Anchorage Resistance Unwanted Tooth Movement
The term anchorage, in its orthodontic application, is
defined in an unusual way: the definition as "resistance to
unwanted tooth movement" includes a statement of what the
dentist desire.
“For every (desired) action there is an equal and
opposite reaction.
Relationship Tooth movement t o Force
An obvious strategy or anchorage control would be to concentrate
the force needed to produce tooth movement where
it was desired, and then to dissipate the reaction force over
as many other teeth as possible ,keeping he pressure in the
PDL of anchor teeth as low as possible. A threshold,below
which pressure would produce no reaction, could provide
perfect anchorage control
since it would only be necessary
to be certain that the threshold for tooth movement was
not reached for teeth in the anchorage unit.
A differential response to pressures, so that heavy pressure produce more tooth movement than lighter pressure would make it possible to move some teeth more than others even though some undesired tooth movement occurred
Reciprocal Tooth Movement :
In a reciprocal situation, the forces applied to teeth and to
arch segments are equal, and so is the force distribution in
the PDL. A simple example is what would occur if two
maxillary central incisors separated by a diastema were
connected by an active spring . The essentially
identical teeth would feel the same force distributed in the
same way through the PDL and would move toward each
other by the same amount
Reinforced Anchorage:
Continuing with the extractions site for example: if it was desired to differentially retract the anterior teeth, the anchorage of the posterior teeth could be reinforced by adding the second molar to the posterior. This would
Change the ratio of the root surface areass o that there would be relatively more pressure in the PDL of the anterior teeth, and therefore relatively more retraction of the anterior
segment than forward movement of the posterior segment
Another consideration n anchorage control is the different
Response of cortical compared with medullary bone. Cortical
bone is more resistant to resorption, and tooth movement
is slowed when a root contacts it. Some authors have
advocated torquing the roots of posterior teeth outward
against the cortical plate as a way to inhibit their mesial
Movement when extractions spaces re to be closed
2. Anchorage Resistance Unwanted
Tooth Movement
The term anchorage, in its orthodontic application, is
defined in an unusual way: the definition as "resistance to
unwanted tooth movement" includes a statement of what the
dentist desire.
“For every (desired) action there is an equal and
opposite reaction.
3. Relationship Tooth movement t o Force
An obvious strategy or anchorage control would be to
concentrate
the force needed to produce tooth movement where
it was desired, and then to dissipate the reaction force over
as many other teeth as possible ,keeping he pressure in the
PDL of anchor teeth as low as possible. A threshold,below
which pressure would produce no reaction, could provide
perfect anchorage control
4. • since it would only be necessary
• to be certain that the threshold for tooth movement was
• not reached for teeth in the anchorage unit.
• A differential response to pressures, so that heavy pressure
produce more tooth movement than lighter pressure would
make it possible to move some teeth more than others even
though some undesired tooth movement occurred
5.
6. Anchorage situations
• Reciprocal Tooth Movement :
• In a reciprocal situation, the forces applied to teeth and to
• arch segments are equal, and so is the force distribution in
• the PDL. A simple example is what would occur if two
• maxillary central incisors separated by a diastema were
• connected by an active spring . The essentially
• identical teeth would feel the same force distributed in the
• same way through the PDL and would move toward each
• other by the same amount
7.
8. •Reinforced Anchorage:
Continuing with the extractions site for example:
if it was desired to differentially retract the
anterior teeth, the anchorage of the posterior
teeth could be reinforced by adding the second
molar to the posterior. This would
Change the ratio of the root surface areass o that
there would be relatively more pressure in the PDL
of the anterior teeth, and therefore relatively
more retraction of the anterior
segment than forward movement of the posterior
segment
9.
10. •Stationary Anchorage:
•the advantage that can be obtained by pitting
bodily movement of one group of teeth against
tipping of
•another . Using our same example of a premolar
•extraction site, if the appliance were arranged so
that the
•anterior teeth could tip lingually while the posterior
teeth
•could only move bodily
11.
12. Cortical Anchorage
Another consideration n anchorage control is the different
Response of cortical compared with medullary bone. Cortical
bone is more resistant to resorption, and tooth movement
is slowed when a root contacts it. Some authors have
advocated torquing the roots of posterior teeth outward
against the cortical plate as a way to inhibit their mesial
Movement when extractions spaces re to be closed
13.
14. Skeletal ( Asolute) Anchorage
It has long been realized that if structures other than the
teeth could be made to serve as anchorage it would be
possible to produce tooth movement or growth modification
without unwanted side effects. Until recently, extra-oral
force (headgear) was the only way to obtain anchorage that
was not from the teeth. Although headgear can be used to
Augment anchorag
