Anchorage

ANCHORAGEDr.Enas Talb

DEFINITION

* Anchorage in orthodontics as the nature and degree of resistance to displacement offered by an anatomic unit for the purpose of tooth movement.


according to Newton's Third Law of Motion“To every action there is an equal & opposite reaction” ANCHORAGE = resistance to unwanted tooth movement.ANCHORAGE UNITS : The areas or units which provide this undesirable movement.

Each orthodontic appliance consists of two elements Anchor Unit Moving Unit

Intra-oral { Extra-oral {
Intra-maxillary
Inter-maxillary
[
Simple Anchorage Stationary Anchorage Reciprocal Anchorage
{
Single Compound Reinforced
Cervical Occipital Cranial Facial
Types of Anchorage
Space Availability {
Minimum Anchorage Moderate Anchorage Maximum Anchorage Absolute Anchorage

Classification of Anchorage

Manner of Force Application Simple Anchorage Stationary Anchorage Reciprocal Anchorage

Simple Anchorage

When the manner & application of force is such that it tends to change the axial inclination of the tooth or teeth that form the anchorage unit in the plane of the space in which the force is applied. ((Resistance to tipping)) Simple anchorage is obtained by engaging a greater number of teeth than are to be moved

Stationary Anchorage

When the application of force tends to displace the anchorage unit bodily in the plane of space in which the force is being applied. (( Resistance to bodily movement)) The anchorage potential of teeth being moved bodily is considerably greater as compare to teeth being moved using a tipping force.

Reciprocal Anchorage

When two teeth or two sets of teeth move to an equal extend in an opposite direction . Here the root surface area of the anchorage unit is equal to that of the teeth to be moved. The effect of the forces exerted is equal.

Classification of Anchorage

According to Jaw Involved Intra-maxillary Inter-maxillary

Intra-maxillary

teeth are to be moved and the anchorage units are in the same arch ( either maxilla or mandible ) Eg.Elastic chains are used to retract the anterior segment using the posterior teeth as anchorage unit. Eg.TPA SUB DIVISION : Simple Stationary Reciprocal

Transpalatal Arch

Lingual Arch

Inter-maxillary
Also called “Baker’s anchorage”Teeth are to be moved in one arch and resistance units are in opposite archEg:-class ii ,class iii elasticsSUB DIVISION :SimpleStationaryReciprocal

Classification of Anchorage

According to Site Involved Intra-oral Extra-oral Cervical Cranial Facial Muscular

Intra-oral

The anchorage units lie within the oral cavity. They include:• The alveolar bone• The teeth• The basal bone• The cortical bone• The musculature

Extra-oral

(anchorage obtained from outside mouth) Cervical Occipital Facial Muscular


1)cranium(occipital anchorage):-anchorage obtained from occipital bone eg:-head gear to restrict maxillary growth 2)cervical:-anchorage from cervical or neck region eg:-cervical head gear 3)facial bones:-face mask used to protract maxilla take anchorage from forhead and chin 4-musculature:hypertonic labial musculature used for anchorage in lip bumper

High Pull Headgear

Cervical headgear

Face Mask

Lip Bumper

Classification of Anchorage
According to Number of Units Single or Primary Anchorage Compound Anchorage Reinforced Anchorage

Single or Primary Anchorage 

The resistance provided by single tooth with greater alveolar support is used to move another tooth with lesser alveolar support. Eg. Molar being used to retract a premolar

Compound Anchorage

The resistance is provided by more than one tooth with greater support is used to move teeth with less support. Eg. Retracting incisors using loop mechanics

Reinforced Anchorage

The anchorage units are reinforced by the use of more than one type of resistance units. Anterior inclined plane Exerts a backward pull On the maxillary appliance through the mandible.


SVED BITE PLANE : Prevent from being inclined labially. A rigid labial bow : To engage labial surface of the incisor at the junction of cervical & medial third of each crown.

Banding of 2nd molar for the retraction of permanent canine.

Classification of Anchorage
According to Space Available Minimum Anchorage

Moderate Anchorage Maximum Anchorage Absolute Anchorage

Minimum Anchorage 
2/3rd space utilized by the movement of anchor unit

Moderate Anchorage

1/2 space utilized by the movement of anchor unit & remaining 1/2 by the movement of moving unit

Maximum Anchorage

Absolute Anchorage
Absolutely no movement of anchor unit e.g. Implants


Classification of Anchorage
Mini implants :Miniscrews are designed to mechanically retains into bone and not to undergo osseointigration for their easy removal. They should be preferably self drilling to make placement procedure simple. The design provide provision for attachment of orthodontic spring or auxiliary or bracket head to receive an archwire.

Implants have become one of the best sources of reliable anchorage.

Factors affecting anchorage
1-Teeth:When one teeth moves the others can act as anchorage units, it depends on -Root form -Root size -No. of roots -Root length -Root inclination

Root form: different root form like,Round – resistance is same in any direction Flat – resist tooth movement in M-D direction eg. mand. Incisors & molars , buccal roots of max. molars ( tripod arrangement of roots )Triangular – offers greater resistance to movement. Eg. Maxillary canine & lateral incisor

Size and number of roots: Multirooted teeth and large surface area >Anchorage Root length;-directly proportional to anchorage Axial inclination;-anchorage is more when force exerted is opposite to that of axial of inclination of teeth

2-Alveolar bone: Alveolar bone resist tooth movement up to its limit, beyond that it allow tooth movement by remodeling. Healthy alveolar bone-more anchorage

3-basal bone: Certain areas act as resistance areas-provide good anchorage like hard palate, lingual surface of mandible

Anchorage planning

Depends on : - The number of teeth to be moved The type of teeth to be moved Type of tooth movement Periodontal condition Duration of tooth movement

Anchorage value can be improved

Incorporate as many teeth as possible in anchorage unit Reduce number of teeth in moving unit Use of anchorage bends Reduce the force applied to the optimal for producing the required tooth movement Reinforce intra-oral anchorage with extra-oral anchorage Use of palatal or lingual arch Use of intra/inter maxillary elastics Use of lip bumper------anchorage from musculature Cortical anchorage

Anchorage to be Considered

In Antero-posterior plane (Anchorage loss appears in the form of movement of anchor unit in antero-posterior plane e.g. bodily mov. or tipping) In Vertical plane (Anchorage loss appears in the form of extrusion of molars or Tip back of molars so care must be taken when planning to treat High angle cases) In transverse plane (anchorage loss in the form of buccal flaring)