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CONTENTS
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indiandentalacademy.c...
 Introduction
 What is Biomechanics
 Center of gravity
 Center of resistance
 Center of rotation
 Various Terminolog...
 Begg Mechanotherapy
 INTRODUCTION
 Objectives of Stage-I
o Biomechanics of incisor intrusion
Degree of anchor bend
Rol...
The literature on orthodontic biomechanics usually
concerns either specific applications of interest to
clinicians or basi...
BIOMECHANICS
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Biomechanics is the study of
mechanics as it affects the biologic
systems. It is the application of
mechanics to the biolo...
Physical properties such as distance,
weight, temperature and force are
treated mathematically as either
SCALARS or VECTOR...
SCALARS include temperature and
weight, they have a definite
magnitude but do not have a direction.
They are completely de...
VECTORS include force, these have
both magnitude and direction. In case
of force, along with magnitude and
direction, poin...
Various terminologies and laws:
FORCE
MOMENT
COUPLE
MOMENT TO FORCE RATIO
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FORCE:
It is defined as an act upon a body that
changes or tends to change the state of
rest or motion of the body.
Force ...
The forces are indicated by straight
arrows
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In case of understanding the magnitude
and direction of tooth movement, point
of application of force is important
www.ind...
CENTER OF MASS
Each body has a point in its mass,
which behaves as if the whole mass is
concentrated at that single point,...
Center of Gravity:
The same is called center of Gravity in
an environment where gravity is
present.
www.indiandentalacadem...
The center of gravity of the tooth is
located more towards the crown of the
tooth as the mass of the tooth is
concentrated...
Since the tooth is partially restrained
as its root is embedded in bone its
center of gravity moves apically and
this is k...
Center of Resistance
Center of Gravity
Center of Resistance
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 In case of single rooted tooth center of
resistance is on the long axis of tooth
between one third and one half of the
r...
 For a multirooted root, the center of
resistance is probably between the
roots 1-2 mm apical to furcation.
www.indianden...
 Center of Resistance Varies (Cres):
Length of root: Maxillary canine have
long root than maxillary lateral incisor.
Thus...
Periodontal status: The center of
resistance shifts apically in
periodontally compromised patients.
Size and shape of the ...
The center of resistance for a single
rooted tooth estimated by different
authors as;
 At 50% of root length – Proffit, N...
Moment
Is defined as a tendency to rotate
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Moments can be symbolized by
curved arrows.
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MOMENT is the product of the force times
the perpendicular distance from the point of
force application to the center of r...
MOMENT OF FORCE:
Moment is a measure of the turning
tendency produced by a force.
When a force is applied at any point
oth...
In case of tooth, since it is embedded in
the alveolar bone, we cannot apply
force directly on Cres, but can apply
force o...
A MOMENT may be referred as
Rotation
Tipping
Torquing.
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Rotation
Tipping
Torquing
Flash Player Movie Flash Player MovieFlash Player Movie
www.indiandentalacademy.com
If a line of action does not pass
through the center of resistance the
force will produce some rotation. The
potential for...
The direction of a moment can be
determined by continuing the line of
action of the force around the center
of resistance....
CENTER OF ROTATION:
It may be defined as a point about
which a body appears to have rotated
as determined from its initial...
A simple method of determining a
Center of rotation - Draw the long axis
of the tooth in its initial and final
positions; ...
Center of Rotation
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Center of rotation could be at the center
of resistance, apical or incisal to Cres
or at infinity. Its position will
deter...
TYPES OF TOOTH
MOVEMENT
POSITION OF THE
CENTER OF ROTATION
A. Translation
B. Uncontrolled tipping
C. Controlled tipping
D....
 Uncontrolled tipping: In this situation,
when force is applied the crown
moves in one direction and root
moves in the op...
Uncontrolled tippingUncontrolled tipping
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 Controlled Tipping: In this situation,
crown moves in the direction of force
but the root position remains the same
or g...
Controlled tippingControlled tipping
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 Translation : In this situation tooth
moves bodily e.g. both crown and
root portion of tooth moves bodily in
the directi...
Bodily MovementBodily Movement
Center of
Rotation
at infinity
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 Root movement: In this situation,
root moves in the direction of force but
the crown position remains the same
or get mi...
RootRoot
MovementMovement
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COUPLE:
Two equal and opposite, non -
collinear forces are called a couple.
Couple consists of two forces of equal
magnitu...
The moment of this couple is equal to
the magnitude of one of the forces
multiplied by the perpendicular
distance between ...
If the two forces of the couple act on
opposite sides of the center of
resistance, their effect is additive.
However, if t...
AdditiveAdditive
+
F1
F2
F1XdM1= M2=F2Xd
d
M=F X D
www.indiandentalacademy.com
SubtractiveSubtractive
-
F1
F2
M1=F1XD1 M2=F2XD2
D1
D2
M= F X (D1-D2)
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DIFFERENCE BETWEEN THE MOMENT OF
A FORCE AND MOMENT OF COUPLE:
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Moment is a measure of the turning
tendency produced by a force.
 Moment of force is always relative to
point of applicat...
MOMENT TO FORCE RATIO:
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It seems that type of movement
exhibited by a tooth is determined by
the ratio of the counter-balancing
moment produced to...
In terms of direction, the counter-
balancing moment is always going to
be in the direction opposite the
moment of force.
...
Moment of force
Force
Counter-balancing moment
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The ratio of the counter-balancing
moment to the force applied
determines the type of tooth
displacement, brought about by...
At one specific level of M/F the
moment which arises from the force
and the applied counter-balancing
moment cancel out ea...
 M/F Ratio values normally quoted of various
types of displacements are
M/F ratio less than 5:1 causes uncontrolled
tippi...
M/F ratio of 10:1 causes translation.
The crown and the root apex move to
same extent in the same direction of
force.
M/F ...
It is important to note that the
differences between the M/F Raito for
controlled tipping, translation and root
movement a...
STATE OF EQUILIBRIUM
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When an appliance is fitted in the mouth, it
assumes a state of equilibrium. The active
elements in the appliance generate...
For example, tip back bend (like the
bite opening bend in Begg appliance)
generates a moment which tends to
tip the molar ...
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BEGG MECHANOTHERAPY
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Begg mechanotherapy is very efficient in
opening the deep anterior overbites. It is
generally agreed that Begg mechanics b...
There are three basic movements in
the Begg mechanotherapy
 Incisor intrusion
 Tipping of teeth
 Root uprighting.
www.i...
The mechanism of intrusion is
understood by considering the net
intrusive force magnitude and direction.
While tipping of ...
OBJECTIVES OF STAGE I:
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 Open the anterior bite :
Proper amount of bite opening bends
or curves in the arch wire.
Continuous wearing of Class II
...
 Close anterior spaces :
Plain arch wire with latex elastic or
elastomeric chain from cuspid to
cuspid.
 Over correct ro...
 Over correct the mesiodistal
relationship of the buccal segments
Continuous wearing of class II
elastics.
Proper bite op...
BIOMECHANICS OF STAGE I
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As we understand today the Begg
appliance is a good example of single
couple system.
Stage I arch wire
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The orthodontic environment created
during stage I is conducive to rapid
movement of anterior teeth under the
light forces...
MECHANISM OF INTRUSION:
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Lack of true intrusion of the maxillary
incisors was one of the major
weaknesses of traditional Begg.
Bite opening occurre...
Stage I arch-wire
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Whether the upper incisors intruded is
a debated issue.
The round archwire derives bite
opening force from the anchor bend...
A anticlockwise moment generated by
the anchor bend in the molar tube
(upper) is automatically balanced by
the generation ...
This flaring tendency of upper incisors
can be resisted by using Class II
elastics during stage I.
But class II force alon...
vertical problem
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Thus the interplay between the
intrusive force from the archwire and
the retractive force from the elastics
determines bot...
VARIOUS TYPES OF BITE
OPENING BENDS:
 The Anchor bend the conventional
bite opening bend causes more
intrusion of canines...
 A Gable bend causes a progressively
more intrusion of central and lateral
incisor, as compared to canine
 Mollenhouer’s...
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 Swain modification: Mild gingival curve
is incorporated in the anterior section,
from mesial of cuspid to mesial of othe...
CONSIDERATION OF THE
MAGNITUDE OF INTRUSIVE
FORCE.
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OPTIMAL INTRUSIVE FORCE VALUE:
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Many authors have suggested
optimum intrusive force values
ranging from 15-30 grams per upper
incisor and slightly higher ...
For active intrusion the upper
anteriors should receive
approximately 60 grams net force in
the midline, after negating th...
ROLE OF LIGHT CLASS II
ELASTICS:
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Hocevar stated that 120 grams of
archwire generated intrusive force in
conjunction with 60 grams of Class II
elastics pull...
According to Dr.Jayade net intrusive
force of 60 grams can be obtained by
a combination of 75 grams of intrusive
force gen...
Sims states the use of 3/8” ultra light
elastics instead of routinely used
5/10” light elastics. He said continue
the same...
Role of Class I Elastic
Forces
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Modifying the force system to achieve
simultaneous intrusion and retraction
using Class I elastic instead of Class
II elas...
 In pure begg technique the direction
of the intrusive vector of the maxillary
arch wire and the extrusive vector of
the ...
 In this technique modification, of
using Class I elastics , it solve the
problem of lack of intrusion of the
maxillary a...
 In this arrangement the vectors are in
the same direction as the elastic pull
and the archwire force are
unidirectional ...
Dr. Jyothindra Kumar introduced
concept of power arms as a point of
attachment high up in the vestibule for
the engagement...
Dr. Jayade has been using Class I
elastics, which were worn from
transpalatal arch (TPA) to the canine
hooks/loops.
CLASS ...
It is impossible to precisely calculate
the required intrusive force every time,
for every patient, since it is dependent
...
 Individual biomechanical response
 Difference in the archwire sizes.
Normally .018” wire will produce more
intrusive fo...
THE CONCLUSION IS, “TO USE
HIGHER INTRUSIVE FORCES IN
COMBINATION WITH VERY
LIGHT CLASS II ELASTIC
FORCES FOR ACTIVE UPPER...
CONSIDERATION OF THE DIRECTION
OF THE RESULTANT FORCE:
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Teeth respond only to the resultant
of the forces which are applied and
not to the individual components of
the force syst...
During Stage I, the upper anteriors are
subjected to two forces i.e. the
retractive force of class II elastics and
the int...
THE INTERPLAY BETWEEN THE
ANCHOR BEND AND CLASS II
ELASTICS
CLASS II ELASTIC
FORCE
INTRUSIONFORC
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The direction and magnitude of
resultant force both depend upon the
interplay between.
 Magnitude of Intrusive Force: Who...
Different inclinations of the anterior
teeth would require different
combinations on of the intrusive and
elastic forces.
...
For example, in case severely
proclined upper anteriors a low
magnitude of intrusive force along
with high class II force ...
45gms
60gms
60 gms
30gms
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In Class II Division 2 cases , where the
upper centrals are retroclined , only
intrusive force should be used
(Avoiding th...
50gms
40gms
20gms
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MECHANICS OF BEGG TIPPING:
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CLASS II ELASTIC
FORCE
The concept of tipping back the
teeth in the first stage & further in
stage II …
INTRUSIONFORC
www....
Generally, uncontrolled tipping is
undesirable because it leads to root
resorption as stated by Reitan. There
is more reso...
Intrusion and tipping are intimately
related not only because they are
carried out simultaneously but also,
when both are ...
This is achieved by manipulating the
intrusive force generated by wire and
retractive component of force from the
Class II...
BOTH THE ANCHOR BEND IN THE
WIRE AND CLASS II ELASTICS
PRODUCE MOMENTS IN THE
SAME LABIO-LINGUAL PLANE
BUT ACT IN OPPOSITE...
The intrusive force produces crown
labial-root lingual moment e.g..
anticlockwise moment on the upper
anteriors. While the...
The moment from the intrusive force
can act as the counter balance
moment against the moment
produced by the elastic force...
The most important consideration is to
keep light Class II elastic and use
adequate amount of intrusive force
so that corr...
PREVENTING UNCONTROLLED
TIPPING OF UPPER
INCISORS
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In the refined Begg mechanics, use of
MAA which provides a moment in the
labio-lingual plane by creating a
couple. This co...
CLASS II ELASTIC
FORCE
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Once the bite is opened in the first
stage, the intrusive force level is
reduced which inturn reduces M/F
ratio. This lead...
Flaring occurs as lower incisors are
subjected to crown labial root-lingual
moment from the intrusive force
generated in a...
PREVENTING UNCONTROLLED
TIPPING OF LOWER INCISORS:
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The flaring can be avoided by two
means;
 Minimizing the clockwise force
moment by reducing the intrusive
force.
 Second...
 Lastly by producing counter moment
using a MAA for labial root torque or a
reverse torquing auxiliary (Udder
arch)
www.i...
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In case of severely lingually tipped
lower anteriors, Cres will be lying
buccal to the point of application of
the intrusi...
So in that case we give a By pass
arch wire in order to upright the lower
incisors .
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BEGG STAGE II
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Amongest the traditionally described
stages of Begg technique, the second
stage of treatment involves closure of
extractio...
During Stage II all the corrections
achieved during Stage I should be
maintained.
 Maintain Edge to Edge relationship of
...
 Maintain anterior space closure :
To give cuspid ties either by
elastomeric rings or steel ligatures.
 To maintain over...
 In addition to the above, the stage II of
the refined Begg aims are
Controlled tipping of the incisors,
when space closu...
OBJECTIVES OF STAGE II:
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When all the objectives of Stage I are
met stage II mechanics can be
instituted.
The sole or main purpose of II stage is
c...
The extraction space can be closed by
either retraction of the anteriors or
protraction of the posteriors or
combination o...
BIOMECHANICS OF STAGE II
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The anchor bend should be sufficient
as to produce a counter clockwise
moment greater than the clockwise
moment produced b...
The M/F ratio should be sufficient or
around 8/1 so as to have a controlled
tipping movement.
www.indiandentalacademy.com
If anticlockwise moment is less than
clockwise moment produce by Class I
and Class II elastics on upper
anterior, then M /...
Class I Elastic
Forces
CLASS I ELASTIC FORCE
INTRUSIONFORC
At the end of Stage II
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Same way in lower arch the clockwise
moment should be greater than
anticlockwise moment produced by
Class I elastics. So a...
Normally 0.016 upper and lower arch
wires with reduced bite opening bends
are used. Some authors say use of
heavy arch wir...
Dr. Swain advocated the use of lingual
attachments on molars and cuspids to
allow the use of lingual space closing
elastic...
Two distinct advantages in using intra
maxillary (Half strength) space closing
elastics
 It gives a better positional con...
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USE OF BRAKING MECHANICS
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When further retraction of anterior
teeth into the remaining extraction
space is deemed undesirable
clinically , then the ...
To achieve mesialization of posterior
teeth heavy elastic forces are
required with concurrent use of brakes
in the anterio...
Various brakes are:
 Using uprighting springs (passive
springs)
 Reverse torque to incisor roots (Udder
arch and MAA)
 ...
Passive Uprighting Springs T PINS
MAAUDDER ARCH
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The brakes reverse the anchorage
site from the posterior to anterior
segment by allowing bodily movement
rather than the t...
 He summarized that the direction of
resultant force should pass through
the center of resistance of anterior
teeth (or c...
Stage I arch-wire
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Thank you
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Copy of biomechanics /certified fixed orthodontic courses by Indian dental academy

  1. 1. CONTENTS INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2.  Introduction  What is Biomechanics  Center of gravity  Center of resistance  Center of rotation  Various Terminologies and laws FORCE MOMENT COUPLE MOMENT TO FORCE RATIO STATEOF EQUILIBRIUM www.indiandentalacademy.com
  3. 3.  Begg Mechanotherapy  INTRODUCTION  Objectives of Stage-I o Biomechanics of incisor intrusion Degree of anchor bend Role of Class II elastics o Biomechanics of Incisor Tipping  Objectives of Stage-II o Biomechanics of space closure  Conclusion  Bibliography www.indiandentalacademy.com
  4. 4. The literature on orthodontic biomechanics usually concerns either specific applications of interest to clinicians or basic questions primarily of interest to researchers. Few articles have attempted to explain biomechanical principles by an approach that would allow the clinician without a background in engineering to understand the concepts and their potential for clinical relevance. In this article, we attempt to review for the clinician the basic relationships between forces and tooth movement. www.indiandentalacademy.com
  5. 5. BIOMECHANICS www.indiandentalacademy.com
  6. 6. Biomechanics is the study of mechanics as it affects the biologic systems. It is the application of mechanics to the biology of tooth movement. Biology + Mechanics = Biomechanics www.indiandentalacademy.com
  7. 7. Physical properties such as distance, weight, temperature and force are treated mathematically as either SCALARS or VECTORS. www.indiandentalacademy.com
  8. 8. SCALARS include temperature and weight, they have a definite magnitude but do not have a direction. They are completely described by their magnitude. www.indiandentalacademy.com
  9. 9. VECTORS include force, these have both magnitude and direction. In case of force, along with magnitude and direction, point of application must be taken into account. www.indiandentalacademy.com
  10. 10. Various terminologies and laws: FORCE MOMENT COUPLE MOMENT TO FORCE RATIO www.indiandentalacademy.com
  11. 11. FORCE: It is defined as an act upon a body that changes or tends to change the state of rest or motion of the body. Force is a vector it has both magnitude and direction. www.indiandentalacademy.com
  12. 12. The forces are indicated by straight arrows www.indiandentalacademy.com
  13. 13. In case of understanding the magnitude and direction of tooth movement, point of application of force is important www.indiandentalacademy.com
  14. 14. CENTER OF MASS Each body has a point in its mass, which behaves as if the whole mass is concentrated at that single point, which we call the CENTER OF MASS in a gravity free environment. www.indiandentalacademy.com
  15. 15. Center of Gravity: The same is called center of Gravity in an environment where gravity is present. www.indiandentalacademy.com
  16. 16. The center of gravity of the tooth is located more towards the crown of the tooth as the mass of the tooth is concentrated more coronally www.indiandentalacademy.com
  17. 17. Since the tooth is partially restrained as its root is embedded in bone its center of gravity moves apically and this is known as CENTER OF RESISTANCE (Cres) www.indiandentalacademy.com
  18. 18. Center of Resistance Center of Gravity Center of Resistance www.indiandentalacademy.com
  19. 19.  In case of single rooted tooth center of resistance is on the long axis of tooth between one third and one half of the root length apical to alveolar crest. www.indiandentalacademy.com
  20. 20.  For a multirooted root, the center of resistance is probably between the roots 1-2 mm apical to furcation. www.indiandentalacademy.com
  21. 21.  Center of Resistance Varies (Cres): Length of root: Maxillary canine have long root than maxillary lateral incisor. Thus center of resistance of canine will be more apically placed as compared with center of resistance of lateral incisor. Alveolar bone height: Center of resistance shifts apically as with the alveolar bone loss. www.indiandentalacademy.com
  22. 22. Periodontal status: The center of resistance shifts apically in periodontally compromised patients. Size and shape of the crown and root. www.indiandentalacademy.com
  23. 23. The center of resistance for a single rooted tooth estimated by different authors as;  At 50% of root length – Proffit, Nikoli  Between 50% to 30% of root length – Smith and Burstone.  At 33% of root length – Burstone  Between 25% to 33% root length – Nanda www.indiandentalacademy.com
  24. 24. Moment Is defined as a tendency to rotate www.indiandentalacademy.com
  25. 25. Moments can be symbolized by curved arrows. www.indiandentalacademy.com
  26. 26. MOMENT is the product of the force times the perpendicular distance from the point of force application to the center of resistance. M = F x d It is measured in grams – millimeters. F x d(X) = M(X) F d www.indiandentalacademy.com
  27. 27. MOMENT OF FORCE: Moment is a measure of the turning tendency produced by a force. When a force is applied at any point other than through the center of resistance in addition of moving the center of resistance in direction of the force, a moment is created. www.indiandentalacademy.com
  28. 28. In case of tooth, since it is embedded in the alveolar bone, we cannot apply force directly on Cres, but can apply force on the exposed part of the tooth, which is at a distance from Cres. Therefore with a single force we invariably create a moment called as moment of force. www.indiandentalacademy.com
  29. 29. A MOMENT may be referred as Rotation Tipping Torquing. www.indiandentalacademy.com
  30. 30. Rotation Tipping Torquing Flash Player Movie Flash Player MovieFlash Player Movie www.indiandentalacademy.com
  31. 31. If a line of action does not pass through the center of resistance the force will produce some rotation. The potential for rotation is measured as moment. www.indiandentalacademy.com
  32. 32. The direction of a moment can be determined by continuing the line of action of the force around the center of resistance. F x d(X) = M(X)www.indiandentalacademy.com
  33. 33. CENTER OF ROTATION: It may be defined as a point about which a body appears to have rotated as determined from its initial to final position. www.indiandentalacademy.com
  34. 34. A simple method of determining a Center of rotation - Draw the long axis of the tooth in its initial and final positions; we will see that both these lines intersect at a point. This is the point around which the tooth rotates and is called Center of rotation. www.indiandentalacademy.com
  35. 35. Center of Rotation www.indiandentalacademy.com
  36. 36. Center of rotation could be at the center of resistance, apical or incisal to Cres or at infinity. Its position will determine the type of tooth movement. The moment to force ratio controls the center of rotation for the intended tooth movement. www.indiandentalacademy.com
  37. 37. TYPES OF TOOTH MOVEMENT POSITION OF THE CENTER OF ROTATION A. Translation B. Uncontrolled tipping C. Controlled tipping D. Root movement or Torquing Lies at infinity Slightly apical to center of resistance Apex of root Incisal or occlusal edge www.indiandentalacademy.com
  38. 38.  Uncontrolled tipping: In this situation, when force is applied the crown moves in one direction and root moves in the opposite direction. Here Center of rotation lies near to center of resistance. This is referred as uncontrolled tipping. www.indiandentalacademy.com
  39. 39. Uncontrolled tippingUncontrolled tipping www.indiandentalacademy.com
  40. 40.  Controlled Tipping: In this situation, crown moves in the direction of force but the root position remains the same or get minimally displaced. Here Center of rotation lies at apex of the root. www.indiandentalacademy.com
  41. 41. Controlled tippingControlled tipping www.indiandentalacademy.com
  42. 42.  Translation : In this situation tooth moves bodily e.g. both crown and root portion of tooth moves bodily in the direction of force. Here Center of rotation lies at infinity. All the points in the tooth move by same distance in the same direction in translation. www.indiandentalacademy.com
  43. 43. Bodily MovementBodily Movement Center of Rotation at infinity www.indiandentalacademy.com
  44. 44.  Root movement: In this situation, root moves in the direction of force but the crown position remains the same or get minimally displaced. Here Center of rotation lies at incisal edge of the crown. www.indiandentalacademy.com
  45. 45. RootRoot MovementMovement www.indiandentalacademy.com
  46. 46. COUPLE: Two equal and opposite, non - collinear forces are called a couple. Couple consists of two forces of equal magnitude, which are parallel to each other but not coincident and they face in opposite direction. www.indiandentalacademy.com
  47. 47. The moment of this couple is equal to the magnitude of one of the forces multiplied by the perpendicular distance between the two lines of action of force. www.indiandentalacademy.com
  48. 48. If the two forces of the couple act on opposite sides of the center of resistance, their effect is additive. However, if they are on the same side of the center of resistance, their effect is subtractive www.indiandentalacademy.com
  49. 49. AdditiveAdditive + F1 F2 F1XdM1= M2=F2Xd d M=F X D www.indiandentalacademy.com
  50. 50. SubtractiveSubtractive - F1 F2 M1=F1XD1 M2=F2XD2 D1 D2 M= F X (D1-D2) www.indiandentalacademy.com
  51. 51. DIFFERENCE BETWEEN THE MOMENT OF A FORCE AND MOMENT OF COUPLE: www.indiandentalacademy.com
  52. 52. Moment is a measure of the turning tendency produced by a force.  Moment of force is always relative to point of application. It means moment of a force will be low relative to a point (point of application) close to line of action and high for a point (point of application) with a large perpendicular distance to line of action.  In case of Couple moment, it is not relative to any point. www.indiandentalacademy.com
  53. 53. MOMENT TO FORCE RATIO: www.indiandentalacademy.com
  54. 54. It seems that type of movement exhibited by a tooth is determined by the ratio of the counter-balancing moment produced to the net force that is applied to a tooth . This is called as the moment to force ratio . www.indiandentalacademy.com
  55. 55. In terms of direction, the counter- balancing moment is always going to be in the direction opposite the moment of force. www.indiandentalacademy.com
  56. 56. Moment of force Force Counter-balancing moment www.indiandentalacademy.com
  57. 57. The ratio of the counter-balancing moment to the force applied determines the type of tooth displacement, brought about by the combined application of a force and counter-balancing moment. As the counter-balancing moment increases, the center of rotation moves apically. www.indiandentalacademy.com
  58. 58. At one specific level of M/F the moment which arises from the force and the applied counter-balancing moment cancel out each other i.e. there is no rotational component, and hence only a translation takes place under the effect of force . www.indiandentalacademy.com
  59. 59.  M/F Ratio values normally quoted of various types of displacements are M/F ratio less than 5:1 causes uncontrolled tipping in which the crown and the root apex move in opposite directions. M/F ratio between 5:1 and 8:1 causes controlled tipping in which the root apex remains stationary and only the crown moves. www.indiandentalacademy.com
  60. 60. M/F ratio of 10:1 causes translation. The crown and the root apex move to same extent in the same direction of force. M/F ratio of 12:1 causes root movement. The crown remains stationary while only the root moves. www.indiandentalacademy.com
  61. 61. It is important to note that the differences between the M/F Raito for controlled tipping, translation and root movement are small. In other words, even small alterations in the magnitude of the applied force or the counter-balancing moment will alter the type of tooth movement brought about. www.indiandentalacademy.com
  62. 62. STATE OF EQUILIBRIUM www.indiandentalacademy.com
  63. 63. When an appliance is fitted in the mouth, it assumes a state of equilibrium. The active elements in the appliance generate certain forces or moments. Other forces or moments arise automatically in the system to balance these forces or moments. Some of them may be beneficial while others may be undesirable. www.indiandentalacademy.com
  64. 64. For example, tip back bend (like the bite opening bend in Begg appliance) generates a moment which tends to tip the molar tooth crown distally. This is balanced by an automatic creation of another moment in the overall system in opposite direction comprising of two forces an intrusive force at the anterior end and on extrusive force on the molar. www.indiandentalacademy.com
  65. 65. www.indiandentalacademy.com
  66. 66. BEGG MECHANOTHERAPY www.indiandentalacademy.com
  67. 67. Begg mechanotherapy is very efficient in opening the deep anterior overbites. It is generally agreed that Begg mechanics bring about bite opening by a combination of molar extrusion (especially of lower molars) and some intrusion of lower anteriors. Upper anteriors may not change in their position in vertical direction (i.e. they are prevented from erupting) or may intrude slightly or may even extrude slightly. www.indiandentalacademy.com
  68. 68. There are three basic movements in the Begg mechanotherapy  Incisor intrusion  Tipping of teeth  Root uprighting. www.indiandentalacademy.com
  69. 69. The mechanism of intrusion is understood by considering the net intrusive force magnitude and direction. While tipping of teeth and root uprighting is explained on the basic of M/F ratio. www.indiandentalacademy.com
  70. 70. OBJECTIVES OF STAGE I: www.indiandentalacademy.com
  71. 71.  Open the anterior bite : Proper amount of bite opening bends or curves in the arch wire. Continuous wearing of Class II (intermaxillary) elastics as required.  Eliminate anterior crowding : Vertical loops between crowded anterior teeth, with bracket areas modified for desired overcorrection. www.indiandentalacademy.com
  72. 72.  Close anterior spaces : Plain arch wire with latex elastic or elastomeric chain from cuspid to cuspid.  Over correct rotated cuspids and bicuspids : Rotating springs Elastomeric traction into the arch wire www.indiandentalacademy.com
  73. 73.  Over correct the mesiodistal relationship of the buccal segments Continuous wearing of class II elastics. Proper bite opening bends in both upper and lower arch wires. www.indiandentalacademy.com
  74. 74. BIOMECHANICS OF STAGE I www.indiandentalacademy.com
  75. 75. As we understand today the Begg appliance is a good example of single couple system. Stage I arch wire www.indiandentalacademy.com
  76. 76. The orthodontic environment created during stage I is conducive to rapid movement of anterior teeth under the light forces generated by the arch wires and intermaxillary elastics www.indiandentalacademy.com
  77. 77. MECHANISM OF INTRUSION: www.indiandentalacademy.com
  78. 78. Lack of true intrusion of the maxillary incisors was one of the major weaknesses of traditional Begg. Bite opening occurred mainly on account of molar extrusion and some intrusion of the lower incisors. www.indiandentalacademy.com
  79. 79. Stage I arch-wire www.indiandentalacademy.com
  80. 80. Whether the upper incisors intruded is a debated issue. The round archwire derives bite opening force from the anchor bends. www.indiandentalacademy.com
  81. 81. A anticlockwise moment generated by the anchor bend in the molar tube (upper) is automatically balanced by the generation of clockwise moment in the anterior segment along with intrusive force on the anterior and extrusive force on the molars in order to establish state of equilibrium. www.indiandentalacademy.com
  82. 82. This flaring tendency of upper incisors can be resisted by using Class II elastics during stage I. But class II force along with horizontal component have vertical component of force which reduces the magnitude of the intrusive force of the arch wire on the upper anteriors. www.indiandentalacademy.com
  83. 83. vertical problem www.indiandentalacademy.com
  84. 84. Thus the interplay between the intrusive force from the archwire and the retractive force from the elastics determines both the magnitude and direction of the net resultant force acting on anterior teeth. www.indiandentalacademy.com
  85. 85. VARIOUS TYPES OF BITE OPENING BENDS:  The Anchor bend the conventional bite opening bend causes more intrusion of canines while the lateral and central incisors progressively lag behind. www.indiandentalacademy.com
  86. 86.  A Gable bend causes a progressively more intrusion of central and lateral incisor, as compared to canine  Mollenhouer’s bite opening curve – Mollenhouers especially recommends it with use of 0.018 wire. www.indiandentalacademy.com
  87. 87. www.indiandentalacademy.com
  88. 88.  Swain modification: Mild gingival curve is incorporated in the anterior section, from mesial of cuspid to mesial of other side cuspid. www.indiandentalacademy.com
  89. 89. CONSIDERATION OF THE MAGNITUDE OF INTRUSIVE FORCE. www.indiandentalacademy.com
  90. 90. OPTIMAL INTRUSIVE FORCE VALUE: www.indiandentalacademy.com
  91. 91. Many authors have suggested optimum intrusive force values ranging from 15-30 grams per upper incisor and slightly higher values for upper canines. www.indiandentalacademy.com
  92. 92. For active intrusion the upper anteriors should receive approximately 60 grams net force in the midline, after negating the extrusive component of Class II elastics. www.indiandentalacademy.com
  93. 93. ROLE OF LIGHT CLASS II ELASTICS: www.indiandentalacademy.com
  94. 94. Hocevar stated that 120 grams of archwire generated intrusive force in conjunction with 60 grams of Class II elastics pull on either side is “efficient for intrusion” www.indiandentalacademy.com
  95. 95. According to Dr.Jayade net intrusive force of 60 grams can be obtained by a combination of 75 grams of intrusive force generated by arch wire and some modification in wearing of elastics that is by using light elastic forces for longer periods from 2-5 days. Very light Class II force is delivered as the elastic force diminishes rapidly in oral environment. www.indiandentalacademy.com
  96. 96. Sims states the use of 3/8” ultra light elastics instead of routinely used 5/10” light elastics. He said continue the same elastic for 4-5 days till they break. www.indiandentalacademy.com
  97. 97. Role of Class I Elastic Forces www.indiandentalacademy.com
  98. 98. Modifying the force system to achieve simultaneous intrusion and retraction using Class I elastic instead of Class II elastics was first illustrated by Shin Yang Liu (1981). www.indiandentalacademy.com
  99. 99.  In pure begg technique the direction of the intrusive vector of the maxillary arch wire and the extrusive vector of the class II elastics are opposite . This accounts for the difficulty in obtaining anterior maxillary teeth intrusion. www.indiandentalacademy.com
  100. 100.  In this technique modification, of using Class I elastics , it solve the problem of lack of intrusion of the maxillary anteriors. www.indiandentalacademy.com
  101. 101.  In this arrangement the vectors are in the same direction as the elastic pull and the archwire force are unidirectional and hence synergistic www.indiandentalacademy.com
  102. 102. Dr. Jyothindra Kumar introduced concept of power arms as a point of attachment high up in the vestibule for the engagement of Class I elastics. CLASS I ELASTIC FORCE www.indiandentalacademy.com
  103. 103. Dr. Jayade has been using Class I elastics, which were worn from transpalatal arch (TPA) to the canine hooks/loops. CLASS I ELASTIC FORCE www.indiandentalacademy.com
  104. 104. It is impossible to precisely calculate the required intrusive force every time, for every patient, since it is dependent on various variables.  Different root sizes and tooth inclination.  Different arch sizes, which affect the length of the wire spans and stretch of the elastics. www.indiandentalacademy.com
  105. 105.  Individual biomechanical response  Difference in the archwire sizes. Normally .018” wire will produce more intrusive force as compared to 0.016” wire when some degree of anchor bend is given. www.indiandentalacademy.com
  106. 106. THE CONCLUSION IS, “TO USE HIGHER INTRUSIVE FORCES IN COMBINATION WITH VERY LIGHT CLASS II ELASTIC FORCES FOR ACTIVE UPPER INCISOR INTRUSION” www.indiandentalacademy.com
  107. 107. CONSIDERATION OF THE DIRECTION OF THE RESULTANT FORCE: www.indiandentalacademy.com
  108. 108. Teeth respond only to the resultant of the forces which are applied and not to the individual components of the force system. www.indiandentalacademy.com
  109. 109. During Stage I, the upper anteriors are subjected to two forces i.e. the retractive force of class II elastics and the intrusive force generated by the anchor bend in the arch wire. The resultant of these two will determine how the upper anterior teeth respond to the intrusion. www.indiandentalacademy.com
  110. 110. THE INTERPLAY BETWEEN THE ANCHOR BEND AND CLASS II ELASTICS CLASS II ELASTIC FORCE INTRUSIONFORC www.indiandentalacademy.com
  111. 111. The direction and magnitude of resultant force both depend upon the interplay between.  Magnitude of Intrusive Force: Whose direction remains constant i.e. tangential to the arc that the anterior segment of the archwire would subscribe, if released from the brackets.  Magnitude and the direction of the elastic force. www.indiandentalacademy.com
  112. 112. Different inclinations of the anterior teeth would require different combinations on of the intrusive and elastic forces. Hocevar states, that the teeth are not affected by the magnitudes of various components of force systems, they experience only the total resultant force www.indiandentalacademy.com
  113. 113. For example, in case severely proclined upper anteriors a low magnitude of intrusive force along with high class II force would give a desired resultant force, passing palatal to Cres, this will help correcting the proclination of incisors . Once the inclination of upper incisors is corrected then the class II elastics force is reduced helping in keeping the resultant force close to Cres . www.indiandentalacademy.com
  114. 114. 45gms 60gms 60 gms 30gms www.indiandentalacademy.com
  115. 115. In Class II Division 2 cases , where the upper centrals are retroclined , only intrusive force should be used (Avoiding the Class II elastics) The intrusive force acts labial to Cres and corrects the retroclination. Once the inclination is corrected then we can use Class II elastics . www.indiandentalacademy.com
  116. 116. 50gms 40gms 20gms www.indiandentalacademy.com
  117. 117. MECHANICS OF BEGG TIPPING: www.indiandentalacademy.com
  118. 118. CLASS II ELASTIC FORCE The concept of tipping back the teeth in the first stage & further in stage II … INTRUSIONFORC www.indiandentalacademy.com
  119. 119. Generally, uncontrolled tipping is undesirable because it leads to root resorption as stated by Reitan. There is more resorption when uncontrolled tipping is in labio-lingual direction. www.indiandentalacademy.com
  120. 120. Intrusion and tipping are intimately related not only because they are carried out simultaneously but also, when both are balanced judiciously it help in overcoming uncontrolled tipping of incisors. www.indiandentalacademy.com
  121. 121. This is achieved by manipulating the intrusive force generated by wire and retractive component of force from the Class II elastics. www.indiandentalacademy.com
  122. 122. BOTH THE ANCHOR BEND IN THE WIRE AND CLASS II ELASTICS PRODUCE MOMENTS IN THE SAME LABIO-LINGUAL PLANE BUT ACT IN OPPOSITE DIRECTIONS. www.indiandentalacademy.com
  123. 123. The intrusive force produces crown labial-root lingual moment e.g.. anticlockwise moment on the upper anteriors. While the retractive force produced the Class II elastics generates clockwise moment e.g. crown lingual-root labial moment www.indiandentalacademy.com
  124. 124. The moment from the intrusive force can act as the counter balance moment against the moment produced by the elastic force. The ratio of the former to the retraction component of the elastic force is the M/F ratio which governs the type of tipping while retracting the anterior teeth. www.indiandentalacademy.com
  125. 125. The most important consideration is to keep light Class II elastic and use adequate amount of intrusive force so that correct M/F ratio (8:1) is obtained to have a controlled tipping. www.indiandentalacademy.com
  126. 126. PREVENTING UNCONTROLLED TIPPING OF UPPER INCISORS www.indiandentalacademy.com
  127. 127. In the refined Begg mechanics, use of MAA which provides a moment in the labio-lingual plane by creating a couple. This couple moment is an anti-clockwise moment. www.indiandentalacademy.com
  128. 128. CLASS II ELASTIC FORCE www.indiandentalacademy.com
  129. 129. Once the bite is opened in the first stage, the intrusive force level is reduced which inturn reduces M/F ratio. This leads to greater likelihood of uncontrolled tipping of upper anterior teeth during later part of the first stage and whole of second stage. Thus the anticlockwise moment produced by anchor bend on anterior is supplemented by with the moment of couple produced by MAA www.indiandentalacademy.com
  130. 130. Flaring occurs as lower incisors are subjected to crown labial root-lingual moment from the intrusive force generated in arch wire, while there is no restraining force on these teeth as similar to Class II elastic force on Upper incisors. www.indiandentalacademy.com
  131. 131. PREVENTING UNCONTROLLED TIPPING OF LOWER INCISORS: www.indiandentalacademy.com
  132. 132. The flaring can be avoided by two means;  Minimizing the clockwise force moment by reducing the intrusive force.  Secondly, cinching tightly the distal ends of the arch wire. www.indiandentalacademy.com
  133. 133.  Lastly by producing counter moment using a MAA for labial root torque or a reverse torquing auxiliary (Udder arch) www.indiandentalacademy.com
  134. 134. www.indiandentalacademy.com
  135. 135. In case of severely lingually tipped lower anteriors, Cres will be lying buccal to the point of application of the intrusive force generated by the anchor bend so there is more chances to tip the lower anteriors more lingually. www.indiandentalacademy.com
  136. 136. So in that case we give a By pass arch wire in order to upright the lower incisors . www.indiandentalacademy.com
  137. 137. www.indiandentalacademy.com
  138. 138. www.indiandentalacademy.com
  139. 139. BEGG STAGE II www.indiandentalacademy.com
  140. 140. Amongest the traditionally described stages of Begg technique, the second stage of treatment involves closure of extraction spaces. This is thought to be the easiest phase of treatment www.indiandentalacademy.com
  141. 141. During Stage II all the corrections achieved during Stage I should be maintained.  Maintain Edge to Edge relationship of anterior teeth: Reduce the anchor bend in arch wire and wear intermaxillary elastics as required . www.indiandentalacademy.com
  142. 142.  Maintain anterior space closure : To give cuspid ties either by elastomeric rings or steel ligatures.  To maintain overcorrected or normal mesiodistal molar relationship : Keep wearing of intermaxillary elastics as required during posterior space closure. www.indiandentalacademy.com
  143. 143.  In addition to the above, the stage II of the refined Begg aims are Controlled tipping of the incisors, when space closure is to be mainly achieved by the anterior retraction. www.indiandentalacademy.com
  144. 144. OBJECTIVES OF STAGE II: www.indiandentalacademy.com
  145. 145. When all the objectives of Stage I are met stage II mechanics can be instituted. The sole or main purpose of II stage is closure of extraction spaces. www.indiandentalacademy.com
  146. 146. The extraction space can be closed by either retraction of the anteriors or protraction of the posteriors or combination of both. www.indiandentalacademy.com
  147. 147. BIOMECHANICS OF STAGE II www.indiandentalacademy.com
  148. 148. The anchor bend should be sufficient as to produce a counter clockwise moment greater than the clockwise moment produced by the Class I and Class II elastics in upper arch. www.indiandentalacademy.com
  149. 149. The M/F ratio should be sufficient or around 8/1 so as to have a controlled tipping movement. www.indiandentalacademy.com
  150. 150. If anticlockwise moment is less than clockwise moment produce by Class I and Class II elastics on upper anterior, then M / F ratio will less and it will uncontrolled tipping of upper anterior teeth. www.indiandentalacademy.com
  151. 151. Class I Elastic Forces CLASS I ELASTIC FORCE INTRUSIONFORC At the end of Stage II www.indiandentalacademy.com
  152. 152. Same way in lower arch the clockwise moment should be greater than anticlockwise moment produced by Class I elastics. So as to have controlled tipping movement. www.indiandentalacademy.com
  153. 153. Normally 0.016 upper and lower arch wires with reduced bite opening bends are used. Some authors say use of heavy arch wire 0.020” as it will function as retainers to maintain arch form and bite opening achieved during stage I. www.indiandentalacademy.com
  154. 154. Dr. Swain advocated the use of lingual attachments on molars and cuspids to allow the use of lingual space closing elastics to aid the traditionally used buccal vector of intra maxillary elastic force during stage II known as half strength elastics. www.indiandentalacademy.com
  155. 155. Two distinct advantages in using intra maxillary (Half strength) space closing elastics  It gives a better positional control over the anchor molar thus obviating the need for a mandatory compensate toe in bend when using elastic force only from buccal side.  Closure of extraction spaces becomes easier. www.indiandentalacademy.com
  156. 156. www.indiandentalacademy.com
  157. 157. USE OF BRAKING MECHANICS www.indiandentalacademy.com
  158. 158. When further retraction of anterior teeth into the remaining extraction space is deemed undesirable clinically , then the posterior teeth are brought forward, that is posterior teeth are mesialized. www.indiandentalacademy.com
  159. 159. To achieve mesialization of posterior teeth heavy elastic forces are required with concurrent use of brakes in the anterior region. www.indiandentalacademy.com
  160. 160. Various brakes are:  Using uprighting springs (passive springs)  Reverse torque to incisor roots (Udder arch and MAA)  Using T pins www.indiandentalacademy.com
  161. 161. Passive Uprighting Springs T PINS MAAUDDER ARCH www.indiandentalacademy.com
  162. 162. The brakes reverse the anchorage site from the posterior to anterior segment by allowing bodily movement rather than the tipping of anterior teeth, this bodily movement provides more resistance hence acting as a anchorage. www.indiandentalacademy.com
  163. 163.  He summarized that the direction of resultant force should pass through the center of resistance of anterior teeth (or close to it).  Therefore, substituting Class II elastic forces by Class I elastic forces would orient the resultant force more vertically passing nearer to the center of resistance of anterior teeth. www.indiandentalacademy.com
  164. 164. Stage I arch-wire www.indiandentalacademy.com
  165. 165. www.indiandentalacademy.com Thank you For more details please visit www.indiandentalacademy.com

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