2. Learning objectives
• Conception of anchorage in orthodontic
• Types of anchorage in orthodontic
• Use of anchorage in treatment of malocclusion
3. introduction
• Whenever a force is applied, it produces an equal and opposite reactive
force
• For tooth movement to occur in the desired direction this reactive force
should be equal or greater then the applied force
• The areas or units which provide the resistance to the reactive force
thereby preventing undesirable tooth movement are called anchorage
units
• White and gardner defined anchorage as “the site of delivery from which a
force is exerted”
• Graber “the nature and degree of resistance to displacement offered by an
anatomic unit when used for the purpose of affecting tooth movement”
5. Sources of anchorage
• These are anatomical units or regions which are used for the purpose
of providing the resistance to movement, anchorage
• These are further divided into two groups depending upon their
location as:
Intraoral sources
Extraoral sources
6. Intraoral sources of anchorage
• The anchorage units lie within the oral cavity. they include:
oThe alveolar bone
oThe teeth
oThe basal bone
oThe cortical bone
oThe musculature
7. Alveolar bone
• Within limits the alveolar bone resists deformation
• This can be seen from the rearrangement of trabecular pattern within
the alveolar bone
• Once the forces generated exceed those that can be resist by the
alveolar bone it permits tooth movement by bone remodeling
• Less dense alveolar bone offers less anchorage
• More mature bone increase anchorage(bone becomes more calcified,
regenerative capacity of the bone decrease)
• forces that are dissipated over a large bone surface area offer
increased anchorage
8. 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:
oThe root form
oThe size of root
oThe number of roots
oThe position of the teeth
oThe axial inclination of the teeth
oTheir intercuspation, etc
9. Teeth…
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 or triangular
• The distribution of the periodontal fibers on the root surface, aid in
anchorage
• The direction of attachment of the fibers
• Round roots have half their periodontal fibers stressed in any given
direction
• Mesiodistally flat roots are able to resist mesiodistal movement better as
compare to labiolingual movement
• Triangular roots, like those of canines are able to provide greater
anchorage
10. Continue…
• The tripod arrangement of roots aids in increasing the anchorage
• Like maxillary molars the round palatal root resist extrusion and the
two flat buccal roots resist intrusion and the mesiodistal stresses
• Under clinical situation where the buccal tube is bonded on the
buccal aspect of these teeth they show a tendency to roll mesially,
the crown rotating mesiopalatally under a mesially directed force
11. Teeth…
root size
• The larger or longer the roots the more is their anchorage potential
• The maxillary canines because of their long roots can, at times, be
most difficult teeth to move in certain clinical circumstance
12. Teeth…
number of roots
• The greater the surface area the greater the periodontal support and
hence, greater the anchorage potential
13. Teeth…
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 premolars which are placed
between two ridge-the mylohyoid and the external oblique
• They provide an increased resistance to mesial movement
mylohyoid
14. Teeth…
axial inclination of the teeth
• when the tooth is inclined in the opposite direction to that of the
force applied it provide greater resistance or anchorage
15. Teeth…
root formation
• Teeth with incomplete root formation are easier to move and are able
to provide lesser anchorage
17. Teeth…
intercuspation
• Good intercuspation leads to greater anchorage potential
• Teeth in one jaw are prevented from moving because of the contact
with those of the opposing jaw
• Posterior teeth
18. 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
19. Cortical bone
• Ricketts floated the idea of using cortical bone for anchorage
• The contention being that the cortical bone is denser with decrease
blood supply and bone turnover
• If the certain teeth were torqued to come in contact with 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
20. musculature
• Hypotonicity of perioral musculature might lead to spacing and flaring
of the anterior teeth
• Hypertonicity of the same muscles has the reverse effect
• Lip bumper is an appliance that makes use of the tonicity of the lip
musculature and enhance the anchorage potential of the mandibular
molars and preventing their mesial movement
21. Anchorage loss
• It is defined as the undesirable movement of anchor tooth in excess
too that of planned treatment
• Reasons for anchorage loss:
oExcessive force
oImpingement of roots of incisors or anterior teeth to the labial
cortical plate
oImproper anchorage preparation
oImproper treatment planning
oResistance between archwire and brackets
22. Continue…
• Anchorage loss in all 3 planes:
o Sagittal plane
Mesial movement of molars
Proclination of anteriors
o Vertical plane:
Extrusion of molars
Bite deepening due to anterior extrusion
o Transvers plane:
Buccal flaring due to over expanded arch form and unintentional lingual root
tourque
Lingual dumping of molars
23. Methods to prevent anchorage loss
• Use of miniscrews
• Use of stabilizing appliances like tarnsplatal arch, nance palatal arch
and lingual arch
• Use of light forces
• Extraoral anchorage using headgears
• Utilizing muscular forces
24. Classification of anchorage
• According to the manner of force application:
oSimple
oStationary
oReciprocal
• According to the jaws involved:
oIntarmaxillary
oIntermaxillary
25. Continue…
• According to the where the anchorage units:
oIntraoral
oExtraoral
oMuscular
• According to the number of anchorage units:
oSingle
oCompound
oreinforced
26. Continue…
• White and grabber classification:
oSimple
oStationary
oReciprocal
oReinforced
oIntermaxillary
oExtraoral
28. Intraoral anchorage
• Exist when and only when all the anchorage units are present within
the oral cavity
• Anchorage from all the intraoral sources of anchorage, including
teeth, palate, etc
Can form part of this type of anchorage
• Intraoral anchorage divided into intermaxillary and intramaxillary
types
29. Intramaxillary anchorage
• When all the elements providing the anchorage as well as those to be
moved are situated within the same jaw
• For example when elastic chains are used to retract the anterior
segment using the posterior teeth as anchorage units
• Intramaxillary anchorage subdivided into three subtypes:
oSimple
oStationary
oReciprocal
30. Intermaxillary anchorage
• When the anchorage units situated in one jaw are used to provide the
force required to move teeth in the opposing jaw
• It 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 mandibular arch
• Intermaxillary anchorage subdivided into three subtypes :
oSimple
oStationary
oReciprocal
31. Simple anchorage
• Exist when the manner and application of force is such that it tends to
change the axial inclination of tooth or teeth that form the anchorage units
in the plane of space in which the force is being applied
• Resistance to tipping of anchorage units might be utilized to retract certain
other teeth
• Simple anchorage obtained by engaging a greater number of teeth than are
to be moved
• The root surface area of anchorage units should be at least double
that of the units to be moved
• Anterior retraction with the help of Hawley’s appliance
or the movement of a single tooth using a screw appliance
32. Stationary anchorage
• Stationary anchorage is said to exist when the application of force
tends to displace the anchorage units bodily in the plane of space in
which the force is being applied
• The anchorage potential of teeth being moved bodily is considerably
greater as compared to teeth being tipped
• For example: in stage II beg technique a combination of anchor
bends and class II elastics pits the mandibular molars against the
maxillary anterior segment.
33. Reciprocal anchorage
• Reciprocal anchorage is said when two teeth or two sets of teeth
move to an equal extent in an opposite direction
• Here the root surface area of the anchorage units is equal to that of
the teeth to be moved
• The effect of the forces exerted is equal
• The two sets of teeth are displaced in the opposing direction but by
the same amount
• For example: cross elastics to correct molar cross bite, arch expansion
using a midline screw and the molar rotator
34. Single or primary anchorage
• Where the tooth to be moved is pitted against a tooth with a greater
alveolar support area is said to display primary or single anchorage
• Example: a molar along with adjacent premolars used to align
another molar.
35. Compound anchorage
• This type of anchorage provides for the use of more teeth with the
greater anchorage potential to move a tooth or group of teeth with
lesser support
• Foer example: retracting incisors using loop mechanics in the fixed
orthodontic appliance
36. 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 the use of a trans palatal arch in fixed
mechanotherapy or simply the banding of the second molar for the
retraction of the permanent canine
37. Exteraoral anchorage
• The anchorage units are situated outside the oral cavity or extraorally
• The extraoral structures most frequently used at the cervical region,
the occiput, the forehead and the chin
• 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 change taking place in the
anchorage units
• The biggest disadvantage of extra oral anchorage is the apparent lack
of patient cooperation and appearance and affecting the time
38. 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
• Trans palatal arches when kept far from the palate may cause the
intrusion of the teeth to which is attached, the maxillary first molars
39. Implants as anchorage units
(absolute anchorage)
• Temporary anchorage devices(TPD)-implants, miniscrews-must have a
primary stability and be able to withstand orthodontic force level
• The TPDs are called as absolute anchorage without space loss due to
movement of anchor teeth
40. Anchorage planning
• At the time of determining the space requirements to resolve the
malocclusion in a given case it is essential to plan for space that is
likely to be lost due to the invariable movement of the anchor teeth
The anchorage requirements
depends on:
The type of teeth to be
Periodontal conditionmoved
The number
of teeth to
be moved
Periodontal
condition
Type of tooth
movement
Duration of
tooth
movement
41. Classifying anchorage requirements
• Estimated that one-third the extraction space is lost as anchor loss if
no additional means are used to conserve anchorage
• cases classified depending upon the space requirements of the
particular case as maximum anchorage, moderate anchorage and
minimum anchorage
42. 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 lost should be minimum
• No more than one-forth the extraction space can be lost to the
forward movement of the anchor teeth
• All care should be taken to preserve anchorage and the use of
additional methods to augment anchorage should be planned in the
treatment plan
43. Moderate anchorage
• These are cases where the anchor teeth can be allowed to move
forward into extraction space for one-forth to half the total extraction
• Reinforced the anchorage may not be required
44. Minimum anchorage
• These include cases where a very less amount(less than half) of the
extraction space is required
• The rest of the space more than half the extraction space need to
close by bringing the anchor teeth forward or to anchor loss
