The document discusses tissue changes that occur during orthodontic tooth movement. It describes how orthodontic treatment works by applying prolonged pressure to teeth to induce bone remodeling around the tooth. When orthodontic forces are applied, they are transmitted through the tooth to the periodontal ligament and alveolar bone, causing areas of pressure and tension. For tooth movement to occur, bone must be resorbed on the pressure side and deposited on the tension side. The rate and type of tooth movement depends on factors like force magnitude, direction, and duration. Light prolonged forces cause minimal discomfort but slower movement, while heavier forces induce hyalinization and delay movement.

1. TissueChangesin Orthodontic Tooth
Movement

2. ILOS
1-understand the physiology of the periodontal ligament.
2- differentiate between normal physiologic tooth movement
and orthodontic tooth movement.
3-define the basic concept of orthodontic tooth movement.
4-undrestand the basic biomechanics in tooth movement
5-compare the effects of different orthodontic force
magnitude on tissues
6-undrestand phases of tooth movements.
7-know the different theories of tooth movement
8-compare between the different manners of force
applications
9-know the adverse effects of orthodontic force

3. Tooth movement can be:
• „Physiologic
• „Pathologic
• „Orthodontic.

4. PHYSIOLOGIC TOOTH MOVEMENT
Physiologic tooth movement can be described in
three phases:
• 1. Pre-eruptive tooth movement
• 2. Eruptive tooth movement
• 3. Posteruptive tooth movement.

5. Pre-eruptive Tooth Movement
Both primary and
permanent tooth germs
move within the jaws
after their
differentiation and
these movements are
facilitated by the jaw
growth. These
movements help the
teeth to occupy their
preparatory positions
within the jaws prior to
their eruption.

6. Eruptive Tooth Movement
Eruption is the movement
of the teeth from their
developmental position
within the jaws to their
functional position in
occlusion. Eruptive
movement generally
begins when about 2/3rd
portion of the root is
formed

7. Posteruptive Tooth Movement
Even after the eruption is complete, the teeth
move in order to maintain their position in
occlusion until the jaw growth is completed.
Teeth also exhibit movements in occlusal and
mesial direction throughout a person’s life to
compensate for occlusal and proximal wear
and move in the space of extracted teeth.

8. Posteruptive Tooth Movement

9. Response to Normal Function
The PDL is beautifully adapted to resist forces of
short duration
Prolonged force, even of low magnitude, produces a
different physiologic response.
Remodeling of the adjacent bone

10. Orthodontic Tooth movement
Orthodontic treatment
is based on the
principle that if
prolonged pressure is
applied to a tooth,
tooth movement will
occur as the bone
around the tooth
remodels

11. What is needed?
• Tooth
• Healthy periodontium
• Applied force
Tooth movement is dependent upon physiology of the
Periodontal ligament and Bone – i.e. Turnover.
Pressure on bone ------- resotption
Tension on bone ------- deposition

13. When force is applied to the crown of a tooth, it is
transmitted through the root of the tooth to the
periodontal ligament and alveolar bone. According to
the direction of the force, there will be areas of
pressure and areas of tension on these supporting
structures.
For a tooth to move, there must be resorption of
alveolar bone in response to this stress, and at the
same time, there must also be the deposition of bone
in the areas of tension so as to maintain the integrity
of tooth attachment.
As a result of this bone remodeling, the socket of the
tooth moves concomitant with movement of the tooth
through the alveolar bone.

14. How does the tooth move?
• Bone resorption in
direction of movement
• Bone deposition in the
opposite direction

16. FORCE
?
movement

17. Orthodontic appliances

19. The forces are delivered via orthodontic appliances
which are Either fixed or removable.
PDL undergoes biological response upon the
mechanical application of a force

20. Force :
is the action applied to a
body and change this body
from a state of rest or
uniform motion to
movement

21. Force applied on non rigid body results
in deformation

22.  Force + rigid
body 
displacement
Force applied on a rigid body results
on displacement

23. The center of gravity (the center of mass)
Every object or free body has one point on
which it can (at least in theory) be perfectly
balanced.
all of the weight is concentrated at this single
point.

24. Center of Resistance
In a restrained body, such as a tooth, a
point analogous to the center of gravity is
used; this is called the center of resistance

25. Center of Resistance
Center of resistance for
single-rooted teeth
with normal alveolar
bone levels is about
one-fourth to one-
third the distance from
the cementoenamel
junction (CEJ) to the
root apex.

26. • For
multirooted
teeth, the center
of resistance is
probably at the
furcation.

27. the center of
resistance
changes with
root resorption
or loss of
alveolar
support
because of
periodontal
disease

31. Moments

32. Moments
A force applied
away from CR
(at the
bracket ) will
result in both
a force and a
moment at
the center of
resistance.

33. • The moment of the force
is the tendency for a force
to produce rotation.
• the magnitude of a
moment (M) is equal to
the magnitude of the
applied force (F) times the
distance (d) measured
perpendicularly from the
line of action of the force
to the center of
resistance. M = Fd.

37. FORCE
Manner
Direction
Magnitude Duration

40. Force Magnitude
1. Optimal orthodontic force:
2. Light prolonged forces
3. Higher prolonged forces

41. Optimal orthodontic force
Optimal orthodontic force moves teeth efficiently
into their desired position, without causing
discomfort or tissue damage to the patient.
Clinically
• „
It produces rapid tooth movement.
• „
Causes minimal patient discomfort.
• Lag phase of tooth movement is shorter.
• The tooth being moved does not become
loosened in its socket

42. Force Magnitude
1. Optimal orthodontic force:

43. Light orthodontic force
frontal bone resorption

44. Light orthodontic force

45. Changes on Pressure Side
Periodontal ligament gets slightly
compressed on the pressure
side. As the mild forces are not
sufficient to occlude the blood
vessels of the periodontal
ligament, vessels may dilate
and there will be recruitment
of osteoclasts to that area of
periodontal ligament. The
osteoclasts will cause
resorption of the alveolar bone
immediately adjacent to the
periodontal ligament. This kind
of resorption where the
periosteal bone from the inner
wall of the socket is resorbed is
called as frontal resorption

46. Light orthodontic force
frontal bone resorption

47. Heavy Orthodontic Force

48. • Compression of periodontal ligament and
occlusion of blood vessels in the areas of
pressure and ischemia.
• Formation of wide zones of hyalinization and
extended lag period.
• „No frontal resorption and no immediate tooth
movement.
• „Increased endosteal vascularity and endosteal
resorption of the socket wall under the
hyalinized area—undermining resorption.
• „
Eventually tooth moves as a result of this
undermining resorption.

49. Undermining Bone Resorption

50. Frontal and Undermining Bone
Resorption

51. Heavier force
• When hyalinization and undermining
resorption occur there is a delay in tooth
movement WHY?
- Delay in cell stimulation and
differentiation as cells are derived from
adjacent area
-The considerable amount of bone that
needs to be removed from the underside
for any movement to take place.