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Orthodontic
tooth
movement
Abdurrahman Mosaad
Orthodontics department
Armed forces medical complex – Kobry
al Qubba
In the name of Allah , most
gracious , most merciful
# What is orthodontics :
= Orthodontics is the specialty of dentistry
with the management and treatment
of malocclusion.

concerned

=In the majority of cases, a malocclusion does not in
itself represent a disease state, but rather a variation
from what is considered ideal
- Andrew’s keys for ideal occlusion
- The nature of orthodontic tooth movement :
= it has a bio – mechanic nature.
= solely based upon stress- strain occurs in the
PDL
environment

= the orthodontic tooth movement results from
forces delivered to the teeth
= the forces are delivered via orthodontic app.
Either fixed or removable
= PDL undergoes biological respond upon the
mechanical application of a force i.e to
achieve a
precise biological respond the mechanical
forces to be delivered should be precise
 = Knowledge of the mechanical principles

governing forces is necessary for the
control of orthodontic treatment
 = The proper application of biomechanics

principles increases treatment efficiency
through improved planning and delivery of
care
Orthodontic tooth movement ppt.
= Knowledge of the mechanical principles
governing forces is necessary for the control
of
orthodontic treatment

= The proper application of biomechanics
principles increases treatment efficiency
through improved planning and delivery of
care
1 = center of
resistance.
- All objects have a
center of mass.
- This is the point
through which an applied
force must pass for a
free object to move
linearly without any
rotation,
- i.e., the center of mass
is an object’s “balance
point.”
analytic studies have
determined that the
center of resistance for
single-rooted teeth
with normal alveolar
bone levels is about
1/4 to 1/3 the distance
from the
cementoenamel
junction (CEJ) to the
root apex.
Location of the center of resistance depends on the alveolar
bone height and root length
. = Location of the center of
resistance with
alveolar bone loss
= with a shortened root
2 - Forces
= they are actions applied to
bodies

= they equals ( mass X
acceleration) F =ma
= in clinical orthodontics its
unit is Grams
= forces has the
characteristics of vectors i.e
magnitude & direction

Note : the diagram shows that the
force vectors characteristics –
magnitude , point of origin &
direction
= 2 vectors could added by
placing one vector at the
head of the another i.e sum
of them called resultant

= a vector could be
resolved into components
along x , y & z axes
= Clinically the determination of the horizontal,
vertical, and transverse components of a force
improves the understanding of the direction of
tooth movement

= An important point of view that the orthodontic
tooth movement is not applied on the center of
rotation of the tooth as it is usually delivered

through the tooth crown
= as the orthodontic forces
are delivered through the
tooth crown they will not

produce a pure linear
movement ,, some rotational
movement will be present ,,
those rotational movements
are called Moment of the
force
= The moment of the force
is the tendency for a force to
produce rotation.
= Its direction is found by
following the line of action

around the center of resistance
toward the point of origin

=It is determined by multiplying
the magnitude of the force by
the perpendicular distance of

the line of action to the center of
resistance
= The importance of the moment of a force
is often not recognized in clinical
orthodontics, but awareness of it is needed
to develop effective and efficient appliance
designs
Clinical examples of moments of the forces
3 – Couple

- A couple is
two parallel forces of equal
magnitude acting in opposite
directions and separated by a
distance (i.e. different lines of
action)
- The magnitude of a couple is
calculated by multiplying the
magnitude of force(s) by the
distance between them
Couples result in pure rotational
movement about the center of
resistance
clinical examples of couples
4 – Torque
= Torque is a common synonym for moment
(both moments of forces and of couples)

= Torque is erroneously described in terms of
degrees by many orthodontists.
= The appropriate unit for the applied torque is
gram/millimeters (force × distance). It is the
description of the moments that more accurately
describes the rotational components of a force
system and appliance design
Orthodontic wire bends
-1st order
-- 2nd order
-- 3rd order
Orthodontic tooth movement ppt.
Orthodontic tooth movement ppt.
Orthodontic tooth movement ppt.
# Anchorage
-Anchorage is the site

of delivery from which
force is exerted
- degree of resistance

to displacement
offered by an anatomic
unit for the purpose of
tooth movement.
# Classification of ortho. Anchorage
-acc. to manner of force application :

* simple * stationary * reciprocal
- according to jaws involved :
* intermaxillary * intramaxillary
- according to site :
* intraoral * extaraoral * muscular
- according to anchorage units :
* primary * compound *reinforced (multiple)
Orthodontic tooth movement ppt.
# anchorage planning :
-Increasing no. of teeth to be move requires
more anchorage
- teeth having more surface area requires more
anchorage

- bodly movement requires more anchorage
- prolonged tx. Plan requires more anchorage
- vertical growth pattern requires more

anchorage due to the less tonicity of muscles
- N.B. Good occlusion = Good anchorage
# Anchorage loss :
-Its is the unwanted tooth movements during

orthodontics that cause space loss
-Maximum anch.
* anch. Demand is very high
*not more than ¼ of ext space should be lost
* augmentation of anchor units is usually done
-Moderate anch.

* ¼ - ½ of ext space should be lost
- Minimum anch.
* more than ½ ext space could be lost
Maximum anch.
Moderate anch.
Minimum anch.
# Equivalent Force systems
= A useful method for
predicting the type of tooth
movement that will occur with
appliance activation is to
determine the equivalent force
system at the tooth’s center of
resistance

= The force system at the
center of resistance accurately
reflects the type of movement
 eg. Intrusion arch force system
# Types of tooth movement :
1 – tipping ( controlled & uncontrolled)
2 – translation ( bodily )
3 – root movement
4 - rotation
5 - intrusion & extrusion
-The relationship between the applied force

system and the type of movement can be
described by the moment/force ratio
-The movement that occurs is dependent on the
(moment/force ) ratio #and# the quality of the
periodontal Support
1- Tipping :
* simplest orthodontic movement
* controlled occurs about the tooth apex
*uncontrolled occurs about CER
* Force needed is about 50 – 75 gm.
Controlled tipping
Uncontrolled tipping
2- Translation :
* all PDL is uniformly loaded with the force
* Force needed is about 100 – 150 gm.
3 – Rotation :
* needs high force
* occurs around the CER
* Force needed is about 50 – 100 gm.
4 – Extrusion :
* needs to produce tension in the PDL
ligaments
* Force needed is about 50 gm.
5 – Intrusion :
* forces are nearly at the apex
* needs minimum force application
* Force needed is about 15 – 25 gm.
Orthodontic tooth movement ppt.
6- Root movement :
* usually expressed as torque
* the crown is held stationary and the root
moves
* CER is the bracket itself
* done by increasing the Moment/Force
ratio
Moment / Force ratios needed for different kinds of
tooth movement :
1 – tipping
* controlled
5:1
* uncontrolled 7 : 1

2 – translation

10 : 1

3 – root movement

12 : 1
Types of orthodontic forces acc. to Duration

- continuous
- interrupted
- intermitted
* Threshold --- 6 hrs per day.
* No tooth movement if forces are applied less
than
6 hrs/d.
* From 6 to 24 hrs/d, the longer the force is
applied, the more the teeth will move.
- Continuous force :

* achievable via fixed orthodontics
*Never declines to zero.
- Interrupted force :

* force starts heavy then decline to optimal
after that may reach zero .
*achievable via removable appliance.
* produces some kind of undermining
resorption .

* reactivated every specific time .
-Intermittent forces :

* declines to zero
* very high force 250 – 500 gm.( anch – dist )
* achievable via extraoral appliance
* needs at least 12 hrs/day to be effective
* 14 hrs/day is optimal
Orthodontic tooth movement ppt.
-Force level :

* Light, continuous forces are currently
considered to be most effective in inducing
tooth movement.
*Heavy forces cause damages and fail to move
the teeth.
N.B. Optimal force : “High enough to stimulate
cellular activity without completely occluding blood
vessels in the PDL”
Orthodontic tooth movement ppt.
Heavy Forces

Tooth movement (mm)

* B.V of PDL is totally occluded --then
* causes cellular necrosis within the bone --then
* hyalinization i.e undermining resorption
occur
Phase 3
Phase 2
Phase 1
Time (Arbitrary Unit)
•
•

Tooth mov.

Light, continuous forces

Osteoclasts formed
Phase 2
*Removing lamina dura.
*Tooth movement begins
Time
*This process is called
“FRONTAL RESORPTION”.
( remodeling process )

Phase 3
Orthodontic tooth movement ppt.
Orthodontic tooth movement ppt.
Orthodontic tooth movement ppt.
-Phases of orthodontic tooth movement :-

* Displacement - no clinical movement
- instantaneous
* Delay – no clinical movement
- short ( partial B.Vs occ. ) or long
1-2
weeks ( more B.Vs occ. )
* Acceleration – rapid tooth displacement
- differs among individuals
Tooth movement (mm)

Phase 3
Phase 2
Phase 1

Time (Arbitrary Unit)
Orthodontic tooth movement adverse
effects :
* Pulp - transient inf. response , can cause
loss of vitality
- in cases of compromised tooth ,,
heavy
force ,, wrong mech.
* Root - usually repaired by cementum
during
rest periods
- resorption may occur up to 2 mm.
in
permanent cases
- At risk : thin roots ,, heavy force ,,
Material considerations :
1 – orthodontic wires
*material of the wire
* effect of increasing wire diameter
2 – orthodontic brackets
* edgewise vs pre-adjusted (roth)
* self ligating brackets
* size of slots
* interbracket distance
* torque of the brackets
Orthodontic tooth movement ppt.
force

deflection
Modulus of elasticity of the wire
100% 200% 300% 400%

Percentage increase in
stiffness

 14’’ 50gm
 16’’ 85gm 71% increase
 18’’ 137gm 173% increase

14’’

16’’

18’’

20’’

22’’

Wire diameter

Effect of increasing wire diameter
Torque selection of lower teeth brackets
Torque selection of upper teeth brackets
Finally :
Optimal force
is the lightest force that will move a
tooth to a desired position in the shortest
possible time without iatrogenic effects
So ,,, we should think optimal ,, it is
orthodontics so we ( work smarter not
harder ) 
Thank You 

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Orthodontic tooth movement ppt.

  • 2. In the name of Allah , most gracious , most merciful
  • 3. # What is orthodontics : = Orthodontics is the specialty of dentistry with the management and treatment of malocclusion. concerned =In the majority of cases, a malocclusion does not in itself represent a disease state, but rather a variation from what is considered ideal
  • 4. - Andrew’s keys for ideal occlusion
  • 5. - The nature of orthodontic tooth movement : = it has a bio – mechanic nature. = solely based upon stress- strain occurs in the PDL environment = the orthodontic tooth movement results from forces delivered to the teeth
  • 6. = the forces are delivered via orthodontic app. Either fixed or removable = PDL undergoes biological respond upon the mechanical application of a force i.e to achieve a precise biological respond the mechanical forces to be delivered should be precise
  • 7.  = Knowledge of the mechanical principles governing forces is necessary for the control of orthodontic treatment  = The proper application of biomechanics principles increases treatment efficiency through improved planning and delivery of care
  • 9. = Knowledge of the mechanical principles governing forces is necessary for the control of orthodontic treatment = The proper application of biomechanics principles increases treatment efficiency through improved planning and delivery of care
  • 10. 1 = center of resistance. - All objects have a center of mass. - This is the point through which an applied force must pass for a free object to move linearly without any rotation, - i.e., the center of mass is an object’s “balance point.”
  • 11. analytic studies have determined that the center of resistance for single-rooted teeth with normal alveolar bone levels is about 1/4 to 1/3 the distance from the cementoenamel junction (CEJ) to the root apex.
  • 12. Location of the center of resistance depends on the alveolar bone height and root length . = Location of the center of resistance with alveolar bone loss = with a shortened root
  • 13. 2 - Forces = they are actions applied to bodies = they equals ( mass X acceleration) F =ma = in clinical orthodontics its unit is Grams = forces has the characteristics of vectors i.e magnitude & direction Note : the diagram shows that the force vectors characteristics – magnitude , point of origin & direction
  • 14. = 2 vectors could added by placing one vector at the head of the another i.e sum of them called resultant = a vector could be resolved into components along x , y & z axes
  • 15. = Clinically the determination of the horizontal, vertical, and transverse components of a force improves the understanding of the direction of tooth movement = An important point of view that the orthodontic tooth movement is not applied on the center of rotation of the tooth as it is usually delivered through the tooth crown
  • 16. = as the orthodontic forces are delivered through the tooth crown they will not produce a pure linear movement ,, some rotational movement will be present ,, those rotational movements are called Moment of the force = The moment of the force is the tendency for a force to produce rotation.
  • 17. = Its direction is found by following the line of action around the center of resistance toward the point of origin =It is determined by multiplying the magnitude of the force by the perpendicular distance of the line of action to the center of resistance
  • 18. = The importance of the moment of a force is often not recognized in clinical orthodontics, but awareness of it is needed to develop effective and efficient appliance designs
  • 19. Clinical examples of moments of the forces
  • 20. 3 – Couple - A couple is two parallel forces of equal magnitude acting in opposite directions and separated by a distance (i.e. different lines of action) - The magnitude of a couple is calculated by multiplying the magnitude of force(s) by the distance between them
  • 21. Couples result in pure rotational movement about the center of resistance
  • 23. 4 – Torque = Torque is a common synonym for moment (both moments of forces and of couples) = Torque is erroneously described in terms of degrees by many orthodontists.
  • 24. = The appropriate unit for the applied torque is gram/millimeters (force × distance). It is the description of the moments that more accurately describes the rotational components of a force system and appliance design
  • 25. Orthodontic wire bends -1st order -- 2nd order -- 3rd order
  • 29. # Anchorage -Anchorage is the site of delivery from which force is exerted - degree of resistance to displacement offered by an anatomic unit for the purpose of tooth movement.
  • 30. # Classification of ortho. Anchorage -acc. to manner of force application : * simple * stationary * reciprocal - according to jaws involved : * intermaxillary * intramaxillary - according to site : * intraoral * extaraoral * muscular - according to anchorage units : * primary * compound *reinforced (multiple)
  • 32. # anchorage planning : -Increasing no. of teeth to be move requires more anchorage - teeth having more surface area requires more anchorage - bodly movement requires more anchorage - prolonged tx. Plan requires more anchorage - vertical growth pattern requires more anchorage due to the less tonicity of muscles - N.B. Good occlusion = Good anchorage
  • 33. # Anchorage loss : -Its is the unwanted tooth movements during orthodontics that cause space loss -Maximum anch. * anch. Demand is very high *not more than ¼ of ext space should be lost * augmentation of anchor units is usually done -Moderate anch. * ¼ - ½ of ext space should be lost - Minimum anch. * more than ½ ext space could be lost
  • 37. # Equivalent Force systems = A useful method for predicting the type of tooth movement that will occur with appliance activation is to determine the equivalent force system at the tooth’s center of resistance = The force system at the center of resistance accurately reflects the type of movement
  • 38.  eg. Intrusion arch force system
  • 39. # Types of tooth movement : 1 – tipping ( controlled & uncontrolled) 2 – translation ( bodily ) 3 – root movement 4 - rotation 5 - intrusion & extrusion
  • 40. -The relationship between the applied force system and the type of movement can be described by the moment/force ratio -The movement that occurs is dependent on the (moment/force ) ratio #and# the quality of the periodontal Support
  • 41. 1- Tipping : * simplest orthodontic movement * controlled occurs about the tooth apex *uncontrolled occurs about CER * Force needed is about 50 – 75 gm.
  • 44. 2- Translation : * all PDL is uniformly loaded with the force * Force needed is about 100 – 150 gm.
  • 45. 3 – Rotation : * needs high force * occurs around the CER * Force needed is about 50 – 100 gm.
  • 46. 4 – Extrusion : * needs to produce tension in the PDL ligaments * Force needed is about 50 gm.
  • 47. 5 – Intrusion : * forces are nearly at the apex * needs minimum force application * Force needed is about 15 – 25 gm.
  • 49. 6- Root movement : * usually expressed as torque * the crown is held stationary and the root moves * CER is the bracket itself * done by increasing the Moment/Force ratio
  • 50. Moment / Force ratios needed for different kinds of tooth movement : 1 – tipping * controlled 5:1 * uncontrolled 7 : 1 2 – translation 10 : 1 3 – root movement 12 : 1
  • 51. Types of orthodontic forces acc. to Duration - continuous - interrupted - intermitted
  • 52. * Threshold --- 6 hrs per day. * No tooth movement if forces are applied less than 6 hrs/d. * From 6 to 24 hrs/d, the longer the force is applied, the more the teeth will move.
  • 53. - Continuous force : * achievable via fixed orthodontics *Never declines to zero.
  • 54. - Interrupted force : * force starts heavy then decline to optimal after that may reach zero . *achievable via removable appliance. * produces some kind of undermining resorption . * reactivated every specific time .
  • 55. -Intermittent forces : * declines to zero * very high force 250 – 500 gm.( anch – dist ) * achievable via extraoral appliance * needs at least 12 hrs/day to be effective * 14 hrs/day is optimal
  • 57. -Force level : * Light, continuous forces are currently considered to be most effective in inducing tooth movement. *Heavy forces cause damages and fail to move the teeth. N.B. Optimal force : “High enough to stimulate cellular activity without completely occluding blood vessels in the PDL”
  • 59. Heavy Forces Tooth movement (mm) * B.V of PDL is totally occluded --then * causes cellular necrosis within the bone --then * hyalinization i.e undermining resorption occur Phase 3 Phase 2 Phase 1 Time (Arbitrary Unit)
  • 60. • • Tooth mov. Light, continuous forces Osteoclasts formed Phase 2 *Removing lamina dura. *Tooth movement begins Time *This process is called “FRONTAL RESORPTION”. ( remodeling process ) Phase 3
  • 64. -Phases of orthodontic tooth movement :- * Displacement - no clinical movement - instantaneous * Delay – no clinical movement - short ( partial B.Vs occ. ) or long 1-2 weeks ( more B.Vs occ. ) * Acceleration – rapid tooth displacement - differs among individuals
  • 65. Tooth movement (mm) Phase 3 Phase 2 Phase 1 Time (Arbitrary Unit)
  • 66. Orthodontic tooth movement adverse effects : * Pulp - transient inf. response , can cause loss of vitality - in cases of compromised tooth ,, heavy force ,, wrong mech. * Root - usually repaired by cementum during rest periods - resorption may occur up to 2 mm. in permanent cases - At risk : thin roots ,, heavy force ,,
  • 67. Material considerations : 1 – orthodontic wires *material of the wire * effect of increasing wire diameter 2 – orthodontic brackets * edgewise vs pre-adjusted (roth) * self ligating brackets * size of slots * interbracket distance * torque of the brackets
  • 70. 100% 200% 300% 400% Percentage increase in stiffness  14’’ 50gm  16’’ 85gm 71% increase  18’’ 137gm 173% increase 14’’ 16’’ 18’’ 20’’ 22’’ Wire diameter Effect of increasing wire diameter
  • 71. Torque selection of lower teeth brackets
  • 72. Torque selection of upper teeth brackets
  • 73. Finally : Optimal force is the lightest force that will move a tooth to a desired position in the shortest possible time without iatrogenic effects So ,,, we should think optimal ,, it is orthodontics so we ( work smarter not harder ) 