View
254
Download
12
Category
Tags:
Preview:
DESCRIPTION
Citation preview
UNIVERSITY OF GLASGOW
Self-Ligating Brackets
Personal notes
Mohammed Almuzian
1/1/2013
.
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
Mohammed Almuzian, University of Glasgow, 2013 Page 2
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
Mohammed Almuzian, University of Glasgow, 2013 Page 3
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
Mohammed Almuzian, University of Glasgow, 2013 Page 4
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
Mohammed Almuzian, University of Glasgow, 2013 Page 5
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.
Mohammed Almuzian, University of Glasgow, 2013 Page 6
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
Mohammed Almuzian, University of Glasgow, 2013 Page 7
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
Mohammed Almuzian, University of Glasgow, 2013 Page 8
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.
Mohammed Almuzian, University of Glasgow, 2013 Page 9
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
Mohammed Almuzian, University of Glasgow, 2013 Page 10
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
Mohammed Almuzian, University of Glasgow, 2013 Page 11
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
Mohammed Almuzian, University of Glasgow, 2013 Page 12
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
Mohammed Almuzian, University of Glasgow, 2013 Page 13
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.
Mohammed Almuzian, University of Glasgow, 2013 Page 14
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
Mohammed Almuzian, University of Glasgow, 2013 Page 15
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.
Mohammed Almuzian, University of Glasgow, 2013 Page 16
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
Mohammed Almuzian, University of Glasgow, 2013 Page 17
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
Mohammed Almuzian, University of Glasgow, 2013 Page 18
• 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.
Mohammed Almuzian, University of Glasgow, 2013 Page 19
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
Mohammed Almuzian, University of Glasgow, 2013 Page 20
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:
Mohammed Almuzian, University of Glasgow, 2013 Page 21
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.
Mohammed Almuzian, University of Glasgow, 2013 Page 22
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.
Mohammed Almuzian, University of Glasgow, 2013 Page 23
Recommended