self ligating brackets by almuzian

UNIVERSITY OF GLASGOW

Self-Ligating Brackets

Personal notes

Mohammed Almuzian

1/1/2013

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Table of Contents

Definition........................................................................................................2

History and past failings..................................................................................2

Factors which have hindered the adoption of self-ligation.............................2

Commonly used SL system.............................................................................3

Properties of an Ideal Ligation System...........................................................6

A. Primary properties.....................................................................................6

B. Secondary features....................................................................................7

Advantages of self-ligating brackets...............................................................7

Disadvantages of the conventional ligation system......................................13

Clinical significance of low friction..............................................................13

The following treatments are not influenced by a low-friction method of

ligation:.........................................................................................................15

Variables which could influence friction......................................................15

Methods to reduce friction in conventional bracket system..........................17

Active or passive ligation..............................................................................17

Clinical tips when using self-ligating brackets, Harradine (2003)................18

Mohammed Almuzian, University of Glasgow, 2013 Page 1

Self-Ligating Brackets

Definition

Self-ligating brackets have an in-built metal face, which can be opened and

closed.

History and past failings

1. The Russell Lock edgewise attachment first described by Stolzenberg

(Russell Lock edgewise attachment) in 1935 was the early examples of self-

ligating brackets were prone to breakages and inadvertent opening

2. New designs continue to appear, with at least twenty four new brackets since

2000.

3. Ormco have recently developed the Damon (passive) system and GAC have

developed the (active) In-Ovation system.

Factors which have hindered the adoption of self-ligation

1. Design and manufacture imperfection.

2. An inherent conservatism amongst orthodontists


3. Lack of widespread appreciation of what low friction, secure archwire

engagement and light forces can achieve

Commonly used SL system

Passive system

Damon SL

brackets

Available in 1996

They had a slide which moved vertically

on the labial surface of an otherwise

fairly conventional twin tie-wing bracket.

Problems: irritating problems and the

slides inadvertently opened and were

prone to breakage.

Damon 2 Placed the slide within the shelter of the

tie wings

Metal injection moulding manufacture

Narrower bracket with the consequent

advantages of a larger inter-bracket span

Damon MX

brackets

Same like D3 but metal

They have a vertical slot behind the

archwire slot into which prefabricated

click-in auxiliary hooks can be added to

any bracket as required and removed


when no longer needed.

Damon Q

brackets

Easier slide,

Immune to the effects of calculus

accumulation.

A clever feature is the reciprocal nature

of the opening forces which leaves

almost no net force on the tooth and the

slide is opened.

The brackets are also smaller in all

dimensions than their predecessors and

space has been found for a horizontal as

well as a vertical auxiliary slot

SmartClip

bracket

Active system

In-Ovation

GAC

SPEED

bracket


Activa

Aesthetic system

In-Ovation C

Damon 3 A tooth-coloured composite resin

base and upper tie-wing which

reduces the visual impact of the

bracket

A rhomboidal shape of the bracket

and slide which facilitates bracket

siting

robust slide

Problems

a high rate of bond failure,

separation of the metal from the

reinforced resin components

fractured resin tie-wings

Damon Clear Same as Damon Q but ceramic

Lingual system


the Philippe

bracket

Adenta LT

brackets

Properties of an Ideal Ligation System

A ligation system for attaching orthodontic wire to brackets should have the

following:

A. Primary properties

1. Inexpensive

2. Biocompatible material

3. Assist good oral hygiene and patient comfortibility.

4. Be quick and easy to use.

5. Be secure and robust.

6. Ensure full bracket engagement of the archwire.

7. Exhibit low friction between the bracket and the archwire.


B. Secondary features

1. Good bond strength and smoothness of contour

2. Easily placed. However a prospective study by Hunt et al 2012 found that

placement accuracy of self-ligating bracket is 10 times less than

conventional bracket especially in term of horizontal and vertical positioning

while the rotational positioning is the same in both gps. (keeping in mind the

tolerance limit described by Andrews 1980 which should be 0.5mm error in

H and V as well as 2 degree error in rotational position.

3. Be tolerant of a reasonable excess of composite material without

obstructing the clip/slide mechanism

4. Withstand the force of torque with minimal plastic deformation (Damon

QH and In-Ovation RH maintain high levels of resistance to plastic

deformation. Speed demonstrates the most plastic deformation with visually

identifiable warping in the bracket slot. (Major 2012)

5. Permit easy attachment and removal of all the usual auxiliary components

6. Have a suitably narrow mesio-distal dimension.

Advantages of self-ligating brackets

Point With Against


All these has been

summarized in a

systematic article by

Fleming et al in 2010 and

Chen et al 2010

Improved

movement

control by

Secure and

robust

ligation

An example of that is the

molar tube.

If a convertible molar

tube is converted to a

bracket by removal of

the slot cap or straps, an

elastomeric or even a

wire ligature can prove

very ineffective at

preventing rotation of the

tooth if it is moved along

the wire.

This can maximises the

potential long range of

action of modern low

modulus wires and

minimises the need to

regain control of teeth

where full engagement is

lost during treatment due


to degradation as in

elastomeric modules.

Wire ligatures are good

in this respect, whilst

elastomeric ligatures are

much less good, The

force decay of

elastomerics has been

well documented

(Taloumis et al 1997).

Less

chairside

assistance

and faster

archwire

removal and

ligation

Harradine 2001, SL

brackets reduce

placement time of an

archwire by 24 sec per

wire.

Bernie 2005 have shown

that wire ligation is very

slow compared to

elastomerics, the use of

wire ligatures added

almost 12 minutes to the

time needed to remove

and replace two

archwires.

In a meta-analysis by Chen

2010 reported mean time

savings of 20 seconds per

arch. This considered

insignificant and would not

make many operators

change their practice.


Assist good

oral hygiene.

Elastomerics accumulate

plaque more than do tie-

wires

The ends of wire ligatures

are however an additional

obstacle to oral hygiene.

The bacteriology results

slightly favoured wire

ligation, the important sign

of bleeding on probing was

substantially higher with

elastomeric ligation.

Turkkahraman et al (2005)

Patient

comfortibility

Mills (2006) in a split mouth

study found lower pain levels

with Damon 2 brackets during

the alignment phase, although

opening the brackets was more

uncomfortable than removing

elastomerics.

Pain during alignment

stage is similar between

victory, Damon and smart

clip (Fleming 2008, Scott

2009) even SL has worse

pain level in replacing

19*25 NITI with ss.

Low friction

between

bracket and

wire with

The low friction and low force

philosophy claimed to be the

cause

NO difference in time

or efficiency during

initial alignment


associated

rapid

treatment,

Better

treatment

quality and

outcomes and

less root

resorption

1. Rapid movement,

2. Little proclination

3. Less anchorage demand

4. Better arch development

5. Wider arches which may

be more aesthetic

6. Wider arches which have

better periodontal health

than those resulting from

more rapid and forceful

expansion

7. Less need for extractions

8. Easier class 2 correction

through a ‘lip-bumper’

effect

9. Better stability.

10.Less root resorption.

11.

Study to support this done by

Harradine 2001 , Treatment

time with SL brackets was on

according to Mills 2005

, Scott 2008, Fleming

2009, Pandis 2011,

Eliades 2008. This

result in upper and

lower arch similar.

During Enmass space

closure as (no

difference in time or

efficiency)) according

to Mills 2007

During canine

retraction (no

difference in time or

efficiency) according to

Mezomo 2011

Overall treatment

duration, Fleming 2010,

DiBiase 2011,

Johannson 2012 no

difference

PAR index improvement

(no difference) DiBiase et


average 4 months shorter than

conventional brackets. The

mean number of visits was

reduced from 16 to 12 per

patient.

al 2011, Johannson 2012

Harradine 2001, SL and

conventional systems

produced the same PAR

reduction.

Regarding the maxillary

arch width, Fleming in

2013 did a study where he

randomized a sample of 96

patients aged 16 and above

to treatment with a passive

self-ligating bracket, an

active self-ligating bracket

and a conventional system.

Importantly, they removed

the effect of archwires by

using the Damon archwire

sequence for all patients.

They found no difference

and the expansion is

related to the wire not the

appliance.

However I should be

remembered that the

Damon bracket are thicker


than conventional one

which should be

considered in the analysis

of Fleming study in 2013

A Cochrane review under

protocol by Smith and

Bearn 2009 to assess the

claims of self-ligation

system

Songra 2014 SL is worse

than conventional

Disadvantages of the conventional ligation system

1. Fails to provide and maintain full arch wire engagement.

2. High friction.

3. Elastomerics exhibit force decay and loose tooth control.

4. Impede oral hygiene.

5. Wire ligation is slow.(Wire ties have lower friction and engage the archwire

fully in the bracket, however they are awkward to use and time consuming.)

Clinical significance of low friction

Rapid movement: With elastomeric ligation, a higher forces must therefore

be applied to overcome the resistance produced by friction and this is more


likely to be undesirably higher than levels best suited to create the optimal

histological response resulting in slow movement.

Less anchorage demand: With low friction, the net tooth-moving forces

can be more predictably low so there will be less anchorage loss. A recent

study by Yee et al (2009) measured canine retraction and anchorage loss

with a light (50 gm) and heavy (300 gm) forces. The percentage of

anchorage loss was significantly higher (62%) with the heavy force than

with the light force (55%).

Little proclination and better arch development: Light forces aid in that

the forces from the soft tissues can compete with the force from the wire.

For example it has been proposed that the lips can restrain labial movement

of the incisors and that the alignment of crowded teeth on a non-extraction

basis will result in more lateral arch expansion and less labial incisor

movement than would be the case with heavier forces and higher resistance

to sliding.

Better stability: Further, it been claimed that expansion brought about by

such light forces is more likely to achieve an archform which is in balance

with the tongue and cheeks and can establish a wider arch which will be

relatively stable because of altered tongue position.


Factors involved in increasing resistance to sliding

1. Friction (depend on material, saliva, cross section, size of wire and slot)

2. Binding which depend on the degree of slop (above 6 degree bending, the

binding will starts) Kusy 2003

3. Notching (depend on the stiffness of the material)

The following treatments are not influenced by a low-friction method of

ligation:

1. Space closure with closing loops placed in the space,

2. Expansion of a well-aligned arch,

3. Torque (inclination) changes

Variables which could influence friction

1. Type of ligation

2. Size of wire

3. Cross section of the wire

4. Material properties

5. Surface topography

6. Angulation of bracket

7. Occlusal and masticatory forces


In details

Type of ligation (passive or active) Kusy, 2002; Berger, 1997 & Bernie,

2005 found passive ligation produce low friction. Elastomeric ligatures are

much less good, especially if left for too long without being renewed.

(Taloumis et al 1997).An elastomeric in a ‘figure of 8’ configuration

increases the friction by a further 70-220% compared to the ‘O’

configuration (Sims et al 1993). The polymeric-coated SuperSlick ligatures

(TP Orthodontics Inc. Indiana) which was designed to reduce friction,

produced more friction than more conventional elastomerics (Iwasaki et al

2003).

Size of wire . increase size cause SL to produce higher friction Kusy (2002)

and Jones 1998

Angulation of bracket: Kusy (2001) and Jones 1998. At a angulation of 6

degrees for an 0.018" x 0.025" stainless steel wire, the difference is 60 gm

while at degree of 0 to 3.5 the friction is zero

Occlusal and masticatory forces , Braun et al (1999) and O’Reilly et al

(1999) who found that various vibrations and displacements of a test jig (to

mimic intra-oral masticatory forces) can substantially reduce the friction

with conventional ligation. A study by Iwasaki et al (2003) concluded,

“These results refute the hypothesis that masticatory forces consistently and

predictably decrease friction”. This conclusion is probably a bit too firm to

be fully justified.

Surface topography;

Material properties.


Methods to reduce friction in conventional bracket system

1. Begg or tip edge brackets have low friction by virtue of an extremely

loose fit between a round archwire.

2. Metal ligation

3. Engaging the modules on two wings.

4. Closing loop

5. Mini bracket

6. Small AW or round AW

7. Incorporated shoulders to distance the elastomeric from the archwire and

thus reduce friction.

8. Bumps in the floor of the archwire slots.

Advantages and disadvantages of active ligation over passive ligation

High forces at early stages

High friction at later stage

Better labiolingual movement

Less torque effectiveness

Aging of spring clips


1. High forces at early stages: With thin aligning wires smaller than 0.018"

diameter, the effect of having an active clip at this early stage of treatment

can be thought of as having a potentially shallower bracket slot. This will

frequently produce higher forces with a given wire.

2. High friction at later stage: With thick rectangular wires, An active places

a lingually directed force on the wire in all circumstances which results in a

higher friction and resistance to sliding.

3. Better labiolingual movement: for wires > 0.018" diameter, On teeth

which are in whole or in part lingual to a neighbouring tooth, the active clip

will again bring the tooth (or part of the tooth if rotated) to same level

labiolingually to the adjacent. But with passive bracket the tooth will slightly

more lingual than adjacent teeth. However, at finishing stage, active bracket

produce less efficient force in lingually direction because the clip is not

strong enough to fully seat the wire permanently. Badawi et al (2008)

4. Less torque effectiveness: Less play in active ligation

5. Aging of spring clips: Pandis et al (2007), the In-Ovation clips lost an

average of 50% of their stiffness during the treatment.

Clinical tips when using self-ligating brackets, Harradine (2003)

1. Changing treatment mechanics

Longer appointment intervals for some stages of treatment 8-10 weeks

Squeezing teeth into alignment by all teeth engagement


• More traction on lighter wires since the ligation is more robust. This can

be achieved by elastic or coil spring. Where teeth are significantly displaced

from the archwire and there is insufficient space to accommodate them in

the dental arch, space should be made using an open nickel titanium coil

spring. The coil spring should be approximately one bracket width wider

than the space in which it is going to fit for normal interbracket spans. At the

same time, a narrow attachment, such as a TP Traction Hook, should be

bonded to the displaced tooth and gently tied on to the archwire with elastic

thread (e.g.: PowerTube) or wire ligature. This prevents proclination of the

teeth during space opening by placing a lingual or palatal restraining force

on the arch wire and speeds up the alignment process

Separate movement of individual teeth and parallel processing due to

controlled teeth movement. Eg. It sensible in some malocclusions to

separately retract canines to a class 1 relationship whilst simultaneously

reducing the overbite. By the time the overbite reduction permits upper

incisor retraction, the canines are already class 1 but in good rotational

control and the case are further advanced with anchorage conserved.

2. Bracket placement and bond-up

Both maxillary and mandibular arches should be bonded at the same time

and that bonding should include second molar to second molar in each arch.

For severely displaced teeth, it is helpful to use a Traction Hook.

Damon Q brackets have a horizontal auxiliary slot which permits a low-

friction application of piggyback archwires for ectopic teeth.


3. Opening and closing

There are three reasons why an archwire does not seat in the slot:

I. There is something in the slot preventing the archwire seating

II. The archwire is not sufficiently deflected (but can be) to seat

fully in the slot

III. The archwire cannot be deflected (too stiff) to seat fully in the

slot

Engage the wire to the bracket by using:

Finger pressure,

Tucker,

Cool instrument,

Dental floss,

First close the clip, slide and then thread the aligning wire through the closed

bracket before engaging the other brackets

4. Archwires

a. Biting out

Initial placement

When placing the initial archwires, do not include the second molars. The

patient will frequently bite an 0.014" archwire out of the second molar tubes;

it is better to terminate the archwires at the first molars for the first visit and


then pick up the second molars on the first nickel titanium rectangular

archwires (0.018” or 0.014" x 0.025" or 0.016" x 0.025").

Long unsupported spans

use laceback

use small tubes bonded to deciduous teeth to reduce the length of the span

Pump sleeve.

b. Prevention of ‘swivelling’

• Small sections of stainless steel tube crimped onto the archwire, place anti-

swivel stops anterior to the crowding and not in an inter-bracket space where

the wire needs to be significantly active

• Flowable composite

• Turning in the ends of flexible archwires.

• Selective locking of individual brackets to the archwire with elastomeric

• Small V-shaped notches in the midline of flexible wires

c. Archwire sequence

• It is important to fill the labio-lingual dimension of the bracket slot before

proceeding to a rectangular stainless steel archwire e.g. to use a 0.016” x

0.025” nickel titanium rather than a 0.016” x 0.022”.

• The primary archwire sequence is as follows:


0.014" nickel titanium superelastic (or 0.013” /0.012” in very irregular

arches)

0.014" x 0.025" nickel titanium superelastic

0.019" x 0.025" nickel titanium superelastic

0.019" x 0.025" stainless steel

• Secondary archwires and wires are as follows:

1. 0.018” nickel titanium Superelastic, this archwire is useful in cases with

substantial residual irregularity or compromised periodontium as the next

archwire step from the initial 0.014" nickel titanium superelastic

2. 0.016" x 0.025" nickel titanium Superelastic, this archwire is useful in cases

with little irregularity as the next archwire step from the initial 0.014" nickel

titanium superelastic

3. 0.016" x 0.022" stainless steel, Can be useful for extensive sliding of

individual teeth in hypodontia cases. Gives low friction with useful rigidity

4. 0.019" x 0.025" RCOS (reverse curve of Spee) nickel titanium Superelastic,

used for managing deep overbites in both the upper and lower arches

5. 0.019" x 0.025" TMA, very useful for individual tooth movements at the end

of treatment where archwire bends are required, especially for inclination

(torque) adjustments.

d. Distal ends , Archwires should be cut flush with the distal end of the tube on

the terminal molar.


e. Archform , The Damon archform provides a little expansion in the premolar

and molar regions but not in the intercanine region to compensate for the

increase distance between the slot base and the tooth surface in comparison

to conventional bracket system. Customisation of archform should take

place when stainless steel archwires are placed.

f. Debonding , Self-ligating brackets are often more rigid than conventional

twin brackets because of the engineering requirements of the body of the

bracket and the need to provide a rigid housing for the clip or door.


self ligating brackets by almuzian

Health & Medicine

adoption of selfligation

conventional ligation

ideal ligation system

passive ligation

conventional bracket

university of glasgow

used sl system

past failings