anchorage in orthodontics part 1

8/13/2019 Anchorage in Orthodontics Part 1

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Anchorage In Orthodontics


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Introduction

Orthodontic tooth movement

Force

Active components???


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Introduction

Active components

Generate forcesIn one direction

Equal and opposite force

Newtons third law of motion


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Introduction

Desired tooth movement is inevitably asso with an

opposing force.

Anchorage units

Anchorage loss

Anchorage management


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Definitions

Moyers :

Resistance to displacement.

Active elements and resistance elements.

T.M. Graber :

The nature and degree of resistance to displacement offered by an anatomic unit when used for thepurpose of effecting tooth movement.


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Definitions

Proffit :

Resistance to unwanted tooth movement.

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.


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Definitions

Nanda :

The amount of movement of posterior teeth (molars,

premolars) to close the extraction space in order to

achieve selected treatment goals.

Reversal of anchorage


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Classification Moyers

Anchorage

Intraoral Extraoral

Cervical

Occipital

Cranial

Facial

Intramaxillary

Intermaxillary

Simple

Stationary

Reciprocal

Single

Compound

Reinforced

Muscular


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Classification

Nanda :

1.A anchorage: critical / severe

75 % or more of the extraction space is needed foranterior retraction

.

2.B anchorage: moderate

Relatively symmetric space closure (50%)

3. C anchorage: mild / non critical

75% or more of space closure by mesial movement

of posterior teeth


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Classification


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Classification

Burstone

Group A:Postr teeth contribute less than one quarterto total space closure

Group B:Postr teeth contribute from one quarter to

one half to total space closure

Group C:Postr teeth contribute more than one half tototal space closure


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Biologic Aspect Of Anchorage

Anchorage value

Teeth to be moved

Active components

Anchorage

Extraoral vs intraoral anchorage


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Factors affecting anchorage value

Force magnitude

Physiologic forceconcept

F/A


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Surface area Major determinant

Lower incisor vs molar anchorage

First principle of orthodontic anchorage


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For a tooth or group of teeth acting as anchorage

unit, pressure within the pdl should be kept as low

as possible

Heavy forces


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Pressure Response Curve for Anchor Teeth (A) andTeeth to be Moved (M)

Pressure in the PDL of A is less than the pressure in

the PDL of M


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2ndfactor pressure distribution

Single force vs force couple

Second principle of orthodontic anchorage


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Proffit

Tipping 50-75 gBodily - 100-150 g

Intrusion - 50-75 g

Extrusion - 50-75 g

Rotation - 50-75 g

Uprighting- 75- 125g


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Tooth which is free to tip has a less anchorage valuethan a tooth which is restricted in tipping by the

application of a force couple


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3rdfactor no. of roots and root morphology

Multirooted > single rootedLonger rooted > shorter rooted

Triangular shaped root > conical or ovoid root

Larger surface area > smaller surface area


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4thfactor neighbouring structures

Quality of the alveolar bone

Traumatic extraction

2ndmolars inclusion


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Soft tissues

Fixed app incorporating lip bumper

Palatal button


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Types of anchorage

Simple Anchorage:

Dental anchorage in which the

manner and application of force

tends to displace or change theaxial incl inationof the teeth

that form the anchorage unit in

the plane of space in which the

force is being applied.


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Types of anchorage

Stationary Anchorage:

Dental anchorage in which the manner and

application of force tends to displace the anchorageunit bodilyin the plane of space in which the force isbeing applied.

Refers to the advantage that can be obtained by

pitting bodily movement of one group of teeth againsttipping of another


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Types of anchorage

Eg: Retraction of

mandibular incisors

using first molars asanchorage

Considerably more than

Simple Anchorage


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Types of anchorage

Reciprocal Anchorage:

Anchorage in which theresistance of one or more dental

units is utilized to move one ormore opposing dental units

Dissipation of equal and

opposite forces

Diastema closure


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Types of anchorage

Correction of posterior cross bite through cross

elastics


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Types of anchorage

Close to reciprocal anchorage


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Types of anchorage

Multiple or ReinforcedAnchorage:

Multiple dental anchorage:

Reduces pressure on the anchorunits moving them down theslope of the pressure-responsecurve

Tissue - borne anchorage:


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Types of anchorage

Cortical Anchorage:

Torquing the roots ofposterior teeth outward againstthe cortical plate to inhibit their mesial movement


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Types of anchorage

Intramaxillry anchorage/ traction

Resistance units are situated within the same jaw


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Types of anchorage

Intermaxillary anchorage/ traction

Resistance units situated in one jaw are used to

effect tooth movement in the other jaw

Class II tractionClass III traction


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Palatal and lingual arches

Maintain intermolar widthRestrict mesial tipping

Correction of rotations


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Two couple orthodontic appliance system :

Transpalatal arches

Two bracket system

Cinched

Passive and rigid


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Transpalatal arches

Bilateral expansion


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Transpalatal arches

Bilateral constriction


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Transpalatal arches

Symmetrical V- Bend

Bilateral First order activations

(Mesiofacial Rotations)


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Transpalatal arches

Required in non-extraction T/t

To counter the M-Li rotations

produced by space closing forces

Before initiating head gear

therapy

Clinical uses


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Transpalatal arches

Mesiolingual Rotations

To decrease the arch perimeter

To close any remaining

posterior spaces

To seat the molar properly fora classII molar finish


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Transpalatal arches

Symmetrical V- Bend

Bilateral Second order

activations(M-D tipping)


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Transpalatal arches

Correction of unilateral classII dental malocclusion


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Transpalatal arches

Symmetrical V- Bend

Bilateral Third order activations

(Facial Root Torque)

To upright the molar roots


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Transpalatal arches

Asymmetrical V- Bend

Unilateral First order activations

(Mesiofacial Rotations)

Correction of unilateralclassII dental malocclusion


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Transpalatal arches


Unilateral First order

activations(Mesiolingual Rotations)

Unilateral Loss of molar anchorage is required


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Transpalatal arches


Unilateral Third order

activations(Facial Root Torque)

To correct the unilateral cross bites


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Transpalatal arches

Step bends


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Anchorage and choice of extraction


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Extra oral anchorage

H

E

AD

G

E

AR

S


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Principle use

Forces derived from EOA

Stabilize the position of the teeth

Produce tooth movement

Orthopedic changes

Extra oral anchorage Extra oral traction


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Mild cases

Cases with severe crowding and overjet

Severe cases additional space is required even after

extraction


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Application of EOF

Face bow


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Stops inner bow


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J hook head gear

fig


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Directional control

Effects of EOF depends on

Duration

Direction

Magnitude

1 ounce 30gms


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Types of head gears


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Basic concept for types of head gears


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Relationship to the occlusal plane

Low pull

High pull

Medium pull


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Low pull head gear

Extrusion of the molars


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undesirable


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High pull head gear


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Intrusion of the molars undesirable


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Medium pull head gear


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Protraction head gear


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Orthopedic effects

Restrict forward and downward movement

350-450 gms/each side 14hrs/day


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Practical aspects

Good fitting bands

Inner bow passiveShould not contact any teeth

Ant. Segment between the lips

Expansion distalization


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Mandibular arch

Use of class III intermaxillary traction with head gear


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Mechanical aspect of anchorage

Sliding mechanics

Force is required for 2 purposes

Bone remodeling

Frictional resistance

Control l ing and minimizing fr iction is an imp. Aspect

of anchorage control


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Friction ???

Frictional force

Nature of surface at the interface (rough or smooth,

chemically reactive or passive, modified by

lubricants)

Independent of the apparent area of contact


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Metal wire in a ceramic bracket

Stick slip phenomenon


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2 other factors can affect the resistance to sliding

Interlocking of surface irregularities

Extent of plowing

I n clinical practice fr iction is largely determined by

the shearing component

anchorage in orthodontics part 1

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