Objectives

The aim of the current study is to evaluate the methodological quality of the available SRs and MAs investigating the effects of FOAs on the periodontium to offer the clinician a summary of the current evidence and the quality of authentication.

Protocol registration

This overview of systematic reviews followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The review protocol was registered at the International prospective register of systematic reviews (PROSPERO) with registration number CRD42018106662. Few changes have been made after the protocol registration including the change in the title.

Information sources, search strategy, and study selection

Search strategy

The electronic literature search was conducted in databases including PubMed, Embase, Cochrane Library, LILACS, Scopus, Web of science, SCIELO, Ovid, CINAHL via EBSCO in March 2018 and was conducted again in January 2019. No restrictions of language or publication date were applied. The implemented search strategy is presented in Appendix 1 .

Manual searching was performed in Google scholar, European Journal of Orthodontics, Journal of periodontology, Periodontology 2000, Journal of oral rehabilitation, Journal of clinical and oral investigations, Quintessence Publishing, American Journal of Orthodontics and Dentofacial Orthopedics, the Angle Orthodontist, and Seminars in Orthodontics. Bibliographies of the included full text articles were scanned for relevant studies. Two investigators independently performed and repeated the searches.

Unpublished literature was searched electronically at ProQuest and PROSPERO using the terms “orthodontic”, “periodont*”, “systematic review”, “meta-analysis” and “gingiva”. Authors were contacted to identify unpublished or ongoing systematic reviews and to clarify data as required.

Eligibility criteria

The selection criteria that were applied for the inclusion of articles in this review are represented in Table 1 .

After removal of internal and external duplicates, articles were screened based on title and abstract. When titles and abstracts were insufficient to decide, the full text of the article was acquired. Assessment of the reviews for inclusion was performed independently and in duplicate by two investigators. Disagreements regarding study inclusion were resolved by discussion to reach a final consensus

Data items and collection

Data extraction sheets were developed, and data were extracted independently by the two investigators . The collected data included: the design of the primary studies; the number of participants and their grouping, description of the interventions and comparator, the quality of the primary studies, the outcomes, results and conclusions.

Risk of bias/ quality assessment for the included reviews

The methodological quality of the included SRs was assessed independently by two reviewers using the A Measurement Tool to Assess Systematic Reviews (AMSTAR 2) checklist. The tool has 16 items to which responses are either yes, no, partial yes. The methodological quality was scored as High (Zero or one non-critical weakness), moderate (more than one non-critical weakness), low (One critical flaw with or without non-critical weaknesses), and critically low (more than one critical flaw with or without non-critical weaknesses).

Assessment of the overall quality of evidence across studies

The results of the SRs that were shown to have moderate or high quality according to the AMSTAR 2 checklist were used to construct the overall body of evidence for each of the main outcomes using the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach. The GRADE profiler was used to evaluate studies for the methodological quality, risk of bias, directness of evidence, inconsistency, precision of effect estimates, and risk of publication bias. The GRADE result was interpreted as follows: “high quality” ‒ further research is very unlikely to change the confidence in the estimate of effect; “moderate quality” ‒ further research is likely to have an important impact on the confidence in the estimate of effect and may change the estimate; “low quality” ‒ further research is very likely to have an important impact on the confidence in the estimate of effect and is likely to change the estimate; and “very low quality” ‒ very uncertain about the estimate.

Study selection and characteristics

A total of 2524 articles were initially identified through electronic search, and five articles were obtained through manual searching. Initially, 55 articles met the inclusion criteria and were retrieved in full text. After reviewing the full texts, 36 articles were excluded. The most common reason for exclusion was the narrative nature of the reviews. The list of excluded studies is presented in Appendix 2 . We contacted the authors of four studies identified from PROSPERO to check the developing status of their SRs, however they didn’t respond. Finally, nineteen articles were included in the analysis. The detailed literature search process is presented in Fig. 1 .

PRISMA flow diagram for the study selection process.

Characteristics of included reviews

The data of the included SRs is summarised in Table 2 . From the included studies SRs, nine included only qualitative analysis and ten included MAs. Regarding the study designs of the included articles in the reviews, two SRs included only RCTs, six reviews included cross sectional and non-controlled studies. Seven reviews included RCTs and CCTs. Most of the remaining reviews included retrospective and prospective cohort studies.

Table 2

Characteristics of included studies.

Study (SR/MA)	Number and Design of primary studies	Search strategy	Total number of participants and grouping	Intervention	Comparator	Outcomes	Quality of primary studies	Results	Authors’ conclusions
Objectives: to compare between SLBs and CBs regarding; oral hygiene, periodontal parameters, accumulation of S. mutans colonies, prevention of malodour
Arnold et al., 2016 (SR and MA)	8 studies (4 in MA) 7 RCTs (3 of them were split mouth) 1 CCT	(May 2016) Medline via Pubmed, CDSR, CENTRAL. Clinicaltrials.gov No language restrictions.	326 subjects (including split mouth subjects) All patients were adolescents	SLB (active and passive)	CBs (elastomeric or stainless-steel ligatures)	Changes in periodontal or gingival inflammation indices including: (PI), (GI), BOP, (PPD).	Cochrane RoB tool 6 unclear RoB 2 high RoB	After 3–6 months: PI: The mean change in the intervention groups was 0.14 higher GI: The mean change in the intervention groups was 0.06 higher PPD: The mean change in the intervention group was 0.01 higher	There is no evidence to support the claim that SLBs have relevant clinical advantages over CBs regarding the periodontal health in adolescents with bonded brackets
Nascimento et al., 2014 (SR)	6 studies 5 RCTs 1 CCT	(December 2012) CENTRAL; Ovid, PubMed and Bireme no language restrictions	209	SLBs	CBs (5 studies elastomeric and 1 study metal ligation)	Adhesion and formation of S. mutans colonies	Jadad scale. All studies had high quality	The increase in oral microbiota (S. mutans and Lactobacillus) is associated with the use of orthodontic appliances with both CBs and SLBs with no differences between them	There is no evidence for a possible influence of bracket design (CB or SLBs) over colony formation and adhesion of S. Mutans
Yang et al., 2016 (SR & MA)	12 studies (8 in MA) RCTs No split mouth studies	(December 2015) Medline via OVID, EMBASE via OVID, CENTRAL, World Health Organization International Clinical Trials Registry Platform and the Chinese BioMedical Literature Database	575 311 SLB-treated patients and 264 CB-treated patients	SLBs, (active and passive)	CBs	Discomfort Oral hygiene evaluated through PI or bacterial colonization	Cochrane RoB tool 10 studies unclear risk, 2 studies low risk of bias	The results showed passive SLB and CB did not differ significantly in plaque control [MD: −0.04, 95% CI (−0.30,0.22)]. SLB was not superior over CB in bacterial colonization.	SLBs do not outperform CBs in reliving patients’ discomfort or promoting oral hygiene
Arbildo et al., 2018 (SR and MA)	12 studies (8 in MA) RCTs 9 parallel 3 split mouth	(2012- December 2017) PubMed, Embase, SciELO, ScienceDirect, LILACS, BBO, Google Scholar and in the CENTRAL Grey literature: SIGLE	485. 234 SLBs 251 CBs Age (13.3–21)	SLBs (active and passive)	CBs	PPD BOP GI PI	Cochrane RoB tool All studies have high ROB	PPD, BOP, GI and PI showed no significant differences between CB, active and passive SL brackets.	No differences were detected in the periodontal clinical effect of orthodontic treatment with conventional and self-ligating brackets
Longoni et al., 2017 (SR)	5 studies RCTs (1 parallel) quasi-RCTs (4; 3 split mouth and 1 parallel)	April 2016 LILACS, PubMed, SCIELO, Science Direct, Scopus, and Google Scholar. Grey literature; Open Grey	148	SLBs (active and passive)	CBs (3 studies elastomeric and 2 study metal ligation)	S. Mutans colonization	MAStARI checklist; 2 low risk, 3 moderate risk of bias	No difference between S. Mutans in CB and SLB after 3 months by PCR. Stereomicroscope ST Mutans colonization was more in CB than SLBs after 1, 4, 5, 12, and 24 weeks.	SL brackets accumulate less S. Mutans than conventional metallic brackets.
Huang et al., 2018 (SR & MA)	4 studies (4 in MA) 3 RCTs, 1 CCT	September 2016 PubMed, Ovid, Embase, and the Cochrane Library	172; SLB: 43 CB: 77 CG: 62	SLBs, CBs	CBs, untreated control	Oral malodour scores, PI, gingival index (GI), and periodontal pocket depths.	Cochrane RoB tool; 3 unclear 1 high risk of bias	Fixed appliance versus control: Malodour: CBs showed worse scores at the first week after bonding only. PI: No difference between CBs and CG at 1 week. At 1 month after bonding; significantly higher PI than control GI: statistically higher in CB only at 1 month after bonding. PPD: No significant changes over the 3-month period after bonding. SLB vs. CBs: Malodour scores were better in SLBs than CBs at 1 week. No significant difference in PI and GI.	FOAs are risk factors for malodour at one week after bonding with SLBs better than CBs. PI was worse one month after bonding.
Objective: To determine the correlation between gingival recession/ bone height and incisor inclination (labial movement of incisors) in non-growing post-orthodontic patients compared to adult untreated subjects or patients treated with different methodologies.
Aziz et al., 2011 (SR)	7 studies, all were retrospective; 2 had no control group	July 2010 Medline, PubMed, Embase, Web of Science, Cochrane Database of Systematic Review, CENTRAL	590 (190 were CG)	Fixed appliance with labial movement of incisors	Fixed appliances with no labial movement of incisors	Gingival recession	Custom made tool for quality assessment	Six studies denied an increased risk of gingival recession after labial advancement of mandibular incisors due to orthodontic treatment. One study concluded that lower incisor proclination greater than 10° would inevitably lead to gingival recession.	There is no association between appliance induced labial tipping and gingival recession. Labial movement of incisors during orthodontic treatment is not contributing to gingival recession
Tepedino et al., 2018 (SR)	2 studies Retrospective	June 2017. MEDLINE via PubMed, EMBASE, Scopus, Web of Science, and Cochrane Library. Grey literature: OpenGrey.	350 (150 untreated control, 26 fixed appliances with extraction, 174 non-extraction fixed appliances) Age (22–65)	FOAs (non-extraction basis)	Adult untreated subjects (1 study) or patients treated with FOAs on extraction basis (1 study)	Gingival recession and/or bone height, and post-treatment position of incisors	New Castle Ottawa scale. Moderate quality of studies.	Recession was significantly higher in treated patients compared to that in untreated controls but the difference was minor and clinically insignificant. No correlation was found between the final inclination of lower teeth and gingival recession.	No scientific evidence exists stating that proclination of incisors following orthodontic treatment with fixed appliance increases the risk of gingival recession
Objective: To assess the effect of comprehensive treatment with fixed orthodontic appliances on periodontal outcomes, inflammation indices and clinical attachment levels in adolescent and adult periodontally healthy patients.
Bollen 2008 (SR and MA)	12 studies; (8 in MA) 1 RCT, 3 CCT, 8 cross sectional studies excluded studies that assessed periodontal outcomes only at the time of appliance removal.	June 2007 MEDLINE; Web of Science; and the CENTRAL, CDSR, DARE and Health Technology Assessment. Grey literature: Clinicaltrials.gov, ProQuest	1670; 821 intervention group, 849 in the untreated CGs. Age (12–47)	Fixed or removable appliances	No treatment	Alveolar bone loss, PPD, clinical attachment loss, gingival recession and gingivitis.	Cochrane RoB tool for RCTs, New Castle Ottawa scale for NRCTs. All had high risk of bias	Alveolar bone loss: was 0.13 mm (0.07–0.20) greater in the intervention group than controls. PPD: intervention group had pocket depths that were, 0.23 mm (0.15–0.30) deeper than those of the control groups. Gingival recession: The intervention group had gingival recession 0.03 mm (0.01–0.04) greater than did the control group.	There is an absence of reliable evidence on the positive effects of orthodontic therapy on periodontal status. The available evidence suggested a small mean worsening of periodontal status after orthodontic therapy.
Verussio et al., 2018 (SR)	10 studies 7 RCTs (2 of them were split mouth), 3 CCTs	July 2016 CENTRAL, Embase, Medline	421, 274: Fixed appliances 78 removable appliances 69 untreated control	Orthodontic treatment	Untreated patients or patients with different orthodontic treatment	BOP GI PI PPD CAL	Cochrane RoB tool (results NR)	Patients undergoing orthodontic therapy show an increase in BOP, GI and PI The highest inflammatory values were associated with fixed traditional orthodontic treatment	The use of orthodontic appliances, particularly fixed appliances, can favour the increase of periodontal tissue inflammation.
Papageorgiou et al., 2017 (SR and MA)	9 studies (9 in MA) prospective non-randomized trials	February 2017 Medline via Pubmed, Scopus, Embase, Web of Knowledge, CENTRAL, CDSR, Virtual Health Library Grey Literature: ISRCTN registry	335; 231 FOAs 104 untreated CG Age (11.4–42.1)	FOAs	Untreated patients (3 studies only) Other orthodontic treatment	Clinical attachment loss during orthodontic treatment	ROBINS-I tool, 8 had moderate RoB, 1 had serious RoB	FOAs were associated with a clinical attachment loss of 0.11 mm, which was neither statistically nor clinically significant. Untreated patients showed CAL 0.07 mm Intrusion of anterior teeth was associated with a slight attachment gain of 0.63 mm	Orthodontic treatment with fixed appliances might have little to no clinically relevant detrimental effect on the CAL
Cerroni et al., 2018 SR	5 studies cohort studies (prospective and retrospective)	From January 1997 to April 2017 Pubmed and Cochrane	128	Fixed orthodontic appliances	NR	BOP GI PI PPD	Customized quality assessment tool (excluded 3 articles who had low quality)	Long term outcomes: studies reported no permanent effects on gingival status and that periodontal values tended to normalize 3 months- 2 years after fixed appliance removal.	There is moderate evidence that fixed appliances influence periodontal status. Orthodontic appliances developed generalized plaque accumulation and gingivitis in a short follow-up.
Objective: to assess evidence from human studies about qualitative changes in the subgingival microbiota/ plaque induced by orthodontic treatment.
Freitas et al., 2014 (SR)	4 studies (1 study prospective longitudinal, 1 study longitudinal, 2 studies NM)	May 2012 PubMed; Web of Knowledge and Ovid databases. (English language)	139	Fixed orthodontic appliances	No control group	Microbial colonization in orthodontic fixed appliances	Customized quality assessment tool (excluded 4 articles who had low quality)	Placement of FOAs increased quantity and quality of oral microbiota. Aa increased in subgingival plaque (2 studies) Aa didn’t increase (1 study) Increased Streptococci (1 study)	Moderate evidence showed that FOAs influenced the quantity and quality of oral microbiota. This might be a transitional effect that depends on oral hygiene control.
Guo et al., 2017 (SR & MA)	13 studies (4 in MA) (two CCTs, three cohort studies and eight non-controlled Studies)	November 2016 PubMed, Cochrane Library, and EMBASE	752 Age 13–36	Fixed orthodontic treatment with metal brackets and bands	3 studies had untreated controls, 8 self-controlled studies	frequency of periodontopathogen in the subgingival plaques	MINORS moderate scientific evidence	Following FOAs insertion, the frequencies of Pg and Aa showed no significant change, the frequency of Tf significantly increased in short-term (0–3 months). During >6 months observation, the levels of subgingival periodontopathogens exhibited a transient increase but decreased to the pre-treatment levels afterwards. After removal of the FOAs, the 4 periodontopathogens showed no significant difference compared with before removal.	The levels of subgingival pathogens presented temporary increases after FOAs placement and appeared to return to pre-treatment levels several months later. Orthodontic treatment might not permanently induce periodontal disease by affecting the level of subgingival periodontal pathogens.
Papageorgiou et al., 2018 (SR and MA)	24 studies 3 were RCTs, 5 were prospective NRCTs, and 16 were nonrandomized studies of unclear design	August 2017 Medline via Pubmed, Scopus, Embase, Web of science, CENTRAL, CDSR, virtual health library, Google Scholar, Grey Literature: ISRCTN registry, ClinicalTrials.gov	1271, only 4 studies had untreated controls	Orthodontic treatment with any fixed appliances	(1) Untreated subjects (2) Other form of orthodontic treatment	Qualitative and quantitative analysis of the subgingival microbiota. Time-points were pre-treatment, short-term mid-treatment; long term mid-treatment; short-term post-treatment; long-term post-treatment.	Cochrane’s RoB tool for RCTs, and a checklist based on Downs and Black tool for nonrandomized studies. All studies had high RoB.	The presence of Aa in the subgingival crevicular fluid of orthodontic patients was increased 3–6 months after FOAs insertion compared to untreated patients (RR = 15.54). There was still increased subgingival prevalence of Aa (RR = 3.98) and Tf in orthodontic patients up to 6 months after appliance removal compared to untreated patients.	Insertion of FOAs seemed to be associated with a qualitative change of subgingival microbiota, which reverts to some extent back to normal in the first months after appliance removal
Lucchese et al., 2018 (SR)	51 studies; (study designs were inadequately reported)	October 2017 PubMed, PMC, Scopus, Lilacs, Scielo, Cochrane Trial Library, Web of Science	1863	Any type of orthodontic appliance. CBs: (29 studies). SLBs: (8 studies) Lingual brackets (4 studies)	NR	Qualitative change in oral microbiota after FOA insertion. Periodontal parameters as PI, BOP	Swedish Council on Technology Assessment in Health Care Criteria for Grading Assessed Studies’ methods. 1 study: high quality. 37 studies: moderate quality. 12 studies: low quality	Orthodontic appliances influence the oral microbiota with an increase in the counts of S. mutans and Lactobacillus and in the percentage of potentially pathogenic gram-negative bacteria.	Orthodontic appliances significantly influence the oral microbiota with alterations appearing one month after the start of treatment. Removable appliances had less impact on oral bacteria than fixed ones.
Objective: to compare periodontal health in patients undergoing orthodontic treatment with clear aligners with that of those undergoing orthodontic treatment with fixed appliances.
Lu et al., 2018 (SR and MA)	7 studies (7 in MA) All were Prospective cohort studies	October 2017 Cochrane Library, EMBASE, PubMed, Medline, Chinese Biomedical Literature Database, CNKI, and Wan Fang Data.	368, 183 patients in the invisalign group and 185 patients in the CG	Invisalign	FOA	GI PI, PPD sulcus bleeding index (SBI).	The Newcastle-Ottawa Scale. All studies were of high quality (more than 7 stars)	GI and PPD: no significant difference between the invisalign group and the CG, at 1,3 and 6 months. PI: Invisalign had a significantly lower PI, at 1 month (OR=−0.53), 3 months (OR=−0.69), and 6 months (OR=−0.91). SBI: Invisalign showed a lower SBI, at 1 month (OR=−0.44), 3 months (OR=−0.49), and 6 months (OR=−0.40)	The meta-analysis indicated that compared with FOAs, patients treated with invisalign had a better periodontal health.
Jiang et al., 2018 (SR/MA)	10 studies; (9 in MA) 3 RCTs, 7 cohort studies	August 2017 PubMed, Web of Science, Cochrane Library, and Embase Grey literature.	427 patients (190 patients used clear aligners, and 237 patients used fixed appliances)	Clear aligners	FOA	GI, PI, BOP, PPD	Cochrane RoB tool for RCTs, The Newcastle-Ottawa Scale for non RCTs 9 studies medium quality, 1 study high quality. GRADE assessment	Clear aligners were better than FOA for; PI (MD −0.53) moderate level of evidence GI (MD, −0.27) – moderate level of evidence PPD: (MD, −0.35) – low level of evidence.	Clear aligners were better for periodontal health than FOAs and might be recommended for patients at high risk of developing gingivitis
Rossini et al., 2015 SR	5 studies (the results of 4 of them were included) 1 RCT, 3 prospective studies	September 2014 Pubmed, National Library of Medicine’s Medline, Embase, CENTRAL, Web of Knowledge, Scopus, Google Scholar, and LILACS.	173 patients 92 with FOA 71 with clear aligners 10 untreated control group	Clear aligners	FOA 1 study had untreated control group	GI, PI, BOP, PPD	A grading system described by the Swedish Council on Technology Assessment in Health Care. Quality of the collected evidences was moderate (grade B) in all the studies	A significant decrease of periodontal indices (GI, PBI, BoP and PPD) during CAT was observed in the analyzed sample of patients.	Periodontal health, as well as quantity and quality of plaque, were better during aligner therapy than during FOA treatments. (moderate evidence)

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