The third law of Newton applies in almost all orthodontic movements; the law of Action and Reaction, which states that to every action there is always opposing and equal reaction. Sometimes the reaction to a movement results in an unwanted movement. An example of the third law of Newton when we want to align extruded or intruded teeth , the same force produced to make these movements will be applied on the surrounding teeth provoking a movement in opposite direction to the one we want to produce. An example of the third law of Newton (Action and Reaction) would be when we want to distalize a molar with NiTi open coils. The molar distalization is accomplished, but the same force applied backwards to distalize is applied on the buccal segment, not only provoking distalization and molar tipping, but also proclination of the buccal segment.

1. ACTION AND REACTION
in orthodontic
movements
ACHIEVED BY: Dr.Maen Dawodi

2. • The third law of Newton applies in almost all orthodontic
movements; the law of Action and Reaction, which states
that to every action there is always opposing and equal
reaction.
• Sometimes the reaction to a movement results in an
unwanted movement.

3. • An example of the third law of Newton when we want to align
extruded or intruded teeth , the same force produced to make these
movements will be applied on the surrounding teeth provoking a
movement in opposite direction to the one we want to produce.

4. An example of the third law of Newton (Action and Reaction) would be when we
want to distalize a molar with NiTi open
coils. The molar distalization is accomplished, but the same force applied
backwards to distalize is applied on the buccal segment, not only provoking
distalization and molar tipping, but also proclination of the buccal segment.

5. • To determined the action of bend we must know where
we put it ,
So now we can identify the type of force and the moment
expected with that bend .
• The easiest way to determine the direction of a movement
of a bend made on an arch wire is to put it in a passive
manner in the slots of two braces, and observe where the
arch is headed to, so that when we activate the wire,
placing it in the slots, we can predict the direction of the
movement to take place.

8. • In this case, what is produced is what we call force equilibrium, where
equal and opposed forces with different moments take place, being the
greater moment the side that receives the shorter segment of the bend.
the short segment of the wire once
inserted in the
molar tube will indicate us that the
force exerted on the incisor area is
an intrusive force and extrusive in the
molar area

9. • if the bend is located in the center of the arch wire,
between both teeth, the forces that are produced cancel
one another when the wire is inserted in the slot of the
braces.
• In this case the system is in equilibrium, because the
associated forces are equal and opposed and cancel each
other
This type of bend is very helpful uprighting divergent
roots

10. 1- Deep bite correction with a tip back:
• If we utilize the tip back bend for the correction of a deep bite, it can
clearly be seen that when the short segment of the bend is inserted
in the molar tube, the large segment directs itself to the apical
portion of the anterior zone.
• This way we know that an intrusive force will be produced on the
anterior zone and extrusive force on posterior zone .

11. • we have to mind with the placement of bends is that the
short segment of the arch wire is going to represent the
anchorage side, and the long segment of wire the side of
no anchorage, this is due to the fact that Moment at the
molar level (short part of the bend) is greater than the one
that is being produced at the incisor level, making the
molar much more resistant to movement

12. • When the arch wire is activated by placing it in the slots of
the 'incisor braces, two moments are going to be
produced, one at molar level and another at the incisor
level, provoking a differential torque on both teeth.
• A mesial root movement and a distal crown movement is
produced in the molars.
• the intrusive force passes buccal to the center of
resistance of the incisors. the moment is going to be lower,
taking the incisor to a more buccal position .

13. At the time of insertion of the tip back in the molar tube. the large segment
of wire directs itself to the apical zone of the anterior segment. indicating
the direction where the forces are going to be produced

14. Tip and torque expressed
in the molar and the
incisor. A slight
molar extrusion is
produced that together
with the tip back bend
helps
the opening of the bite
and the correction of the
overbite

15. • Action taken
1. Apically directed Tip back.
• Produced reaction
1. Molar extrusion.
2. Incisor intrusion.
3. Distal inclination of the molar crowns.
4. Mesial inclination of the molar roots.
5. Buccal movement of the incisors.
6, Increase of dental arch length.
7. Posterior anchorage.

16. 2- Spee curve leveling with reverse curves
• When we use reverse curves to level a deep curve of Spee , we find
that the intrusive forces exercised in the anterior and posterior
sectors are balanced with the extrusive forces that are exercised in
the premolar region.
• the intrusive forces are going to provoke at the molar level a positive
torque and a distal inclination of the crowns and a mesial movement
of their roots .
• the intrusive forces exercised at the incisor level will provoke a
buccal movement (positive torque).

17. The extrusive forces at the premolar level are going to be
equilibrated by the intrusive forces exercised at the molar and
incisor level

18. The moments produced by the action of an inverse curve are evidenced
at the molar level with a distal inclination of the crown and a mesial in
the roots and at the incisor level with a buccal movement of them
(positive torque).

19. • Action taken
1. Use of an inverse curve in the inferior arch.
• Produced reaction
1. LeveIing of the deep Spee curve.
2. Overbite reduction.
3. Extrusion of the premolar sector.
4. Intrusion of the molar and the incisors.
5. Positive torque in molars and incisors.
6. Distal inclination of the crown and mesial inclination of
the roots.
7. Increase in length in the lower dental arch.

20. 3- Correction of a bilateral posterior open bite
with reverse curves:
• The action principle of the curves, in this case, is exactly the same
one that we use for the leveling of a deep Spee curve.

21. The curves will provoke premolar extrusion in the upper and
lower dental arches, and the intrusion of molars and incisors in both dental
arches.

22. Provoking the distal inclination of the molar crowns and mesial
inclination of the roots, and a positive torque at the incisor level
in both dental arches

23. • Action taken
1. Use of curves on both dental arches.
• Produced reaction
1. Intrusion of upper and lower molars and incisors.
2. Extrusion on the upper and lower premolar sector in
order to level the dental arches.
3. Increase in length in both dental arches.
4. Distal inclination of the crowns and mesial inclination of
the roots in both dental arches.
5. Positive torque in molars.
6. Positive torque at upper and lower incisor level

24. 4- Correction of a deep bite with a bite plane
and bilateral box elastics
• The use of an anterior bite plane for the correction of an
anterior deep bite is a very simple practical and stable
solution for this malocclusion.
• This way, the extrusion of molars and premolars in a
passive way is stimulated or it can be accelerated with the
use of bilateral box elastics .
• The bite plane should be kept in the mouth until the
occlusion in the posterior sector is definitely assented .

25. the extrusion of the anterior
segment and the extrusion of the posterior sector;
this can be assisted
with the use of intermaxillary box elastics.

26. • Action taken
1. Use of an anterior bite plane.
2. Use of intermaxillary box elastics.
• Produced reaction
1. Intrusion of inferior incisors.
2. Extrusion of canines, premolars and molars .
3. Improvement of the interincisal relation

27. 5- Correction of an anterior open bite with
the use of a posterior bite block:
• Caused by extrusion of posterior sector and intrusion of
anterior sector .
• to correct this, the intrusion of the posterior sector and
the extrusion of the anterior sector are necessary.
• The purpose of the use of the bite block is the intrusion of
the posterior segment, resulting in an auto rotation of the
mandible, producing the satisfactory closure of the open
bite.

28. Posterior intrusion will be produced by the pressure of occlusion over
the bite block and anterior extrusion by the lack of dental contact in
this zone .
For closure of the anterior bite with a bite block we can use
of intermaxillary elastics to facilitate bite closure .

31. • Action taken correction
1. Bite block placement for open bite closure.
• Produced reaction
1. Molar and premolar intrusion.
2. Extrusion of the anterosuperior sector.
3. Shortening of the inferior facial height.
4. Overbite .
S. Mandible auto rotation

32. 6-Correction of an anterior cross bite with the use
of a forward arch wire:
• this should only have a dentoalveolar component, and
not a skeletal one.
• The forward arch is made by doing two small stops at the
entrance of the molar tubes and leaving 2 mm or 3 mm of
separation between the arch wire and the slot of the
anterior braces .
• This arch wire is not only going to produce an anterior
proclination for the correction of the cross bite, but will
also provoke a mild molar distalization .

35. • Action taken
1. Placement of a forward arch in order to correct an
anterior cross bite.
• Produced reaction
1. Proclination of the upper incisors.
2. Upper molar distalization.
3. Positive torque in the upper incisor
4. Distal inclination of the crown and mesial inclination of
the roots of the upper molars.
5. Posterior anchorage.
6. Reduction of the nasolabial angle.

36. 7- Root uprighting :
• In order to do this second order bends must be made on a
stainless steel arch, round or rectangular .
• and The direction of the bends will depend upon whether
the roots are divergent or convergent among themselves .
• The forces cancel each other cause they has same
magnitude and different directions , so the moments are
going to make root rotation movement .

37. DIVERGENT ROOTS

40. • Action taken
1. "V" second order bends to upright divergent roots.
• Produced reaction
1. The forces cancel each other.
2. Root up righting by the action of the Moments

41. 8- Diastema closure with closing loops:
• A diastema is defined as a space between two teeth; these can be
treated with orthodontics or with cosmetic dentistry .
• closing loops are going to exert their forces in a perpendicular mode
to the center of resistance of the tooth, resulting in bodily movement
with out rotation

43. • Produced reaction
l. Placement of a vertical closure loop for diastema correction.
• Produced result
l. Closure of the diastema with a bodily movement of the root.

44. Thank you