WELCOME

Presented BySK. MD. Noman Rasel

Roll No: D-28Session: 2010-2011Dental Unit, R.M.C

ANCHORAGE & IT’S VARIANTS

ANCHORAGE & IT’S VARIANTS

• Submitted to׃ Dr. Anjuman Ara Akter LukyDr. A.K.M. Asad PalashDr. Shahina Soheli Sweety Department of Orthodontic Dentistry Dental Unit of R.M.C

Prepared by:Beckrom Munda Batch: 24th B.D.S.Roll No. : 42Session:2012-13

Definition:• According to Graber, Anchorage refers to the nature and

degree of resistance to displacement offered by an anatomic unit when used for the purpose of effecting tooth movement.

• According to Profit, Anchorage as resistance to unwanted tooth movement.

• So, in short we may define- Anchorage may define as the site from which a force is exerted.

Classification Of Anchorage:• Moyer has classified anchorage in the following ways—• According to manner of force application:

– Simple anchorage:• Single simple: when a tooth with a longer root area is used to move another tooth with a

smaller root area in the same dental arch. Compound simple: when a greater number of teeth are used to move a smaller number of teeth in

the same dental arch.

Stationary anchorage: resistance to bodily movement is called stationary anchorage. This type of anchorage can only be obtained by multiband technique such as, Edgewise appliance or Highly lower appliance.

Fig: Edgewise appliance

Reciprocal anchorage: when the two with an equal root area, or two similar group of teeth are used to move each other reciprocally to an equal extent (towards each other or in opposite direction). e.g.Finger spring to close midline diastema.

Fig: A. Finger spring. B. Correction of midline diastema using elastics. C. Cross bite elastics D. Coffin spring.

2)According to jaw involved: a) Intramaxillary (anchorage from the same jaw)b) Intermaxillary (anchorage from the both jaw) e.g.Baker’s anchorage.

Fig: Baker’s anchorage

According to site of anchorage: Intraoral: e.g. Baker’s anchorage.

Intramaxillary: SimpleStationaryReciprocal

Intermaxillary:SimpleReciprocal Stationary

b)Extra oral: e.g. head gear, chin cap.CervicalCranialOccipital

Facial

c)Muscular: Muscular force can be used for anchorage purpose.e.g. Vestibular shield, lip bumper.

4. According to number of anchorage units:Single anchorage:- anchorage involving one tooth.Compound anchorage:- multiple teeth involved. Reinforced anchorage:- e.g. transpalatal / lingual arch.

Fig: Transpalatal arch.

Sources of Anchorage:The sources of anchorage can be broadly classified into intra oral and extra oral.(1)Intra oral source:Teeth: The most frequently used anatomic unit for anchorage purpose. Anchorage resistance of a tooth depends on various factors like:

Number of roots.Shape of roots.Size of roots.Length of roots.

Palate: The vast expanse of palate provides a suitable source of anchorage mainly in removable appliances.Lingual alveolar supporting bone: provides tissue borne anchorage source for removable appliance.Cortical bone / cortical anchorage: The response of cortical bone when compared to medullary bone is different.Cortical bone offers more resistance to resorption.This principle is being used by rickets and is called cortical anchorageImplants as anchorage units: Recently microimplants are being used for anchorage purpose.Muscular anchorage: Muscular forces can be used for anchorage purpose. e.g. vestibular shield. g) Ankylosed teeth: Ankylosed teeth acts as a good anchor unit.2) Extra oral sources: Extra oral sites are used for extra oral appliances like-

Head gearReverse pull head gearChin cap

Cortical bone / cortical anchorage: The response of cortical bone when compared to medullary bone is different.Cortical bone offers more resistance to resorption.This principle is being used by rickets and is called cortical anchorage

Implants as anchorage units: Recently microimplants are being used for anchorage purpose.Muscular anchorage: Muscular forces can be used for anchorage purpose. e.g. vestibular shield. g) Ankylosed teeth: Ankylosed teeth acts as a good anchor unit.

2) Extra oral sources: Extra oral sites are used for extra oral appliances like-Head gear Reverse pull head gear Chin cap

Factors affecting anchorage:

Factors affecting anchorage can be considered under 2 headings-

Biological factor.Mechanical factor.Biological factors:Size of the anchor unit.Axial inclination of teeth.Delaying extraction of teeth.Use of optimum force.Differential force system.Abnormal muscular force.Teeth.

2.Mechanical factors:

1. Friction:

Most important mechanical factors is friction. Frictional resistance increases the strain on anchorage unit.brackets. Frictional resistance is low with stainless steel wire & brackets.

Type of tooth movement planned:Frictional resistance is more with bodily movement & during space closure.

Technique employed:It is more in sliding mechanics.

Maximum anchorage cases:In cases where the anchorage demand is very high, not more than 1/4th of the extraction space should lost by forward movement of the anchor teeth. Moderate anchorage cases:In these cases, the anchor teeth can be permitted to move forward into 1/4th to ½ of the extraction case. Minimum anchorage cases:In these cases, the anchorage demand is very low. More than half of the extraction space can be lost by the anchor teeth moving mesially.

Means to increase anchorage value: •Inter maxillary traction.•Inclined anterior bite plane.•Extra oral traction-occipital, occipito-cervical or cervical.•Toe-in and tip back bends & “apical torque” (for anterior anchorage) on arch wire so that anchor teeth can only move bodily.•Banding or using good number of teeth for anchorage or moving small number of tooth at a time.•Use of palatal & lingual arches.•Use of vertical springs on anchor teeth to encourage bodily movement only.

Causes of loss of anchorage:

oNot wearing the appliance adequately.oToo much activation of spring or active component.oPresence of acrylic or any obstruction on path of tooth movement.oPoor retention of appliance.oAnterior bite plane: as this withdraws the occlusal interlock.oAnchor root area not sufficiently greater than the root area of tooth or teeth to be moved.oIf appliance encourage tipping movement of anchor teeth & bodily movement of the teeth to be moved.

Signs of anchorage loss:

Mesial movement of molar.Closure of extraction space by movement of posterior teeth.Proclination of anterior teeth.Spacing of teeth.Increasing in overjet.Change in molar relations.Buccal crossbite of upper posteriors.

Prevention of anchorage loss:

•The anchorage loss may be prevented or reduced by the adoption of the following measures:•By moving minimum number of tooth at a time & using maximum number of teeth for anchorage.•By using gentle force, 30-50 grams per single rooted tooth.•By perfect fitting of the appliance around all the anchor teeth.•By taking the advantage of the principle of reciprocal movement whenever possible.•By encouraging the pt to wear appliance adequately.•If above measures are found inadequate, the anchorage may be reinforced by extra oral or inter maxillary traction.