mandibles superimposed on their external contours. Note divergence of the implant lines indicative of "intramatrix rotation" not reflected in dimensional change or alteration of mandibular contours. B, The same two mandibles superimposed on the implant markers. Note lack of concordance of mandibular contours, indicating extensive remodeling during development.
Source: AJO-DO on CD-ROM (Copyright © 1998 AJO-DO), Volume 1985 Jun (473 - 480): Puzzle of growth rotation - Dibbets.--------------------------------
• Rotation of the corpus inside the soft tissue matrix
• Centre of rotation some where in the corpus
• Dependent on the rotation of maxilla and occlusion of teeth
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TOTAL ROTATION = MATRIX ROTATION +
INTRAMATRIX ROTATION
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Posterior growth is greater than the anterior growth
Forward RotationForward Rotation
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Anterior growth is greater than posterior growth
Backward Backward RotationRotation
Positional and Morphogenetic Positional and Morphogenetic RotationRotation
• Introduced by Lavergne and Gasson
Positional Rotation-• Describes the position of mandible within
the head
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Morphogenetic Rotation-• Concerns the shape of the mandible• Superimposition done on line through
condylion and pogonion• The angle formed between the 2 implant
lines-degree of morphogenetic rotation• Similar to Bjork’s intramatrix but not
identical32
references• Contemporary orthodontics – W.R. Proffit
• Prediction of mandibular growth rotation – A. Bjork, AJO, June 1969, pg. 585-599
• The puzzle of growth rotation – J.M.H. Dibbets, AJO, June 1985, pg. 473-480
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Thank you…
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GOOD MORNING…
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GROWTH ROTATIONS
DR. DIVYA SWARUP1st YEAR
CONTENTS• Introduction • Terminologies• Concepts of Mandibular Rotations • Concepts of Maxillary Rotations• Clinical implications of Rotations• Conclusion
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Bjork’s concept• Implant studies show-growth of the mandible
occurs essentially at the condyles
• The anterior aspect of the chin-stable
• Lower border of the mandible-
At the symphysis-apposition
At the angle -resorption
• The appositional and resorptive areas may change-determining the type of growth
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• The growth of the condyle occurs in a upward and forward curving manner
• The center of rotation may be located-posteriorly or anteriorly or somewhere in between
• The center may not always lie at the TMJ
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FORWARD ROTATION• THREE TYPES:
TYPE I
-center at the TMJ
- deep bite
- lower dental arch is pressed into the upper - underdevelopment of the anterior face height
Cause: Occlusal imbalance due to loss of teeth or powerful muscular pressure
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Type II - center at the incisal edges of the lower
anterior teeth - posterior face height - anterior face height
Increase in posterior face height
Lowering of the Increased height of middle cranial fossa ramus
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• Increase in ramus height maybe due to vertical growth of the condyle
• But this vertical lowering manifestes as forward rotation –muscular and ligamentous attachments
• Eruption of the molars keep pace with the rotation
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Type III
- center of rotation is at the premolars
- anterior face height becomes underdeveloped when the posterior face height increases
- basal deep bite occurs
Cause: Anomalous occlusion-large overjets 46
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BACKWARD ROTATION• TWO TYPES: Type I -center at the TMJ -increase in AFH -underdevelopment
of the posterior face height occurs-open bite
Causes: 1.middle cranial fossa is raised
2.orthodontic bite raising appliance
3.oxycephaly
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TYPE II -center at distal most occluding molars -growth in the sagittal direction at the
mandibular condyle. The direction of this sagittal growth curves increasingly backward. As the mandible grows in the direction of its length it is carried forward more than it is lowered in the face, and because of its attachment to muscles and ligaments it is rotated backward
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- the eruption of lower molars was hindered-the rotation not due to overeruption
- seen in condylar hypoplasia
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Structural Signs 1. Condylar head inclination
2. Mandibular canal curvature
3. Shape of lower border of mandible
4. Symphysis inclination
5. Interincisal angle
6. Intermolar angle
7. Anterior lower face height
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Condylar head inclination
– Characteristic sign- Forward or backward inclination of the condylar head
– In forward growers condyle is upright backward growers inclined backward
– Is difficult to identify on the lateral cephalogram
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Condylar inclination
MANDIBULAR CANAL
– The mandibular canal curvature remains the same throughout the life
– Backward growers the curvature of the canal is more than that of the mandibular contour
Forward growers the canal may be flat or less curved
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Mandibular canal inclination
Shape of the lower border of mandible
Forward rotation – Lower border will be flat
Subtle or no antegonial notch
Backward growth rotation - Lower border will be concave
– A prominent antegonial notch is found
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04/08/23 GROWTH ROTATIONS 58
Lower border of mandible (Antegonial notch)
Symphysial inclination
• In Backward rotation – symphysis swings forward in face
Chin is prominent
• In Forward rotation – symphysis swings back
Chin is receded
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Symphysis inclination
INTERINCISAL ANGLE
– The difference in the interincisal angle is evident, in spite of the compensatory tipping of the lower incisors
– In backward rotation angle is less
– In forward rotation there is an increased interincisal angle
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Interincisal angle
INTERMOLAR ANGLE
Forward rotation the molars get more upright increasing the intermolar and interpremolar angle
Backward rotation the molars become mesially tipped - decreasing the intermolar and interpremolar angle
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Intermolar angle
LOWER FACE HEIGHT
– Increased in backward rotation
– Less in forward rotation
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LOWER ANTERIOR FACIAL HEIGHT
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Clinical implicationsForward rotation-
• Short face type• “Square jaw” type• Low mandibular plane
angle• Skeletal anterior deep bite• Crowding of anterior teeth• Palatal plane is nearly
horizontal • smile - lower incisors are
visible with the upper incisors hidden behind the upper lip
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Backward rotation-• Long face type• “Round jaw” type• Steep mandibular
plane angle• Skeletal anterior open
bite• Dental protrusion• Negative inclination
of palatal plane
references• Contemporary orthodontics – W.R. Proffit
• Prediction of mandibular growth rotation – A. Bjork, AJO, June 1969, pg. 585-599
• The puzzle of growth rotation – J.M.H. Dibbets, AJO, June 1985, pg. 473-480
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Thank you…
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FORWARD ROTATION BACKWARD ROTATION
AFH Type I – Decreased(At TMJ)
Type II – normal or increased
(At incisors)Type III – Decreased
(At premolars)
Type I – Increased (At TMJ)
Type II – Increased (At distal most
occluding molar)
PFHType I – normal or
increasedType II – Increased Type III - Increased
Type I – DecreasedType II - Increased
CONDYLAR HEAD INCLINATION
Upright Inclined backwards
MANDIBULAR CANAL Flat or decreased curvature
Increased curvature
LOWER BORDER OF MANDIBLE
Flat Concave
ANTEGONIAL NOTCH Prominent Subtle or less pronounced
SYMPHYSIAL INCLINATION
Chin receded Chin prominent
INTERINCISAL, INTERPREMOLAR,
INTERMOLAR ANGLE
Increased Decreased
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• Counterclockwise (Schudy) 1965 /
Forward rotation (Bjork) 1969
• Clockwise (Schudy)1965 /
Backward rotation (Bjork) 1969
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Positional and Morphogenetic Positional and Morphogenetic RotationRotation
• Introduced by Lavergne and Gasson
Positional Rotation-• Describes the position of mandible within
the head
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Morphogenetic Rotation-• Concerns the shape of the mandible• Superimposition done on line through
condylion and pogonion• The angle formed between the 2 implant
lines-degree of morphogenetic rotation• Similar to Bjork’s intramatrix but not
identical74
GROWTH ROTATION OF MAXILLA
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• Growth of maxilla occurs by two ways– Passive displacement- in primary
dentition period– Active growth is by surface remodeling
Internal rotation of Maxilla
• If Implants are placed above the maxillary alveolar process, one can observe a core of maxilla that undergoes a small and variable degree of rotation ,forward or backward
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External rotation of Maxilla
• 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
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For most patients ,the external rotation is opposite in direction & equal in magnitude to the internal rotation, so that the two equal rotations cancel & the net change in jaw orientation as evaluated by the palatal plane is zero
Until implant studies, rotation of maxilla during normal growth had not been suspected
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Superimposition on implants in maxilla reveals that this patient experienced a small amount of backward internal rotation of the maxilla (i.e,down anteriorly)
A small amount of forward rotation is the more usual pattern ,but backward rotation occurs frequently
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references• Contemporary orthodontics – W.R. Proffit
• Prediction of mandibular growth rotation – A. Bjork, AJO, June 1969, pg. 585-599
• The puzzle of growth rotation – J.M.H. Dibbets, AJO, June 1985, pg. 473-480
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Thank you…
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AUSTRALIAN ARCHWIRES
AUSTRALIAN ARCHWIRES
• In 1952, Dr.P.R.Begg in collaboration with an Australian metallurgist Mr. Arthur J. Wilcock, developed a high tensile stainless steel wire that is heat treated and cold drawn to yield excellent clinical properties.
• It was made thin enough to distribute force at an optimal level for tooth movement over a considerable period of time, over long distance and with minimal loss of force intensity while doing so.
• The diameter of the wire initially produced was progressively decreased from .018” to .014”.
There are 6 types of Australian arch wires :
Regular grade (white label) lowest grade easiest to bend used for practice bending and forming auxillaries.
Regular plus (green label) Relatively easy to form, yet more resilient than regular grade. Used for auxillaries and arch wires when more pressure and resistance to deformation are desired.
• Special grade (black label) highly resilient yet can be formed into shape
with little danger of breakage.
• Special plus grade (orange label) Hardness and resiliency of .016” wire is
excellent for supporting anchorage and reducing deep overbites.
Must be bent with care. Routinely used by experienced operators.
• Extra special plus grade (blue label)
Also referred to as premium plus in Australia. This grade is unequalled in resiliency and
hardness. More difficult to bend and more subjected to
fracture. ESP’s ability to move teeth, open bites and
resist deformation are excellent.
• Supreme grade (blue label) Further develop by Mr. A. J Wilcock Jr. In 1982 on
request of Dr. Mollenhauer of Australia. Is ultra light tensile fine round stainless steel
wire. Was initially introduced in the .010” diameter and
was further reduced to .009” diameter. Is primarily used in early treatment for rotation,
alignment and leveling. Although, supreme exceeds the yield strength of
ESP, it is intended for use in either short section or full arches where sharp bends are not required.
NEWER WILCOCK ARCH WIRES
Recently, A.J. Wilcock scientific and engineering company, have introduced a new series of wire grade and sizes with superior properties by use of new manufacturing process called pulse straightening.
The new grades available now are :
premium .020”
premium plus .010”, .011”, .012”, .014”, .016” .018”
supreme .008”, .009”, .010”, .011”