ANCHORAGE IN
ORTHODONTICS
Presented by: Namuna Ghimire
Rollno: 12
Bds 4 th year
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Contents
◦ Introduction
◦ Sources of anchorage
◦ Indications for anchorage placement
◦ Classification of anchorage
◦ Temporary anchorage devices
◦ Anchorage planning
◦ Classification of anchorage demands
◦ Loss of anchorage
◦ Questions
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INTRODUCTION
The forces used to move teeth is derived from certain anatomic areas (anchors)
◦ According Newton's third law of motion, For every (desired) action, there is an equal and
opposite reaction.
◦ In orthodontics, Forces used to move teeth may induce an equal and opposite force on
anchorage units tending to cause their movement (not desirable)
◦ Resistance offered by anchorage units to these
unwanted tooth movement is called anchorage
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Definition
◦ Graber: Nature and degree of resistance to displacement offered by an anatomic unit for
the purpose of affecting tooth movement.
◦ White and Gardiner: Anchorage is site of delivery from which force is exerted
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Sources of anchorage
Intraoral sources
◦ Teeth
◦ Alveolar bone
◦ Basal jawbone
◦ Musculature
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Sources of anchorage
Extraoral sources
◦ Cranium
◦ Back of neck
◦ Facial bones
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Teeth
Anchorage potential of teeth depends on:
1. Root surface area :The wider the area covered by the root,
higher resistance to movement the tooth will have.
◦ e.g.lower incisors, will respond faster to movement,
compared with the first molars
◦ Ratio of root surface of anchor unit to moving unit=
4:1(ideally)
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◦ 2. Root form:
◦ Flat roots: Mandibular incisors and molars, buccal roots of maxillary molars
Resist movement in mesiodistal direction
◦ Round roots: Bicuspid and palatal root of maxillary molars
Resist horizontally directed forces in any direction
◦ Triangular root: canines and maxillary incisors
Maximum resistance to displacement
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3. Size and number of roots:
Multirooted teeth with large roots have greater ability to withstand stress
4. Root length: Longer the root, deeper it is embedded in bone and greater is the
resistance to displacement
5. Inclination of tooth: force exerted to move teeth is opposite to axial inclination, greater
the resistance
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6. Ankylosed teeth: No PDL,
so orthodontic movement not possible,
excellent anchors
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Alveolar bone
◦ Offers resistance to tooth movement upto certain amount of force
◦ When force applies exceeds certain limit, alveolar bone permits tooth movement by
bone remodelling
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Basal bone
◦ Include Hard palate and lingual surface of mandible in region of roots
◦ Can be used to augment intra-maxillary or inter-maxillary anchorage
Nance buttons
◦ Can be the source of anchorage when using Nance buttons, removable appliances
and lingual flanges on functional appliances
◦ Appliance covering greater area of mucosa provides greater anchorage
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Musculature
◦ Hypotonic- flaring and spacing of teeth
◦ Hypertonic- exert restrictive forces in lingual direction
◦ Dental anchorage may be increased by making used of hypertonic labial musculature
e.g lip bumper
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Extraoral sources:
◦ Cranium: Obtained by using accipital/ parietal headgear
◦ Back of neck : Obtained by using cervical headgear
◦ Facial bones: Frontal bone and mandibular symphysis
Obtained by using reverse headgears
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Indications for anchorage
placement
◦ There must be good bone support
◦ No dental mobility.
◦ healthy teeth with no caries and well adjusted restorations on which to cement
anchorage.
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Moyer's classification of
anchorage
According to manner of
application of force
Simple
Stationary Reciprocal
anchorage anchorage anchorage
According to
jaws involved
Intramaxillary
anchorage
According to site
of anchorage
Intermaxillary
anchorage
Single or primary
anchorage
Intra oral anchorage
Intramaxillary
anchorage
Intermaxillary
anchorage
Simple , stationary,
reciprocal
According to number
of anchorage units
Compound
anchorage
Multiple/
reinforced
anchorage
Extra oral anchorage
Cervical
Cranial Occipital Frontal
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According to manner of
force application
◦ 1. Simple Anchorage
◦ Manner and application of force is such that it tends to change
the axial inclination of the tooth/teeth that form the anchorage
unit in the plane of space in which force is being applied
◦ Resistance of anchorage unit to tipping is utilized to move
another tooth/teeth
◦ obtained by engaging with the appliance a greater number of
teeth than are to be moved within same dental arch
◦ Combined root surface area of teeth forming anchorage unit=
2*teeth to be moved
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2. Stationary Anchorage
◦ Manner and application of force tends to displace the
anchorage unit bodily in the plane of space in which the
force is being applied
◦ Greater than in one resisting tipping force
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3. Reciprocal anchorage
◦ Resistance offered by two malposed units
◦ when the dissipation of equal and
opposite forces tends to move each unit
towards a more normal occlusion
◦ Two teeth/ group of teeth of equal
anchorage value are made to move in
opposite directions
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According to site of anchorage
1. Intraoral anchorage: teeth to be moved and anatomic areas that offer anchorage
are all within oral cavity
Include:
◦ teeth
◦ alveolar bone
◦ basal jawbone
◦ musculature
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2. Extraoral anchorage : Mainly used when adequate resistance cannot be obtained
from intraoral sources
Include:
◦ Cranium
◦ Back of neck
◦ Frontal bone
◦ Mandibular symphysis
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Muscular anchorage:
◦ Perioral musculature is employed as resistance units
◦ Makes use of forces generated by muscles to aid in the movement of teeth
◦ e.g use of lip bumper to distalize molars
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According to jaws involved
1. Intra maxillary anchorage
◦ All units offering resistance are situated in same jaw
◦ teeth to be moved and anchorage unit situated entirely on maxilla or mandible
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2. Inter maxillary anchorage ( Baker's anchorage)
◦ Resistance unit situated in one jaw are used to affect tooth movement in another jaw
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According to number of anchorage
units
1. Single/ primary anchorage
◦ Resistance provided by single tooth with greater alveolar support
◦ Is used to move another tooth with lesser support
◦ e.g : molar being used to retract premolar
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2. Compound anchorage
◦ Resistance provided by more than one tooth with greater support is used to move
teeth with lesser support
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3. Reinforced anchorage
◦ Anchorage in which more than one type of resistance unit is utilized
◦ Augmentation of anchorage by various means such as:
Extraoral forces to augment anchorage
Upper anterior inclined plane
upper anterior inclines plane
Use of transpalatal arch and lingual arches
Sved appliance
lingual arch
transpalatal arch
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Temporary anchorage device (TAD)
◦ Cope: A device that is temporarily fixed to bone for the purpose of enhancing
orthodontic anchorage either by supporting the teeth of reactive (anchorage) unit or
by obviating the need for the reactive unit altogether, and which is subsequently
removed after use
◦ Titanium alloy miniscrew
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Size
◦ Ranges from: Length: 6-12 mm, Width-1.2-2mm
◦ Maxilla: 7-8 mm in length
◦ Mandible: 5-6mm in length
◦ Driven 4-6mm into bone
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Indications of TAD
◦ In patients whose posterior teeth are missing
◦ As anchorage for distalization of molars
◦ For intrusion of maxillary teeth
◦ Anterior open bite and deep crossbites correction
◦ Sources of anchorage for retraction of canine and anteriors
◦ Correction of canted occlusal plane
◦ As an aid in treatment of class 3 malocclusion
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Applications of TAD
Maxillary intrusion using implants
placed over roots of maxillary molars
Implants on palate to gain
anchorage during distalization
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implants placed on interradicular
bone between maxillary 2nd
premolar and 1st molar for
retraction of anterior teeth
implants placed on retromolar
area of mandible for
anchorage when posterior
teeth are missing
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implants for intrusion of
anterior teeth for correction of
deepbite
implants placed to help
mesial movement of 2nd
molar when 1st molar is
missing
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Classification of
microimplants
According to
exposure of head
Open
method
Closed
method
According to method
of placing implant
Self Tapping
method
Self Drilling
method
According to path of
insertion
oblique direction
Perpendicular
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According to exposure of head
1. Open method
◦ head of microimplant is exposed to oral cavity
◦ used when implants are placed in area where soft
tissue are not movable e.g attached gingiva
2. Closed method
◦ head of microimplant is embedded under soft
tissue
◦ used when implant is placed in area where soft
tissue is movable
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According to method of placing the
implant
1. Self tapping method
◦ tunnel is drilled into bone
◦ implant is tapped in
◦ used for smaller diameter microimplants
2. Self drilling method
◦ implants drills itself into bone
◦ used for larger diameter microimplants
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According to path of microimplants
insertion
1. Oblique direction
◦ inserted diagonally at angle of 30-60
degree to long axis of tooth
◦ used in area where interradicular bone is
very narrow
2. Perpendicular
◦ inserted perpendicular to bony surface
◦ used if there is sufficient interradicular
bone
maxillary
mandibular
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Sites for placement of microimplants
Maxillary area
Mandibular area
◦ Maxillary tuberosity
◦ Retromolar region
◦ infrazygomatic crest area
◦ Buccally between mandibular 1st and
2nd molars
◦ bucally between maxillary 1st and 2nd
premolar
◦ Buccally between maxillary canine
and 1st premolar
◦ Labially between maxillary incisors
◦ Palatally between maxillary 2nd
premolar and 1st molar
◦ Buccally between mandibular 1st molar
and 2nd premolars
◦ Buccally between mandibular
premolars and canine
◦ Facially in symphyseal region
◦ Mid palatal area
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Complications of TAD
◦ Contact with adjacent roots
◦ Breakage of implant
◦ Damage to anatomic structures
◦ Soft tissue overgrowth
◦ Implant loosening
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For anchorage control.
◦ concentrate the force needed to produce tooth movement where it is desired,
◦ and then to dissipate the reaction force over as many other teeth as possible, keeping
the pressure in the PDL of anchor teeth as low as possible.
◦ Involving as many teeth in the anchorage unit as possible to distribute the force over a
larger root surface area
◦ Only moving one tooth at a time per quadrant
◦ Using a light force sufficient to move the tooth, but not large enough to move the
anchor unit.
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Anchorage planning
Anchorage requirement depends on following factors:
◦ Number of teeth being moved: greater the number of teeth greater demand on anchorage
◦ Type of teeth being moved: movement of slender anterior teeth offers lesser strain on anchorage
◦ Type of tooth movement: Bodily movement offers greater strain than tipping
◦ Duration of tooth movement: treatment of prolonged duration places undue strain on anchorage
◦ Skeletal pattern: vertical growth pattern- tendency for mesial tooth movement and anchorage loss
◦ Occlusal interlock: good buccal occlusion may act to resist tooth movement
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Classification of anchorage demand
1.Minimum Anchorage
2.Moderate Anchorage
3.Maximum Anchorage
4.Absolute Anchorage
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Loss of anchorage
Defined as unplanned and unexpected movement of anchor teeth during orthodontic
treatment
Causes:
◦ Poor appliance design
◦ Poor appliance adjustment
◦ Poor patient wear
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conclusion
◦ The success of an orthodontic treatment depends upon many factors, but without any doubt
one of them is anchorage control.
◦ If we do not have the anchorage that we need, this will lead us to certain failure, so it is very
important to apply all our knowledge in this subject during orthodontic treatment
◦ In planning orthodontic therapy, it is simply not possible to consider only the teeth whose
movement is desired.
◦ Reciprocal effects throughout the dental arches must be carefully analyzed, evaluated, and
controlled.
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Refrences
◦ Orthodontics the art and science- S.I. Bhalajhi
◦ Textbook of orthodontics- Gurkeerat Shingh
◦ Contemporary orthodontics- William R. Proffit
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Any Questions?
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Past questions
◦ What is anchorage? Mention reinforced of multiple anchorage
◦ Sources of anchorage during orthodontic treatment
◦ types of anchorage demand for extraction case
◦ Reciprocal anchorage
◦ Temporary anchorage device
◦ How do you plan anchorage in different cases of crowding?
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