Download Self-ligating brackets in orthodontics: do they deliver what they claim?

REVIEW
Australian Dental Journal 2009; 54: 9–11
doi: 10.1111/j.1834-7819.2008.01081.x
Self-ligating brackets in orthodontics: do they deliver what
they claim?
PG Miles*
*Private Orthodontic Practice, Caloundra, Queensland.
ABSTRACT
Self-ligating brackets have enjoyed recent popularity in the orthodontic marketplace with various claims made including
faster ligation, lower friction, faster treatment, less pain, waking up the tongue, and fewer appointments. Although various
designs of self-ligating brackets have been available for many years they have only recently surged in popularity on the back
of these claims but what evidence is there to support these claims? This review article examines the current available
evidence regarding treatment duration, influence on archform, and the speed of tying and untying self-ligating brackets
compared with conventional brackets and methods of ligation.
Key words: Self-ligating, orthodontics.
(Accepted for publication 29 May 2008.)
INTRODUCTION
Self-ligating (SL) brackets are becoming more common
in the orthodontic marketplace with many manufacturers offering one form or another. Some SL brackets
are promoted on the premise that elimination of
ligatures reduces friction and allows for better sliding
mechanics. If true, SL brackets could reduce the
treatment time.1 Self-ligating brackets are not new with
the ‘Russell Lock’ edgewise attachment being described
in 1935.2 More recently, other designs have appeared
including the Speed bracket in 1980, the Time bracket
in 1994, the Damon SL bracket in 1996, the TwinLock
bracket in 1998, and the Damon 2 and In-Ovation
brackets in 2000.3 The popularity and marketing of
some of the self-ligating brackets has led other companies to introduce similar systems in an effort to be up
with the current trends. In 2008, all major orthodontic
companies now offer some form of self-ligating appliance. Claims by manufacturers in their advertising
literature range from faster ligation, lower friction,
faster treatment, less pain, and fewer appointments but
what evidence exists to support these claims?
Is orthodontic treatment faster with self-ligating
brackets?
Several papers have reported that in the laboratory
setting self-ligating brackets demonstrate lower friction
ª 2009 Australian Dental Association
than conventional brackets tied with modules.4–6
Damon described the clinical use of his Damon brackets
and proposed that this low friction is a major factor in
enabling more efficient treatment.7 However, the
assumption has been made that along with low friction
in vitro, comes more rapid alignment and a reduction in
treatment time in the clinical setting. One of the first
clinical studies on treatment efficiency found a mean
reduction of four months in treatment time and four
visits during active treatment.3 Another clinical study in
three practices found an average reduction in treatment
time of six months and seven visits for Damon SL cases
compared to conventional ligation.1 These reports
support a view of clinically significant improvements
in treatment efficiency with SL brackets. However,
these studies are not clear as to what techniques were
used or which variables were controlled. Retrospective
studies such as these are potentially biased as there
are many uncontrolled factors which may affect the
outcome. These include greater experience, differing
archwires, altered wire sequences, changes in treatment mechanics, and modified appointment intervals.
Observer bias may inadvertently affect the outcome as
the practitioner may unknowingly be doing ‘‘a bit
more’’ due to enthusiasm with the new product. These
other variables may have played a major role in
reducing treatment duration. For these reasons, a
prospective study with randomized or consecutive
assignment is preferred.
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PG Miles
The first published prospective clinical trial compared a Smart-Clip self-ligating bracket with a
conventional bracket in the mandibular arch and
examined the initial reduction in crowding over the
first 20 weeks of treatment.8 This study used identical
wire sequences and found no difference between the
two bracket types. In a similar study comparing the
Damon 2 bracket and conventional brackets, again
no difference was found in the clinical ability to align
the teeth.9 Another prospective trial comparing
Damon and conventional brackets found no significant difference in severely crowded cases but a small
difference in favour of the Damon bracket in the
moderately crowded cases.10 However, this study
used different wire sequences for each bracket type
and the thicker rectangular wires used in the Damon
cases could explain the more rapid alignment
achieved than the round wires used in the conventional brackets.
Other prospective evidence is starting to emerge such
as a recent abstract presented at the International
Association for Dental Research in 2007 which found
no difference in total treatment time between conventional edgewise (27.3 ± 6.6 months) and self-ligating
(28.0 ± 4.7 months) brackets.11 Another recent paper
also found no difference in initial alignment between
the Damon 3 bracket and a conventional bracket.12 The
only published study so far to evaluate the rate of space
closure in extraction cases also found no difference in
the rate of tooth movement between a self-ligating
bracket and conventional brackets tied with steel
ligatures.13
Do self-ligating brackets result in wider arches?
Claims have been made that self-ligating brackets can
‘‘waken the tongue’’ resulting in broader archforms
than conventional brackets. Research examining the
effect of self-ligating brackets on archform has found
that conventional and self ligating brackets resolve
crowding in a similar manner.10 The lower incisors
proclined and slight expansion (1.6 mm) of the dental
arches in the molar region occurred. However, the
wires used were not of the same shape for the two
bracket systems with the Damon 0.014 · 0.025’’
Copper NiTi wire having a wider archform and being
thicker compared to the 0.020’’ Sentalloy archwire used
with the conventional bracket. This difference in
posterior expansion may therefore be solely attributed
to the differences in the archwire forms and crosssectional thicknesses and not necessarily related to the
bracket used.
Another study using low friction ligatures which
simulate SL brackets, also found a 1.7 mm increase in
intermolar width when compared with conventional
module ligation.14 This study also examined any loss of
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torque control and demonstrated that the molars tipped
buccally 4. This supports the possibility that molar
expansion observed with SL brackets is related to
rolling or tipping of the molars rather than bodily
movement. This expansion in the order of 1–2 mm
is negligible and could be a spontaneous effect of
treatment. Such small changes in molar expansion only
result in an additional 0.3 to 0.6 mm in arch perimeter
which is clinically insignificant.15
Are self-ligating brackets faster to tie and untie?
Self-ligating brackets were initially introduced to
reduce the time of ligation, particularly at a time when
elastic modules did not exist and only steel ligatures
were available. In one study comparing four types of SL
brackets with steel ligatures and elastic modules, SL
brackets saved 10–12 minutes per patient compared
with tying steel ligatures and 2–3 minutes compared
with modules, the Speed bracket being the fastest.16
Another study of treatment efficiency found an average
time saving from a reduction in archwire placement ⁄ removal of 24 seconds per arch.3 Other studies
have supported the improved speed of archwire changes
when using SL brackets.4,17 These modest time savings,
however, represent only a small fraction of the actual
chair time during an orthodontic treatment visit. It
would therefore be up to the individual practitioner to
determine if this is a significant contribution to the
efficiency of their practice.
CONCLUSIONS
The current prospective evidence regarding duration of
treatment indicates that no clinically significant difference exists between conventional brackets and selfligating brackets. Self-ligating brackets have similar
effects on archform to conventional brackets. Selfligating brackets offer modest time savings when tying
and untying compared with conventional brackets but
the time saving varies with the particular design of the
SL bracket used. Currently, the evidence is limited and
more prospective clinical trials using identical wire
sequences and mechanics are required.
REFERENCES
1. Eberting JJ, Straja SR, Tuncay OC. Treatment time, outcome,
and patient satisfaction comparisons of Damon and conventional
brackets. Clin Orthod Res 2001;4:228–234.
2. Stolzenberg J. The Russell attachment and its improved advantages. Int J Orthod Dent Children 1935;21:837–840.
3. Harradine NWT. Self-ligating brackets and treatment efficiency.
Clin Orthod Res 2001;4:220–227.
4. Shivapuja PK, Berger J. A comparative study of conventional
ligation and self-ligation bracket systems. Am J Orthod Dentofac
Orthop 1994;106:472–480.
ª 2009 Australian Dental Association
Self-ligating brackets
5. Sims APT, Waters NE, Birnie DJ, Pethybridge RJ. A comparison
of the forces required to produce tooth movement in vitro using
two self-ligating brackets and a pre-adjusted bracket employing
two types of ligation. Eur J Orthod 1993;15:377–385.
6. Pizzoni L, Raunholt G, Melsen B. Frictional forces related to selfligating brackets. Eur J Orthod 1998;20:283–291.
7. Damon DH. The rationale, evolution and clinical application of
the self-ligating bracket. Clin Orthod Res 1998;1:52–61.
8. Miles PG. Smartclip versus conventional twin brackets for initial
alignment: is there a difference. Aust Orthod J 2005;21:123–127.
9. Miles PG, Weyant RJ, Rustveld L. A clinical trial of Damon 2
versus conventional twin brackets during initial alignment. Angle
Orthod 2006;6:480–485.
10. Pandis N, Polychronopoulou A, Eliades T. Self-ligating vs. conventional brackets in the treatment of mandibular crowding: a
prospective clinical trial of treatment duration and dental effects.
Am J Orthod Dentofacial Orthop 2007;132:208–215.
11. Yorita R, Sameshima GT. Comparison of self-ligating and conventional orthodontic bracket systems. J Dent Res (Spec Iss A)
2007:86. Abstract 1918.
12. Scott P, DiBiase AT, Sherriff M, Cobourne MT. Alignment efficiency of Damon 3 self-ligating and conventional orthodontic
bracket systems: a randomized clinical trial. Am J Orthod
Dentofacial Orthop 2008;134:470.e1–470.e8.
ª 2009 Australian Dental Association
13. Miles PG. Self-ligating versus conventional twin brackets during
en-masse space closure with sliding mechanics. Am J Orthod
Dentofacial Orthoped 2007;132:223–225.
14. Franchi L, Baccetti T, Camporesi M, Lupoli M. Maxillary arch
changes during leveling and aligning with fixed appliances and
low-friction ligatures. Am J Orthod Dentofacial Orthop
2006;130:88–91.
15. Germane N, Lindauer SJ, Rubenstein LK, Revere JH, Isaacson
RJ. Increase in arch perimeter due to orthodontic expansion. Am
J Orthod Dentofacial Orthop 1991;100:421–427.
16. Berger J, Byloff FK. The clinical efficiency of self-ligated brackets.
J Clin Orthod 2001;35:304–308.
17. Turnbull NR, Birnie DJ. Treatment efficiency of conventional vs
self-ligating brackets: effects of archwire size and material. Am J
Orthod Dentofacial Orthop 2007;131:395–399.
Address for correspondence:
Dr Peter Miles
Private Orthodontic Practice
10 Mayes Avenue
Caloundra QLD 4551
Email: [email protected]
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