Fixed orthodontic Appliance

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Fixed appliance

By Khalil Raziq


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Definition

An appliance fixed to teeth by attachments

through which force application is by

archwires or auxiliaries.


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indications

1)Correction of mild to moderate skeletal

discrepancies :As fixed appliances can be used

to achieve bodily movement it is possible,

within limits, to compensate for skeletal

discrepancies and treat a greater range of

malocclusions.


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indications

2)Intrusion/extrusion of teeth Vertical

movement of individual teeth, or tooth

segments, requires some form of attachment

on the tooth surface onto which the force can

act.

Intrusion/extrusion of teeth Vertical

movement of individual teeth, or toothsegments, requires some form of attachment

on the tooth surface onto which the force can

act.


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Indications

3)Correction of rotations

4) Overbite reduction by intrusion of incisors

5) Multiple tooth movements required in onearch


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Indications

6) Active closure of extraction spaces, or

spaces due to hypodontia :Fixed appliances

can be used to achieve bodily space closure

and ensure a good contact point between the

teeth.


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fixed appliances should only be embarked upon

in patients who are willing to:

1)maintain a high level of oral hygiene;

2)avoid hard or sticky foods and the

consumption of sugar-containing foodstuffs

between meals;

3)cooperate fully with wearing headgear or

elastic traction, if required;

4)attend regularly to have the appliance

adjusted.


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components

1)Bands

2)Bonds

3)orthodontic adhesives 4) Auxiliaries

5)Archwires

6)


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components

Bands:These are rings encircling the tooth to

which buccal, and as required, lingual,

attachments are soldered or welded.

It was very popular before the acidetching

techniques were introduced

Now its rarely used except in molars where

band remain in situ if the cements fails


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Bands

A lower first permanent molar band. Note the

gingivally positioned hook, which is useful for

applying elastic traction


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Bands

Bands can be used on teeth other than

molars, most commonly following the failure

of a bonded attachment or where de-rotation

or correction of a crossbite dictate the need

for both lingual and buccal attachments.

However, this must be balanced against the

poorer aesthetics of a band (look at thyephoto below)


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Fixed appliance case where bands have been used for the canines, premolars

and molar teeth. The impact of bands upon the aesthetics of the appliance can

be readily appreciated


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Prior to placement of a band it may be necessary to

separate the adjacent tooth contacts. The most

widely used method involves placing a small elastic

doughnut around the contact point


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Bonds

2)Bonds:Bonded attachments were

introduced with the advent of the acid-etch

technique

Adhesion to the base of metal brackets is

gained by mechanical interlocksite


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Brackets for bonding showing a mesh base which

increases the surface area for mechanical

attachment of the composite


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A patient with ceramic brackets on the upper anterior teeth.


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Orthodontic adhesives

The most popular cement for cementing bands isglass ionomer ,mainly because of its fluoride-releasing potential and affinity to stainless steeland enamel. Glass ionomers can also be used for

retaining bonded attachments, but unfortunatelythe bracket failure rate with this material isgreater than that with composite. Much currentresearch work is directed towards hybrid

compomer materials which it is hoped willcombine the advantages of composites and glassionomer adhesives.


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Orthodontic adhesive

Glass ionomer cement.


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Use of the acid-etch technique with a compositeproduces clinically acceptable bonded attachmentfailure rates of the order of 510 per cent for both self-and light-cured material.Following this, a small amount

of the composite itself is applied to the bracket, whichis then placed on the tooth surface under pressure.Squeezing the sandwich of composite and catalyst intoa thin layer mixes the two components, and the

material usually sets within a few minutes. s


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No-mix composite for orthodontic bonding


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Auxiliaries

Elastics or elastomeric

modules/chain/thread springs.


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Coloured elastomeric modules

used to secure the archwire into

the bracket slot.


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This patient's upper archwire has been

tied into place with wire ligatures in the

upper arch and with elastomeric modules

in the lower arch


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Head gears


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A palatal arch, which is used to help provide additionalanchorage in the upper arch by helping to resist

forward movement of the maxillary molars.


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Archwires.

These may be round or rectangular.

in treatment round active wire is used initially Usually, rrectangular passive wire with

auxiliaries is used later

Th h i l ti f h i


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The physical properties of an archwirematerial which are of interest to the orthodontist are

as follows. Springback:This is the ability of a wire to return

to its original shape after a force is applied. Highvalues of springback mean that it is possible to tiein a displaced tooth without permanent

distortion. Stiffness: The amount of force required to deflect

or bend a wire. The greater the diameter of anarchwire the greater the stiffness.

Formability: This is the ease with which a wirecan be bent to the desired shape, for example theplacement of a coil in a spring, without fracture.


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Resilience :This is the stored energy availableafter deflection of an archwire withoutpermanent deformation.

Biocompatibility Joinability: This is whether the material can be

soldered or welded.

Frictional characteristics :If tooth movement isto proceed quickly a wire with low surfacefriction is preferable.


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archwires

The most popular archwire material is stainless steel which is

available in straight lengths, as a coil on a spool, or pre-formed into

archwires.


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Material varies eg. Nickel Titanium alloy

(NiTi), Titanium Molybdenum Alloy (TMA),

Stainless Steel


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Appliance types

Most common pre-adjusted appliances: 1)Edgewise.: Uses an individual bracket with a

rectangular slot for each tooth to give it 'average'

i nclination and angulation and to allow placement

of flat archwires. Bracket prescriptions described

by Andrews and Roth are available.

2)Tip-edge. :Based on the Begg philosophy but the

narrow brackets also have preadjusted values to

allow the placement of rectangular wires in the

final stages of treatment


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3)Lingual appliance: Uses brackets bonded to the lingual/palatal

surfaces of the teeth and specially configured

archwires. Aesthetic, but uncomfortable for the

patient and difficult to adjust.

4)Sectional appliance:

Components are attached to teeth in (usually) one

segment of the arch, normally for localised

alignment as part of adjunctive treatment,

especially in adults


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5)Fixed

removable:

URA with bands cemented to _6s for extraoral

traction bracket bonded to a rotated

incisor and whip spring hooked to labial bow for derotation; bracket bonded to a favourably

inclined

palatal canine and traction applied from thebuccal

arm on the appliance to the bracket via elastic


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Preadjusted edgewise appliance


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Tip edge appliance


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URA with bands on 6s for extraoral

traction


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Reference

1) An Introduction to Orthodontics , 2nd

Edition by laura mitchelle

2)orthodontics and paediatric dentistry by

declan millet, richard wulbery

3) Kapila, S. and Sachdeva, R. (1989).

Mechanical properties and and clinical

applications of orthodontic wires


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Fixed orthodontic Appliance

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