This systematic review aimed to critically appraise the evidence regarding the effect of bracket ligation type on the periodontal conditions of adolescents undergoing orthodontic treatment.
Search terms included randomized controlled trial (RCTs), controlled clinical trials, ligation, bracket, periodontal, inflammation. Risk of bias assessment was made using the Cochrane risk of bias tool and the quality of evidence was assessed with GRADE.
Electronic Database search of published and unpublished literature was performed without language restriction in May 25, 2016 (MEDLINE via Pubmed, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Clinical Trials.gov and National Research Register).
Of 140 articles initially retrieved, 8 were eligible for inclusion in the systematic review, while 4 RCTs with unclear risk of bias were included in the quantitative synthesis, all comparing self-ligating to conventional steel ligated brackets. Random effects meta-analyses were implemented. At 4–6 weeks after bracket placement there was no evidence to support the use of either type of bracket for achieving improved plaque- (PI) and gingival index (GI). At 3–6 months, there was scarce evidence of greater PI increase for conventional brackets. GI and pocket depth pooled estimates did not reveal significant differences between the two systems. The quality of the evidence was moderate according to GRADE for all outcomes.
Overall, non-significant differences on the periodontal status of adolescents undergoing orthodontic treatment with either conventional or self-ligating brackets were detected.
The periodontal status of adolescents undergoing orthodontic treatment is of considerable importance. The synthesis of the available evidence on oral hygiene related factors will provide insights to best clinical practice during the course of orthodontic treatment.
Despite its universal use and recent technical advancements, orthodontic treatment with bonded braces remains an impediment to an adequate oral hygiene, providing niches for food residues and bacteria . Negative effects on dental hard tissue as well as on the periodontium owing to orthodontic bands and brackets have been described, and several investigations showed that the presence of plaque at the gingival margin is the most important factor in the development of periodontal diseases . Several reports have highlighted the fact that orthodontic brackets are not only associated with noticeable periodontal adjustments, but that the method of archwire ligation onto fixed braces itself has an apparent influence on bacteria accumulation and periodontal status .
In conventional edgewise brackets (CBs) systems, the archwire is ligated either with elastomeric rings or steel ligatures to the brackets. According to a number of studies an increase in biofilm accumulation has been reposted in patients with elastomeric ligatures .
Self-ligating brackets (SLBs), which entrap the archwire with an inbuilt component and do not necessitate further elastomeric rings or steel ligatures, were first introduced by Stolzenberg in the early 1930s . Whilst SLBs were hardly used in the past, an increasing number of orthodontists have come to use them in recent years. Compared to 8.7% of American orthodontists who bonded SLBs in 2002, as many as 42% did so in 2008 . This increase can probably be explained by the fact that various newly developed systems entered the market in the past years, claiming advantages over CBs . Indeed, many studies have been published in which the performance of SLBs and CBs have been compared, in various terms, such as friction, sliding mechanics and anchorage, number of appointments, treatment time, chair time, chair assistance, ergonomics, infection control, comfort for the patient, and oral hygiene . Most of these studies have been analysed within the framework of systematic reviews, and while certain differences between SLBs over CBs could be discerned through individual trial reports, the synthesis of most studies confirm the apparent equivalency of the bracket systems .
The influence of the ligating method (SLBs over CBs) on periodontal health has also been investigated in several randomized controlled trials and other study designs , yet these investigations have never been pooled in a systematic way. As mentioned above, negative effects on the periodontium remain an unsolved problem in fixed orthodontic therapy, and any substantiated impact of the ligation method on periodontal health through a systematic review would be of high clinical relevance.
The aim of this study was therefore to systematically review the available literature on the effects of different ligation methods on periodontal health in adolescent orthodontic patients with fixed braces, while differentiating within CBs according to the type of ligature (steel ligature and elastomeric ligature). To assess periodontal health, the reported impact of SLBs and CBs on plaque index (PI), gingival index (GI) and probing depth (PD) was evaluated, respectively.
Material and methods
The Preferred Reporting Items for Systematic Reviews and Meta-Analyses were followed for reporting of this systematic review. The review was not registered and no protocol was developed.
The following selection criteria were applied for this systematic review:
Study design: Randomized Controlled Trials (RCTs) or Controlled Clinical Trials (CCTs) with more than 10 patients per group were considered.
Participants: Adolescent patients or permanent dentition children wearing fixed orthodontic appliances.
Interventions: Any type of ligation used with fixed appliances, either self-ligating or any type of conventional brackets with either elastomeric or stainless steel (ss) ligatures.
Outcome measures: Changes in periodontal or gingival inflammation indices recorded throughout orthodontic treatment course. These included but were not confined to: Plaque Index (PI), Gingival Index (GI), Bleeding on Probing (BoP), Pocket Depth (PD).
Exclusion Criteria: Studies involving patients with systematic or other diseases undergoing orthodontic treatment and studies involving adult patients (ie. >18 years of age).
Electronic search within the following databases was undertaken in May 25, 2016, while no language restrictions were applied: Medline via Pubmed, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials (CENTRAL). Moreover, unpublished literature was searched in ClinicalTrials.gov ( www.clinicaltrials.gov ) and the National Research Register ( www.controlled-trials.com ), using the terms «orthodontic» AND «periodontal». Hand searching of the reference lists of the retrieved full text articles was also conducted. Authors of original studies were contacted for data clarification where needed. Full search strategy employed in Medline via Pubmed is presented in Appendix A .
Eligibility assessment, data extraction and Risk of Bias (RoB) assessment was implemented independently and in duplicate by two reviewers (SA and DK), while disagreements were resolved through discussion and after consultation with a third author (TE).
Data extraction was performed on standardised piloted forms by two independently working reviewers (SA and DK) who were not blinded to author identity and study origin. Titles and abstracts were examined first followed by full text screening of the potential for inclusion articles. Information was obtained from each included study on study design, observation period and methods, participants, interventions, comparators and outcomes.
Risk of bias within studies
Risk of bias in individual studies was assessed according to the Cochrane Risk of Bias tool for both RCTs and CCTs. In particular, the following domains were considered: 1. random sequence generation, 2. allocation concealment, 3. blinding of participants and/or personnel involved in the study, 4. blinding of assessors, 5. incomplete outcome data reporting, 6. selective reporting of outcomes, 7. other sources of bias. An overall assessment of the risk of bias was made for each included study (high, unclear, low). Trials with at least 1 item designated to be at high risk of bias were regarded as having an overall high risk of bias. Trials with unclear risk of bias for one or more key domains were considered to be at unclear risk of bias and trials with low risk of bias in all domains were rated as low risk of bias. By convention it was regarded that CCTs were to be rated as of high risk of bias for the first two domains pertaining to the risk for selection bias.
Summary measures and data synthesis
Clinical heterogeneity of included studies was assessed through the examination of individual trial settings, eligibility criteria, ligation methods used and data collection methods. Statistical heterogeneity was examined through visual inspection of the confidence intervals (CIs) for the estimated treatment effects on forest plots. Also, a chi-square test was applied to assess heterogeneity; a p-value below the level of 10% (p < 0.1) was considered indicative of significant heterogeneity . I 2 test for homogeneity was also undertaken to quantify the extent of heterogeneity.
Only studies at unclear or low risk of bias overall were included in meta-analyses, therefore only RCTs were deemed eligible for inclusion. Random effects meta-analyses were conducted as they were considered more appropriate to better approximate expected variations in trial settings. Treatment effects were calculated through pooled weighted mean differences (WMD) in periodontal/gingival index changes along with associated 95% Confidence Intervals (95% CIs) and Prediction Intervals where applicable (at least 3 trials needed). As a number of included studies were designed as split-mouth, the mean differences for those were calculated between quadrants and the standard deviation of the difference was approximated by the formula:
S D d i f f = s d 1 2 + s d 2 2 − 2 r s d 1 s d 2