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Anchorage

Anchorage

Anchorage in orthodontics is defined as
resistance to unwanted tooth movement.

The nature and degree of resistance to
displacement offered by an anatomic unit
when used for the purpose of affecting tooth
movement.


The dentist or orthodontist always constructs an
appliance to produce certain desired tooth movements.

For every (desired) action there is an equal and
opposite reaction. Inevitably, reaction forces can
move other teeth as well if the appliance contacts
them.

Anchorage, then, is the resistance to reaction forces
that is provided (usually) by other teeth , or (sometimes)
by the palate , head or neck (via extraoral force), or
implants in bone .

Classification of anchorageClassification of anchorage

1- Depending on manner of force application:
a. Simple
b. Stationary
c. Reciprocal


Simple anchorage : anchor tooth will
be tipped if it can not overcome the
resisting force.

Stationary anchorage : anchor tooth
would be moved bodily if it can not
overcome the resisting force.

Reciprocal anchorage : It involves
pitting of two teeth or two groups of
teeth of equal anchorage value
against each other to produce
reciprocal tooth movement .• Eg:
closing of diastemas: two central
incisors are pitted against each other.

2- Depending on jaws involved:

a. Intermaxillary anchorage
b. Intramaxillary anchorage


Intra-maxillary Anchorage : is obtained from
teeth in one jaw to move other teeth in same
jaw.

Inter-maxillary Anchorage : is obtained from
teeth in one jaw to move other teeth in opposite
jaw. E.g. class II elastic traction between upper
anteriors to lower molar as well as classIII
elastic traction between lower anteriors and
upper molar

3- Depending on site of anchorage:

a. Intra oral
b. Extra oral
c. Muscular

1. Intra oral : Anchorage established within the

mouth. (teeth, palate, alveolar bone and basal bone)
Factors affecting anchorage:
a. Number and Size of roots (multirooted > single
rooted)
b. Shape (triangular shaped root > conical or ovoid
root larger surface area > smaller surface area)
c. Length of each root (longer rooted > shorter
rooted)

d. Inclination of tooth: A greater resistance to

displacement is offered when the force exerted
to move teeth is opposite to that of their axial
inclination.
e. Ankylosed teeth: such teeth are directly fixed
to the alveolar bone and lack periodontal
ligaments. Orthodontic tooth movement of such
teeth is not possible and therefore they are
excellent anchorage.

2. Extra oral : Anchorage

obtained outside the oral cavity.
1)CRANIUM(OCCIPITAL OR
PARIETAL ANCHORAGE:-
ANCHORAGE OBTAINED
FROM OCCPITAL OR
PARIETAL BONE .EG:-
HEAD GEAR TO RESTRICT
MAXILLARY GROWTH
2)CERVICAL:-ANCHORAGE
FROM CERVICAL OR NECK
REGION .EG:-CERVICAL
HEAD GEAR .

3)FACIAL BONES:- FACE

MASK USED TO
PROTRACT MAXILLA
TAKE ANCHORAGE
FROM MANDIBULAR
SYMPHYSIS .
REVERSE HEAD
GEARS TAKE
ANCHORAGE FROM
FOR HEAD AND CHIN

Extra oral forces to augment anchorage

Advantage
 The anchorage unit is far away from the actual site
where the movement is taking place, so less
chances of any change in the anchorage units
Disadvantage

 Lack of patient’s co- operation

 Anchorage assembly is bulky & externally visible

 Decrease in the number of hours for which the
anchorage assembly is worn, so affects quality of
result achieved


3. Muscular Anchorage :
Anchorage derived from
action of muscles. Peri oral
musculature is not so
strong but also resilient.
The forces generated by
the musculature sometimes
used to bring about tooth
movement. eg.Lip bumper
appliance (to distalize
mandibular 1st molars)

4- Depending on no. of anchor units:

a- Single / primary
b- Compound
c- Multiple/ reinforced


Single anchorage : a tooth of
greater support in the alveolar
process is used to move a
tooth of lesser support. Eg.
Molar being used to retract a
pre molar

Compound anchorage :
number of teeth of greater
support in the alveolar
process used to move teeth of
lesser support. Eg. Retracting
incisors using loop mechanics

Reinforced Anchorage :• It involves reinforcing the

anchorage or resistance area either by adding more
resistance units or by the use of various adjuncts.
• A simple way of reinforcing anchorage is to band
the second molars.
• Various other ways include, the use of T.P.A.,
Nance holding arch, lower lingual arch.
• Tissue anchorage such as obtained by lip bumper
can be efficiently used to distalize molars.

Prepared anchorage pre sets the teeth into disto-
axial inclination, greatly increasing the irresistance
to displacement.

Miniscrew.


Cortical anchorage :The cortical bone is
more resistant to resorption than the medullary
bone. The cortical anchorage concept makes
use of this.


Rickett’s advocated torquing the roots of
buccal teeth outwards against the cortical plate
as a way to inhibit their mesial movement.
Torquing movements are limited by facial and
lingual cortical plates. If a root is persistently
forced against the cortical plate, tooth
movement is greatly slowed, root resorption is
likely and eventual penetration of cortical
bone may sometimes occur.

Anchorage planning


Its essential to assess the anchorage demand of
an individaual case so the appropraite treatment
modalities can be excuted. The anchorage
requirements depend on number of factors:
1- Number of teeth to be moved: the greater
number of teeth to be moved, the greater is the
demand on anchorage.

2- Type of teeth being move: the movement of

selender anterior teeth offers less strain on
anchorage than multirooted teeth
3- Type of tooth movement:
Bodily movement cause more strain on
anchorage
Tipping movement cause less strain on
anchorage

4- Duration of tooth movement: prolonged

duration of treatment places undue strain on
anchorage

Anchorage loss


Anchorage loss: is the unwanted movements of
anchor teeth.
According to anchorage loss that is permissible,
the anchorage demand of an extraction case can
be of three types:

1- maximum anchoage

In cases where the anchorage demand is very high , not
more than ¼ th of the extraction space should be lost
by forward movement of the anchor teeth. The
anchorage of these patients should be augmented to
avoid unwanted movement of the anchor teeth

2- moderate anchorage

In cases, the anchor teeth can be permitted to move
forward into ¼th to ½ of the extraction space .
3- minimum anchorage
In these cases, the anchorage demand is very low . More
than half the extraction space can be lost by the
anchor teeth moving mesially.


رفعت المحاضرة من قبل: Mustafa Shaheen
المشاهدات: لقد قام 5 أعضاء و 53 زائراً بقراءة هذه المحاضرة






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