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Possible Advantages of Self-Ligating Brackets: From Claims to Evidence, a Literature Review

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Iran J Ortho. In Press(In Press):e90579.
Published online 2019 March 28.
doi: 10.5812/ijo.90579.
Review Article
Possible Advantages of Self-Ligating Brackets: From Claims to
Evidence, a Literature Review
Homa Farhadifard 1, Mohammad Ali Keshvad 2, Aryan Hesamarefi 2and Elahe Soltan Mohammadi 3,*
1Department of Orthodontics, School of Dentistry , Hamedan University of Medical Sciences, Hamedan, Iran
2Department of Orthodontics, Tehran University of Medical Sciences, Tehran, Iran
3Department of Orthodontics, School of Dentistry, Qom University of Medical Sciences, Qom, Iran
*Corresponding author: Assistant Professor, Orthodontic Department, School of Dentistry, of Qom University of Medical Sciences, Saheli St., Qom, Iran. Tel: +98-9123058172,
Received 2019 February 12; Accepted 2019 March 06.
Self-ligating brackets are ligature-less brackets with the mechanical device built into them to close edgewise slot. It was claimed
that self-ligating brackets (SLBs) have advantages over conventional-ligating brackets brackets (CLBs). The most claimed advanta-
geous feature is reduced friction between the archwire and the bracket and full archwire engagement, resulting in faster alignment
and space closure. Greater arch expansion with less incisor proclination, also faster ligation, reduced number of visits and less pain
is mentioned as the beneficial features of SLBs in different articles. In this review article, we compared SLBs with CBs in aspect of
resistance to sliding, speed of archwire ligation, quality of alignment and amount of pain during treatment base on the most re-
cent articles published in literature. We concluded that although self-ligating brackets are proved to have some advantages over
conventional brackets, but more studies are needed to discard doubts about using them, routinely.
Keywords: Self-Ligating Brackets, Review, Friction, Alignment, Pain, Ligation, Engagement
1. Context
Traditionally wire or elastomeric ligatures are used to
engage the archwire in the bracket slot. These conven-
tional ligation systems have limitations with respect to
ergonomics, efficacy, discoloration, plaque accumulation,
and friction. Self-ligation has been developed to overcome
these deficits. Self-ligating brackets (SLBs) are ligature-less
brackets with the mechanical device built into them to
close edgewise slot (1).
Self-ligation is not a new concept. The first self-
ligating bracket, the Russell attachment, was introduced
by Stoltenberg in the early 1930s and during the past sev-
eral decades, interest in SLBs has been remarked (2). SLBs
are divided into 2 groups according to their mechanisms
of closure: active and passive. Active SLBs like in-ovation,
SPEED, and time, have a spring clip that stores energy to
press against the arch- wire for rotation and torque con-
trol. Passive SLBs usually have a slide that can be closed to
the slot lumen, so they exert no active force on the arch-
wire (Damon and Smart Clip) (3). It was claimed that SLBs
have advantages over conventional brackets (CB). The most
advantageous feature is reduced friction between the arch-
wire and the bracket and full archwire engagement, result-
ing in faster alignment and space closure. Greater arch ex-
pansion with less incisor proclination (4). Also, faster liga-
tion with reduced number of visits and less pain are men-
tioned as the benefits of SLBs (5).
2. Evidence Acquisition
In order to compare different allegations around
these kind of brackets we searched databases including:
PubMed, Google Scholar, Scopus and Medline. Two or-
thodontic experts reviewed articles in English language
only and those published from 2010 to 2018. Our keywords
were: “self-ligate AND orthodontic” - “ligation method AND
orthodontic “-“active self-ligated AND brackets” -“passive
self-ligated AND brackets”. Clinical trials (randomized or
non-randomized), systematic reviews and meta-analysis
on patients with no anomalies like syndrome or lip and
palate cleft and experimental in vitro studies were chosen
3. Results
In this review we compared SLBs with CBs in aspect of
resistance to sliding, speed of archwire ligation, quality
Copyright © 2019, Iranian Journal of Orthodontics. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0
International License ( which permits copy and redistribute the material just in noncommercial usages, provided the
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Farhadifard H et al.
of alignment (arch expansion and incisor pro-inclination)
and amount of pain during treatment by using newest pa-
pers according to the criteria mentioned earlier.
3.1. Resistance to Sliding
Friction is defined as resistance to motion when one
surface attempts to slide over another, which has contact
with (6). It has been proposed that approximately 50%
of the force applied to slide a tooth through an archwire
is used up to overcome friction (7). There is lots of as-
sertions considering this factor in self ligating and con-
ventional brackets and sometimes contradicting conclu-
sions (8). Ehsani et al. reported that SLBs maintain lower
friction than CBs when engaged with small round arch-
wires in the absence of tipping and/or torque in an ide-
ally aligned arch. Also, they announced that as the arch-
wire size increased, friction of both self-ligated and con-
ventional brackets increased (1). Harradine concluded that
for self-ligation, lower resistance to sliding is one of 3 main
features that are increasingly supported by valid studies
(9). Thapa and Wu reported that major portion of the resis-
tance is because of the ligation forces applied to the arch-
wire and self-ligation decreases the amount of friction due
to binding but only when thin archwires are used along
with it (10). Rinchuse and Miles reported that SLBs showed
good performance in vitro with smaller wires that are used
during early stages of treatment. But when larger wires
are used (like 0.016 ×0.022 and 0.019 ×0.025 nickel- ti-
tanium), no differences were found between SLBs and CBs
(11). Pillai et al. by evaluating frictional resistance gener-
ated by conventional stainless steel, radiance ceramic, self-
ligating and composite brackets concluded that SLB has
the least friction among these four types of brackets (12).
Leite et al. also confirmed this finding in his research in
2014. According to him, SLBs had lesser frictional resis-
tance than steel or elastomeric-tied conventional brackets
(13). Other studies also found the same conclusion (8,14-
18). In an in-vitro study by Vinay K which assessed fric-
tion in different combinations of wire, bracket and lig-
ation method, it was concluded that self-ligating brack-
ets offered least friction followed by conventional stain-
less steel brackets, ceramic with metal insert bracket and
ceramic brackets (19). In spite of these articles, Pliska et
al. found that with the exception of CL monocrystalline
bracket, CBs & SLBs displayed comparable amounts of re-
sistance to sliding regardless of ligation method or bracket
slot material (20).
Saporito et al. compared the effectiveness of space clo-
sure of CBs & SLBs. No significant difference was seen in
the efficiency of space closure between the self-ligating
bracket and conventional bracket tied with stainless steel
ligatures (21).
Karim Soltani et al. compared the resistance to slid-
ing in 4 subgroups of brackets including: metallic and
clear Damon brackets and metallic and clear conventional
brackets in a wet condition resembling oral cavity environ-
ment. Statistically, there was no significant difference ob-
served between either of the subgroups in resistance to
sliding and static frictional forces meaning that neither
the type of bracket materials (clear and metal) nor their
type of ligation made any difference in resistance to slid-
ing and static friction (22).
Muguruma et al. investigated the effects of torque on
frictional properties of SLBs. He founded that in most sit-
uations, increasing the torque produced a significant in-
crease in static friction but most SLB-wire combinations at
all torques produced less friction than that of the conven-
tional bracket. Active-type SLB-wire combinations showed
higher friction than passive-type SLB-wire combinations in
most conditions (23). Huang et al. (24) and Oliver et al. (25)
also confirmed this finding.
3.2. Pain During the Treatment
The belief that treatment with SLBs is less painful may
be because of the lighter archwires that can be used with
equal effectiveness with these brackets; so forces on the
teeth are lower and also the teeth move more readily in
response to the applied forces because of decreased re-
sistance to sliding (25,26). Celar et al. in their meta-
analysis announced that there were no significant differ-
ences in perceived pain between self-ligating and conven-
tional brackets during the first week of treatment (27,28).
Fleming and Johal declared that analysis of the effect of
bracket type on pain experience confirmed that SLBs do
not have a clinically significant stance on pain experience
(29). Othman et al. found the same conclusion in their
randomized clinical trial (30). Zhou et al. found that Pa-
tients with self-ligating brackets were associated with less
pain and discomfort at any intervals compared with con-
ventional brackets but no significant difference of overall
oral health-related quality of life (OHRQoL) scores could be
found between two groups (31).
Bertl et al. in their study declared that engagement
and disengagement of rigid rectangular archwires caused
more pain with Smart Clip self-ligating brackets than con-
ventional ones (32). In a randomized clinical trial by Rah-
man et al. with the aim of comparing pain perception
between self-ligating and conventional preadjusted edge-
wise brackets, it was concluded that patients treated with
self-ligating brackets reported more pain perception but
statistically it was not significant and was higher in day 1
compared to day 3 and 5 after bonding brackets (33) which
is confirmed by the work of Scott et al. who did not report
2Iran J Ortho. In Press(In Press):e90579.
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Farhadifard H et al.
any significant differences in pain perception during ini-
tial alignment between patients who randomly were pre-
scribed by self-ligating and conventional brackets (34). Dis-
cussing active or passive self-ligating brackets Kohli and
his colleagues in 2012 stated that patients with active self-
ligating brackets experienced more pain in the first 2 days
after bonding which was significant (35).
3.3. Quality of Alignment
It is believed that with self-ligation mechanics,
lesser incisor proclination and greater arch expansion
is achieved, and so fewer extractions are required to pro-
vide space to do aligning of teeth (3). Chen et al. stated
that there was no significant difference between the
SLB and CB for intercanine and intermolar widths. For
incisor proclination, their meta-analysis indicated that
self-ligating brackets resulted in slightly lesser incisor
proclination (1.5° leser proclination with SLBs versus CBs)
(3). Prettyman et al. declared that the use of SLB and
CB does not cause differences in incisor proclination and
intercanine expansion (4). Songra et al. concluded that the
time of initial alignment was significantly shorter in the
conventional bracket than for either the active or passive
self-ligating brackets. There was no statistically significant
difference in passive, active, or total space-closure times
among the 3 brackets under investigation (36). Pandis et
al. found that use of conventional or self-ligating brackets
did not seem to be a significant indicator of mandibular
intermolar width in non-extraction patients when the
same wire sequence is used (37). Celikoglu et al. found
that bracket type has little influence on improvement in
anterior ambiguity during initial mandibular alignment
(38). Wahab and his colleagues compared the aligning
efficacy of damon self-ligating brackets and mini-diamond
conventional brackets at each appointment and showed
that in the first month of therapy CLB group lead to sig-
nificantly faster alignment compared with SLB group but
there were no significant differences in the alignment
speed between the second and third month and third and
fourth month. After four month of alignment, CLB group
showed 98 percent of alignment which was significantly
more than 67 percent of SLB group (39).
3.4. Sped of Archwire Ligation
The initial motivation of developing self-ligating
brackets was to speed up the process of archwire ligation.
Several authors have reported that self-ligating brackets
save of up to nine minutes per visit compared with wire
ligation and approximately two minutes compared with
elastomeric ligation (9). In the study of Chen et al. results
showed a mean saving of 20 seconds per arch for opening
the slides of SLB compared with removing the ligatures of
CB, but there was no significant differences between the
time needed for closing the slides of SLBs and replacing
the ligatures of CBs and self-ligation does appear to have a
significant advantage in aspect of chair time (5). Paduano
et al. revealed that SLB had significantly shorter ligation
time compared with elastomeric or stainless steel liga-
tions in both arches. He also claimed that speed of arch
wire ligation in SLB was dependent to self-ligating bracket
type (40).
4. Conclusions
As shown in a recent systematic review by Dehbi and
colleagues which evaluated the tooth alignment, space clo-
sure, treatment duration, arch expansion and patient dis-
comfort in SLB and CB systems, and found no significant
differences (41). Evidence shows that self-ligating brackets
can have little advantages over conventional ones. But as
the results of articles are contradictory, more studies are
needed to survey different aspects of these brackets, more
Authors’ Contribution: Study concept and design:
Homa Farhadifard; acquisition of data: Mohammad Ali
Keshvad; drafting of the manuscript: Elahe Soltan Moham-
madi; critical revision of the manuscript for important in-
tellectual content: Aryan Hesamarefi; study supervision:
Elahe Soltan Mohammadi.
Conflicts of Interests: The authors have no conflicts of
interest to disclose.
Funding/Support: No funding support was needed.
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Full-text available
Background: Fixed orthodontic mechanotherapy is associated with friction between the bracket - wire - ligature interfaces during the sliding mechanics. A sound knowledge of the various factors affecting the magnitude of friction is of paramount importance. The present study was done to analyze and compare the frictional forces generated by a new ceramic (Clarity Advanced) bracket with the conventional, (metal and ceramic) brackets using unconventional and conventional ligation system, and the self-ligating (metal and ceramic) brackets in the dry condition. Materials and methods: The various bracket wire ligation combinations were tested in dry condition. The brackets used were of 0.022″ × 0.028″ nominal slot dimension of MBT prescription: Stainless steel (SS) self-ligating bracket (SLB) of (SmartClip), SS Conventional bracket (CB) (Victory series), Ceramic SLB (Clarity SL), Conventional Ceramic bracket with metal slot (Clarity Bracket), Clarity Advanced Ceramic Brackets (Clarity(™) ADVANCED, 3M Unitek). These brackets were used with two types of elastomeric ligatures: Conventional Elastomeric Ligatures (CEL) (Clear medium mini modules) and Unconventional Elastomeric Ligatures (UEL) (Clear medium slide ligatures, Leone orthodontic products). The aligning and the retraction wires were used, i.e., 0.014″ nickel titanium (NiTi) wires and 0.019″ × 0.025″ SS wires, respectively. A universal strength testing machine was used to measure the friction produced between the different bracket, archwires, and ligation combination. This was done with the use of a custom-made jig being in position. Results: Mean, standard deviation, and range were computed for the frictional values obtained. Results were subjected to statistical analysis through ANOVA. The frictional resistance observed in the new Clarity Advanced bracket with a conventional elastomeric ligature was almost similar with the Clarity metal slot bracket with a conventional elastomeric ligature. When using the UEL, the Clarity Advanced bracket produced lesser friction than the conventional metal bracket; but not less than the ceramic metal slot bracket. Ceramic SLB produced lesser friction when compared with the Clarity Advanced bracket with UEL, but the metal SLB produced the least friction among all the groups and subgroups. Conclusion: The present study concluded that the SS SLB produced least friction among all groups. Using the archwire and ligation method, frictional forces observed in the Clarity Advanced bracket and the conventional ceramic with metal slot bracket were almost similar; but the least resistance was determined in SS CB using both the ligation (CEL and UEL) system.
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Frictional forces are considered as important counterforce to orthodontic tooth movement. It is claimed that self-ligating brackets reduce the frictional forces. The aim of this study was to compare the resistance to sliding in metallic and clear Damon brackets with the conventional brackets in a wet condition. The samples included 4 types of brackets; metallic and clear Damon brackets and metallic and clear conventional brackets (10 brackets in each group). In this study, stainless steel wires sized 0.019×0.025 were employed and the operator's saliva was used to simulate the conditions of oral cavity. The tidy-modified design was used for simulation of sliding movement. The resistance to sliding and static frictional forces was measured by employing Testometric machine and load cell. The mean (±SD) of resistance to sliding was 194.88 (±26.65) and 226.62 (±39.9) g in the esthetic and metallic Damon brackets, while these values were 187.81(±27.84) and 191.17(±66.68) g for the clear and metallic conventional brackets, respectively. Static frictional forces were 206.4(±42.45) and 210.38(±15.89) g in the esthetic and metallic Damon brackets and 220.63(±49.29) and 215.13(±62.38) g in the clear and metallic conventional brackets. According to two-way ANOVA, no significant difference was observed between the two bracket materials (clear and metal) and the two types of bracket (self-ligating versus conventional) regarding resistance to sliding (p= 0.17 and p= 0.23, respectively) and static frictional forces (p= 0.55 and p= 0.96, respectively). Neither the type of bracket materials nor their type of ligation made difference in resistance to sliding and static friction.
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To test the null hypothesis that SmartClip self-ligating brackets are more effective than conventional brackets for initial mandibular alignment and identify influential factors. Fifty patients were randomly allocated to two equal treatment groups by using an online randomization program: self-ligating group (SmartClip brackets) and conventional group (Gemini brackets). The archwire sequence was standardized. Changes in anterior irregularity index, intercanine width, and intermolar width were assessed on plaster models at 8th and 16th weeks. Changes in incisor position and inclination were assessed on lateral cephalometric radiographs at 16 weeks. Intragroup and intergroup comparisons were performed with paired t-test and Student's t-test, respectively. Multiple linear regression was performed to identify variables affecting improvement in anterior ambiguity. Data of 46 patients were analyzed; those missing an appointment (n = 2) or showing bracket breakage (n = 2) were excluded. Incisor inclination (p < 0.05), intercanine width (p < 0.05), and intermolar width (p > 0.05) increased at 8 and 16 weeks in both the groups; no significant intergroup differences were noted (p > 0.05). Initial anterior irregularity index and intercanine width change were significantly associated with improvement in anterior irregularity (p < 0.001). The null hypothesis was rejected. Bracket type has little effect on improvement in anterior ambiguity during initial mandibular alignment.
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Objective: To compare the degree of debris and friction of conventional and self-ligating orthodontic brackets before and after clinical use. Materials and methods: Two sets of three conventional and self-ligating brackets were bonded from the first molar to the first premolar in eight individuals, for a total of 16 sets per type of brackets. A passive segment of 0.019 × 0.025-inch stainless steel archwire was inserted into each group of brackets. Frictional force and debris level were evaluated as received and after 8 weeks of intraoral exposure. Two-way analysis of variance and Wilcoxon signed-rank test were applied at P < .05. Results: After the intraoral exposure, there was a significant increase of debris accumulation in both systems of brackets (P < .05). However, the self-ligating brackets showed a higher amount of debris compared with the conventional brackets. The frictional force in conventional brackets was significantly higher when compared with self-ligating brackets before clinical use (P < .001). Clinical exposure for 8 weeks provided a significant increase of friction (P < .001) on both systems. In the self-ligating system, the mean of friction increase was 0.21 N (191%), while 0.52 N (47.2%) was observed for the conventional system. Conclusion: Self-ligating and conventional brackets, when exposed to the intraoral environment, showed a significant increase in frictional force during the sliding mechanics. Debris accumulation was higher for the self-ligating system.
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Introduction: Although the associations between orthodontic and oral health-related quality of life (OHRQOL) have been explored, little research has been done to address the influence of brackets type on perceived OHRQOL. The aim of this study was to assess whether the levels of OHRQOL in Chinese adolescence patients were influenced by the type of brackets. Materials and methods: One hundred fifty Chinese orthodontic adolescence patients completed the 14-item Oral Health Impact Profile (OHIP-14, Chinese version) at five distinct intervals: after insertion of the fixed appliance at 1 week (T1), 1 month (T2), 3 months (T3), and 6 months (T4); and after treatment (T5). Results: Patients with self-ligating brackets were associated with less pain and discomfort at any intervals compared with conventional brackets, but no significant difference of overall OHIP-14 scores could be found between two groups. Moreover, in both groups, overall scores at T1 and T2 were significantly higher than the scores at any other intervals in both groups. Conclusions: The type of orthodontic appliance did not affect oral health-related quality of life in Chinese adolescence patients.
Introduction: Over the last few years, the use of self-ligating brackets in orthodontics has progressed considerably. These systems have been the subject of numerous studies with good levels of evidence making it possible to evaluate their efficacy and efficiency compared to conventional brackets. The aim of this study was to evaluate the therapeutic efficacy of self-ligating brackets by means of a systematic review of the scientific literature. Materials and methods: A systematic study was undertaken in the form of a recent search of the electronic Pubmed database, oriented by the use of several keywords combined by Boolean operators relating to the therapeutic efficacy of self-ligating brackets through the study of tooth alignment, space closure, expansion, treatment duration and degree of discomfort. The search was limited to randomized controlled studies, and two independent readers identified studies corresponding to the selection criteria. Results and discussion: The chosen articles comprised 20 randomized controlled trials. The studies analyzed revealed the absence of significant differences between the two types of system on the basis of the clinical criteria adopted, thereby refuting the hypothesis of the superiority of self-ligating brackets over conventional systems.
Many authors have been involved in developing brackets in order to improve the quality, stability, speed and efficiency of orthodontic treatment. In order to reduce friction between bracket and archwire, new therapeutic approaches have been devised based on novel technologies. Among these innovative techniques, self-ligating brackets are increasingly popular. SLBs can be classified into several categories according to their mode of action and their materials. We performed an experimental study to compare the friction forces generated during the sliding of orthodontic archwires made from various alloys through conventional and self-ligating brackets. Results show the favorable influence of SLBs, compared to conventional systems using elastomeric or metal ligatures, on the level of friction, particularly when shape-memory Ni-Ti archwires are used. © EDP Sciences, SFODF, 2015.
To compare pain experience between self-ligating and conventional preadjusted edgewise appliance systems with a two-arm parallel trial. A prospective multicenter randomized controlled clinical trial was conducted in three hospital orthodontic departments. Subjects were randomly allocated to receive treatment with either a self-ligating (3M SmartClip™) or conventional (3M Victory™) bracket system with stratification for operator and center. Standardized protocol was followed for bracket bonding procedure and archwire sequence. Subject pain was recorded using a Verbal Rating Scale to assess discomfort felt on the teeth and soft tissues at the time of the appointment and 1, 3, and 5 days after each archwire change up to the working archwire. Multilevel modeling was used to analyze the data by blinded assessors. One hundred thirty-eight subjects (mean age 14 years 11 months) were enrolled in the study, of which 135 subjects (97.8%) completed the study and 113 (82%) returned the required data regarding pain/discomfort. Perceived pain was statistically higher with the SmartClip™ system compared to the Victory™ system, but this difference was not deemed to be clinically significant. Discomfort was greatest after placement of the initial 0.014-inch nickel-titanium archwire, compared with subsequent wires, and was greatest on day 1, less on day 3, and much less on day 5 after each archwire change. Age and gender did not affect the level of discomfort experienced by subjects undergoing fixed appliance treatment. No clinically significant difference in pain experience was found between patients treated with a self-ligating bracket system compared to those treated with a conventional ligation system.
Background and Objectives: The purpose of this study is to evaluate the frictional resistance generated by conventional stainless steel, radiance ceramic bracket, self-ligating and composite brackets using a 0.019 × 0.025 stainless steel straight length wires in a 022 slot and to select brackets based on their frictional characteristic. Methodology: In order to conduct this study, four different types of bracket system were selected of the mclaughlin-bennet-trevesi (MBT) discipline. They are Group 1 - stainless steel, Group 2 - composite bracket Group 3 - (American Orthodontics) radiance ceramic bracket Group 4 - self-ligating bracket (SLB) (Empower). In this study, five maxillary brackets of an arch of each type were used. All brackets are 0.022 × 0.028 in preadjusted edgewise appliance which simulates the dental arch. Five brackets were bonded to a stainless steel bar of dimension 150 mm × 25 mm × 3 mm. The bracket-arch wire units were submitted to mechanical test with an Instron universal testing machine 3365. A testing apparatus or holding jig was designed to hold the bracket during the mechanical test. Each sample was pulled at a speed of 6 mm for 1 min. Descriptive statistical information including mean and standard deviation of maximum friction force was calculated for each bracket wire combination. Interpretation and Conclusion: The SLB has the least friction among the four groups. The ceramic bracket showed the highest friction followed by stainless steel bracket, composite bracket, and SLB.