Anchorage in Orthodontics: Types and Sources

Faculty of dentistry-Mansoura universityFaculty of dentistry-Mansoura university
- Egypt- Egypt

Definition
Anchorage: Resistance to 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 desires. The usage, though unusual, is clearest
when presented this way. 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.
An introduction to orthodontic. Laura mitchell. Second edition

CLASSIFICATION OF ANCHORAGE
A. Anchorage classified according to the manner of
force application as:
1. Simple
2. Stationary
3. Reciprocal.
B. Anchorage classified according to the jaws
involved as:
1. Intramaxillary
2. Intermaxillary.
C. Anchorage classified according to the site where
the anchorage units as:
1. lntraoral
2. Extraoral
3. Muscular.

D. Anchorage classified according
to the number of anchorage units
as:
1. Single
2. Compound
3. Reinforced.
E. White and Gardiner classified
anchorage into six categories as:
1. Simple
2. Stationary
3. Reciprocal
4. Reinforced
5. Intermaxillary
6. ExtraoraI.

Types of anchorage :-
A- intra oral anchorage which include :-
1- simple anchorage:- active movement of single tooth versus several
anchor teeth.
2- compound anchorage:- teeth of greater resistance to movement are
utilized as anchorage for the translation of teeth which have less
resistance to movement.
compound anchorage
Simple anchorage
An introduction to orthodontic. Laura mitchell. Second edition

3- stationary anchorage:-this is a misnomer as it is extremely
difficult to prevent movement of anchor teeth altogether.
Displacement of anchor teeth can be
minimized by arranging the force system so
that the anchor teeth must move bodily if they
move at all, while movement teeth are allowed
to tip, as in this example of retracting incisors
by tipping them posteriorly. The approach is
called "stationary anchorage." In this
example, treatment is not complete because
the roots of the lingually tipped incisors will
have to be uprighted at a later stage, but
two-stage treatment with tipping followed by
uprighting can b used as a means of
controlling anchorage. Distributing the force
over a larger PDL area ofthe anchor teeth
reduces pressure there
CONTEMPORARY ORTHODONTICS, William . Proffit 2000

4- 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.
-crossbite elastic was used to move the
upper molars buccally and lower molars
liguanlly.
-Maxillary expansion screw was used to
move the upper molars bucally.
Textbook of Orthodontics © 2007, Gurkeerat Singh

5- Reinforced anchorage
Here the anchorage units are reinforced by the use of
more than one type of resistance units. For example,
the use of headgears along with routine fixed
Mechanotherapy or (extraoral anchorage and intraarch
compound anchorage) or the use of a transpalatal
arch in fixed mechanotherapy or simply
the banding of the second molar for the retraction of
the permanent canine

MUSCULAR ANCHORAGE
The perioral musculature is not only very strong but
also resilient. The forces generated by the musculature
Can some times be used to bring about tooth movement.
The lip bumper appliance may be used to distalize the
mandibular first molars (Fig. 22.8) or the transpalatal
arch when kept away from the palate, may cause the
intrusion of the teeth to which it is attached, the
maxillary first molars.

INTERMAXillARY ANCHORAGE
When the anchorage units situated in one jaw are used
to provide the force required to move teeth in the
opposing jaw the anchorage is called intermaxillary.
This type of anchorage is also termed as Baker's
anchorage.
For example, when Class II elastics are used
to retract the maxillary anteriors the anchorage units
are situated in the mandibular arch.
Intermaxillary anchorage can also be further
subdivided into three subtypes depending upon the
manner of force application as:
1. Simple
2. Stationary
3. Reciprocal.

EXTRAORALANCHORAGE
As the name implies, here the anchorage units are
situated outside the oral cavity or extraorally. The
extraoral structures most frequently used at the cervical
region (as with the use of the cervical pull headgear,the
occiput (as with the occipital pullheadgear , the forehead
and the chin (e.g.,
the face mask with the use of extraoral anchorage the
anchorage units are situated far away from the actual
site where the movement is taking place hence there is
hardly any chance of any changes
taking place in the anchorage units. The biggest
disadvantage of extraoral anchorage is the apparent
lack of patient cooperation. The anchorage assembly is
bulky and externally visible making patients.

.A , High-pulhl eadgear (headcap)to the
first molar.T o produceb odilymovement
of the molar (no tipping), the line of force
(blackarrow) musl passt hrough the
centero f resistanceof the molar tooth.
This will produce both backward and
upward movement of the molar.
B , Cervical headgear( neck strap) to the first
molar. Again, bodily movement is produced
by an outer bow length and position that
places the line of force through the center of
resistance of the molar; but with a lower
direction of pull, the tooth is extruded as well
as moved backward.

CLASSIFYING ANCHORAGE REQUIREMENTS
Begg, the inventor of the light wire differential force
technique or the Begg technique, as it is frequently
referred to estimated that one-third the extraction
space is lost as anchor loss if no additional means
are used to conserve anchorage. Based on this
premise he classified cases depending upon the
space requirements of the particular case as
maximum anchorage, moderate anchorage and
minimum anchorage.

1-MAXIMUM ANCHORAGE
These include cases where the anchorage demand is
critical Or in other words maximum space should be
used to correct the malocclusion proper and anchor
loss should be minimum. In such cases no more than
one-fourth the extraction space can be lost to the
forward movement of the anchor teeth, i.e. anchor loss.
All care should be taken to preserve anchorage and
the use of additional methods to augment anchorage
should be planned in the treatment plan.

MODERATE ANCHORAGE
These are cases where the anchor teeth can be allowed
to move forward into the extraction space for one fourth
to half the total extraction space. Reinforcing
the anchorage might not be required.

MINIMUM ANCHORAGE
These include cases where a very less amount (less
than half) of the extraction space is required for the
actual resolution of the malocclusion. The rest of the
space, Le. more than half the extraction space needs
to be closed by bringing the anchor teeth forward or
to anchor loss.

Sources of anchorage:-
Anchorage can be obtained from intra-oral and extra-oral sources and we should
not forget the possibility of favourable growth and the question of our ability to
enhance it. It is sensible to firstly summarise the possibilities for maximising intraoral
anchorage.
Sources of intra-oral anchorage
• root surface area
, this is a fundamental source of anchorage
• bony cortex
In spite of widespread hope that this may prove source of anchorage, there seems
little evidence that this is indeed the case. It is clearly not difficult to move teeth
labially right through the cortex. Rebellato et al (1997) found that lingual arches did
not prevent mesial migration of molars even when no intra-arch traction was
applied. A study by Ellen, Schneider and Sellke (1998) found no enhancement of
vertical or horizontal anchorage when using utility arches to set up cortical
anchorage. These papers would also suggest that palatal arches would not be
expected to add to posterior anchorage.
Excellence in Orthodontics 2005Lecture Course Manual

• mucosa and underlying bone
This is the source of anchorage which is sought with Nance buttons, removable
appliances and lingual flanges on functional appliances. It is hard to measure, but
appliances which cover a larger area of mucosa would be expected to provide
additional anchorage.
• occlusal interferences
Some extraction patterns e.g. upper first and lower second premolars can create
useful
interlocking of the dentition and increase the root surface area resisting a loss of
upper arch posterior anchorage. Conversely upper canines stuck mesial to lower
canines can lose upper arch anchorage as can attempted reduction of an overjet in
the presence of a complete overbite.
• implants/onplants
These are a powerful source of intra-oral anchorage and are discussed more fully
in a
separate section later in this presentation.

Maximising root surface area
Although far from proven, there seems strong indirect evidence that the
differential force theory has substance. I.e. that within limits, the rate of tooth
movement is related to the applied force per unit root surface area. For example,
the study by Saelens and De Smit (1998) showed a greater mesial movement
of molars and a lesser amount of anterior crowding resolved when second
premolars rather than first premolars were extracted. Other studies supporting
this theory are discussed in the chapter on Diagnosis and Treatment Planning in
the section on planning extractions. Maximising root area in the anchorage unit.
is therefore sensible when anchorage is at a premium. In addition to choosing
more anterior extractions,root surface area in the anchorage unit can be
increased by:
• including second molars
• separate retraction of canines
• correcting centrelines one tooth at a time.
• semi-transverse forces eg. pushing rather than pulling canines distally.
Practical considerations may lessen the applicability and effectiveness of any of
these in a given situation,but they are all useful sources of anchorage.

Retracting six teeth at once
In extraction cases where anchorage is not at a premium, clinicians traditionally retract
the canines until there is sufficient space to align the incisors and then the complete
labial segment of six teeth is retracted as a unit as opposed to fully retracting the canines
to a class 1 relationship and then retracting the incisors.
On theoretical grounds, retracting all six teeth simultaneously would be expected to
increase anchorage demands and although this increase is not necessarily apparent
clinically, there must be good reasons for choosing this theoretically more anchorage
demanding plan. These reasons fall into two categories,namely, simplicity and not re-
tracing steps of tooth movement.
Sliding all six teeth as a unit along a stiff wire involves very simple archwire
fabrication and activation when compared with three sectional archwires and
closing loops. Also, the chances of trauma to the lips, cheeks and gingivae are
very small and the obstacles to oral hygiene are minimised. This method also
makes it easy to keep all teeth under control and at the end of space closure, there
is no need to align the teeth for a second time before finishing. These advantages
must be weighed against the possible increase in anchorage required.

Straight-Wire Appliance and anchorage
Johnston et al (1998) reported that use of the Straight-Wire Appliance - probably
involving the retraction of the six front teeth simultaneously - cost 0.8 mm more
anchorage (measured by his pitchfork analysis) in the maxilla when compared to
treatment with plain edgewise appliances. It must also be remembered in this
context that a fully programmed appliance makes it harder for the clinician to finish a
case with inadequate palatal root torque of the upper incisors and the slight extra
anchorage requirement may be partly explained by the achievement of more
anchorage - demanding occlusal goals.

Self-ligating brackets and anchorage
The chapter Self-ligating brackets – theory and practice discuss in detail the
potential benefits of using self ligating brackets such as SPEED, Opal, In-Ovation
or Damon 2 and 3. One such benefit is the ability to slide a tooth along a wire with
very low friction and with no loss of control. This previously unusual combination
reduces the potential disadvantages of separate retraction of canines. We would
therefore expect anchorage preservation to be enhanced if these mechanics are
used with self-ligating brackets. It has certainly been reported in a very interesting
study by Rajcich and Sadowsky (1997), that retraction of canines with sliding
mechanics when the molar is prevented from tipping or sliding mesially incurs
impressively low anchorage loss. There are simpler ways of controlling molar tip
and slide than the one they suggest which uses an auxiliary arch. A crimped stop or
hook is one of them. This combination of a self-ligating bracket, a stopped archwire
and separate canine retraction is worth close consideration for
anchorage enhancement.

MECHANICAL ASPECTS
OF ANCHORAGE CONTROL
When teeth slide along an arch wire, force is needed for
two purposes: to overcome frictional resistance, and to create
the bone remodeling needed for tooth movement. As
we have pointed out in Chapter 9, controlling the position
of anchor teeth is accomplished best by minimizing the reaction
force that reaches them. Use of unnecessarily heavy
force to move teeth creates problems in controlling anchorage.
Unfortunately, anchor teeth usually feel the reaction
to both frictional resistance and tooth movement
forces, so controlling and minimizing friction is an important
aspect of anchorage control.
CHAPTER 10 Mechanical Principles in Orthodontic Force Control
contemporary orthodontic 2000 proffit

Frictional Effects on Anchorage
When one moving object contacts another, friction at their
interface produces resistance to the direction of movement.
The frictional force is proportional to the force with which
the contacting surfaces are pressed together and is affected
by the nature of the surface at the interface (rough or
smooth, chemically reactive or passive, modified by lubricants,
etc.). Interestingly, friction is independent of the apparent
area of contact. This is because all surfaces, no matter
how smooth, have irregularities that are large on a
molecular scale, and real contact occurs only at a limited
number of small spots at the peaks of the surface irregularities. These
spots, called asperities, carry all the load between the two surfaces.
Even under light loads, local pressure at the asperities may cause
appreciable plastic deformation of those small areas.
Because of this, the true contact area is to
a considerable extent determined by the
applied load and is directly proportional to it.

When two solid surfaces are pressed together
or one slides over the other, real contact occurs only at a
limited number of small spots, called asperities, that
represent the peaks of surface irregularities. Even under
light loads, as when an orthodontic arch wire is tied into
a bracket, local pressure at the asperities is likely to form
junctions between the two surfaces. These junctions
shear as sliding occurs. If two materials of
differenthardness slide past each other (for instance, a
metal wire in a ceramic bracket), the coefficient of
friction is mainly determined bythe shear strength and
yield pressure of the softer material.

Surfaces of Wires and Brackets.
The concept that surface qualities are an important
variable in determining friction has been emphasized by
experiences in the late1980s with both titanium wires
and ceramic or plastic brackets. Stainless steel brackets
slide reasonably well on steel wires, but the situation is
not so fortunate with some other possible combinations.

Surface Qualities of Wires.
When NiTi wires were first introduced, manufacturers claimed
that they had an inherently slick surface compared with
stainless steel, so that all other factors being equal, there
would be less interlocking of asperities and thereby less
frictional resistance to sliding a tooth along a NiTi wire than
a stainless steel one.
This is erroneous-the surface of NiTi is rougher (because
of surface defects, not the quality of polishing) than that of
beta-Ti, which in turn is rougher than steel. More importantly,
however, there is little or no correlation for orthodontic wires
between the coefficients of friction and surface
roughness' 8 (i.e., interlocking and plowing are not significant
components of the total frictional resistance). Although
NiTi has greater surface roughness, beta-Ti has
greater frictional resistance.

Surface Qualities of Brackets.
Bracket surfaces also are important in friction. Most modern
orthodontic brackets are either cast or milled from
stainless steel, and if properly polished have relatively
smooth surfaces comparable with steel wires. Titanium
brackets now are coming into use, primarily because of
their better biocompatibility- some patients have an allergic
response to the nickel in stainless steel and do not tolerate
steel appliances. Ceramic brackets became quite popular
in the 1980s because of their improved esthetics, but
problems related to frictional resistance to sliding have
limited their use. The ones made from polycrystalline
ceramics have considerably rougher surfaces than steel
brackets.

Force of Contact.
The amount of force between the wire and the bracket strongly influences
the amount of friction.This is determined by two things. First, if a tooth is
pulled along an arch wire, it will tip until the corners of the bracket contact
the wire and a moment is generated that prevents further tipping. If the
initial tipping is to be prevented and true bodily movement produced, any
wire that is smaller than the bracket initially
must cross the bracket at an angle. The greater the angle, the greater the
initial moment and the greater the force between the wire and the bracket.
As, friction goes up rapidly as the angle between the bracket and the wire
increases. Because of this, the elastic properties of the wire influence
friction, especially as bracket angulation increases. A more flexible wire
bends and reduces the angle between wire and bracket. As noted earlier,
when teeth slide along an arch wire, it is easier to generate the moments
needed to control root position with a wide bracket because the wider the
bracket, the smaller the force needed at its edges to generate any
necessary moment. The smaller force also should reduce the frictional
force proportionally.

A second force, however, is the one that largely determines
friction: the force that pulls the wire into the bracket,
which would be produced by the ligature holding the wire
in place. 25 Perhaps this explains why laboratory data indicate
that bracket width has surprisingly little effect on friction.
More importantly, it illustrates why sliding along
arch wires works much better when the system that holds
the arch wire in the bracket does not hold the wire tightly
the bracket.

Magnitude of Friction.
Perhaps the most important information to be gained from a
consideration of friction isan appreciation of its magnitude,
even under the best of circumstances. if a 19 x 25 steel
wire is placed in a 22-slot bracket and tied with a (presumably
typical) wire ligature, the minimum frictional resistance
to sliding a single bracket is about 100 gm. In other
words, if a canine tooth is to slide along an arch wire as part
of the closure of an extraction space, and a 100 gm net force

is needed for tooth movement, approximately another 100
gm will be needed to overcome friction (Figure below ).
The total force needed to slide the tooth therefore is twice
as great as might have been expected. The frictional resistance
can be reduced, but not eliminated, by replacing the
ligature tie with a bracket cap so that the wire is held in
place loosely.

In terms of the effect on orthodontic anchorage, the
problem created by friction is not so much its presence as
the difficulty of knowing its magnitude. To slide a tooth
or teeth along an arch wire, the clinician must apply
enough force to overcome the friction and produce the biologic
response. It is difficult to avoid the temptation to
estimate friction generously and add enough force to be
certain that tooth movement will occur. The effect of any
force beyond what was really needed to overcome friction
is to bring the anchor teeth . Then either un
necessary movement of the anchor teeth occurs, or additional
steps to maintain anchorage are necessary (e.g.,
headgear).

Methods to Control Anchorage
Nearly all the possible approaches are actually used in clinical
orthodontics, and
each method is affected by whether friction will be encountered.
Considering them in more detail :-
Reinforcement. The extent to which anchorage should be reinforced
depends on the tooth movement that is desired. In practice, this
means that anchorage requirements must be established individually
in each clinical situation.
Reinforcement of anchorage can be
produced by adding additional teeth within
the same arch to the anchor unit, or by using
elastics from the opposite arch to help
produce desired tooth movement, as with the
interarch elastic shown here. Additional
reinforcement can be obtained with extraoral
force, as with addition of a facebow to the
upper molar to resist the forward pull of the
elastic.
CONTEMPORARY ORTHODONTICS, FOURTH EDITION William . Proffit 2000

Once it has been determined that reinforcement is desirable,however, this
typically involves including as many teeth as possible in the anchorage unit. For
significant differential tooth movement, the ratio of PDL area in the anchorage
unit to PDL area in the tooth movement unit should be at least 2 to 1 without
friction, 4 to 1 with it. Anything less produces something close to reciprocal
movement. Obviously, larger ratios are desirable if they can be obtained.
This anchorage could be reinforced
even further by having the patient
wear an extraoral appliance
(headgear) placing backward force
against the upper arch. The
reaction force from the headgear is
dissipated against the bones of the
cranial vault, thus adding the
resistance of these structures to the
anchorage unit.

The only problem with reinforcement outside
the dental arch is that springs within an arch
provide constant forces, whereas elastics from
one arch
to the other tend to be intermittent, and extra-
oral force is likely to be even more intermittent.
Although this time factor can significantly
decrease the value of cross-arch and extra
oral reinforcement, both can be quite useful
clinically.

Subdivision of Desired Movement. A common
way to improve anchorage control is to pit the resistance
of a group of teeth against the movement of a single
tooth, rather than dividing the arch into more or less equal
segments. In our same extraction site example, it would
be perfectly possible to reduce the strain on posterior
anchorage by retracting the canine individually, pitting its
distal movement against mesial movement of all other
teeth within the arch. After the canine tooth had
been retracted, one could then add it to the posterior
anchorage unit and retract the incisors. This approach
would have the advantage that the reaction force would
always be dissipated over a large PDL area in the anchor
unit. Its disadvantage is that closing the space in two
steps rather than one would take nearly twice as long.
one at a time without friction, of course, will
put less strainon anchorage than sliding
them one at a time.
Retraction of the canine by
itself, as the first step in a
two-stage space closure,
often is used to conserve
anchorage, particularly
when sliding teeth along
an arch wire.

Tipping/Uprighting. Another possible strategy for anchorage control is to tip the teeth
and then upright them,rather than moving them bodily. In our familiar extraction
site example, this would again require two steps in treatment. First, the anterior teeth
would be tipped distally by being pitted against mesial bodily movement of the posterior
segment. As a second step, the tipped teeth would be uprighted, moving the canine
roots distally and torquing the incisor roots lingually, again with stationary
anchorage in the posterior segments. It would be extremely important to keep forces
as light as possible during both steps, so that the teeth in the posterior segment were
always below the optimum force range while the anterior teeth received optimum force.
Displacement of anchor teeth can be minimized by
arranging the force system so that the anchor teeth
must move bodily if they move at all, while movement
teeth are allowed to tip, as in this example of
retracting incisors by tipping them posteriorly. The
approach is called "stationary anchorage." In this
example, treatment is not complete because the roots
of the linguallytipped incisors will have to be
uprighted at a later stage, but two-stage treatment
with tipping followed by uprighting can beused as a
means of controlling anchorage.

Friction and Anchorage Control
Strategies. Anchorage control is
particularly important when protruding
incisors are to be retracted. The goal is
to end up with the teeth in the correct
position, not necessarily to retract them
as much as possible. The desired
amount of incisor retraction for any
patient should be carefully planned, and
the mechanotherapy should be selected
to produce the desired outcome.

At this point, however, it is interesting to consider a
relatively typical extraction situation, in which it is desired
to close the extraction space 60% by retraction of the anterior
teeth and 40% by forward movement of the posterior segments.
This outcome would be expected from any of three possible
approaches: (1) one-step space closure with a frictionless
appliance; (2) a two-step closure sliding the canine along the arch
wire, then retracting the incisors (as in the original Tweed
technique); or (3) two step space closure, tipping the anterior
segment with some friction, then uprighting the tipped teeth (as in
the Beggtechnique).

Factors affecting the anchorage
Teeth
Teeth by themselves resist movement. Forces can be
exerted from one set of teeth to move certain other
teeth. The anchorage potential of teeth depends upon
a number of factors including-the root form, the size
of roots, the number of roots, the position of the teeth,
the axial inclination of the teeth, their intercuspation,
etc.
Root form The root form, to a large extent is responsible
for the degree of anchorage provided by a tooth.
The root in cross section can be either round, flat
(mesiodistally) or triangular . The distribution
of the periodontal fibers on the root surface aidin anchorage.

The more the fib ers the better the anchorage potential.
The direction of attachment of the fibers also effects the
anchorage offered by a tooth.Round roots have only half
their periodontal fibers stressed in any given direction.
Hence, offer the least anchorage. Mesiodistally flat roots
are able to resist mesiodistal movement better as
compared to labiolingual movement, as more number of
fibers are activated on the flatter surfaces as compared to
the relatively narrower labial or lingual surfaces.
Triangular roots, like those of the canines are able to
provide greater anchorage. Their flatness adds to
resistance.

The tripod arrangement of roots , like
that seen on maxiUary molars also aids in increasing
the anchorage. The round palatal root resists extrusion
and the two flat buccal roots resist intrusion and the
mesiodistal stresses. Under clinical situations where
the buccal tube is bonded/welded on the buccal aspect
of these teeth they show a tendency to 'roll' mesially,
the crown rotating mesiopalatally under a mesially
directed force .

Size of roots The larger or longer the roots the more is their anchorage potential.
The maxillary canines, because of their long roots can, at times, be the most
difficult teeth to move in certain clinical circumstances
Number of roots The greater the surface area the greater the periodontal support
and hence, greater the anchorage potential. Multirooted teeth provide greater
anchorage as com pa red to single rooted teeth wi th similar root length.
Position of tooth Sometimes the position of the teeth in the individual arches also
helps in increasing their anchorage potential. As in the case of mandibular second
prernolars, which are placed between two ridges-the mylohyoid and the external
oblique, they provide an increased resistance to mesial movement.
Axial inclination of the tooth When the tooth is inclined in the opposite direction to
that of the forceapplied, it provides greater resistance or anchorage.

Root formation Teeth with incomplete root formation
a re easier to move and are able to provide lesser
anchorage.
Contact points Teeth with intact contacts and/ or
broad contact provide greater anchorage.
Intercuspation Good intercuspation leads to greater
anchorage potential . This is mainly because
the teeth in one jaw are prevented from moving
because of the contact with those of the opposing jaw,
this is especially true for teeth in the posterior segment
which also show the presence of attrition facets.

Basal Bone
Certain areas of the basal bone like the
hard palate and the Lingual surface of the
mandible in the anterior region can be used
to augment the anchorage. The
Nance palatal button is one such appliance
that makes use of the hard palate to
provide resistance to the mesial movement
of the maxillary molars

Cortical Bone
Ricketts floated the idea of using cortical bone for
anchorage. The contention being that the cortical bone
is denser with decreased blood supplies and bone
turnover. Hence, if certain teeth were torqued to come
in contact with the cortical bone they would have a
greater anchorage potential. The idea as such remains
controversial as tooth roots also show resorption in
such conditions and the risk of non-vitality of such
teeth is also more.

Musculature
Under normal circumstances the perioral musculature
plays an important part in the growth and development
of the dental arches. Hypotonicity of the perioral
musculature might lead to spacing and flaring of the
anterior teeth. The hypertonicity of the very same
muscles has the reverse effect. Lip bumper is an
appliance that makes use of the tonicity of the lip
musculature and enhances the anchorage potential of the
mandibularmolars preventingtheir mesialmovement
musculature and enhances the anchorage potential of
the mandibular molars preventing their mesial
Movement .

LOSS OF ANCHORAGE
This is defined as the unplanned and unexpected
movement of the anchor teeth during orthodontic
treatment.
There are several causes of loss of anchorage.
Some examples of these are:
• Poor appliance design
• Poor appliance adjustment
• Poor patient wear
Poor appliance design
Failure to adequately retain the appliance, or
incorporate as many teeth into the anchor block
as possible are common causes of anchorage
loss. If fixed appliances are used, as many anchor
teeth as possible should be banded in
order to produce optimum anchorage. Removable
appliances should have adequate retention
using appropriate well-adjusted cribs or clasps
with as much contact with the teeth and oral
mucosa as possible.
258 BRITISH DENTAL JOURNAL VOLUME 196 NO. 5 MARCH 13 2004

Poor appliance adjustment
The use of excessive force or trying to move too
many teeth at the same time may result in
unwanted movement of the anchor teeth. To
avoid loss of anchorage, simultaneous multiple
teeth movement should be avoided. If the
appliance is poorly adjusted so that it doesn't
fit very well, or the force levels applied to the
teeth are too high, then undesired tooth movement
may occur. High force levels produced by
over activation are one of the key reasons for
anchorage loss.
BRITISH DENTAL JOURNAL
VOLUME 196 NO. 5 MARCH 13 2004

The optimal force for movement of a
single rooted tooth is about 25–40 g for
tipping and about 75 g for bodily
movement. If the force is too low there will
be very little movement, whereas too
much force may result in loss of
anchorage. Excess force does not
increase the
rate of tooth retraction, As the force levels
rise the rate of tooth tipping also
increases up to about 40 g. Beyond this
very little extra tooth movement occurs.
Thus increasing the force levels above
about 40 g willnot increase the rate of
tooth tipping.

The force levels that wires from fixed or removable appliances exert on teeth usually
depends on the following:
• The material the wire is made from
• The amount it is deflected
• The length of the wire
• The thickness of the wire
Steel wire will exert a force that is directly proportional to the amount the wire is
deflected up to its elastic limit. Figure 11 demonstrates how decreasing the wire
thickness and increasing the length (sometimes by adding loops) controls
the force produced. Modern alloys such as super elastic nickel titanium wires do not
act in the same way as steel.These remarkable wires are capable of producing

a continuous level of force almost independent of
the amount of deflection and have transformed
the use of fixed appliances in recent years. Heat
activated wire is now available that will increase
its force level as the temperature changes. These
wires exhibit a so-called shape memory effect. If
the wire is cooled and tied into the teeth it deflects
easily into position. As the wire warms in the
mouth it gradually returns to its original shape
moving the teeth with it.

• Absolute anchorage
• Mini implant anchorage is excellent for
• - adjunctive tooth movement
• -En masse retraction
• -molar distalization
• - molar intrusion or extrusion

Complications:-
- root injury from inadequate inter radicular
space.
-Vessels injury and sinus injury.
-soft tissue inflammation around the screw if
bad oral hygiene.
-screw may break during insertion or
removal.
-uncomfortable to the patient if placed in
lingual aspect of mandible.
-some times can loosen and become lost.

Anchorage in Orthodontics: Types and Sources

Anchorage in Orthodontics: Types and Sources

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Anchorage in Orthodontics: Types and Sources