Prabhakar Veginad1, Siva Subramanian2, Sridevi Padmanabha3
1. Department of Orthodontics, Sri Ramachandra University
2. Department of Orthodontics, Sri Ramachandra University
3. Department of Orthodontics, Sri Ramachandra University
Objective: The purpose of this systematic review is to identify and review the literary evidence on the efficiency of self-ligating bracket (SLB) system in bringing about transverse arch dimension changes when treated either extraction or non-extraction, as compared to conventional system.
Methods: An online search was conducted through 4 electronic data bases from their inception to September 2014. Randomized controlled trials (RCTs) and Controlled clinical trials (CCTs) comparing SLB and conventional systems for transverse arch dimensional changes were included. Quality assessment of the included articles was performed.
Results: Seven studies were identified, including 4 RCTs with low risk of bias, 3 prospective CCTs with high risk of bias. Of the seven studies, 5 studies investigated mandibular dental arch changes alone, while 2 studies investigated changes in both maxillary and mandibular arches.
Conclusion: Four of the seven studies reported no statistically significant difference in transverse arch dimensional changes between SLB and conventional systems, while three studies reported a greater increase with self-ligating system.
The “swinging pendulum” of extraction versus non-extraction treatment began with the Dewey – Case debates of 19111, and remains unresolved to this day. E. H. Angle (1905), initially provided extraction treatment for his patients, but modified his approach to non-extraction therapy based upon the philosophy that ‘a full complement of teeth’ can be maintained by modifying the environment surrounding the dentition.2 Opposed to this non-extraction mode of therapy were several of his pupils, including Tweed and Begg (1963), who advocated that more stable results could be achieved through treatment with extraction.
In order to arrive at a decision on the preferred modality of treatment, either extraction or non-extraction, aspects such as stability of occlusion, characteristics of dental arches- arch width and arch perimeter, facial and smile esthetics, must be considered and their effects on the dentofacial complex need to be clarified.4
Extraction is believed to have a negative effect on profile, smile esthetics and final occlusion.5 However evidence states the contrary. Investigations showed that extraction treatment had an affirmative effect on the profile, resulted in a better occlusion as compared to non-extraction and the results obtained were stable over a long term.6,7,8,9,10 Considering this present state of evidence, one would expect a higher percentage of extraction cases. But studies have shown that “the pendulum” has swung back towards the non-extraction mode of treatment over the past decennia (26.8% of cases treated with extraction in the last decade compared to 50% in 1980s).11
Fixed appliance treatment of Class I malocclusions without extraction inevitably results in an increase in the arch perimeter. This is achieved by generalized expansion at the inter-canine region and the buccal segments, along with advancement of the incisors irrespective of the treatment modalities used.12The expansion is usually greater at the premolar region. However, the magnitude and the nature of arch dimensional changes have an influence on long-term stability: inter-canine dimension and excessive proclination of mandibular incisors are regarded as considerably unstable.13
Self-ligating brackets are ligatureless bracket systems that have a mechanical device built into the bracket to close off the edgewise slot.14 There are three types of self-ligating bracket systems being used in contemporary orthodontic practice; described depending on the mode in which they interact with the archwire: Passive, Active and Interactive. Since the advent of the concept of self-ligation, manufacturers and advocates have proposed many advantages of self-ligating brackets over conventional brackets. Some of these include more certain engagement of the archwire, less friction between the bracket and the archwire, minimal chairside assistance, faster archwire ligation and removal.15 In addition, the proponents of passive self-ligating system claim that more stable transverse arch expansion with minimal incisor proclination can be achieved with self-ligating system, as the alteration of archform with this system, is “physiologically determined.” 16 These claims render a paradigm shift in treatment that warrants fewer extractions and more arch expansion. However, it subsequently raised questions about the stability of results and the feasibility of long-term retention provided by this technique.17Also, studies have shown that the increase in arch length achieved with self-ligating system is by the buccal tipping of premolars and molars, contradicting the original claims by the proponents.18
The proposed advantages of self-ligating brackets challenge several aspects of conventional orthodontic approach. The recent widespread use of self-ligating brackets indicates that this technique is likely a viable alternative to conventional methods.19However several conflicting studies comparing conventional and self-ligating brackets have caused controversy regarding the clinical outcome. In addition, development of several self-ligating bracket designs, in the recent years, has augmented the controversy. As a result, there is uncertainty of the claimed advantages or disadvantages of self-ligating system over conventional system.15
Therefore, the aim of this systematic review is to compare the transverse dimension changes achieved with self ligating and conventional bracket systems, after orthodontic treatment.
Materials and Methods:
The first step of this systematic review involved formulation of a research question and subsequently a specific protocol based on Population Intervention Control Outcome Study Design (PICOS) format (Table 1). Based on these criteria, the systematic review should be able to answer the question: ‘Does the self-ligating bracket system bring about more transverse arch expansion than conventional system?’
Table 1. PICOS format and research question
|Population||Angle’s Class I subjects with mild to moderate crowding treated with fixed appliance|
|Intervention||Complete arch fixed appliance therapy treated with SLBs or Conventional brackets (CBs), with or without premolar extractions, and without adjunct treatment modalities|
|Comparison||Conventional PEA bracket systems|
|Outcome||Transverse arch dimension changes after orthodontic alignment|
|Study design||Randomized clinical trial, Prospective cohort studies|
The studies included in this systematic review were identified through a literature search carried out through the following electronic databases: PubMed (1960- September 2014), Google Scholar (1960-2014), and the Cochrane Library from inception to September 2014. Detailed search strategy for PubMed database is given in Appendix 2.
Two reviewers (P.V) and (S.S.C), who were not blinded to the authors or the results of the research, participated in the selection process. Firstly, titles and abstracts of potential articles for inclusion were examined. Full texts of articles that met the inclusion criteria21,22,23,24,25,26,27 were then obtained from the published journals and reference lists of the included studies were manually screened for relevant research. Disagreements, if any, were resolved by discussion between the reviewers and a third reviewer (S.P) to reach a consensus.
The inclusion and exclusion criteria formulated for selection of the studies are listed in Table 2. The studies retrieved had to be either randomized controlled trials (RCTs) or either prospective or retrospective controlled clinical trials (CCTs), comparing transverse arch dimension changes for extraction or non-extraction treatment with the self-ligating or conventional bracket systems. No restrictions were set on the:
- type of self-ligating or conventional systems used
- parameters selectedt
- mode of quantifying or measuring the changes
- stage of fixed appliance treatment
Table 2. Inclusion and Exclusion Criteria
|Inclusion Criteria||Exclusion Criteria|
|Randomized controlled trials (RCTs), Prospective Controlled clinical trials (CCTs)||In-vitro studies, ex-vivo studies, Animal studies, Retrospective studies, Case reports, Case series, Cross-sectional studies, Descriptive studies, Reviews, Opinions and Editorials|
|Studies comparing self-ligating and conventional systems for transverse arch dimensional changes||Studies with no control group|
|Angle’s Class I malocclusion with mild to moderate crowding in the anteriors||Adjunct therapy for expansion of arch before fixed appliance|
|All age groups and genders||Severe crowding, Angle’s Class II and Class III malocclusion|
|Articles in English|
|All stages of treatment|
Quality Assessment of Included Studies
The quality assessment of the included studies was performed according to the Cochrane Collaboration’s tool for assessing risk of bias.28 The following criteria were used for assessment (Table 3):
- Sample size calculation
- Randomized sequence generation
- Allocation concealment reported
- Blinding of participants, personnel and outcome assessors
- Reporting of withdrawals
- Intention to treat analysis
An overall assessment of risk of bias (high, unclear, low) was also made for each included trial using the Cochrane Collaboration risk of bias tool. Studies with one or more criterion adjudged to be at high risk of bias were considered to be at high risk of bias overall.
Table 3. Quality Assessment of Included studies
|Study||Design||Sample size Calculation||Random Sequence generation||Allocation Concealment||Blinding of measurement||Reporting of withdrawals||Intention to treat analysis||Risk of Bias|
The electronic database search (Appendix 1) identified 153 titles and abstracts, of which 13 deemed potentially relevant to the present systematic review. Following the review of full articles, 8 satisfied the inclusion criteria. However one article was excluded as the data presented was republished from earlier trials. Eventually seven articles21,22,23,24,25,26,27 were suitable for final analysis. Details of the electronic search is provided in Appendix 2.
The seven studies included four randomized controlled trials,23,24,25,26 three prospective controlled clinical trials.21,22,27
Assessment for Risk of Bias
Seven studies investigating the self-ligating system with the conventional system for transverse arch dimension changes were identified. The outcomes assessed included changes in intercanine, interpremolar, intermolar width and incisor proclination, following either extraction or non-extraction treatment.
All the studies except two,24,27 investigated only mandibular dental arch changes. Study casts and lateral cephalometric radiographs for quantitative analysis of the results. A priori sample calculation was carried out in only four studies.23,24,25,26 Generation of random-number sequence was undertaken in three studies23,24,26 using electronically generated random allocation. One study25 achieved randomization using random permuted blocks. Four trials had acceptable allocation concealment.23,24,25,26 Blinding of participants and personnel was not done in any of the studies, but outcome assessors and data analysts were blinded in four studies.23,24,25,26
The four RCTs identified, had low risk of bias, and the three CCTs had high risk of bias.
A definitive conclusion should not be drawn from this systematic review, considering very few high quality evidence were available in relation to transverse expansion of dental arches following treatment with self-ligating system. Insufficient trials of low or medium risk of bias in homogenous groups precludes a meta-analysis of the outcome of interest.
The description of studies included in this review is given in Table 4. These studies showed conflicting results, the reason for which could be attributed to the difference in sample selection, the stages of treatment, the type of brackets used. Archwire sequence in all the four high quality studies23,24,25,26 were same in the two bracket groups, while they were different in the rest of the studies.21,22,27
The following parameters were evaluated in the studies (Table 5):
- Intercanine dimension
- Interpremolar dimension
- Intermolar dimension
- Incisor proclination
Table 4. Description of included studies
|Fleming (2009)||RCT||66||SmartClip||Victory||0.016”round, 0.017”x0.025” rectangular,||IC * , IPM # , IM ^ ,|
|0.019”x0.025” rectangular martensitic active NiTi,||Mand Incisor Incl|
|Pandis (2011)||RCT||50||Damon MX||Microarch||0.014” CuNiTi, 0.016”x0.025” CuNiTi,||IC, IM|
|(Roth Px)||0.019”x0.025” beta-titanium, 0.019”x0.25” SS|
|Fleming (2013)||RCT||96||Damon Q InOvation||Ovation||0.013”/0.014” round CuNiTi, 0.014”x0.025”, 0.018”x0.025”CuNiTi, 0.019”x0.025” SS||IC, IPM, IM, Molar Incl,|
|(87 analyzed)||Max Incisor Incl|
|Pandis (2007)||CCT||54||Damon 2||Microarch||0.014” CuNiTi Damon TM||0.016” CuNiTi (Ormco)+elastics,||IC, IPM, IM, Mand Incisor Incl|
|0.014”x0.025” CuNiTi Damon TM||0.020” Sentalloy archwire+elastics|
|Tecco (2009)||CCT||40||Damon 3 MX||Victory||0.014” and 0.016”,||0.016” and||IC, IPM, IM|
|Ni-Ti form II|
|Pandis (2010)||CCT||56||Damon 2||Microarch||0.014” CuNiTi||0.016” CuNiTi+elastics,||IC, IM,|
|(54 analyzed)||0.014”×0.025” CuNiTi 0.016”×0.025” SS||0.020” Sentalloy archwire+elastics||Mand Incisor Incl|
|Scott (2008)||RCT||62||Damon 3||Synthesis||0.014”x0.025”, 0.018”x0.025” NiTi,||IC, IM, Mand Incisor Incl|
|(60 analyzed)||0.019” x 0.025” SS|
All the studies included in this review evaluated the changes in intercanine dimensions, and have reported an increase in intercanine dimension, irrespective of the bracket design. But only Fleming et al (2013)24 identified slightly greater increase in passive self-ligating group (Damon Q) with a mean of 1.97 and SD of 2.16. Canine is considered the most stable structure in the arch and any significant change in its position would result in relapse; lesser the change in its position, the more stable is the treatment.12,29
Only three studies included interpremolar dimension changes.23,24,27 These studies found no statistically significant difference between the two bracket groups. The greatest amount of increase was reported by Fleming et al (2013)24 and Tecco et al (2009),27 at around 4.5 mm of expansion with the self-ligating in the first premolar region. In another study, Fleming et al (2009)23 suggested that the increase in inter-second premolar dimensions contributed to a great extent in relieving the crowding (1.8mm of total 2.65mm of crowding relieved).
Three studies,24,25,27 reported increase in the intermolar dimension, but the increase with self-ligating system was not statistically significant as compared to conventional system. Scott et al (2008)26 in a study on treatment with self-ligating system in patients with extraction, reported no increase in the intermolar width. This was attributed to the forward sliding of the molars into the extraction spaces, in the narrower part of the arch. However, other three studies21,22,23 did show a significant increase in intermolar width in self-ligating groups as compared to conventional groups. Pandis et al (2007)21 showed intermolar width increase in the self-ligating group was 1.5 times greater than in the conventional appliance group. They suggested that this difference could reflect unidentified confounding variables or systematic error in the measuring process.
Proponents of passive self-ligating system claim that significant increase in arch perimeter can be achieved without the labial movement of incisors.16 However the studies in this review point the contrary. Three of the four high quality studies24,25,26 concluded that, use of self-ligating brackets do bring about significant incisor proclination. But there was no difference reported in the amount of proclination between the two bracket groups in all the three studies. Scott et al (2008)26 related this to the identical tip and torque prescription values between the bracket systems used. Fleming et al (2009),23 suggested the association between amount of crowding resolved, age, and duration of treatment, to the incisor proclination.
The greatest amount of transverse expansion in treatment with self-ligating system occurs at the interpremolar region followed by intercanine and the least expansion occurs at the intermolar region. And statistically significant changes in arch dimensions were found to be occuring between baseline (insertion of .014”) and removal of .018”x .025” Cu NiTi.20
The findings of Fleming et al (2013)24 confirmed that the intermolar width increase was by buccal tipping of molars, and not by translation of buccal segment and buccal bone remodeling, as claimed by Damon(1998).16 Further studies describing the pattern of buccal bone changes following transverse arch expansion with self-ligating system, are required to corroborate the efficiency of these systems over the conventional approach.
This study was undertaken to answer the question: Does the self-ligating system bring about more transverse arch expansion than conventional system?
Of the seven retrieved articles:
- All seven studies21,22,23,24,25,26,27 found that self-ligating bracket system brings about transverse expansion of dental arches.
- Four studies24,25,26,27 reported no statistically significant difference in transverse arch dimensional changes between self-ligating and conventional bracket systems, while three studies21,22,23 reported a greater increase with self-ligating system.
- Two studies24,27 in maxillary arch, and one study25 in mandibular arch, reported no significant difference in the arch width changes at the intercanine and the intermolar regions, between the two bracket systems. Fleming et al (2013)24and Tecco et al (2009)27 also reported no difference at the interpremolar region. Scott et al (2008)26 evaluating extraction patients, reported that the intercanine width increased, while the intermolar width did not show an increase, with self-ligating bracket. According to the authors, this was related to the forward sliding of the molars into a narrower part of the arch.
- Fleming et al (2009)23, Pandis et al (2010)22 and Pandis et al (2007)21 reported that, self-ligating bracket system produced greater expansion in the intercanine, interpremolar and intermolar regions as compared to the conventional system which was statistically significant.
- Five studies21,22,23,24,27confirmed that transverse arch expansion, irrespective of the bracket systems used, resulted in incisor proclination.
More evidence through larger and higher quality studies is required to support the efficiency of self-ligating system in transverse arch expansion.
- Asbell, MB- A brief history of orthodontics: American orthodontics 1900 to 1910. Am J Orthod Dentofacial Orthop 1990;98:206-213
- Lee RT- Arch width and form. Am J Orthod. Dentofac. Orthop 1999; 115:305-13
- Brandt S, Tweed CH- JPO interviews Dr. Charles H. Tweed. J Clin Orthod, 1967; 1(12): 142-148
- Bowman SJ, Johnston LE Jr- The esthetic impact of extraction and nonextraction treatments on Caucasian patients. Angle Orthod 2000; 70:3-10
- Spahl TJ, Witzig JW- The clinical management of basic maxillofacial orthopaedic appliances. Littleton (Massachusetts): PSG Publishing Co; 1987.
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- Farhadian N, Miresmaeili, Soltani M – Comparison of Extraction-Non-extraction Orthodontic Treatment using the Objective Grading System. Journal of Dentistry, Tehran University of Medical Sciences, Tehran, Iran 2005; 2(3)
- Johnson DK, Smith RJ- Smile aesthetics after orthodontic treatment with and without extraction of four first premolars. Am J Orthod Dentofacial Orthop 1995; 108:162-7
- Gianelly A- Arch width after extraction and non-extraction treatment. Am J Orthod Dentofacial Orthop 2003; 123:25-8
- Işiksal E, Hazar S, Akyalçin S- Smile aesthetics: perception and comparison of treated and untreated smiles. Am J Orthod Dentofacial Orthop 2006; 8-16
- Dimitrios Konstantonis, Chrysi Anthopoulou, Margarita Makou- Extraction decision and identification of treatment predictors in Class I malocclusions. Progress in Orthodontics 2013; 14:47
- Weinberg M, Sadowsky C-Resolution of mandibular arch crowding in growing patients with Class I malocclusions treated non-extraction. Am J Orthod Dentofac Orthop 1996; 110:359-64
- Little RM- Stability and relapse of mandibular anterior alignment: University of Washington studies. Semin Orthod 1999;5:191-204
- Byloff FK, Berger J-The clinical efficiency of self-ligating brackets J. Clin. Orthod. 2001; 35(5):304-308
- Harradine NW- The history and development of self-ligating brackets. Semin Orthod.2008; 14(1):5-18
- Damon DH- The Damon Low-Friction Bracket: A Biologically Compatible Straight-Wire System. JCO/November 1998:670-680
- Birnie D, Harradine NW- Introduction. Semin Orthod. 2008; 14(1):1-4
- Cattaneo PM, Treccani M, Carlsson K, Thorgeirsson T, Myrda A, Cevidanes LHS, Melsen B- Transversal maxillary dento-alveolar changes in patients treated with active and passive self-ligating brackets: a randomized clinical trial using CBCT-scans and digital models. Orthod Craniofac Res 2011;14:222-33
- Harradine NW- Self-ligating brackets and treatment efficiency. Clin Orthod Res 2001; 4 :220-7
- PS Fleming, Robert T Lee, Tom Mcdonald, Pandis N, Amal Johal- The timing of significant arch dimensional changes with fixed orthodontic appliances: Data from a multicenter randomised controlled trial- Journal of Dentistry 2014; 42: 1-6
- 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(2):208-15
- Pandis N, Polychronopoulou A, Makou M, Eliades- T. Mandibular dental arch changes associated with treatment of crowding using self-ligating and conventional brackets. Eur J Orthod. 2010:1-6
- PS Fleming, DiBiase A, Sarri, Lee R- Comparison of mandibular arch changes during alignment and leveling with 2 preadjusted edgewise appliances. Am J Orthod Dentofacial Orthop. 2009; 136(3):340-7
- PS Fleming, Lee RT, Marinho V, Johal A- Comparison of maxillary arch dimensional changes with passive and active self-ligation and conventional brackets in the permanent dentition: a multicenter randomized controlled trial. American Journal of Orthodontics and Dentofacial Orthopedics 2013; 144:185–93
- Pandis N, Polychronopoulou A, Katsaros, Eliades T- Comparative assessment of conventional and self-ligating appliances on the effect of mandibular intermolar distance in adolescent non-extraction patients: a single-center randomized controlled trial. Am J Orthod Dentofacial Orthop 2011;140:e99-105
- Scott P, DiBiase AT, Sherriff M, Cobourne MT. Alignment efficiency of Damon3 self-ligating and conventional bracket systems: a randomized clinical trial. Am J Orthod Dentofacial Orthop 2008;134: 470.e1-8.
- Simona Tecco, Stefano Tetè, Letizia Perillo, Claudio Chimenti, Felice Festa- Maxillary Arch width changes during orthodontic treatment with self-ligating and traditional straight-wire appliances;World J Orthod 2009;10:290–294
- Higgins JPT, Altman DG– Chapter 8: Assessing risk of bias in included studies; in Cochrane Handbook of Systematic Reviews of interventions. Edited by Higgins JPT, Green S. Chichester: John Wiley & Sons Ltd., 2008;187-241
- Sadowsky C, Sakols EI– Long-term assessment of orthodontic relapse. Am J Orthod. 1982;82(6):456-63
Database search strategies
PubMed: self-ligat* AND conventional AND (transverse OR arch OR dental OR dimension OR changes)
Pub Med Search (1960 – September 2014)