ANCHORAGE - dental.subharti.orgdental.subharti.org/orthodontics/ANCHORAGE.pdf · INTRAORAL...

ANCHORAGE DEPARTMENT OF ORTHODONTICS

SUBHARTI DENTAL COLLEGE

SWAMI VIVEKANAND SUBHARTI UNIVERSITY

Presented By:

Dr Amit Khera

NEWTON’S third law of motion :

“ Every action has an equal and opposite

reaction.”

Dr Amit Khera, Subharti Dental

College, SVSU


College, SVSU

DEFINITIONS

GRABER defined Anchorage as the nature and

degree of resistance to displacement offered

by anatomic unit for the purpose of effecting

tooth movement.

.


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According to PROFFIT Anchorage is resistance

to unwanted tooth movement.

MOYERS defined Anchorage as resistance to

displacement


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CLASSIFICATION

1. According to the manner of force

application :

a. Simple Anchorage

b.Stationary Anchorage

c.Reciprocal Anchorage

2.According to jaws involved

a.Intramaxillary

b.Intermaxillary


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According to site of Anchorage:

1. Intra oral

2.Extra oral:

a.Cervical

b.Occipital

c.Cranial

d.Facial

3. Muscular


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According to number of anchorage units:

a.Single or primary anchorage

b.Compound anchorage

c.Multiple or reinforced anchorage


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SIMPLE ANCHORAGE

Resistance to tipping, that is tooth is free to tip during movement.

Here application of force tends to change the axial inclination of the tooth or teeth that form the anchorage unit. Thus the resistance of the anchorage unit to tipping is utilized to move another tooth or teeth.


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STATIONARY ANCHORAGE Dental anchorage in which the manner &

application of force tend to displace the

anchorage unit bodily in the plane

of space in which the force is being applied.


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STATIONARY ANCHORAGE

Resistance to bodily movement, that is

the tooth is permitted to translate only

Dental anchorage in which the manner

& application of force tends to displace

the anchorage unit bodily


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RECIPROCAL ANCHORAGE Two or more teeth moving in opposite directions and pitted

against each other by the appliance. Usually, the resistance to

each other is equal and opposite.

Examples

- Closure of midline diastema

-use of cross bite elastics

-Arch expansion using a removable appliance incorporating a

screw

Anchorage obtained outside the oral cavity.


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College, SVSU

INTRAMAXILLARY

ANCHORAGE Anchorage in which resistance units

are all situated within the same jaw.

Eg. A rapid expansion device

employing the teeth of the same jaw as

anchorage units


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INTERMAXILLARY

ANCHORAGE

Anchorage in which the

resistance units situated in

one jaw are used to effect

tooth movement in the other

jaw.

It is also termed BAKER’S

ANCHORAGE. E.g class II

and classIII elastic traction

to treat inter arch

discrepancies.


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INTRAORAL ANCHORAGE

Anchorage in which all the resistance units are

situated within the oral cavity.The teeth to be

moved and the anatomic areas that offer

anchorage are all within the oral cavity.Various

intra oral anatomic units that maybe employed

are the teeth,palate and lingual alveolar bone of

mandible.


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EXTRAORAL ANCHORAGE

Cervical – Utilizing the neck for anchorage (e.g., neck straps)

Occipital – Utilizing the occipital region for anchorage (e.g., head gears)

Cranial – Involving the cranium as a source of anchorage (e.g high pull head gears)

Facial – Involving aspects of the face as a source of anchorage (e.g. face masks)


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HEAD GEAR

CLASSIFICATION

Cervical

Occipital

Combination


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MUSCULAR ANCHORAGE

Anchorage in which the perioral

muculature is employed as

resistance units. E.g. Lip bumper

deriving anchorage from the perioral

musculature.


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SINGLE OR PRIMARY

ANCHORAGE

Resistance provided by a single

tooth with greater alveolar support

is used to move another tooth

with lesser support.


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COMPOUND ANCHORAGE

Anchorage where the resistance

provided by more than one tooth

with greater support is used to move

teeth with lesser support.


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THE SOURCES OF ANCHORAGE

Orthodontic tooth movement is produced by

forces that are derived from active

components of orthodontic appliances.

These employ anchorage that can be:

1. INTRAORAL

2.EXTRAORAL


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INTRORAL SOURCES

ALVEOLAR BONE

TEETH

BASAL BONE

MUSCULTURE


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ALVEOLAR BONE

When force is applied to move a tooth

rearrangement of alveolar trabaculae

occurs to offer resistance to the force. In

an ideal anchorage situation the

reactive force is distributed over enough

root surfaces to cause only this

rearrangement, beyond which the bone

yields, permitting tooth movement.


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TEETH

The teeth themselves can resist

movement although this ability

varies greatly due to variations in

the form, size, number, length,

position & inclination of the roots.


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ROOT FORM

Root cross sections can be of three types:

1. Round

2. Flat

3. Triangular

ROUND ROOTS as seen in bicuspids & palatal root of maxillary molars, can tense only 50% of their periodontal ligament fibers to resist a horizontally directed force & its resistance is the same in any direction.


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FLAT ROOTS, for examples those of mandibular incisors, and molars and the buccal roots of maxillary molars can resist movements in the mesiodistal direction but have little resistance to movement on their edges found on the buccal and lingual sides

TRIANGULAR ROOTS of canines and maxillary central and lateral incisors permit tensing of 2/3rd of their PDL fibers when pushed and the moderately flat surface on one side adds to the resistance.


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SIZE AND NUMBER OF

ROOTS

Multirooted teeth with large roots have

greater ability to withstand stress since

the greater surface area has more

number of PDL fibers and hence

increases its stability.


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ROOT LENGTH

The root length indicates the depth to

which it is embedded in bone and the

deeper it is embedded the stronger is its

resistance to dislodgment.


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POSITION OF TOOTH IN THE

ARCH

Position of the tooth in the arch may be

significant as in the case of the mandibular

second molar which is located between two

high ridges of basal bone mesial to the

retromolar fossa I.e the mylohoid line and

external oblique ridge.

Due to its position it offers more resistance to

bodily mesial movement than any other tooth

in the mouth..


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INCLINATION OF ROOTS

The axial inclination is important in assessing

the value of a tooth as a source of

anchorage.

A greater resistance to dislodgement is offered

when the force is opposite to the axial

inclination. As the force is partly expended

down the axis of the root to the underlying

bone, more of the tooth’s PDL fibers are

tensed causing the roots to dig in.


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MUTUAL SUPPORT In addition to the above mentioned factors

contributing to the anchorage potential of teeth, the mutual support offered by their relationship to other teeth in the arches should be considered.

Each tooth with the exception of the terminal molars are supported by contact with another on either side. In addition the entire mandibular arch is confined by the maxillary arch buccally.

Teeth mutually supporting each other can best contribute to the over all resistance value when they are in line because the reactive force can pass in a relatively straight line through the contact points and receive maximal support from each tooth.


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ANKYLOSED TEETH

Ankylosed teeth are directly fused to the

alveolar bone and hence the absence of

the PDL does not permit them to be

moved orthodontically. They can thus

be used as sources of anchorage

whenever possible.


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BASAL BONE

Certain areas of the hard basal bone available

intraorally as sources of anchorage providing

stability of the immobile type.

These areas such as hard palate and lingual

surface of the mandible in the region of the

roots augment intramaxillary or intermaxillary

anchorage.


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MUSCULATURE

The normal tonus of the facial and masticatory muscles exert pressure on the dentition to equalize pressures form within and has an important part in moulding the form of the dental arches.

In addition abnormal musculature tone also has its effects hypotonic muscles permit flaring and spacing of teeth while hypertonic muscles exert forces in a lingual direction.

The stability of the anchorage of a dental arch may be increased by temporary utilization of hypertonic labial musculature


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EXTRAORAL SOURCES

In most instances, extraoral anchorage

is used in cases where the resistance

offered by intraoral sources is

insufficient to effect tooth movement.


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Extraoral anchorage can be used to:

Stabilize the position of teeth. For

example, a distallty directed extraoral

force applied to upper first molars

prevents their mesial movement.

Produce mesiodistal, vertical and angular

changes in tooth positions.

Produce an orthopedic change.


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The various extraoral sources include

various areas of the head and face such

as:

Cervical region

Occipital

Parietal region

Frontal region

Chin region


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The appliances that employ extraoral anchorage are head gears and face masks.Head gears derive anchorage either from the cervical, occipital, parietal regions or a combination of these.

Face masks derive anchorage from the chin or forehead region or both.

The variables associated with the use of extraoral appliances necessitates the understanding of their mechanical action. The mechanics involved are related to their duration, magnitude and direction and careful consideration must be given to them to achieve desired results.


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ACHORAGE

REINFORCEMENT

The process of increasing the Anchorage value of the reactive segment to resist anchorage loss.So the reaction force is distributed over a larger PDL area which reduces the pressure on anchor units.

This can be done in a number of ways

By inorporating more teeth into reactive segment

Transpalatal arch

Lingual arch

Nance holding arch

Extraoral or intermaxillary traction.


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TRANS PALATAL ARCH

Extends from one maxillary first molar along

the contour of the palate to the molar on the

opposite side

Removable

Fixed Dr Amit Khera, Subharti Dental

College, SVSU

NANCE PALATAL BUTTON

INDICATIONS

Class I, crowding cases

To hold the maxillary expansion achieved by

expansion appliances

CONTRAINDICATION

Class II maxillary protrusion cases Dr Amit Khera, Subharti Dental

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LOWER LINGUAL ARCH

Similar functions like TPA

Indications

Class I crowding

Class III patients


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ANCHORAGE CONTROL

Anchorage control is done in three planes

1. Horizontal

2.Vertical

3.Transverse


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HORIZONTAL ANCHORAGE CONTROL means limiting the mesial movement of the posterior segment while encouraging distal movement of the anterior segment. It is done by:

UPPER ARCH: Head gears, Transpalatal arch, Nance holding arch.

LOWER ARCH: Lingual arch, ClassIII elastics,Lipbumper.


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VERTICAL ANCHORAGE CONTROL involves the limitation of the vertical skeletal and dental development in the posterior segments and the limitation of the vertical eruption of, or even intrusion of the anterior segments.It is done by

Upper second molar banding to be avoided initially(in high angle cases)

Expansion if required should be achieved by bodily movement of the posterior teeth(in high angle case.


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Transpalatal arch should be 2-3 mm away

from the palate.

High pull or combi pull headgear to be

used.

Posterior bite planes or bite blocks.


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TRANSVERSE PLANE MOLAR CONTROL comprises the maintenance of expansion procedures, primarily in the upper arch, and he avoidance of tipping or extrusion of the posterior teeth during expansion. It is done by:

Rapid maxillary expander

Quad helix or Transpalatal arch.


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ANCHORAGE LOSS

The undesirable movement of the

reactive anchorage segment,which

happens as a side effect of the

movement of the active segment.


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MAXIMUM ANCHORAGE

In cases where the anchorage demand is very high, not more than 1/4th of the extraction space should be lost by forward movement of the anchor teeth. The anchorage in these patients should be augmented to avoid unwanted movement of the anchor teeth.


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MODERATE ANCHORAGE

In these cases,

anchor teeth can be

permitted to move

forward into 1/4th to

1/2 of the extraction

space.


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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.


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IMPLANTS :

Impacted titanium posts:

Bousquet and Mauran (1996)

Post impacted between upper

right first molar and second

premolar extraction space on

labial surface of alveolar process

Perpendicular to bone surface


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Molar connected to

implant with 0.040 ss

wire


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College, SVSU

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