ANCHORAGE IN ORTHODONTICS Copyright by Ortho Department, Yangon

1. ANCHORAGE IN ORTHODONTICS
K.Thein

2. Newton’s third law states that –
“ Every action has an equal and opposite reaction ”
(Third law of dynamics. I.Newton, 1642-1727)

3. Anchorage may be defined as –
“ the resistance to the reaction forces ”
Anchorage may be considered similar to ‘a tug of war.’
Action force Reaction force

4. Action force Reaction force
The reaction force is
acted upon the posterior teeth
and moving it forward.
When the action force
is applied to retract
the anterior teeth

5. When the action
force is applied to
move the tooth 11
measially
The reaction force
will also move the
tooth 21 mesially.

6. The reaction force will also
move the tooth 26 buccally.
Action forceReaction force
When the action force is
applied to move the tooth 16
buccally

7. When you move the tooth 25 down
The reaction force will move 24, 26 up

8. There is always an associated reaction forces or reciprocal
effects which may be desirable or undesirable
desirable undesirable

9. The undesirable reciprocal effects or unwanted reaction
forces are detriment to the outcome of treatment.
The reciprocal effects or the reaction force throughout
the dental arches must be carefully analyzed, evaluated
and controlled to maximize the desired tooth movement
and minimize the undesirable side effects.
Anchorage need to be carefully considered when planning
orthodontic tooth movement.
The resistance to undesirable or unwanted reaction force
is called anchorage.

10. In orthodontics it is not possible to consider only the desired
tooth movements“.
There is no such things as –
“An isolated orthodontic act.”
“Every intentional movement is accompanied by
several usually unwanted side-effects.”

11. Therefore, to achieve the successful outcome of treatment –
“Much more effort is required
to prevent or control unwanted movements
than to apply the primary forces.”

12. Anchorage may be derived from the four sources:
Teeth
Oral mucosa and underlying bone
Head and neck (extra oral devices)
Implants

13. (1)Teeth
The anchorage supplied by teeth can be divided into:
Intramaxillary anchorage:
The resistance supplied by the teeth to
prevent unwanted reaction effects comes from within
the same arch as the teeth that are being moved.
Intermaxillary anchorage:
The resistance come from the opposing arch.

14. Intramaxillary anchorage
• The resistance supplied by the teeth come from within the
same arch as the teeth that are being moved.
• Every orthodontic appliances consists of two elements:
- An active element
- A resistance element.
• An active element consists of units (action units) concerning
with desired tooth movements, and

15. • the resistance element consists of units (anchorage units)
providing resistance or anchorage that makes tooth
movement possible.
• The anchorage value of a tooth or its resistance to movement
can be thought of as a function of its root surface area which
is the same as its PDL area.

16. • The more teeth that are incorporated into the anchorage unit ,
greater the anchorage resistance………. and
the less likely the unwanted tooth movement will occur.

17. The 100 gm distalizing force is
optimal for canines to move
back…
However, suboptimal for
mesial movement of anchor
teeth.
Increasing the distalizing
force on canines …
also increase the reciprocal
force on the anchorage unit
……with greater risk of
anchorage loss.

18. Tooth movemen
The amount of tipping force applied to the
tooth.

19. Retention crib
Retention crib
Base plate
Finger spring
• If upper canines are to be retracted with a removable appliance
the base plate and retention cribs should contact
as many teeth as possible.

20. • If fixed appliance are to be used,
the more teeth that are bracketed or banded,
greater the will be the anchorage resistance.

21. Intermaxillary anchorage
Anchorage provided by teeth in the opposite arch.
• Good interdigitation of the buccal teeth can help prevent
mesial movement of the buccal segment.

22. Class II elastics run from the
lower molars to the upper
incisor region
Class III elastics run from the
upper molars to the lower
incisor region
Class II elastics Class III elastics
• By means of elastics running from one arch from the other.

23. Functional appliances are the another source of
intermaxillary anchorage

24. (2) Oral mucosa and underlying
In removable appliance…
Close contact between an orthodontic appliance and
the vault of the palate provides resistance to the mesial
movement of posterior teeth.
High palatal vault Low palatal vault

25. In fixed appliance….
The mucosa and underlying bone can be used
to provide anchorage by means of Nance palatal arch.
Band on first molar
Palatal arch wire
Acrylic button

26. Figure 5.20 Palatal arch with
Nance button.Figure 5.19 Transpalatal arch.

27. Figure 5.22
Midline palatal implant providing anchorage
via a palatal arch.

28. Implants –
• absolute anchorage can be provided by implants, which can be
placed in any cancellous bone, but are routinely used in the
palate.
• Implants require a period to osseointegrate and can be attached
to the dentition by palatal arches to provide anchorage support
(Fig. 5.22);

29. (3) Head and neck (Extra oral devices)
• Anchorage from the head and neck can be applied via
a number of devices.
• It can be used in conjunction with either removable or
fixed appliances.
Headgear
Cervical pull
Occipital pull
Variable pull (Occlusal pull)
Reverse or protraction headgear

30. Headgear :
• Consist of face bow and head cap or neck strap.
• The force from the headgear is usually applied
to the teeth via a face bow.

31. Cervical pull Occipital pull Variable pull

32. Reverse or protraction head gear

35. (4) Implants
Provide a secure source of anchorage for orthodontic
tooth movement.

37. Anchorage
-is the resistance to the reactive forces generated by the active
components of the appliance.
Anchorage may be preserved by :
1. Placement of clasps or bows on teeth which are not being
moved.
2. Contact the baseplate with other teeth not being moved.
3. Contact of the baseplate with the vertical part of the palate
in the area of the rugae (for distal movement of teeth)
4. Use of light forces to move teeth.
5. Movement of a single tooth per quadrant
6. Intermaxillary elastics.
7. Extra-oral traction – headgear

38. The resistance to tooth movement is related to
1.The surface area of the roots.
2.The type of tooth movement permitted teeth can be tipped more
readily than they can be moved bodily.
By designing the appliance so that the anterior teeth cannot tip,
the anchorage is increased.
However , although this is a common practice with fixed
appliances, it is not easy with removable appliances
3- Intercuspation of the teeth may contribute to the anchorage.