3. MECHANICSIntroduction
Success in an orthodontic treatment
Two factors must be combined
A good treatment plan
Excellent biomechanics
called
Describes the effect of:
forces on objects (teeth and bone)
Contemplated within
a part of Engineering
4. شرحآلياتأجهزة عمللحركة المستخدمة القوة ونظام األسنان تقويماألسنان
Biomechanics the part of Mechanics that:
studies movement in relation with biological systems
Biomechanical principles
Explain
The mechanisms of action of the orthodontic
appliances
Force system utilized for dental movement
الحركةفيالنظمالبيولوجية
الميكانيكاالحيوية
5. for Greater Benefit of the patient
Whoever gets to understand HOW these physics principles work
will be able to:
Design
Select Use
كلمنيفهمهذه عمل كيفيةالمبادئ
Orthodontic Appliances
7. The law of inertia:
The law of acceleration
The law of action and reaction
قانونالذاتي القصور
قانونالتسارع
قانونالفعل ورد الفعل
The three laws of motion
In 1686, Newton presented the fundamental laws of Mechanics
The three laws of motion are the following:
9. Forces must be applied in order to obtain movement
A dental malposition can never resolve itself spontaneously
because of this
In orthodontics
Teeth tend to remain almost motionless
unless
A force applied to provoke tooth displacement
10.
11. The larger the force that has to
be exerted to produce
physiologic movement
In orthodontics
Tooth that we want to move
Said in another way
we can affirm that
Teeth move in the direction
of the applied force
The larger the Root Volume
تتحركالقوة اتجاه في األسنانالمطبقة
Diverse forces with Different intensities
we can apply
Depends on
12. To every action there is always
opposing and equal reaction)
The law of action and reaction:
13. to minimize or eliminate:
1. Therapy efficiency can improve; thus,
2. Rapid and painless treatments with negligible damage to teeth and supporting
tissues can be achieved with
3. Less collateral damage and
4. More pleasing and durable results
These three laws offer evident benefits to the orthodontist and the patient
If applied in a appropriate manner
The "SECRET“ in orthodontics is :
secondary or collateral effects of treatment
إذامناسبة بطريقة طبقت
16. Pharmaceuticals
In medicine,
the physician makes a diagnosis and then
selects the proper medication to
accomplish his goals
In pharmacology,
medicines are used to act upon cells,
tissues and specific organs
The collateral effects of medicines are
unavoidable and must be well managed
17. Orthodontic appliances
In orthodontics,
the orthodontist must make his diagnosis and then
select the best appliance design to reach his
objectives
In orthodontics
moments and forces are used to act upon cells and
specific tissue that support teeth and bone
Secondary effects are also produced during tooth
movement and should also be recognized and
managed with care. When such effects are known
beforehand, precaution measures can be taken to
counter these harmful effects, which in some
instances can be managed to our benefit
19. What is force?
What is the center of resistance?
What is the Center of Rotation?
What is a moment?
20. What is force?
= they are Actions applied to bodies
(wire, coil, elastic, etc.) over another
body (teeth or bone)
= in clinical orthodontics its unit is Grams
Ig=0.00981N, or IN=101.937 g
21. - every free body has a point
known as Mass Center
What is the center of resistance?
- The center of resistance is the point a force has to pass through
- in order to move an object freely in a linear manner
Said in another way,
- every time that the line
of action of a force
passes through mass
center of a free body
therefore
- will suffer a translation movement
22. - Any force that acts through the center of resistance of a tooth makes it translate in
a bodily manner
- A tooth in the mouth is not a free body
because periodontal support tissue does not let it move freely
The center of resistance
equivalent to
The mass center for free bodies
23. - Level of support of the alveolar bone
The center of resistance of a tooth depends on
- Length and morphology of the root,
- Number of roots
24. The center of resistance
Single root tooth
between the middle and
cervical third part of the root
Multiple root tooth
At one or two millimeters apical
from the furcate
25. - to produce pure
dental translation
Because braces can only be bonded on the crowns of teeth,
there are
very few opportunities in which it is possible to apply a force
that can act through the center of resistance of the tooth
26. - The center of rotation can be very close
What is the Center of Rotation?
- Arbitrary point located at a distance from the center of resistance
on which a tooth is going to turn around if a force is applied
- but it will never coincide with
the center of resistance
27. Rotation or
first order dental
movement (in-out
movement)
along the larger axis of the tooth
Angulation or
second order dental
movement (Tip)
around the mesiodistal axis
Torque or third order
movement
around the buccolingual axis
In orthodontics
28. What is a moment?
a force applied on a brace that does not act through the center of resistance
provokes the rotation of the tooth
- said in another way,
العزم=القوةذراعها في
29. Dental movement physiology
Dental movement
A biological response to the physiologic
reaction toward forces
استجابةلرد بيولوجيةفسيولوجي فعل
30. This union is done by the periodontal insertion represented
by:
- Dental cement
- Periodontal ligament and
- Alveolar bone
Maxillary bonesTeeth
united to
Dentoalveolar Joint
31. - intermingling with:
- blood vessels
- cellular elements
- nerve endings and
- interstitial fluids
The periodontal ligament
= occupies a space of approximately 0.5 mm
(between the alveolar wall and the tooth
cement)
= it is responsible for the dental joint
= Made out of collagen fibers that
insert themselves in the root cement
and in the alveolar bone
32. Tooth movementForce
Tooth
PDL/Bone
Biological electricity
Blood flow
Microfractures
Osteoblasts (tension)
Osteoclasts (compression)
Resorption and Deposition
of bone
Dental movement begins two days
after the force is applied
alveolus dislocates in the direction of the
applied force, with orthodontic movement as
a consequence
33. 4. Rotation
Types of dental movement
Dental movement can be classified in many ways:
1. Inclination
a. Uncontroled inclination
b. Controlled inclination
2. Translation 3. Root displacement
34. a. Uncontrolled inclination: b. Controlled inclination:
Center of rotation Slightly apical to center of resistsnce Apex of root
Wire ROUND arch wire Rectangular Arch Wires
This type of inclination happens when
- This movement can be obtained by
any orthodontist, but is usually not
wanted
- This is a wanted
movement
35. - with the use of
Elastomeric Power Chains
in order to close spaces
This uncontrolled inclination happens when we have
- ROUND arch wire
in the slot of the brace and
force is applied to the tooth
36. - a MOMENT is produced and this
provokes both teeth to rotate over
their center of rotation
Uncontrolled inclination of the incisors
- with Elastomeric Power Chain
on a round arch wire
during space closure
- The force is placed on the crown,
and because there is
- no other force to counter react,
37. - This happens because the force is applied on the crown
away from the center of resistance
When an Elastomeric Power Chain is placed from a molar to a canine, with a round arch,
Inclination
(moment)
of the crowns
toward the space
the roots
will become
completely
divergent
the outcome is :
38. b. Controlled inclination:
it is obtained with the application of:
to move the crown
A force
in order to:
control or maintain
the position of the root apex
the placement of A moment
39. - It counteracts (torque) part of the moment caused by the dental retraction
b. Controlled inclination:
- to retract the anterior sector
without
moving the location of the tooth apex
An Example of this inclination
when we want
Rectangular Arch Wires
obtained with
When we softly insert the wire in the slot of the brace
40. 2. Translation:
the anatomical characteristics that surround teeth
- Is one of the most difficult movements in orthodontics
The application of a force through the center of
resistance very difficult
Make
This is caused by:
41. - in-mass or bodily movement
the line of action of a force passes through
the center of resistance of the tooth
It is also known as
Happens when
- This is only possible when:
• crown
• apex
- horintzoally displaced
42. - We obtain this type of
movement with the use of
power arms:
allow the line of action of the
force to pass directly through
the center of resistance
43. - Root displacement is commonly used:
- to torque incisors
- to upright canine roots after space closure
- upright posterior teeth that are mesially
inclined, etc.
3. Root displacement:
- In this movement:
- Moment and a force are applied to
displace only the root,
- meanwhile the crown is NOT displaced
44. produce a pure rotation around the longitudinal axis of
the tooth (seen from the occlusal view)
4. Rotation:
To make this movement: a couple or coplanar forces are required
45. In this case the tooth maintains its position because
- both forces annul each other since both lines of force act at a same distance
perpendicular to the center of resistance,
- leaving only the pure Moment (pure rotation)
What is a couple?
Two parallel forces of the same magnitude but in opposite directions
46. Select, apply and control in an efficient manner the force systems that
will be utilized.
Clearly understanding
the basic concepts of orthodontic biomechanics
the physiology of dental movement
Analyze the different actions and reactions
that can happen during the different stages
of orthodontic treatment
47. ACTION AND REACTION
The third law of Newton applies
in almost all orthodontic movements
- Sometimes the reaction to a movement
results in an unwanted movement
48. 1. Align intruded or extruded teeth,
- where 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.
Example of the third law of newton
49. 2. 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
50. 3. The action of a bend
put it in a passive manner in the slots of two braces
activate the wire, placing it in the slots
to determine the direction of a movement
predict the direction of the movement to take place
51. put it in a passive manner in the slots of two
activate the wire, placing it in the slots
to determine the direction of a movement
predict the direction of the movement to take place
52. Where to place the bend
Far from the center of the arch wire Center of the arch wire
two segments: a short one and a long one
Equal forces in different directions
The greater moment :
the side that receives the shorter segment of the bend
the forces cancel one another
Equal moments oppose each other
Different moments take place
with
54. Deep bite correction with a tip back
Spee curve leveling with reverse curves
Correction of a bilateral posterior open bite with reverse curves
Correction of a deep bite with a bite plane and bilateral box elastics
Correction of an anterior open bite with the use of a bite block (Posterior bite block)
Correction of an anterior cross bite with the use of a forward arch wire
Diastema closure with closing loops
Root uprighting
55. Deep bite
one of the most common malocclusion
seen in children as well as adults
56. one of the most deleterious malocclusion
of the future health of:
- the masticatory apparatus and
- the dental units
when considered
مؤذ
from the viewpoint
It is said to be
57. 1. Intrusion of upper and or lower incisors
2. Extrusion of upper and or lower posterior teeth
3. A combination of anterior intrusion and posterior extrusion
4. Proclination of incisors
5. Adult surgery
Treatment modalities include:
58. Technique
Removable appliance The anterior bite plane
Headgear
Functional appliance
Fixed appliance • Fixed orthodontic appliances
Orthognathic surgery Mandibular advancement
Lower labial segment setdown
Restorative treatment Restoration of the posterior
occlusal vertical dimension
Occlusal splints
Dahl appliance
Methods of reducing a deep overbite
59. - the large segment directs itself to the
apical portion of the anterior zone
Deep bite correction
- If we utilize the tip back bend for the correction of a deep bite
with a tip back
when the short segment of the bend is
inserted in the molar tube,
- it can clearly be seen that:
(before being inserted in the slots of the braces of the incisors)
Intrusion Arch
60. Intrusive Force : Extrusive Force:
anterior zone
posterior zone
This way
61. - with the placement of bends is that:
Another consideration that we have to mind
Short segment
Anchorage side
represent
Long segment
no anchorage
- Moment at the molar level is greater than the one that is being
produced at the incisor level
This is due to the fact that
making the molar much more resistant to movement
62. - When the arch wire is activated by placing it in the slots of the incisor braces
at molar level at the incisor level
Two moments are going to be produced
Provoking a differential torque on both teeth
A mesial root
movement
a distal crown
movement
the moment is going to be
lower, taking the incisor to a
more buccal position
Passes buccal to
the center of resistance
since
intrusive force
63. 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.
1. Apically directed Tip back
Action taken Produced reaction
64. Class I molar relationship Correct crown angulation
Correct crown inclination No rotation
No spaces Flat to slight curve of spee
Andrews 6 keys of Normal Occlusion(1972)
66. - When we use Reverse Curves to level a deep curve of Spee
Intrusive Forces
exercised in the
posterior sectors
we find
- with
balanced with Extrusive Forces premolar region
anterior sectors
Intrusive Forces
67. a positive torque
- a distal inclination of the crowns
- a mesial movement of their roots
Another effect is
intrusive forces
at the molar level at the incisor level
- buccal movement
(positive torque)
provoke
68. 1. LeveIingof 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.
1. Use of an inverse curve
in the inferior arch
Action taken Produced reaction
69. Correction of a bilateral posterior open bite
with reverse curves
70. - The reactions that are produced
at molar, premolar and incisor
levels are the same in the upper
and lower dental arches
far from solving the problem we can COMPLICATE it even more
- Same one that we use for the
leveling of a deep Spee curve
We simply have to know how to place the reverse
curves in order to have the desired effect
The action principle of the curves
On the contrary,
if we do not place the curves correctly,
71. 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.
1. Use of curves on both dental arches
Action taken Produced reaction
72. Correction of a deep bite
with a bite plane and bilateral box elastics
a very simple, practical and stable
solution for this malocclusion
- The use of an Anterior Bite Plane
73. - increase in the vertical dimension in the lower third of the face
- Put a top on the anterior sector
producing a posterior disclusion
the use of bilateral box elastics
This way,
- With the bite plane we seek to:
in a passive way
stimulated or it can be accelerated with
Extrusion of molars and premolars
There will also be an
74. 1. Intrusion of inferior incisors
2. Extrusion of canines, premolars and molars
due to the disclusion provoked by the bite plane
3. Improvement of the interincisal relation
1. Use of an anterior bite plane
2. Use of intermaxillary box elastics
Action taken Produced reaction
75. Correction of an anterior open bite
with the use of a bite block (Posterior bite block)
Intrusion of the anterior sector
- Anterior open bite is caused in the majority of cases by:
Extrusion of the posterior sector
76. the pressure of occlusion over the bite block
The purpose of the use of the bite block is:
Intrusion of the posterior segment
resulting in
Auto rotation of the mandible
producing the satisfactory closure of the open bite
lack of dental contact in this zone
Posterior intrusion
produced by
Anterior extrusion
77. we can help ourselves with the use of intermaxillary elastics to facilitate bite closure
For closure of the anterior bite with a bite block
78.
79. 1. Molar and premolar intrusion
2. Extrusion of the anterosuperior sector
3. Shortening of the inferior facial height
4. Overbite correction
S. Mandible auto rotation
1. Bite block placement for open bite closure
Action taken Produced reaction
81. Correction of an anterior cross bite
Dentoalveolar Component
not a Skeletal one
with the use of a forward arch wire
this should only have:
82. leaving 2 mm or 3 mm of
SEPARATION
between the arch wire and
the slot of the anterior braces
- Anterior proclination
- Provoke a mild molar distalization
The forward arch is made by
doing two small stops at the entrance of the molar tubes
This arch wire
going to produce
83. 1. Proclination of the upper incisors
2. Upper molar distalization
3. Positive torque in the upper incisors
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
1. Placement of a forward archAction taken
Produced reaction
84.
85. 1. The forces cancel each other.
2. Root up righting by the action of the
Moments
1. "V" second order bends to
upright divergent roots
Action taken
Produced reaction
Root uprighting
must be made on (a stainless steel
arch, round or rectangular)
86. making these move bodily
without any Moment that may make them rotate
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
The orthodontist must determine the cause of it
before designing an appliance to correct it
Usually closing loops are:
going to exert their forces in a perpendicular mode to the center of resistance of the tooth
87. l. Closure of the diastema with a bodily
movement
Produced reaction
l. Placement of a vertical closure loop
Produced result
