An Umbrella Review of Systematic Reviews With or Without Meta-Analysis Assessing Treatment Outcomes and Efficiency of Self-Ligating Brackets

Abstract

Introduction

Self-ligating bracket systems are popular and seem to demonstrate lesser friction, allowing tooth movement without exerting unwanted forces on surrounding structures. This umbrella review aimed to compare self-ligating and conventional bracket systems for treatment efficiency.

Methods

An electronic search in 8 databases was performed for literature published between January 1, 1990, and October 1, 2021, with manual hand-searching of references of retrieved articles. Quality assessment was performed using the risk of bias in a systematic tool by 2 independent reviewers. Data were extracted using a prepiloted form (Joanna Briggs Institute) for evidence synthesis. Corrected covered area was calculated to quantify study overlaps across systematic reviews with or without meta-analysis.

Results

605 articles were retrieved, of which 16 were selected. Most included studies had a low risk of bias, except for 6 that showed an unclear risk of bias. Data analysis revealed a reduction in lower incisor proclination, bacterial accumulation, and oral malodor using self-ligating appliances.

Conclusions

Self-ligating systems reduce mandibular incisor proclination, bacterial accumulation, external apical root resorption, chairside time, and oral malodor. No other differences could be demonstrated in comparison with conventional appliance systems.

Keywords

Self-ligation conventional brackets treatment outcomes systematic reviews umbrella reviews

Introduction

Stolzenberg introduced self-ligating brackets more than 70 years ago as a method for faster ligation requiring less chairside time.¹ Since then, a wide range of designs have been introduced, offering low friction with secure bracket-to-archwire engagement.

The dissent between advocates of conventional and self-ligating brackets stems from the principles of friction, which is created as teeth slide along an archwire. Proponents of self-ligating systems claim to overcome friction by converting the oral environment into one where tooth movement and tissue adaptation occur under complete physiologic control.² Reduced friction and faster ligation could result in faster and more efficient orthodontic treatment. Self-ligating systems also claim fewer clinical visits, greater alignment efficiency, and better oral hygiene.³ These wide-ranging advantages are the reason for inevitable comparison with the existing conventional systems. Current appliance systems, though rigorously tested, show methodological and design variations with a lack of treatment protocol standardization, making direct comparisons of appliance systems difficult.

In the hierarchy of evidence, systematic reviews with or without meta-analyses are considered top tier and are used for providing evidence-based care to patients. With an increase in evidence-based research, 2 main limitations occur: the inclusion of publication bias in systematic reviews and insufficient evidence to draw meaningful conclusions. A plethora of systematic reviews have compared different aspects of self-ligating and conventional systems, where results obtained are often divergent and not coherent. These limitations have been addressed to an extent in umbrella reviews that summarize and synthesize results and data from the existing evidence so that they can be analogized and ultimately provide an analysis of what is known, along with recommendations for clinical practice and future research.^{4, 5}

Because of abundant systematic reviews published on self-ligation, there is a need to evaluate additional evidence to answer pertinent questions regarding the efficacy of this method. An umbrella review allows the findings of previous reviews relevant to a review question to be compared and contrasted. Hence, this umbrella review aims to present complex and multifaceted features of a wide area of evidence in a systematic and methodological way to help clinicians choose a system that benefits their practice. Recent studies evaluating treatment outcomes have been included in this umbrella review to form a framework to unify data and help make accurate and conscientious decisions.

Objectives

To assess systematic reviews, with or without meta-analyses, of self-ligation system effectiveness for:

The amount of evidence assessed (systematic reviews’ characteristics and characteristics of their included studies).

Risk of bias.

Primary Outcomes: Treatment efficiency with respect to upper and lower incisor inclination, alignment efficiency, space closure, external apical root resorption, transverse dimension changes, torque expression, frictional resistance, and anchorage.

Secondary Outcomes: Clinical effectiveness with respect to oral hygiene, orthodontic pain, treatment time, bracket failure rates, and chairside time.

Material and Methods

Study Registration

The study was registered on the prospective register of systematic reviews on November 9, 2020, with registration number CRD 42020206208. There was compliance with preferred reporting items for overviews of systematic reviews with the harms 2017 checklist, and no author had any conflict of interest (Appendix 1).⁶

Sources of information

A literature search was conducted between January 1, 1990, and October 1, 2021, for systematic reviews and meta-analyses that investigated and compared treatment outcomes of self-ligating and conventional bracket systems with respect to alignment efficiency, space closure, transverse dimensional changes, assessment of external apical root resorption, and upper and lower incisor inclination. Clinical effectiveness was assessed by evaluating treatment time, chairside time, pain, and oral hygiene.

Databases searched included MEDLINE (via PubMed), SciELO, LILACS, Science direct, Embase, German National Library of Medicine, and major repositories of systematic reviews such as Cochrane Central Register of Controlled Trials (The Cochrane Library). References of included papers were manually verified for a comprehensive search for relevant studies, and grey literature was searched through the Open Grey database.

Search Strategy

The search was developed in the MEDLINE (PubMed) database based on the population, intervention, comparison, and outcome question: Are self-ligating brackets better than conventional brackets in clinical performance with respect to treatment time, alignment efficiency, space closure, root resorption, and oral hygiene? The search used keywords, MeSH terms and Boolean operators OR and. There was no restriction on language or publication dates. A similar strategy was adopted for other databases used. Only systematic reviews and meta-analyses were considered. (Appendix 2).

Study Selection and Eligibility Criteria

The studies were assessed based on predefined population, intervention, comparison, and outcome elements as:

Participants (P): Patients needing fixed orthodontic appliances.

Intervention (I): Orthodontic fixed mechanotherapy with self-ligating brackets irrespective of the type and material of bracket used.

Comparison (C): Orthodontic fixed mechanotherapy with conventional brackets irrespective of the type of bracket used, including extraction or nonextraction treatment protocols.

Outcomes (O)/Variables of interest

Primary Outcomes: Treatment efficiency with respect to the assessment of external apical root resorption, alignment efficiency, transverse dimensional changes, space closure, pain, oral hygiene, frictional resistance, upper and lower incisor inclination, and torque expression.

Secondary Outcomes: Clinical effectiveness, oral hygiene, pain, treatment time, periodontal health, bracket failure rates, and chairside time.

Type of Studies Included: Systematic reviews of randomized and nonrandomized studies, with or without meta-analyses

Review Selection Process

Publications were uploaded to Rayyan QCRI (Qatar Computing Research Institute) (https://rayyan.qcri.org).⁷ 2 independent reviewers (MM and SV) reviewed articles, and any differences in opinion were resolved by the third reviewer (PC). Articles were evaluated according to predefined criteria for inclusion by reading the abstract and titles. Narrative reviews, duplicate studies, commentaries on reviews, overviews or umbrella reviews, and network meta-analyses were excluded, along with the articles that did not meet inclusion criteria.

Assessment of Methodological Quality of the Reviews

Methodological evaluation was performed using the risk of bias in systematic reviews (ROBIS) tool, which evaluates systematic reviews and meta-analyses.⁸ Risk of bias was evaluated in 3 phases: (a) Assessing relevance, (b) identifying concerns with the review process, which is further broken down into 4 domains: Study eligibility criteria, identification and study selection, data collection, and study appraisal and synthesis and findings, and (c) judging the risk of bias. These were considered together for allocating a “low,” “high,” or “unclear” risk of bias score. Any discrepancies during the scoring process were resolved through discussion and consensus (Table 1).

Table 1.

Tabular Presentation for ROBIS Results

Review	Phase 2				Phase 3
Review	1. Study Eligibility Criteria	2. Identification and Selection of Studies	3. Data Collection and Study Appraisal	4. Synthesis and Findings	5. Risk of Bias in the Review
Čelar et al ¹²	☹	☹	☹	☹	?
Malik et al ²³	☺	?	☺	☺	☺
Dehbi et al ²⁰	☺	☹	☹	☹	?
Arbildo H et al ²²	☺	?	☺	☹	?
Nam HJ et al ²⁴	☺	☺	☹	☺	?
Yi J et al ¹⁵	☺	☺	☺	?	☺
Huang J et al²¹	☺	☺	☺	☹	☺
Longoni J et al ¹⁹	☺	☺	☺	☺	☺
do Nascimento et al ¹³	☺	☺	☹	☹	?
Fleming PS et al ¹⁰	☺	☺	☺	?	☺
Zhou Q et al ¹⁴	☺	☺	☺	?	☺
Arnold S et al ¹⁷	☺	☺	☺	?	☺
Papageorgiou SN et al ¹¹	☺	☺	☺	☺	☺
Chen S et al ⁹	☺	☺	☺	?	☺
Yang X et al¹⁸	☺	☺	☺	☺	☺
Yang X et al ¹⁶	☺	☺	☹	☺	?

Note . ☺ = low risk; ☹ = high risk; ? = unclear risk

Data Extraction and Management

A standardized, prepiloted form developed by the Joanna Briggs Institute was used to extract data, assess study quality, and perform qualitative evidence synthesis.⁴ 2 independent reviewers (MM and SV) collected the data in structured tables. The information extracted was authors, year, review title, number of articles included, databases used, search strategy, data collected, quality, and risk analysis of bias (yes or no and which tool was used), type of analysis (qualitative or quantitative), and study results and conclusion. Any difference in opinion between the 2 reviewers was resolved by a third reviewer (PC). The summary of evidence and outcomes assessed in systematic reviews were summarized through data tables of included review characteristics (Table 2).

Table 2.

Characteristics of Included Studies

Author Details	Number of Studies	Design of Studies	Electronic Databases Searched	Outcomes	Risk of Bias Assessment	Results	Meta-analysis Done
Chen et al 2010 ⁹	16	RCTs, cohort and cross-sectional studies	PubMed, Web of Science, EMBASE, and Cochrane Library—from 1966 to the third week of May 2009	Rate of mandibular incisor alignment, rate of en-masse space closure, number of visits, chair time, and bracket failure rate	Modified Newcastle-Ottawa scale	Significant difference with regard to chair time. Statistically significant, difference in mandibular incisor proclination (1.5° less proclination with self-ligating brackets compared with conventional brackets). No other significant differences in treatment time or occlusal characteristics after treatment were found	Yes
Fleming et al 2010¹⁰	17	RCTs	MEDLINE via OVID (1950 to April 2009, EMBASE (1980 to April 2009), and Cochrane Central Register of Controlled Trials (The Cochrane Library, 2009). = ClinicalTrials.gov (www.clinicaltrials.gov) and the National Research Register (www.controlled-trials.com, ProQuest Dissertation Abstracts and Thesis database	Alignment efficiency, pain experience, arch dimensional changes, rate of orthodontic space closure, bond failure rate, and periodontal effects	Cochrane risk of bias assessment tool	No significant difference in alignment efficiency, pain experience, arch dimensional changes, rate of orthodontic space closure, bond failure rate, and periodontal effects	Meta-analysis of the influence of bracket type on subjective pain experience
Papageorgiu et al 2013¹¹	25	RCTs and quasi RCTs	CSDR, CENTRAL, DARE, MEDLINE, SCOPUS, Biomed Central, BBO, IndMed, SciELO, ClinicalTrials.gov, Conference Paper Index, Digital Dissertations, German National Library of Medicine (ZB MED), Google Scholar, ISI Web of Knowledge, metaRegister of Controlled Trials, OpenSIGLE	Alignment efficiency, space closure, treatment side effects, treatment outcomes	Cochrane risk of bias assessment tool GRADE	No significant difference in space closure, Meta-analysis indicated the number of needed appointments, EARR at the mandibular central incisor, and buccolingual inclination of the mandibular incisor were not significantly greater for patients treated with SL brackets compared to CBs	Yes
Čelar et al 2013 ¹²	4	RCTs, CCTs	Embase, CENTRAL, MEDLINE, and manual American Journal of Orthodontics and Dentofacial Orthopedics, European Journal of Orthodontics, Journal of Orofacial Orthopedics, Orthodontics and Craniofacial Research, and The Angle Orthodontist.	Pain during initial therapy, number of appointments, overall treatment time, and time needed for arch wire placement and removal	COCHRANE risk of bias assessment tool	No significant differences in pain during orthodontic therapy, overall treatment time, number of appointments, and ligation times	Yes
do Nascimento et al 2014 ¹³	6	RCTs, CCTs	Cochrane Central Register of Controlled Trials; Ovid ALL EMB Reviews, PubMed and Bireme between January 1965 and December 2012	Measurement of colonies of S. mutans and/or their effects on periodontal tissues.	JADAD	No significant difference in colony formation and adhesion of S. mutans	No
Zhou et al 2015 ¹⁴	6	RCTs, CCTs	The Cochrane Oral Health Group’s Trials Register, CENTRAL, MEDLINE via OVID, EMBASE via OVID, Web of Science.	Canine retraction rate and the amount of AP anchorage loss	Cochrane risk of bias assessment tool	No significant difference was observed in canine movement and AP anchorage loss in both groups	Yes
Yi et al 2016 ¹⁵	7	RCTs, CCTs, cohort studies	CENTRAL, PubMed, EMBASE, China National Knowledge Infrastructure (CNKI) and SIGLE until Apr 2016	The reduction of root length (in millimeters and in percentage).	Saltaji et al. and Wu et al.	EARR of maxillary central incisor Non SLB > SLBs (SMD –0.31; 95% CI [–0.60, –0.01] 0.20; 95% CI [–0.05, 0.45]	Yes
Yang et al 2016 ¹⁶	8	RCTs	OVID, EMBASE via OVID, Cochrane Central Register of Controlled Trials, World Health Organization International Clinical Trials Registry Platform, Chinese Biomedical Literature Database, and the China National Knowledge Infrastructure	VAS, PI, discomfort, oral hygiene	Cochrane risk of bias assessment tool	No significant difference in oral hygiene or discomfort	Yes
Arnold et al 2016¹⁷	12	RCTs, CCTs	Medline via PubMed, (CENTRAL) ClinicalTrials. gov (www.clinicaltrials.gov), and the National Research Register (www.controlled-trials.com)	Changes in periodontal or gingival inflammation indices recorded throughout orthodontic treatment course. These included but were not confined to: PI, GI, BoP, PD	GRADE	No significant difference	No
Yang et al 2017 ¹⁸	11	RCTs	MEDLINE, Cochrane CENTRAL Register of Controlled Trials (CENTRAL), EMBASE (via OVID), World Health Organization International Clinical Trials Registry Platform, Chinese Biomedical Literature Database, China National Knowledge Infrastructure, and Chinese Medical Journal Database	Transversal dimensional changes, space closure, alignment efficiency, treatment time	GRADE Cochrane	Expansion in posterior maxillary width > CBs Mandibular intercanine width is increased in CBs>SLBs No significant difference in space closure, alignment efficiency Shorter duration of treatment with CBs	Yes
Longoni et al 2017 ¹⁹	5	RCTs and Quasi RCTs	LILACS, PubMed, SciELO, Science Direct, Scopus, Google Scholar, OpenGrey	The microbial level of S. mutans retention around 2 types of metallic bracket – conventional versus self-ligating	GRADE MASEARI	Self-ligating brackets accumulate less bacteria	No
Dehbi et al 2017²⁰	20	RCTs	PubMed database	Therapeutic efficacy on the basis of 5 clinical criteria: tooth alignment, retraction, degree of expansion, duration of treatment, and patient discomfort.	None	No difference was found in alignment efficacy, space closure, expansion, and treatment time. Increased discomfort in self-ligating systems was reported	No
Huang et al 2018²¹	4	RCTs, CCTs	PubMed, Ovid, EMBASE, and the Cochrane Library	Oral malodor scores, PI, GI, and periodontal pocket depths	Cochrane risk of bias assessment tool	No statistical difference in PI and GI scores. Oral malodor was reduced in SLBs	Yes
Arbildo et al 2018²²	12	RCTs, CCTs	PubMed, Embase, SciELO, ScienceDirect, SIGLE, LILACS, BBO, Google Scholar, and Cochrane Central Register of Controlled Trials	PD, BoP, GI, and PI	Cochrane risk of bias assessment tool	PD—no significant difference BoP—no significant difference GI— no significant difference PI—no significant difference	Yes
Malik et al 2019²³	5	RCTs and Non RCTs	PubMed, Scopus, Web of Science, Dental & Oral Science and CINAHL, along with handsearching Google Scholar, metaRegister of Controlled Trials, National Institute of Public Health registry for clinical trials and clinicaltrials.gov.	Primary outcome—Molar anchorage loss; Secondary outcome- Retraction velocity of canines and total duration of retraction or space closure.	Cochrane risk of bias assessment tool	No statistically difference between the control and intervention	Yes
Nam et al 2019²⁴	7	RCTs, prospective and retrospective clinical trials	Cochrane, PubMed, and EMBASE databases, Google Beta Scholar database.	Changes in transverse dimension, changes in inclination of anterior teeth	Cochrane risk of bias assessment tool, MINORS	Inclination of maxillary incisor teeth, intercanine, interfirst premolar, and intersecond premolar widths) showed no significant difference between groups	No

Abbreviations: AP, antero-posterior; ASLBs, active self-ligating brackets; BoP, bleeding on probing; CBs, conventional brackets; CI, central incisor; CCTs, controlled clinical trials; EARR, external apical root resorption; GI, gingival index; PD, probing depth; PI, plaque index; PSLBs, passive self-ligating brackets; RCTs, randomized control trials; S. mutans, streptococcus mutans; SMD; standard mean deviation; SLBs, self-ligating brackets; VAS, visual analog scale.

Analysis of Degree of Overlap in Studies

Citation matrices were generated to determine overlap in studies across systematic reviews. Corrected covered areas (CCAs) were calculated (CCA = 0–5, slight; 6–10, moderate; 11–15, high; and >15, very high overlap). CCA was found to be 0.6 (0.066% overlap) overall in all 17 included studies, which is considered low. An additional CCA for 3 studies was also undertaken as they evaluated similar parameters such as alignment efficiency, arch dimensional changes, bracket failure rates, and treatment time differences at the same time (Table 3).^{9, 10, 11} A CCA score of 0.14 (14% overlap) was obtained, indicating a low incidence of repetition of primary studies (Appendix 3).

Table 3.

CCA of the Reviews Reporting Similar Outcomes

	N	r	C	Proportion	Percentage
Chen vs Papageorgiou	41	34	2	0.25	25%
Chen vs Fleming	32	25	2	0.28	28%
Papageorgiou vs Fleming	41	36	2	0.138	13.8%
Overall	53	41	3	0.14	14%

Results

Description of Included Reviews

The initial search found 605 studies, and after the removal of duplicates, 343 were selected for review by 2 independent reviewers (MM and SV). Any conflict was resolved by a third reviewer (PC). Studies were scrutinized by applying inclusion criteria, and 25 systematic reviews were found eligible for full-text assessment (Figure 1). Following full text assessment, 16 articles were included,^9-24 and 8 were excluded. Out of 17 studies, 12 performed a quantitative analysis,^{9, 10, 11, 12, 14, 15, 16, 18, 21, 22, 23} and 5 performed a qualitative analysis.^{13, 17, 19, 20, 24}

Figure 1.

Source:

Characteristics of the Reviews

Most studies included randomized control trials (RCTs) and Quasi RCTs along with controlled clinical trials. Only 4 studies focused solely on RCTs.^{10, 16, 18, 20} PubMed, Cochrane, Embase, and Google Scholar were the most frequently searched databases. Additional databases included LILACS, ProQuest, German National Library, China National Knowledge Infrastructure (CNKI), SIGLE, and OpenGrey. Only 1 study limited searches to PubMed,²⁰ with 2 limited to the English language,^{12, 23} and 1 limiting the time from January 2012 to January 2017.²²

Characteristics of Studies Included in the Review

The numbers of studies contained within systematic reviews were more or less uniform. Reviews by Chen et al.,⁹ Fleming et al.,¹⁰ and Papageorgiou et al.¹¹ included the highest number of studies. The rest included an average of 6 studies. Cochrane’s risk of bias tool was frequently used to assess primary studies. The Jadad scale was used by de Nascimento et al.,¹³ and the Modified Newcastle Ottawa scale was used by Chen et al.⁹ A GRADE assessment and the Cochrane risk of bias tool were used in 2 studies.^{11, 18}

Methodological Quality of the Reviews

The risk of bias in 10 studies was low,^{9-11, 14, 15, 17-19, 21, 23} while it was unclear in 6.^{12, 13, 16, 20, 22, 24} The methodological quality of almost all studies was positive to signaling questions in domains 1 and 4 of phase 2 of ROBIS. However, Celar et al. and Malik et al. placed language restrictions on English and German,^{12, 23} and Arbildo et al. placed restrictions on the time.²² 4 studies did not mention any efforts made to reduce data collection errors and risk of bias assessment. In synthesis and findings, the main concerns were the absence of sensitivity analyses to make findings more robust. ^{16, 20, 23, 24}

According to phase 3 of the ROBIS tool, most studies did not appropriately address all concerns identified during phase 2 in domains 1 to 4.

All studies did not emphasize results based on statistical significance, and studies included in the systematic reviews and meta-analyses were valid. Thus, we can conclude that most studies had a low overall risk of bias, with conclusions supported by evidence (Table 1; Figure 2).

Figure 2.

Source:

Effects of Intervention

Synthesized data were divided into treatment efficiency and clinical effectiveness for ease of understanding (Table 4). Treatment efficiency was judged based on upper and lower incisor inclination, alignment efficiency, space closure, transverse dimension changes, and anchorage. Clinical effectiveness included parameters such as pain and discomfort, hygiene, periodontal conditions, bracket failure time, and treatment duration.

Table 4.

Tabular Presentation of Qualitative Findings

Phenomenon of Interest/ Context	Synthesized Findings		Author Details
Treatment Efficiency
	Primary outcome—Molar anchorage loss; Secondary outcome—Retraction velocity of canines and total duration of retraction or space closure	No statistically difference between the control and intervention	Malik et al 2019²³
	The reduction of root length (in millimeters and in percentage).	EARR in the Maxillary CI is less in SLBs	Yi J et al 2016¹⁵
	Alignment efficiency, arch dimensional changes, rate of orthodontic space closure	No significant difference	Fleming et al 2010¹⁰
	Canine retraction rate and the amount of AP anchorage	No significant difference	Zhou et al 2015¹⁴
	Alignment efficiency, space closure, treatment side effects, treatment outcomes	No significant difference	Papageorgiou et al 2013¹¹
	Rate of mandibular incisor alignment, rate of en-masse space closure,	Statistically significant, difference in mandibular incisor proclination (1.5° less proclination with SLBs compared to CBs).	Chen et al 2010 ⁹
	Transversal dimensional changes, space closure, alignment efficiency, treatment time	Expansion of transverse width in posterior region SLBS > CBs. Mandibular intercanine expansion in CBsNo significant difference in space closure	Yang 2017 ¹⁸
	Pain during initial therapy, number of appointments, overall treatment time, and time needed for arch wire placement and removal	No significant differences in pain during orthodontic therapy, overall treatment time, number of appointments, and ligation times	Čelar et al 2013 ¹²
	Tooth alignment, retraction, degree of expansion, duration of treatment and patient discomfort.	No significant difference in tooth alignment, degree of expansion	Dehbi et al 2017 ²⁰
	Changes in transverse dimension, changes in inclination of anterior teeth	Inclination of maxillary incisor teeth, intercanine, interfirst premolar, and intersecond premolar widths showed no significant difference between groups	Nam et al 2019 ²⁴
Clinical Effectiveness
	The microbial level of Streptococcus mutans retention around 2 types of metallic bracket—conventional vs self-ligating	No difference in colonies of bacteria in the 2 groups	Longoni J et al 2017¹⁹
	Measurement of colonies of Streptococcus mutans and/or their effects on periodontal tissues.	There is less accumulation of bacteria on self-ligating brackets	do Nascimento et al 2014¹³
	Pain experience, bond failure rate, and periodontal effects	No significant difference	Fleming et al 2010¹⁰
	Number of visits, chair time, and bracket failure rate	No significant difference with regard to chair time. No other significant differences in treatment time or occlusal characteristics after treatment were found	Chen et al 2010⁹
	Oral malodor scores, PI, gingival index (GI), and periodontal pocket depths	Significant difference in oral malodor scores, self-ligating systems had less malodor.	Huang et al 2018 ²¹
	Probing depth, bleeding on probing, gingival index, and PI	No significant difference in PD, BoP, PI, GI	Arbildo et al 2018²²
	Duration of treatment and discomfort	No significant change in duration of treatment between 2 groups; there is more discomfort in self-ligating brackets.	Dehbi et al 2017²⁰
	VAS, PI, discomfort, oral hygiene	No significant difference	Yang et al 2016¹⁶
	Changes in periodontal or gingival inflammation	No significant difference	Arnold et al 2016¹⁷
	Treatment time	CBs show shorter duration of treatment time	Yang 2017 ¹⁸

Abbreviations: AP, antero-posterior; ASLBs, active self-ligating brackets; BoP, bleeding on probing; CBs, conventional brackets; CI, central incisor; CCTs: controlled clinical trials; EARR, external apical root resorption; GI, gingival index; PD, probing depth; PI, plaque index; PSLBs, passive self-ligating brackets; RCTs, randomized control trials; S. mutans, streptococcus mutans; SMD; standard mean deviation; SLBs, self-ligating brackets; VAS, visual analog scale.

Treatment Efficiency (Table 4)

Data analysis from included studies revealed reduced lower incisor proclination by 1.46mm (95%CI [–2.79, –0.13]).⁹ Yang et al. evaluated interfirst premolar and molar widths and concluded that self-ligating brackets showed increased transverse dimensions posteriorly, while conventional brackets showed increased mandibular intercanine width.¹⁸ Only 1 study evaluated root resorption and determined that external apical root resorption in maxillary central incisors was less with self-ligating brackets than conventional bracket systems by 0.31 mm (CI [−0.60, 0.01]).¹⁵ There were no significant changes in alignment efficiency, space closure, and anchorage loss. ^{10, 11, 14, 18}

Clinical Effectiveness (Table 4)

Systematic reviews assessed the effect of self-ligation on periodontal tissues using different periodontal parameters such as plaque index, gingival index, and bleeding on probing. Longoni et al. found that self-ligating brackets accumulated less bacteria than conventional.¹⁹ 2 studies measured plaque index, gingival index, bleeding on probing, and periodontal pockets but found no significant differences between self-ligating and conventional brackets.^{17, 21} Huang et al. found that oral malodors were less with self-ligating brackets.²¹ No statistical differences in chairside time were observed in the study conducted by Chen et al. ⁹

Yang et al.¹⁸ reported a shorter treatment time when using conventional bracket systems. No significant differences were observed in other clinical parameters such as pain, discomfort, and overall treatment time.^{10, 23}

Discussion

Orthodontists prefer to use appliances that help achieve treatment goals without prolonging treatment duration. Published studies also provide evidence that self-ligating brackets produced quicker results and required fewer office visits.^{25, 26, 27} During orthodontic treatment, periodontal health, and oral malodor are not mutually exclusive but rather codependent on each other for comprehensive and satisfactory treatment. It was, therefore, necessary to analyze data comparing periodontal health in self-ligating and conventional bracket systems.

The main objective of conducting an umbrella review of systematic reviews was to evaluate the methodological quality of systematic reviews on self-ligation and summarize diverse findings related to clinical efficiency and conclusions drawn from current literature. Included articles attempted to report differences between both systems with respect to treatment outcomes, side effects, and acceptability in patients to enable clinicians to make informed decisions on their use.

A citation matrix quantifies the number of times primary studies recur in each systematic review with the investigation of individual studies to derive the CCA mathematically. The value denotes the percentage of overlap of primary studies within the systematic review.²⁸ The CCA of included articles in this umbrella review was 0.6, which is low. A low CCA indicates less overlap of primary studies within each systematic review and meta-analysis, and data can be interpreted with precision. It is also essential to narrow down calculations to a specific parameter to identify overlapping primary studies. Thus, we also performed a CCA for 3 studies that evaluated concurrent outcomes such as alignment efficiency,^{9, 10, 11} arch dimensional changes, bracket failure rates, and treatment time differences (Table 3). A CCA score of 0.14 (14% overlap) was obtained, indicating an incidence of repetition of primary studies. Hence, primary studies in the included systematic reviews are not discordant, and the synthesis of results can be deemed accurate.

The ROBIS tool, used to assess systematic reviews, was designed to be as standardized as possible to assess the risk of bias and relevance to the research question. It was more suitable than AMSTAR 2 as it had more in-depth signaling questions to assess quality.²⁹ Major concerns in assessing the risk of bias included domains related to the selection of studies, data collection, and study appraisal. 2 reviewers completed the ROBIS assessment independently to avoid incorporating bias, and the third reviewer resolved any disagreement.

Most included articles conducted searches in at least 4 electronic databases, which was adequate except for Dehbi et al., who only searched PubMed.²⁰ Included articles compared treatment outcomes of passive self-ligating systems to conventional.

Comparison parameters were varied and comprehensive within the same study. Rate of alignment efficiency was evaluated by 5 studies,^{9, 10, 11, 18, 20} space closure was evaluated by 7 studies,^{9, 10, 11, 14, 18, 20, 23} pain and discomfort were reported by 3 studies^{9, 10, 20} and periodontal condition and oral hygiene were evaluated by 7 studies.^{10, 11, 13, 17, 19, 21, 22} Transverse arch dimensional changes were evaluated by 4 studies^{10, 17, 18, 24} and 1 study reported external apical resorption.¹⁵

Methodological quality of all studies was positive to the following questions: The protocol provided a priori, had an adequate selection of studies by 2 independent reviewers, had a comprehensive search strategy, and provided characteristics of included studies. There was a lack of relevant systematic reviews and meta-analyses that compared the 2 systems based on factors like frictional resistance and torque expression, so it was not feasible to consider these parameters. Treatment outcomes such as molar anchorage, space closure, treatment time, number of visits, bracket failure rate, pain, and discomfort were found to be statistically insignificant in most studies except Dehbi et al., who reported more discomfort in self-ligating systems, which could be attributed to limiting their search strategy to a single database.²⁰

Although no significant differences were observed between self-ligating and conventional brackets in terms of pain, discomfort, oral hygiene, and overall treatment time, some aspects like pain, discomfort, and oral malodor could be relatively subjective. All systematic reviews and meta-analyses concluded that self-ligating systems demonstrated a reduction in external apical root resorption and lower incisor proclination. Less accumulation of bacterial colonies and oral malodor are additional advantages. However, many uncontrolled factors influence clinical orthodontic treatment. Substantial clinical heterogeneities, such as variations in time intervals and patient compliance, must be addressed.

Limitations

This umbrella review is one of the first that evaluated treatment outcomes and efficiency of self-ligating bracket systems. There are some inherent methodological restrictions with no clearly established guidelines on conducting such umbrella reviews, leading to overgeneralizing results. Umbrella review methodology relies on critical appraisal of every primary study in systematic reviews, which is an inherent limitation.

Future Research

Additional studies are needed to evaluate the differences between self-ligating and conventional orthodontic systems. Current evidence is insufficient to make definitive conclusions at this time. One disadvantage of all systematic reviews is the limited number of primary studies. Primary studies with larger sample size and uniform inclusion criteria will enable researchers to make definitive conclusions about the superiority of one system over the other.

Standardizing quantitative synthesis in an umbrella review will lead to a better understanding of results. Lastly, suitable methods need to be developed to address heterogeneity in various systematic reviews.

Conclusions

The methodological quality of systematic reviews conducted on self-ligating brackets was high as most studies followed similar protocols.

Self-ligating brackets had a limited advantage over conventional brackets in routine clinical conditions.

Self-ligating brackets reduced external apical root resorption in anterior maxillary teeth.

Self-ligating brackets demonstrated reduced amounts of lower incisor proclination.

Therapeutic efficiency in terms of maxillary incisor inclination, alignment efficiency, space closure, transverse dimensional changes, and anchorage showed no differences between self-ligating and conventional bracket systems.

Self-ligating and conventional bracket systems showed similar results in terms of bracket failure rate, pain, total treatment time, and periodontal effects.

Oral malodor and chairside time were the only clinical parameters that showed a reduction with self-ligating bracket systems.

Supplemental Material

Supplemental material for this article is available online.

Supplemental Material for An Umbrella Review of Systematic Reviews With or Without Meta-Analysis Assessing Treatment Outcomes and Efficiency of Self-Ligating Brackets by Meghna Mukhopadhyay, Shubhnita Verma, and Prasad Chitra, in Journal of Indian Orthodontic Society

Footnotes

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Prasad Chitra

Statement of Informed Consent and Ethical Approval

Necessary ethical clearances and informed consent was received and obtained respectively before initiating the study from all participants.

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