The effects of fixed orthodontic retainers on periodontal health: A systematic review

Introduction

The objective of this systematic review was to assess the available evidence in the literature for the effects of fixed orthodontic retainers on periodontal health.

Methods

The following databases were searched up to August 31, 2019: Medline, EMBASE, the Cochrane Oral Health Group’s Trials Register, CENTRAL, ClinicalTrials.gov, the National Research Register, and Pro-Quest Dissertation Abstracts and Thesis database. Randomized controlled trials (RCTs), controlled clinical trials, cohort studies of prospective and retrospective design, and cross-sectional studies reporting on periodontal measurements of patients who received fixed retention after orthodontic treatment were eligible for inclusion. The quality of the included RCTs was assessed per the revised Cochrane risk of bias tool for randomized trials (RoB 2.0), whereas the risk of bias of the included cohort studies was assessed using the Risk Of Bias In Nonrandomized Studies of Interventions tool. A modified version of the Newcastle-Ottawa scale was used for cross-sectional studies.

Results

Eleven RCTs, 4 prospective cohort studies, 1 retrospective cohort study, and 13 cross-sectional studies fulfilled the inclusion criteria. The quality of evidence was low for most of the included studies. In contrast to the general consensus, 2 RCTs, 1 prospective cohort study, and 2 cross-sectional studies reported poorer periodontal conditions in the presence of a fixed retainer. The results of the included studies comparing different types of fixed retainers were heterogeneous.

Conclusions

Highlights

•
Eleven RCTs, 4 prospective cohort studies, 1 retrospective cohort study, and 13 cross-sectional studies were eligible for inclusion.
•
Because of the high amount of heterogeneity identified across the included studies and the lack of high-quality evidence, a meta-analysis was deemed inappropriate.
•
In contrast to the general consensus, 2 RCTs, 1 prospective cohort study, and 2 cross-sectional studies reported poorer periodontal conditions in the presence of a fixed retainer.
•
Orthodontic fixed retainers seem to be a retention strategy rather compatible with periodontal health.

Retention after treatment remains 1 of the greatest challenges in orthodontics. The etiology of orthodontic relapse is complex and multifactorial; identified related factors include tension from the periodontal fibers, the final occlusion, pressure from the soft tissues, growth, and age advancement. ^, The risk of relapse is unpredictable and concerns a high proportion of postorthodontic patients. There is evidence that during the postretention period, 70%-90% of the cases show some relapse in the lower arch; the upper arch is also affected but to a lesser extent. There is no consensus for the ideal duration of retention ; however, the first 8-month posttreatment period, when the remodeling of the periodontal fibers occurs, appears to be critical. Most clinicians choose a retention period longer than 8 months and often recommend life-long retention for all patients. ^, Fixed and removable retainers continue to be the most common retention methods. Adjunctive procedures like pericision (or circumferential supracrestal fiberotomy), a surgical technique aimed at cutting the periodontal fibers around the neck of the teeth, and interproximal enamel reduction (or reproximation) have been proposed, but are rarely implemented. ^, Over the last 50 years, several kinds of bonded retainers of varying sizes, cross-section forms, and materials have been suggested. The first nonbanded fixed retainer appeared in the 1970s and consisted of a thick, round stainless steel wire that was bonded only to the canines. Shortly after, the multistranded wire retainer was introduced and proposed in 2 types: the relatively rigid and thick multistranded wire fixed to the canines and the flexible smaller size multistranded wire bonded to each tooth in the anterior segment. The alternatives to wire retainers are the fiber-reinforced composite retainers and the ceramic alumina retention elements which, however, are less popular.

The flexible multistranded wire bonded to each anterior tooth is currently considered the gold standard. ^, The preference to this retainer is attributed to the assumed extra mechanical retention to the composite resin due to the strands, and the wire flexibility that permits physiological tooth mobility and reduced tension in the composite. Bonding on all anterior teeth is also effective in preventing relapse of the incisors. The thick stainless steel wire bonded only to the canines was proposed for its effectiveness in maintaining the intercanine width and for the easier cleaning of the incisors, whereas the fiber-reinforced composite retainer was selected for its esthetics and biocompatibility.

Fixed orthodontic retainers are compliance free, invisible, and worn continuously. However, teeth are more prone to plaque and calculus accumulation, and appropriate oral hygiene procedures are more complex and require more time. Widespread use of fixed retainers and the need for long-term wear demonstrate the importance of assessing the effects of this increased accumulation of deposits on the periodontium. Previous systematic reviews on the subject were inconclusive and also, most importantly, did not include all available studies existing in the literature. ^, Therefore, the first aim of this review was to perform a more recent evaluation of the potentially deleterious effects of fixed orthodontic retainers on periodontal health. The secondary objective was to compare different kinds of fixed retainers according to their effects on periodontal health, and if possible, to recommend 1 of them.

Material and methods

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses were followed in reporting this systematic review. The protocol of this study was not registered in a publicly assessable database. This review was conducted per the Cochrane Handbook for Systematic Reviews of Interventions .

Criteria for considering studies for this review

Types of studies

Randomized controlled trials (RCTs), controlled clinical trials, cohort studies of prospective and retrospective design, and cross-sectional studies were considered eligible for inclusion in this review. Case reports, review articles, and animal studies were excluded.

Types of participants

Patients of any age who received fixed retention after orthodontic treatment.

Types of interventions

All kinds of fixed retainers were considered eligible, irrespectively of the wire type, bonding materials, and the number of teeth bonded.

Types of control groups

Groups of individuals without fixed retainers (removable retainers accepted), repeated measurements of the same patients, or groups with different wires for fixed retention.

Types of outcomes

Periodontal measurements (of any type) during fixed retention, assessing periodontal health or disease, with no limit on the observation period.

Search methods for study identification

Detailed search strategies were developed and appropriately revised for each database, considering the differences in controlled vocabulary and syntax rules. The following electronic databases were searched: Medline (via Ovid and PubMed from 1946 to August 31, 2019; Appendix 1 ), EMBASE (via Ovid), the Cochrane Oral Health Group’s Trials Register and CENTRAL. Unpublished literature was searched on ClinicalTrials.gov , the National Research Register, and Pro-Quest Dissertation Abstracts and Thesis database. The search attempted to identify all relevant studies irrespective of language. The reference lists of all eligible studies were hand-searched for additional studies.

Data collection and analysis

Selection of studies

Study selection was performed independently and in duplicate by the first 2 authors (M.A. and K.D.) of the review, who were not blinded to the identity of the authors of the studies, their institutions, or the results of their research. The study selection procedure was comprised of a staged reading of titles, abstracts, and full-text. After exclusion of not eligible studies, the full report of publications considered by either author eligible for inclusion was obtained and assessed independently. Disagreements were resolved by discussion and consultation with a third author (D.K.). A record of all decisions on study identification was kept.

Data extraction and management

The first 2 authors (M.A. and K.D.) performed data extraction independently and in duplicate. Disagreements were resolved by discussion or the involvement of a third author (D.K.). The following data were collected on a customized data collection form: (1) author, title, and year of study; (2) design of the study; (3) number, age, and gender of participants in intervention or control groups; (4) type of retainer, dimensions of wire; (5) number of teeth upon which the retainer was bonded; (6) observation period (follow-up of patients); and (7) method of outcome assessment. If stated, sources of funding, trial registration, and publishing of the trial’s protocol were recorded.

Measures of effect

For continuous outcomes, mean differences and standard deviations were used to summarize the data from each study. For dichotomous data, the number of participants with events, and the total number of participants in the experimental and control groups were analyzed. We planned to assess outcomes at more than 1 time point in the follow-up period, where applicable. All such assessments were recorded, and decisions on which time-of-outcome assessment to use from each study were based on the most commonly reported timing of assessment among all included studies.

Unit-of-analysis issues

In all cases, the unit of analysis was the patient. We anticipated that some of the included studies would present data from repeated observations on participants, which could lead to unit-of-analysis errors. In this case, we followed the advice provided in Section 9.3.4 of the Cochrane Handbook for Systematic Reviews of Interventions .

Dealing with missing data

In studies where data were unclear or missing, we contacted the principal investigators or the corresponding author, or both.

Assessment of heterogeneity

We assessed clinical, methodological, and statistical heterogeneity by examining the characteristics of the studies, the similarity between the types of participants, the interventions, and the outcomes as specified in inclusion criteria for considering studies for this review.

Assessment of reporting biases

Reporting biases arise when the reporting of research findings is affected by the nature or direction of the findings themselves. We attempted to minimize potential reporting biases, including publication bias, multiple (duplicate reports) publication bias, and language bias in this review, by conducting an accurate and at the same time, a sensitive search of multiple sources with no restriction on language. We also searched for ongoing trials.

Quality assessment of included studies

The quality of the included RCTs was assessed per the revised Cochrane risk of bias tool for randomized trials (RoB 2.0). The risk of bias of the included cohort studies of the prospective and retrospective design was assessed using the Risk Of Bias In Nonrandomized Studies of Interventions Tool. A modified version of the Newcastle-Ottawa scale (NOS) was used for cross-sectional studies. For the sample selection process, a maximum of 3 stars was given, for the comparability of the groups, 2 stars, and the outcome domain, again, 2 stars. When scoring a total of 7 stars, the study was considered as “good.”

Data synthesis

We planned to conduct meta-analyses if there were studies of similar comparisons reporting the same outcomes. Risk ratios would have been combined for dichotomous data using the random-effect models. In the case of qualitative synthesis, it was planned to include all eligible studies in the synthesis but to emphasize their weight according to their quality.

Results

Selection of studies

Of the 395 studies initially identified through database searching, 29 studies fulfilled our inclusion criteria and were included in this systematic review. The flow diagram for the study selection is shown in Figure . Of the 29 studies, 11 were RCTs, 4 prospective cohort studies, 1 retrospective cohort study, and 13 cross-sectional studies.

Risk of bias assessment

Randomized controlled trials

The quality of the included RCTs was assessed per the revised Cochrane risk of bias tool for randomized trials (RoB 2.0) and is presented in Table I .

Table I

Risk of bias of the included RCTs

No.	Author(s)/y	Bias arising from the randomization process	Bias due to deviations from intended interventions	Bias due to missing data	Bias in measurement of outcomes	Bias in the selection of the reported result	Overall
1	Al-Moghrabi et al 2018	Low risk	Low risk	Some concerns	Some concerns	Some concerns	Some concerns
2	Artun et al 1987	Some concerns	Low risk	Low risk	Low risk	Some concerns	Some concerns
3	Artun et al 1997	Some concerns	Low risk	High risk	Low risk	Some concerns	High risk
4	Bazargani et al 2012	Low risk	Low risk	Low risk	Low risk	Some concerns	Some concerns
5	Liu 2010	Low risk	Low risk	Low risk	Some concerns	Some concerns	Some concerns
6	Rose et al 2002	Some concerns	Low risk	Low risk	Some concerns	High risk	High risk
7	Storey et al 2018	Low risk	Low risk	Low risk	Some concerns	Some concerns	Some concerns
8	Störmann and Ehmer 2002	Some concerns	Low risk	Low risk	Some concerns	High risk	High risk
9	Tacken et al 2010	High risk	Low risk	Low risk	Some concerns	Some concerns	High risk
10	Torkan et al 2014	Low risk	Low risk	Low risk	Some concerns for the outcomes PI/CI/GI/BOP Low risk for the outcome “width of the PDL space”	Low risk	Some concerns for the outcomes PI/CI/GI/BOP Low risk for the outcome “width of the PDL space”
11	Xu et al 2011	Some concerns	Low risk	High risk	Some concerns	Some concerns	High risk

PI , plaque index; CI , calculus index; GI , gingival index; BOP , bleeding on probing; PDL , periodontal ligament.

Five RCTs reported a proper randomization process; Tacken et al used a predictable allocation sequence, whereas the rest of the RCTs did not report enough information to assess this domain. Because of the nature of the intervention, the blinding of the outcome assessor(s) was challenging. Nevertheless, a low risk of bias was awarded when the vested interest of the outcome assessor(s) regarding the results of the study was estimated as low.

Two RCTs ^, showed a high risk of selective reporting. A preregistered protocol is necessary to control any risk of selection of the reported results and was available only for Torkan. Finally, 2 studies ^, had a high percentage of missing data, without balanced reasons and proportions across the groups. Torkan et al was judged overall to be at low risk of bias for 1 outcome and unclear for the other 4.

Cohort studies

None of the 5 cohort studies fulfilled adequately the criteria dictated by the Risk Of Bias In Nonrandomized Studies of Interventions Tool in order to be graded at a low risk of bias ( Table II ). The tool requires, among other things, absence of confounding, blinding of the outcome(s) assessor(s), and a preregistered protocol to consider a nonrandomized study equivalent to a well-performed randomized trial. Three trials had an overall moderate risk of bias, and therefore appear to provide sound evidence for nonrandomized studies. Juloski et al used a control group with a different population (different era) than the intervention group, which could involve uncontrollable confounding. Furthermore, in Gökçe and Kaya, because of the retrospective design, the selection of participants was related to the intervention, which implies selection bias. Finally, Wu et al was graded at serious risk of bias because of the absence of a control group.

Table II

Risk of bias of the included cohort studies

No.	Author(s)/y	Confounding	Selection bias	Bias in the classification of interventions	Bias due to deviations from intended interventions	Bias due to missing data	Bias in measurement of outcomes	Bias in selection of the reported result	Overall
1	Gökçe and Kaya 2019	Moderate risk	Low risk	Low risk	Low risk	Low risk	Moderate risk	Moderate risk	Moderate risk
2	Heier et al 1997	Moderate risk	Low risk	Low risk	Low risk	Low risk	Moderate risk for the outcomes MGI/BOP/PI/CI Low risk for the outcome GCFF	Moderate risk	Moderate risk
3	Juloski et al 2017	Serious risk	Serious risk	Low risk	Low risk	Low risk	Moderate risk	Moderate risk	Serious risk
4	Kaji et al 2013	Moderate risk	Low risk	Low risk	Low risk	Low risk	Moderate risk for the outcomes PPD/BOP/GI/PI/CI Low risk for the biochemical and bacteriologic analysis	Moderate risk	Moderate risk
5	Wu et al 2014	Not applicable	Low risk	Low risk	Low risk	Low risk	Moderate risk	Moderate risk	Serious risk No control group

MGI , modified gingival index; BOP , bleeding on probing; PI , plaque index; CI , calculus index; GCFF , gingival crevicular fluid flow; PPD , pocket probing depth; GI , gingival index.

Cross-sectional studies

The 13 cross-sectional studies were graded according to a modified version of the NOS. None of the studies scored 7 stars (necessary to be considered as a “good” study), mostly because of the lack of blinding and adequate control of confounding factors. The scores ranged from 2 to 6 stars ( Table III ).

Table III

Risk of bias of the included cross-sectional studies

No.	Author(s)/y	Selection			Comparability	Outcome(s)		NOS score
No.	Author(s)/y	Representativeness of the sample	Nonrespondents	Ascertainment of the exposure (risk factor)	Comparability factors and confounding factors	Assessment of the outcome(s)	Statistical test	NOS score
1	Al-Nimri et al 2009	b*	a*	a*	a* b*	d	a*	6*
2	Artun 1984	b*	c	a*	No star	a*	a*	4*
3	Booth et al 2008	a*	a*	a*	No star	d	a*	4*
4	Cerny et al 2010	d	c	a*	No star	d	a*	2*
5	Neto et al 2010	c	a*	a*	No star	d	a*	3*
6	Corbett et al 2015	a*	a*	a*	No star	d	a*	4*
7	Dietrich et al 2014	a*	a*	a*	No star	d	a*	4*
8	Knaup et al 2019	a*	a*	a*	No star	d	a*	4*
9	Levin et al 2008	a*	a*	a*	No star	d	a*	4*
10	Pandis et al 2007	b*	c	a*	No star	d	a*	3*
11	Rody et al 2011	b*	c	a*	a*	d	a*	4*
12	Rody et al 2016	b*	c	a*	No star	d	a*	3*
13	Westerlund et al 2017	b*	c	a*	a*	d	a*	4*

Note. See Supplementary Data for the meaning of a-d for each domain.

Qualitative synthesis of the included studies

Because of the great heterogeneity in study designs, types of wire used, comparisons made, outcomes reported ( Supplementary Table I ), and the overall low quality of the included studies, a meta-analysis was not conducted. For descriptive reasons, the 29 included studies were divided into the following 5 categories. The results of the included studies are summarized in Supplementary Tables II and III .

Studies comparing fixed retainers to orthodontically treated or untreated controls without retainers

Ten studies compared individuals with fixed retainers to a control group without retainers. In contrast to the general consensus, 1 RCT and 2 cross-sectional studies ^, concluded that the presence of a fixed retainer was associated with poorer periodontal conditions. The 7 other studies, ^, ^, 1 prospective cohort study, 1 retrospective cohort study, and 5 cross-sectional studies, did not describe any periodontal complications related to fixed retainers. On the contrary, Booth et al and Artun reported that more gingival inflammation was present in the lingual areas of participants without a fixed retainer, meaning that patients with a fixed retainer could have improved oral hygiene because of the more regular recalls for prophylaxis. Finally, Westerlund et al did not find any difference in marginal bone levels between orthodontically treated patients with a fixed retainer and orthodontically treated patients without a fixed retainer.

Studies comparing fixed retainers to removable retainers

5 RCTs, ^, ^, ^, ^, 2 prospective cohort studies, ^, and 4 cross-sectional studies ^, ^, ^, compared fixed retainers to removable retainers. Of the 11 studies, only Gökçe and Kaya reported more gingival inflammation in the presence of a wire retainer, although no significant difference in plaque accumulation, probing depth, and marginal recession was reported between the groups.

Some of the studies ^, ^, ^, ^, reported and increased accumulation of deposits (plaque and calculus) in patients wearing fixed retainers, but no related periodontal complications. Therefore, the higher calculus accumulation described in Xu et al cannot be considered per se as proof of a negative effect on the periodontium.

Studies assessing different time-points of the same patients

Three RCTs ^, ^, and 1 prospective cohort study assessed the same patients at different time-points. Liu observed a higher level of gingival inflammation after the implementation of the interventions, whereas Störmann and Ehmer and Wu et al did not find any detrimental effects on gingival conditions. In Torkan et al, the fiber-reinforced composite retainer was related to an increased accumulation of plaque and gingivitis, whereas the results for the multistranded wire retainer were unclear.

Studies comparing different types of fixed retainers

Eight RCTs, 1 prospective cohort study, and 5 cross-sectional studies compared different types of fixed retainers.

Artun published 2 RCTs ^, that included the same participants, but with different follow-up periods. In both studies, spiral wires bonded to the canines or all anterior teeth did not seem more deleterious to periodontal health when compared with plain wires bonded to the canines.

Four RCTs ^, ^, ^, compared fiber-reinforced composite retainers to multistranded wire retainers. Two of them found no difference in gingival bleeding and periodontal pocket depth or calculus accumulation between the groups. However, Tacken et al and Torkan et al agreed that multistranded wires were better in terms of gingival inflammation.

Bazargani et al reported that the application of resin during the bonding procedure reduces the deposition of calculus, whereas Störmann and Ehmer found similar periodontal outcomes for customized wires when compared with prefabricated wires.

All cross-sectional studies ^, compared smooth wires to multistranded wires. Three of them did not observe any difference in gingival conditions between the 2 types of retainers, whereas Knaup et al and Rody et al found a higher degree of gingivitis in the presence of multistranded wire retainers. The results of the accumulation of deposits were more in favor of the smooth wire retainers. Artun described an increased accumulation of plaque and calculus along the wire in the plain wire group, whereas the other cross-sectional studies reported more plaque deposition in the multistranded wire group. Corbett et al observed that the wave-type wire was related to a higher frequency and easiness of flossing; nevertheless, even so, self-reported flossing compliance did not improve the periodontal status in this group.

Studies assessing different vertical wire positions

One prospective cohort study and 1 cross-sectional study observed that positioning a fixed retainer more incisally or more gingivally does not influence the periodontal outcomes.

Other studies

A cross-sectional study compared the short- and long-term effects of fixed retainers on periodontal health. The long-term retention group showed higher calculus accumulation, greater marginal recession, and increased probing depth. However, the difference in age between the 2 groups could be the cause of these findings and not the longer presence of a fixed retainer itself.

Discussion

This systematic review aimed to evaluate the potentially deleterious effects of fixed retainers on periodontal health. As a secondary aim, different kinds of fixed retainers were compared according to their effects on the periodontium. Eleven RCTs and 18 nonrandomized studies fulfilled the inclusion criteria.

Most of the included studies seem to indicate that fixed retainers do not affect periodontal health. In contrast to the general consensus, 2 RCTs, ^, 1 prospective cohort study, and 2 cross-sectional studies ^, reported poorer periodontal conditions in the presence of a fixed retainer. One RCT showed that fiber-reinforced composite retainers could be associated with periodontal complications, but found unclear results for multistranded wire retainers. However, no severe detrimental effects on periodontal health were reported in any of the included studies.

The results of the studies comparing smooth round wires to multistranded wires ^, ^, ^, were not unanimous, although most of them reported no difference between the interventions. On the other hand, fiber-reinforced composite retainers could be more deleterious to the periodontium than wire retainers. ^, Two studies ^, also showed that positioning the retainer more incisally or more gingivally does not seem to influence the periodontal outcomes. Nevertheless, because of the limitations of this review, recommendations on the best type of fixed retainer to use cannot be given.

The current systematic review presents several limitations that have to be highlighted. The first limitation was the high amount of methodological heterogeneity in study designs, types of wire used, comparisons made, and outcomes reported, which could be identified across the included studies. A second limitation was the lack of high-quality evidence. All included RCTs were indeed at unclear or high risk of bias. Most of them had issues with the blinding of the outcome(s) assessor(s), which will be a recurrent problem in prospective studies since the intervention appraised is evident and easy to detect. Three prospective cohort studies were graded as good with a moderate risk of bias; the other 2 cohort studies ^, showed; however, a serious risk of bias. Included cross-sectional studies were also unsatisfactory with a NOS score of 3 or 4 stars for most of them. Therefore, a meta analysis could unfortunately not be conducted, and despite the significant amount of included studies, clear recommendations for usual practice according to the currently available literature were difficult to draw.

Another limitation of this systematic review was the observation period of the included studies. Many practitioners indeed recommend life-long retention, but relevant evidence on the potential side effects after such a long time is missing. The follow-ups of the included RCTs and cohort studies ranged from 4 months to 4 years and from 2 months to 5 years, respectively. Some of the included cross-sectional studies had long follow-up periods ^, ^, ^, ; for example, Booth et al assessed a gingival index after 20-29 years. Nevertheless, their quality was questionable.

The findings of this review are consistent with previous systematic reviews. ^, However, the number of included studies was substantially lower, ranging from 1 to 7 trials evaluating periodontal outcomes. The paucity of high-quality evidence was also pointed out, and none of them was capable of providing clinical guidance according to the available literature. The more recent review, which included 4 RCTs and 3 prospective cohort studies, highlighted the relatively minor changes in periodontal parameters but concluded that more prospective studies with matched controls incorporating baseline assessment are needed to develop useful conclusions.

Conclusions

According to the currently available literature, orthodontic fixed retainers seem to be a retention strategy rather compatible with periodontal health, or at least not related to severe detrimental effects on the periodontium. However, a lack of high-quality evidence is indisputable. Well-performed RCTs, comparing fixed retainers to untreated subjects and different kinds of fixed retainers, during prolonged periods of follow-up, are needed to provide definitive conclusions about the effects of fixed retainers on periodontal health and clinical recommendations.

Appendix

Supplementary Table I

Characteristics of the included studies

Author(s)/y	Study design	Setting and date	Sample size, sex, and age of participants	Intervention(s)	Periodontal outcome(s)	Follow-up period(s)
Al-Moghrabi et al 2018	RCT	Queen Mary University of London Date not reported	n = 42 10 male, 32 female Mean age = 21.15 ± 2.41 y	In the lower arch: − 0.0175″ Coaxial wire from canine to canine (n = 21; 3 male, 18 female; mean age = 21.54 ± 3.06 y) − Vacuum-formed retainer, wear time progressively reduced (n = 21; 7 male, 14 female; mean age = 20.77 ± 1.49 y)	On the lower anterior teeth: − Modified gingival index (Lobene 1986) − Calculus and plaque levels − Clinical attachment level − Bleeding on probing	4 y (mean retention period = 4.16 ± 0.35 y)
Artun et al 1987	RCT	One private practice Date not reported	n = 44 Sex and age not reported	In the lower arch: − 0.032″ Plain wire bonded to the canines (n = 11) − 0.032″ Spiral wire bonded to the canines (n = 11) − 0.025″ Spiral wire bonded to all anterior teeth (n = 11) − Removable retainer (n = 11)	Along the wire and the composite: − Modified plaque index (Löe 1967) − Modified calculus index (Ramfjord 1959) Along the gingival margin of the lower anterior teeth (ID/L): − Plaque index (Löe 1967) − Calculus index (Ramfjord 1959) − Gingival index (Löe 1967) − Gingival bleeding (GI score 2)	0/4 mo
Artun et al 1997	RCT	One private practice Date not reported	n = 49 Sex and age not reported	In the lower arch: − 0.032″ Plain wire bonded to the canines (n = 11) − 0.032″ Spiral wire bonded to the canines (n = 13) − 0.025″ Spiral wire bonded to all anterior teeth (n = 11) − removable retainer (n = 14)	Along the wire and the composite: − Modified plaque index (Löe 1967) − Modified calculus index (Ramfjord 1959) Along the gingival margin of the lower anterior teeth (ID/L): − Plaque index (Löe 1967) − Calculus index (Ramfjord 1959) − Gingival index (Löe 1967) − Probing attachment level (L only)	0/3 y
Bazargani et al 2012	RCT	Postgraduate Dental Education Center, Orebro, Kingdom of Sweden Between 2008 and 2010	n = 52 26 male, 26 female Mean age = 18.3 ± 1.3 y	In the lower arch: − 0.0195″ Multistranded wire bonded to all anterior teeth with composite only (n = 26; 12 male, 14 female; mean age = 18.2 ± 1.6 y) − 0.0195″ Multistranded wire bonded to all anterior teeth with 2-step bonding resin and composite (n = 26; 14 male, 12 female; mean age = 18.4 ± 1.6 y)	Calculus accumulation (present or not) adjacent to the wire and the composite	2 y (mean retention period = 24.4 ± 4.7 mo)
Liu 2010	RCT	Hospital of Stomatology, Peking University School December 2007 to April 2008	n = 60 Sex and age not reported	In the lower arch: − 0.0295″ Fiber-reinforced composite retainer bonded to all anterior teeth (n = 30) − 0.0354″ Multistranded stainless steel wire bonded to all anterior teeth (n = 30)	On the lingual aspect of the lower anterior teeth (Ml/L/DL): − Bleeding index − Pocket depth	0/6/12 mo
Rose et al 2002	RCT	Freiburg University, Federal Republic of Germany Date not reported	n = 20 12 male, 8 female Mean age = 22.4 ± 9.7 y	In the lower arch: − 0.0393″ Plasma-treated woven polyethylene ribbon bonded to all anterior teeth (n = 10) − 0.0175″ Multistranded stainless steel wire bonded to all anterior teeth (n = 10)	Amount of calculus in the gingival area on the lingual surface of the incisors	3/6/9/12/15/18/21/24 mo
Storey et al 2018	RCT	St Luke’s Hospital, Bradford and York Hospital, and Leeds Dental Institute, United Kingdom of Great Britain and Northern Ireland March 2012 to September 2013	n = 60 30 male, 30 female Mean age not reported	In both arches: − 0.0195″ Three-stranded twistflex stainless steel wire bonded to all anterior teeth (n = 30; 15 male, 15 female; median age = 16 y) − Vacuum-formed retainer at night (n = 30; 12 male, 18 female; median age = 17 y)	On all erupted teeth in both arches (B/L/M/D): − Plaque index (Silness and Löe 1964) − Gingival index (Löe 1967) − Calculus index (Greene and Vermillion 1964)	0/3/6/12 mo
Störmann and Ehmer 2002	RCT	Not reported	n = 103 Sex not reported Age range = 13-17 y	In the lower arch: − 0.0195″ Customized wire bonded to all anterior teeth (n = 31) − 0.0215″ Customized wire bonded to all anterior teeth (n = 38) − Prefabricated retainer bonded to the canines (n = 34)	− Plaque index (Lange 1977) − Bleeding on probing	1/3/2012/24 mo
Tacken et al 2010	RCT	Three private practices Date not reported	n = 184 90 male, 94 female Mean age = 14 y	In the upper arch, bonded to all incisors, and in the lower arch, bonded to all anterior teeth: − GF-reinforced retainer – 500 unidirectional GF (n = 45; 23 male, 22 female; mean age = 14.8 ± 1.3 y) − GF-reinforced retainer – 1000 unidirectional GF (n = 48; 23 male, 25 female; mean age = 14.6 ± 2.7 y) − 0.0215″ Multistranded wire (n = 91; 44 male, 47 female; mean age = 15.0 ± 1.3 y) − Untreated subjects (n = 90; 45 male, 45 female; mean age = 14.1 ± 1.1 y)	At 3 sites per tooth (M/C/D): − Plaque index (Quigley and Hein 1962) − Modified gingival index (Lobene et al 1986) − Bleeding on probing (Cosyn and Verelst 2006)	6/12/2018/24 mo
Torkan et al 2014	RCT	Shiraz University of Medical Sciences, Islamic Republic of Iran September 2008 to January 2010	n = 40 After exclusion and attrition: 10 male, 20 female	In both arches: − Fiber-reinforced composite retainer bonded to all anterior teeth (n = 20; after exclusion/attrition: 6 male and 9 female, mean age = 16.2 ± 1.9 y) − 0.0175″ Multistranded stainless steel wire bonded to all anterior teeth (n = 20; after exclusion/attrition: 4 male and 11 female, mean age = 15.7 ± 2.1 y)	On the lingual aspect of the upper and lower anterior teeth: − Plaque index (Löe 1967) − Calculus index (Ramfjord 1959, Greene and Vermillion 1960) − Gingival index (Löe 1967) − Bleeding on probing On the upper and lower anterior teeth: − Width of the PDL space (on periapical radiographs)	0/6 mo
Xu et al 2011	RCT	Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine Date not reported	n = 45 16 male, 29 female	− Combined retainers: 0.0195″ multistranded NiTi wire bonded 3-3 + Hawley retainer at night (n = 20; 6 male, 14 female; mean age = 15.2 y) − Vacuum-formed retainer, for both arches, worn the whole day (n = 25; 10 male, 15 female; mean age = 13.6 y)	Calculus index of the upper and lower arches	6/12 mo
Gökçe and Kaya 2019	Prospective cohort	Baskent University, Ankara, Republic of Turkey Orthodontic treatment completed between February and November 2016	n = 100 39 male, 61 female Median age range = 16.5-18.0 y	In the lower arch: − 0.0215″ Multistranded wire direct bonded to all anterior teeth (n = 20; 8 male, 12 female; median age = 17.5 y) − 0.0215″ Multistranded wire indirect bonded to all anterior teeth (n = 20; 7 male, 13 female; median age = 18 y) − 0.0175″ Multistranded wire direct bonded to all anterior teeth (n = 20; 6 male, 14 female; median age = 16.5 y) − 0.0175″ Multistranded wire indirect bonded to all anterior teeth (n = 20; 11 male, 9 female; median age = 17.5 y) − Removable Essix appliance (1-mm thickness) to wear day and night (n = 20; 7 male, 13 female; median age = 16.5 y)	On the lower anterior teeth: − Plaque index (Löe 1967) (B/L) − Gingival index (Löe 1967) (B/L/M/D) − Probing depth (Ml/L/DL) − Marginal recession (Ml/L/DL) − Bleeding on probing (MB/B/DB/Ml/L/DL)	0/1 week-1/3/6 mo
Heier et al 1997	Prospective cohort	One private practice and the dental clinic at the Free University of Brussels Date not reported	n = 36 Sex not reported Age range = 12.8-21.1 y; mean age = 16.3 y	In both arches (majority of participants): − 0.0175″ Multistranded wire bonded to all anterior teeth (n = 22) − Removable retainer (n = 14)	On the upper and lower anterior teeth: − Modified plaque index (Quigley and Hein 1962) (B/L) − Calculus index (Volpe et al 1967) (Löe 1967) − Modified gingival index (Lobene et al 1986, 1989) (B/L/ID) − Bleeding on probing (B/L/ID) On 11M/B, 23D/L, 31D/L, 43M/B: − GCF flow	0/1/3/6 mo
Kaji et al 2013	Prospective cohort	One private practice Date not reported	n = 31 6 male, 25 female Mean age = 27.5 ± 7.0 y	In the lower arch: − Stainless steel wire bonded to all anterior teeth (n = 17; 4 male, 13 female; mean age = 28.6 ± 7.8 y) − No fixed retainer, no evidence of visual malalignment between the lower bicuspids (n = 14; 2 male, 12 female; mean age = 26.1 ± 5.9 y) Subgroups based on wire position: − Wire within the upper one-third of clinical crown (n = 7) − Wire within the lower two-thirds of clinical crown (n = 10)	On the mesiolingual area of the lower left canine: − Plaque index (Silness and Löe 1964) − Calculus index (Greene and Vermillion 1960) − Gingival index (Löe and Silness 1963) − Pocket probing depth − Bleeding on probing − GCF collection (volume, elastase activity, protein content, quantity of IL-1β and PGE ₂) − Stimulated saliva [LDH activity, F-Hb, counts of P.g and T.f ]	0/1/4/8 weeks
Wu et al 2014	Prospective noncontrolled cohort	Shanghai Stomatological Disease Center April 2011 to August 2013	n = 12 5 male, 7 female Age range = 17-25 y	Glass fiber-reinforced composite retainer bonded to all lower anterior teeth	On the lingual aspect of the lower anterior teeth: − Gingival index − Sulcus bleeding index	0/6/12/18/24 mo
Juloski et al 2017	Retrospective cohort	University of Oslo, Kingdom of Norway Orthodontic treatment between 2008 and 2015	n = 144 65 male, 79 female	− Past orthodontic treatment and fixed mandibular retainer (n = 48; 24 male, 24 female; mean age = 12.78 ± 1.36 y) − Past orthodontic treatment, no form of retention in the mandible (n = 48; 25 male, 23 female; mean age = 12.39 ± 1.52 y) − Untreated subjects (n = 48; 16 male, 32 female; mean age = 11.73 ± 0.36 y)	On the lower anterior teeth: − Gingival recession − Calculus accumulation	before treatment/after/5 y posttreatment Mean retention/observation period: − TR+ group: 5.24 ± 0.66 y − TR- group: 5.28 ± 0.53 y − UnT group: 6.47 ± 0.31 y
Al-Nimri et al 2009	Cross-sectional	Jordan University of Science and Technology Between 2003 and 2005	n = 62 18 male, 44 female	In the lower arch: − 0.036″ Round stainless steel wire bonded to the canines (n = 31; 9 male, 22 female; mean age = 20.23 ± 3.8 y) − 0.015″ Multistranded wire bonded to all anterior teeth (n = 31; 9 male, 22 female; mean age = 19.97 ± 4.2 y)	On the lower anterior teeth: − Plaque index (Silness and Löe 1964) (B/L/M/D) gingival index (Löe and Silness 1963) (B/L) − Oral Hygiene Index (with the exclusion of the lower anterior segment) (Greene and Vermillion 1964)	>12 mo Mean retention period: − RW group: 21.31 ± 8.97 mo − MW group: 19.35 ± 6.67 mo
Artun 1984	Cross-sectional	Setting and date not reported	1st comparison: n = 74 Sex not reported	First comparison, in the lower arch: − 0.032″ Spiral wire bonded to the canines (n = 31; mean age = 17.10 ± 3.11 y) − 0.032″ Plain wire bonded to the canines (n = 18; mean age = 19.4 ± 3.0 y) − No fixed retainer (n = 25; mean age = 17.2 ± 0.8 y) Second comparison, in the upper arch: − 0.0195″ Spiral wire bonded to all anterior teeth (n = 14; mean age = 21.6 ± 3.8 y) − Jensen retention plate (n = 20; mean age = 16.10 ± 0.9 y)	Along the wire: − Plaque along Wire Index − Calculus along Wire Index Along the gingival margin of the anterior teeth: − Plaque index (Silness and Löe 1964) (ID/L) − Calculus index (Ramfjord 1959) (ID/L) − Modified gingival index (Löe and Silness 1963) (ID/L) − Loss of attachment (Ramfjord 1959) (L) − Crevice depth Interdentally: − Papillitis (NBP system, Dolles and Gjermo 1980)	First comparison—mean retention period: − SW group: 1.4 ± 0.7 y − PW group: 5.4 ± 2.3 y − NR group: 2.7 ± 0.8 y Second comparison—mean retention period: − SW group: 2.3 ± 1.10 y − RP group: 1.2 ± 0.7 y
Booth et al 2008	Cross-sectional	One private practice Date not reported	n = 60 Sex and age not reported	In the lower arch: − Fixed retainer bonded to the canines: majority of 0.025″ stainless steel wire, minority of 0.032″ multistranded wire (n = 45) − No more fixed retainer (n = 15)	Gingival index (Löe and Silness 1963) of the upper and lower arches from first molar to first molar on the buccal and lingual aspects	20-29 y
Cerny et al 2010	Cross-sectional	Setting and date not reported	n = 61 Sex and age not reported	In one arch (maxilla or mandible) or in both: − Permanent bonded retainer (n = 46) − Removable retainer (n = 43) − Subgroup: PBR + RR (n = 28; the patients who had worn both retainers were included in both groups as appropriate)	− Plaque index (Greene and Vermillion 1960) − Calculus index (Greene and Vermillion 1960) − Gingival recession index − Modified gingival index (Lobene 1989) − Alveolar bone index (Adams and Nystrom 1986)	PBR group: >15 y RR group: 2 y
Neto et al 2010	Cross-sectional	Setting and date not reported	n = 40 14 male, 26 female Age not reported	− Past orthodontic treatment and fixed mandibular retainer (n = 20; 5 male, 15 female) − Untreated subjects (n = 20; 9 male, 11 female)	On the lower anterior teeth (MB/B/DB/Ml/L/DL): − Plaque index − Bleeding on probing − Gingival recession − Clinical attachment level − Probing depth	2-8 y
Corbett et al 2015	Cross-sectional	One private practice Date not reported	n = 74 30 male, 54 female Age range = 13-22 y	− In both arches: 0.022″ round Blue Elgiloy wave-type wire bonded to all anterior teeth (n = 39; 13 male, 26 female; mean age = 16.9 ± 0.96 y) − Maxilla: 0.0215″ multistranded stainless steel straight wire bonded to all anterior teeth; mandible: 0.0315″ multistranded stainless steel straight wire bonded to the canines and central incisors (n = 35; 17 male, 28 female; mean age = 18.3 ± 1.3 y)	On the upper and lower anterior teeth: − plaque index (Löe 1967) − calculus index (Greene and Vermillion 1964) − pocket probing depth (MB/B/DB/Ml/L/DL) − bleeding on probing − gingival recession (B/L) On teeth 11 and 41: − GCF volume (B/L)	2-4 y Mean retention period: − WR group: 31.6 ± 3.2 mo − SR group: 42.3 ± 2.4 mo
Dietrich et al 2014	Cross-sectional	University of Zurich Date not reported	n = 41 16 male, 25 female Age not reported	0.016 × 0.016″ Stainless steel wire bonded to all upper incisors	On the upper incisors: − Plaque index (Silness and Löe 1964) (B/P) − Gingival index (Löe and Silness 1963) (B/P) − Probing depth (MB/B/DB/MP/P/DP) − Bleeding on probing (MB/B/DB/MP/P/DP)	Retention period: − Range = 5 y and 2 mo – 11 y and 7 mo − Mean = 7 y and 5 mo
Knaup et al 2019	Cross-sectional	University Aachen, Federal Republic of Germany September 2014 to June 2015	n = 61 Age range = 22 – 56 y Sex not reported	In the lower arch: − 0.0175″ Twistflex stainless steel wire bonded to all anterior teeth (n = 31) − 0.014 × 0.014″ computer-aided design/computer-aided manufacturing electropolished nitinol wire bonded to all anterior teeth (n = 30)	On the lower anterior teeth: − Plaque index (Löe 1967) (B/L/M/D) − Gingival index (Löe 1967) (B/L/M/D) − Probing depth (MB/B/DB/Ml/L/DL) − Bleeding on probing (Ainamo and Bay 1975) (MB/B/DB/Ml/L/DL) − Marginal recessions (B/L)	Mean retention period = 7.2 ± 0.8 mo
Levin et al 2008	Cross-sectional	Military dental clinic of the Israeli Defense Forces May to August 2007	n = 92 46 male, 46 female Age range = 18-26 y; mean age = 20.6 ± 1.7 y	− Past orthodontic treatment + 1 or 2 fixed retainer(s) (n = 25) • Subgroups: o Fixed retainer(s) placed in a more gingival position o Fixed retainer(s) placed in a more incisal position − No fixed retainer, with or without past orthodontic treatment (n = 67) • Subgroup: past orthodontic treatment + no fixed retainer (n = 39)	On the upper and lower anterior teeth (6 sites per tooth): − Plaque index (Silness and Löe 1964) − Gingival index (Löe and Silness 1963) − Probing depth − Bleeding on probing − Gingival recession	Mean retention period = 4.57 ± 2.2 y
Pandis et al 2007	Cross-sectional	Long-term group: one private practice Short-term group: not reported Date not reported	n = 64 21 male, 43 female	In the lower arch: − 0.195″ Multistranded wire bonded at least 9 y ago (n = 32; 11 male, 21 female; mean age = 25 ± 1.29 y) − Similar fixed retainer bonded for 3-6 mo (n = 32; 10 male, 22 female; mean age = 16.4 ± 1.26 y)	On the lower anterior teeth: − Plaque index (Löe 1967) (B/L) − Calculus index (Greene and Vermillion 1960) − Gingival index (Löe 1967) (M/L/B/D) − Probing depth (MB/B/DB/Ml/L/DL) − Marginal recession − Bone level (distance between the CEJ to the alveolar crest on radiographs)	Retention period: − LT group: range = 9 – 11 y; mean = 9.65 y − ST group: 3-6 mo
Rody et al 2011	Cross-sectional	Not reported	n = 31 17 male, 14 female Age range = 20-35 y	In the lower arch: − 0.028″ Round stainless steel wire bonded to the canines (n = 10; 3 male, 7 female; mean age = 28 ± 4.9 y) − Hawley retainer (n = 11; 9 male, 2 female; mean age = 24 ± 3.6 y) − No retainer (n = 10; 5 male, 5 female; mean age = 26.9 ± 4.22 y)	On the lingual aspect of a lower central incisor and of a second premolar: − Plaque accumulation − Probing depth − Bleeding on probing − GCF collection (volume, biomarkers of inflammation and periodontal remodeling)	Retention period: − Range = 4 – 10 y − Mean = 5.6 y
Rody et al 2016	Cross-sectional	University of Florida Date not reported	n = 36 13 male, 23 female Age range = 18-45 y	In the lower arch: − 0.028″ Round smooth wire bonded to the canines (n = 12; 4 male, 8 female; mean age = 28.75 ± 7.1 y) − 0.016″-0.0195″ Round multistranded wire bonded to all anterior teeth (n = 12; 5 male, 7 female; mean age = 28.75 ± 6.9 y) − Removable retainer at night (n = 12; 4 male, 8 female; mean age = 23.25 ± 4.69 y)	On the lower anterior teeth (6 sites per tooth): − Plaque score − Gingivitis score − Probing depth − Bleeding on probing − Gingival recession On the lingual aspect of the tooth 31: − GCF collection (volume, biomarkers)	At least 6 mo Mean retention period: − SW group: 76 ± 63.62 mo − MW group: 44.50 ± 26.80 mo − RR group: 43.67 ± 26.85 mo
Westerlund et al 2017	Cross-sectional	Clinic of Orthodontics, Public Dental Service, Gothenburg, Kingdom of Sweden Date not reported	n = 62 21 male, 41 female Mean age = 27 y	− Past orthodontic treatment + 0.0195″ multistranded wire bonded to all anterior teeth in the lower arch (n = 34) − Past orthodontic treatment without fixed retainer (n = 14) − Untreated subjects (n = 14)	On the lower anterior teeth: distance of the cementoenamel junction to the marginal bone crest (D/M/B/L surfaces) measured by cone beam computed tomography	10 y

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Tags: American Journal of Orthodontics and Dentofacial Orthopedics Volume 157 Issue 2

Mar 9, 2020 | Posted by drzezo in Orthodontics | Comments Off

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The effects of fixed orthodontic retainers on periodontal health: A systematic review

Introduction

Methods

Results

Conclusions

Highlights

Material and methods

Criteria for considering studies for this review

Types of studies

Types of participants

Types of interventions

Types of control groups

Types of outcomes

Search methods for study identification

Data collection and analysis

Selection of studies

Data extraction and management

Measures of effect

Unit-of-analysis issues

Dealing with missing data

Assessment of heterogeneity

Assessment of reporting biases

Quality assessment of included studies

Data synthesis

Results

Selection of studies

Risk of bias assessment

Randomized controlled trials

Cohort studies

Cross-sectional studies

Qualitative synthesis of the included studies

Studies comparing fixed retainers to orthodontically treated or untreated controls without retainers

Studies comparing fixed retainers to removable retainers

Studies assessing different time-points of the same patients

Studies comparing different types of fixed retainers

Studies assessing different vertical wire positions

Other studies

Discussion

Conclusions

Appendix

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