Introduction to Orthodontics Fifth Year

1. 16th Lecture
Biology of Tooth
Movement-II
April 28, 2012
Dr. Ahmed Basyouni
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2. •
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April 28, 2012
Clinical consideration of the periodontium:
Periodontal Ligament:
Mechanisms of Orthodontic tooth
movement:
Tissue Reaction To Tooth Movement:
Physiologic Tooth Movement:
a) Resorptive bone wall
b) Depository bone wall
Dr. Ahmed Basyouni
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3. Orthodontic Tooth Movement
(OTM):
a) Dentoalveolar tissue reaction:
i. Pressure side:
ii. Tension side:
b) Hyalinization
April 28, 2012
Dr. Ahmed Basyouni
3

4. Factors Influencing
Orthodontic Tooth
Movement
April 28, 2012
Dr. Ahmed Basyouni
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5. Factors Influencing Orthodontic Tooth Movement
Tissue changes associated with OTM are affected by:
A) Characteristics of supporting bone:
i. Cancellous
ii. Compact
iii. Recent extraction space
B) Physiologic activity:
Hormonal balance, age, health & general
condition of the patient.
C) Force application:
Type, Amount, direction.
April 28, 2012
Dr. Ahmed Basyouni
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6. Factors Influencing Orthodontic Tooth Movement
A) Character of bone:
i. Cancellous
OTM within cancellous bone offer a large surface
area for cellular activity, allowing faster tooth
movement.
ii. Compact
In cortical bone surface area for cellular reactions
is vastly reduced, so tooth movement is more
difficult and much slower, with high risk of creating
over compression and hyalinization.
Practically, tooth should be kept in center of the
alveolar process, rather than being allowed to move
against compact cortical bone.
April 28, 2012
Dr. Ahmed Basyouni
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7. Factors Influencing Orthodontic Tooth Movement
A) Character of bone:
iii. Recent extraction space contain tissue
undergoing reconstruction which is rich in
cells and vascular supply.
Such area is ideally suitable for tooth
movement, so treatment should start as soon as
possible following an extraction.
April 28, 2012
Dr. Ahmed Basyouni
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8. Factors Influencing Orthodontic Tooth Movement
B) Physiologic activity:
Tissue reaction and turnover varies from one
patient to another and is dependent on numbers
of variables such as:
1. Hormonal balance
2. Patient age
3. Health & general condition of the patient
April 28, 2012
Dr. Ahmed Basyouni
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9. Factors Influencing Orthodontic Tooth Movement
B) Physiologic activity:
4. Histologic picture of PDL of a growing
young patient
5. Histologic picture of PDL of adult patient
6. Patient receives medication (e.g. steroids, or
non-steroids) as tissue changes & cellular
reactions will be influenced.
April 28, 2012
Dr. Ahmed Basyouni
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10. Factors Influencing Orthodontic Tooth Movement
C) Force application:
Force type, magnitude, direction and duration are
affecting OTM.
i. Types of applied force:
Intermittent: It is associated with removable
appliances.
Dissipating: It is a continuous force but demonstrates
a decreasing amount of force within a short period of
time (e.g. elastic bands).
Continuous: It is achieved by fixed orthodontic
appliance with application of coil springs.
April 28, 2012
Dr. Ahmed Basyouni
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11. Factors Influencing Orthodontic Tooth Movement
C) Force application:
ii. Amount of applied force:
Ideal force should not exceed capillary blood
pressure and result in optimum rate of tooth
movement of about 1mm/month.
“Optimum force is high enough to stimulate
cellular activity without completely occluding
blood vessels in the PDL” (Proffit et al. 2000).
April 28, 2012
Dr. Ahmed Basyouni
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12. Factors Influencing Orthodontic Tooth Movement
C) Force application:
April 28, 2012
Dr. Ahmed Basyouni
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13. Factors Influencing Orthodontic Tooth Movement
C) Force application:
iii. Direction of force:
Force direction results in different types of
tooth movements:
1. Tipping movement: This is the simplest and
most readily carried out. Center of rotation is
assumed to lie near center of the root, but
actual location depends on dimensions of
roots, condition of supporting tissues and point
of force application.
April 28, 2012
Dr. Ahmed Basyouni
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14. Factors Influencing Orthodontic Tooth Movement
C) Force application:
iii. Direction of force:
2. Rotational movement: Rotation requires
application of force couple. Center of rotation
lies along long axis of the tooth. There is
greater tendency for relapse so, overcorrection
is a must.
April 28, 2012
Dr. Ahmed Basyouni
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15. Factors Influencing Orthodontic Tooth Movement
C) Force application:
iii. Direction of force:
3. Bodily movement: means complete
transmission of a tooth to a new position, all
parts of the tooth moving an equal distance.
Center of rotation is at infinity. This type
requires a greater force than simple tipping
movement. Only, it can be carried out with
fixed orthodontic appliances.
April 28, 2012
Dr. Ahmed Basyouni
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16. Factors Influencing Orthodontic Tooth Movement
C) Force application:
iii. Direction of force
4. Torque movement: It is commonly
applied to root torque when movement
of the root is desired with little
movement of the crown. In this sense it
is opposite of the tipping. It is usually
achieved by applying couple to the
crown of the tooth, same time
mechanically restricting crown
movement in opposite direction.
April 28, 2012
Dr. Ahmed Basyouni
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17. Factors Influencing Orthodontic Tooth Movement
C) Force application:
iii. Direction of force
5. Vertical movement: It is essentially
bodily movement but considered
separate because they are easier to
produce, they involve:
a) Extrusion: of the tooth from its
socket which can be achieved without
much resorption of bone.
b) Intrusion: of the tooth involves
resorption of bone, particularly
around apex of the tooth.
April 28, 2012
Dr. Ahmed Basyouni
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18. April 28, 2012
Dr. Ahmed Basyouni
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19. Factors Influencing Orthodontic Tooth Movement
C) Force application:
iii. Direction of force
•
Center of Resistance --- A point on the tooth around which
the tooth shall move. For most teeth, COR is ½ way
between the apex and the crest of the alveolar bone.
April 28, 2012
Dr. Ahmed Basyouni
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20. Limitation to Tooth Movements
A)
B)
C)
D)
E)
Size and form of basal bone of the jaw.
Adverse forces on the tooth.
Intensity of applied force.
Age.
Individual variations
April 28, 2012
Dr. Ahmed Basyouni
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21. Limitation to Tooth Movements
A) Size and form of basal bone of the jaw:
Tooth apex must remain on the basal bone.
Therefore, severe discrepancies in skeletal form, size or
relationship can not be completely overcomed by tooth
movement alone.
The cooperation between Orthodontist and Maxillofacial
surgeon is helpful in treatment of skeletal defects.
April 28, 2012
Dr. Ahmed Basyouni
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22. Limitation to Tooth Movements
B) Adverse forces on the tooth:
Adverse forces on the tooth are usually brought about by oral
musculature.
It is possible to overcome the forces of oral muscles during
orthodontic treatment, but it would be difficult to retain teeth
in their final position thereafter.
Therefore, if tooth position at end of treatment is to be stable,
the muscular forces acting on the teeth must hold teeth in
balance in their final position.
April 28, 2012
Dr. Ahmed Basyouni
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23. Limitation to Tooth Movements
C) Intensity of applied force:
Both light and heavy forces will result in orthodontic tooth
movement.
However, if light forces are used, minimizing hyalinization of
the periodontal ligament, rate of tooth movement will be
greater.
April 28, 2012
Dr. Ahmed Basyouni
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24. Limitation to Tooth Movements
D) Age:
In adults, periodontal ligament is much less cellular than in
children.
Also, alveolar bone in children is less dense than in older
patient.
In general, tooth movement in adults will be slower.
April 28, 2012
Dr. Ahmed Basyouni
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25. Limitation to Tooth Movements
E) Individual variations:
Depend on density of alveolar bone.
In some individuals, alveolar bone is loose and cancellous with
large marrow spaces.
Whereas, in others it is dense lamellated bone with few
marrow spaces. Tooth movement will be much slower in the
latter.
April 28, 2012
Dr. Ahmed Basyouni
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26. Potential Complications of Orthodontic Tooth
movement:
• The pulp
• Root resorption
• Alveolar bone height
April 28, 2012
Dr. Ahmed Basyouni
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27. Potential Complications of Orthodontic Tooth movement:
Orthodontic effects on the pulp
•
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Rare if light, continuous forces are applied.
Occasional loss of tooth vitality.
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History of previous trauma
Excessive orthodontic forces
Moving roots against cortical bone
Endodontically treated teeth can be moved like
natural teeth, with proper management.
April 28, 2012
Dr. Ahmed Basyouni
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28. Potential Complications of Orthodontic Tooth movement:
Root Resorption Concurrent with OTM
Roots of permanent teeth are very resistant
to resorption because it is protected by a
barrier of unmineralized hard tissue
(cementoid) which is resorbed only with great
difficulty.
April 28, 2012
Dr. Ahmed Basyouni
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29. Potential Complications of Orthodontic Tooth movement:
Explanation:
Teeth are permanent
depositories of mineral salts
with continuous apposition,
While, bony system is a
mineral reservoir for whole
organism, with physiologic
resorption and apposition
going on all time.
April 28, 2012
Dr. Ahmed Basyouni
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30. Potential Complications of Orthodontic Tooth movement:
Root Resorption Concurrent with OTM
Development of root resorption seems to be
interrelationship between:
1. Temporary damage of the root surface
barrier (cementoid).
2. General resistance against resorption and
remodeling of the alveolar bone.
April 28, 2012
Dr. Ahmed Basyouni
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31. Potential Complications of Orthodontic Tooth movement:
Root Resorption Concurrent with OTM
Root resorption ceases if orthodontic forces
is interrupted or stopped. Repair will take
place cause new deposits of pre-cementum on
the root surface, thus establishing a new
barrier.
Rest periods without force application should
be included in treatment of patient with high
tendency for root resorption
April 28, 2012
Dr. Ahmed Basyouni
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32. Orthodontic tooth movement remains one of the
most successful procedures with predictable
outcome in medicine and dentistry.
April 28, 2012
Dr. Ahmed Basyouni
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33. Summary
• Factors Influencing Orthodontic Tooth Movement:
A) Characteristics of supporting bone:
B) Physiologic activity:
C) Force application:
i. Types of applied force:
ii. Amount of applied force:
iii. Direction of force:
1. Tipping movement:
2. Rotational movement:
3. Bodily movement:
4. Torque movement:
5. Vertical movement:
April 28, 2012
Dr. Ahmed Basyouni
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34. Summary
Limitation to Tooth Movements
A) Size and form of basal bone of the jaw.
B) Adverse forces on the tooth.
C) Intensity of applied force.
D) Age.
E) Individual variations
April 28, 2012
Dr. Ahmed Basyouni
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35. Summary
Potential Complications of Orthodontic Tooth movement:
•
•
•
The pulp
Root resorption
Alveolar bone height
April 28, 2012
Dr. Ahmed Basyouni
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36. Buccal Canine Retractor
April 28, 2012
Dr. Ahmed Basyouni
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37. Buccal Canine Retractor
• Used for buccally erupted canine.
• To Retract the canine palatally and distally.
April 28, 2012
Dr. Ahmed Basyouni
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38. Coil high enough, not interfering with muscle
attachment, just distal to Canine long axis
April 28, 2012
Dr. Ahmed Basyouni
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39. April 28, 2012
Dr. Ahmed Basyouni
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