JJOD 2464 1–21 journal of dentistry xxx (2015) xxx–xxx

Available online at www.sciencedirect.com

ScienceDirect journal homepage: www.intl.elsevierhealth.com/journals/jden 1 2 3

Review

Failure of fixed orthodontic retainers: A systematic review

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Q1

Anna Iliadi a, Dimitrios Kloukos b, Nikolaos Gkantidis b, Christos Katsaros b, Nikolaos Pandis b,* a

Q2 Department of Orthodontics, University of Athens, 1a Strofiliou Str, 14561 Athens, Greece b

Department of Orthodontics and Dentofacial Orthopedics, University of Bern, Freiburgstrasse 7, CH-3010 Bern, Switzerland

article info

abstract

Article history:

Objective: To evaluate the risk of failure of fixed orthodontic retention protocols.

Received 17 February 2015

Data: Screening for inclusion eligibility, quality assessment of studies and data extraction

Received in revised form

was performed independently by two authors.

25 April 2015

Sources: The electronic databases MEDLINE, EMBASE and CENTRAL were searched with no

Accepted 1 May 2015

restrictions on publication date or language using detailed strategies. The main outcome

Available online xxx

assessed was bond failure. Study selection: Twenty-seven studies satisfied the inclusion criteria. Randomised controlled

Keywords:

trials and prospective studies were evaluated according to the Cochrane risk of bias tool.

Orthodontic retention

Retrospective studies were graded employing the predetermined criteria of Bondemark.

Fixed retainers

Results: Nine randomised controlled trials, four of which were of low quality, were identi-

Bond failure

fied. Six studies had a prospective design and all were of low quality. Twelve studies were

Detachment

retrospective. The quality of trial reporting was poor in general. Four studies assessing glass-fibre retainers, three RCTs and one prospective, reported bond failures from 11 to 71%, whereas twenty studies evaluating multistranded retainers – nine RCTs, two prospective and nine retrospective – reported failures ranging from 12 to 50%. One comparison was performed, multistranded wires vs. polyehtylene woven ribbon (RR: 1.74; 95% CI: 0.45, 6.73; p = 0.42). Conclusion: The quality of the available evidence is low. No conclusive evidence was found in order to guide orthodontists in the selection of the best protocol. Clinical significance: Although fixed orthodontic retainers have been used for years in clinical practice, the selection of the best treatment protocol still remains a subjective issue. The available studies, and their synthesis, cannot provide reliable evidence in this field. # 2015 Published by Elsevier Ltd.

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* Corresponding author. E-mail addresses: [email protected] (A. Iliadi), [email protected] (D. Kloukos), [email protected] (N. Gkantidis), [email protected] (C. Katsaros), [email protected] (N. Pandis). http://dx.doi.org/10.1016/j.jdent.2015.05.002 0300-5712/# 2015 Published by Elsevier Ltd.

Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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1.

Introduction

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2.

Materials and methods

2.1.

Protocol and registration

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Q3 Orthodontic relapse is a common finding after successful

orthodontic treatment.1,2 It has been reported that in 70–90% of the orthodontically treated cases, a varying degree of compensation in the lower dental arch occurred during the post retention period, whereas in the upper arch the observed changes were milder.3 A number of factors have been associated with orthodontic relapse such as retention protocol, patient compliance, age, and final occlusion after treatment.3 Relapse is common even when orthodontic treatment includes premolar extractions with crowding continuing to increase during a period of 10–20 years post retention. Little4 concluded that only 10% of the orthodontically treated cases were considered to have clinically acceptable mandibular alignment, with overbite and overjet showing minimal changes 10–20 years post retention. The etiology of orthodontic relapse is complex and unclear. It has been suggested that the elastic fibres of the periodontal ligament are implicated in relapse of derotated teeth.5 Sinclair6 and Bishara7 documented that, in patients with normal dentition, arch length decreased and mandibular incisor crowding increased throughout life. Relapse prevention is an important and challenging problem in orthodontics,2 often requiring long-term retention.8 Retention strategies usually include removable and fixed retainers, with the latter having the advantage of minimal need for patient compliance. Various types of fixed retainers have been described in the literature.9 The fixed retainers proposed consist of braided or solid metallic wires bonded to enamel with resin composite orthodontic adhesives.10 Aramid, polyethylene and glass-fibres impregnated with resin and coated with resin-composite orthodontic adhesives have also been used.11,12 Bonding protocols vary in the number of teeth bonded (all 6 anterior or only canines), the bonding material (restorative resin composite or flowable orthodontic adhesive), the type (solid or multistranded) and dimensions of the wire. Fibre retainers offer the capacity of tailormade composite materials with a specific modulus of elasticity, enhanced load bearing, high esthetics and formability.13–15 A common clinical complication of fixed retention is the failure of the bonded lingual retainers. For wire retainers, this can occur through detachment either at the wire-composite interface or at the adhesive-enamel interface. A stress fracture of the wire is also possible at inter-proximal areas.16 Bond failure in metal retainers is reported between 3.5 and 53%.17,18 whereas for fibre retainers, the corresponding risk varies from 11% to 51%.19,20 Despite the fact that many studies have been published on fixed retainer bond failures a systematic review and synthesis of the available evidence is lacking from the literature. Therefore, the aim of the present review was to systematically search the relevant literature to assess lingual retainer failures and to identify factors that influence the risk of failure of fixed orthodontic retainers.

Not available.

2.2.

Selection criteria applied for the review

 Study design: Randomised clinical trials (RCTs), controlled clinical trials (CCTs) and retrospective studies were considered eligible for inclusion in this review.  Types of participants: Patients of any age who received fixed retention after orthodontic treatment.  Types of intervention: All types of fixed retainers were considered eligible, irrespectively of the wire type, bonding materials and number of the teeth bonded.  Outcome: Failure rate of fixed retainers with respect to loosening, breakage and bond failure, with no limits to the observation period.  Exclusion criteria: Removable retainers, auxiliary procedures (e.g. inter-proximal reduction or surgical adjuncts). Animal studies and case reports were also excluded.

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Detailed search strategies were developed, 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, Appendix 1, from 1946 to December 1st, 2014), 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.

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2.4.

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2.3.

Search strategy for identification of studies

Selection of studies

Study selection was performed independently and in duplicate by the first two authors of the review, who were not blinded to the identity of the authors of the studies, their institutions, or the results of their research. Study selection procedure comprised of title-reading, abstract-reading and full-text-reading stages. 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 the third author. A record of all decisions on study identification was kept.

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2.5.

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Data extraction and management

The first two authors performed data extraction independently and in duplicate. Disagreements were resolved by discussion or the involvement of two collaborators (third author and last author). Data collection forms were used to record the

Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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desired information. The following data were collected on a customised data collection form.

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For continuous outcomes, mean differences and standard deviations were used to summarise the data from each study. For dichotomous data, number of participants with events and total number of participants in experimental and control groups were analysed. Regarding meta-analysis for dichotomous data risk ratios (RR) and their 95% confidence intervals (Cls) were calculated. For continuous data mean difference (MD) and 95% Cls were calculated.

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2.7.

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In all cases, the unit of analysis was the patient and mandibular or maxillary retainers were not combined, either in experimental or control group.

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2.8.

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We contacted study authors per e-mail to request missing data where necessary. In case of no response or no provision of the missing data, only the available reported data were analysed.

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2.9.

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Heterogeneity was assessed using a Chi2 test and the I2 statistic, where I2 values over 50% indicated substantial heterogeneity. Significant heterogeneity was present when the p value was less than 0.1.

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2.10.

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In the presence of more than 10 studies in a meta-analysis, the possible presence of publication bias was investigated.

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2.11.

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A meta-analysis was planned only if there were at least two studies of low or unclear risk of bias, reporting similar comparisons, similar outcomes at similar time points. Metaanalysis was performed using the DerSimonian and Laird statistical method, measuring the treatment effect with risk ratios. Chi-squared (chi2) test was included in the forest plot of this review in order to assess the presence of statistical heterogeneity among studies. Data were analysed with Review Manager 5.2 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen 2012).

Author/title/year of study. Design of the study. Number/age/gender of patients recruited. Type of retainer, dimensions of wire. Composite used. Number of teeth, upon which the retainer was bonded. Observation period (follow-up of patients). Outcome assessed. Failure of retainer.

2.6.

Measures of treatment effect

2.12.

3

Quality assessment

The methodological quality for RCTs and prospective studies was assessed by two review authors, independently and in duplicate, using the Cochrane risk of bias tool.21 Risk of bias was assessed and judged for seven separate domains.

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 Sequence generation: was the allocation sequence adequately generated?  Allocation concealment: was allocation adequately concealed?  Blinding of participants and investigators: was knowledge of the allocated intervention adequately prevented during the study?  Blinding of outcome assessors: was knowledge of the allocated intervention adequately prevented before assessing the outcome?  Incomplete outcome data: were incomplete outcome data adequately addressed?  Selective outcome reporting: were reports of the study free of suggestion of selective outcome reporting?  Other sources of bias: was the study apparently free of other problems that could put it at a high risk of bias?

Retrospective studies were graded with a score of A, B or C (Grade A: high value of evidence; Grade B: moderate value of evidence and Grade C: low value of evidence) according to predetermined criteria of the Bondemark scoring system.22 This system describes the criteria for grading the studies as follows:

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 Grade A: high value of evidence (all criteria should be met): - Randomised clinical study or a prospective study with a well-defined control group. - Defined diagnosis and endpoints. - Diagnostic reliability tests and reproducibility tests described. - Blinded outcome assessment.  Grade B: moderate value of evidence (all criteria should be met): - Cohort study or retrospective cases series with defined control or reference group. - Defined diagnosis and endpoints.

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Unit of analysis issues Each study received a judgment of low risk, high risk or unclear risk of bias (indicating either lack of sufficient information to make a judgment or uncertainty over the risk of bias) for each of the seven domains. Studies were finally grouped into the following categories:

Dealing with missing data

Assessment of heterogeneity

Assessment of reporting bias

Data synthesis

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 Low risk of bias (plausible bias unlikely to seriously alter the results) if all key domains of the study were at low risk of bias.  Unclear risk of bias (plausible bias that raises some doubt about the results) if one or more key domains of the study were unclear.  High risk of bias (plausible bias that seriously weakens confidence in the results) if one or more key domains were at high risk of bias.

Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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- Diagnostic reliability tests and reproducibility tests described.  Grade C: low value of evidence (one or more of the following conditions): - Large attrition. - Unclear diagnosis and endpoints. - Poorly defined patient material. The Grading of Recommendations Assessment, Development and Evaluation (GRADE)21 was implemented to assess the overall quality of evidence for the studies included in the meta-analysis, according to which the overall evidence is rated as high, moderate, low and very low. High quality of evidence implies that further research is unlikely to change our confidence in the estimated effect; moderate that further research is likely to have an impact on our confidence in the estimated effect and may change the estimate; low that further research is likely to have an impact on our confidence in the estimated effect and is likely to change the estimate; and very low that any estimated effect is very uncertain.

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3.

Results

3.1.

Description of studies

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A total number of 1162 studies, identified from the electronic search as relevant, were retrieved and the specific inclusion criteria were applied. Many studies concerning fixed retainers were found assessing gingival index, irregularity and plaque indexes but their outcome was not relevant for this particular review. The process of study identification is presented in Fig. 1. After excluding all duplicates, and following abstract- and full text-reading stage, 27 studies were considered eligible for inclusion in this review (Table 1). Out of the 27 studies, nine were RCTs, six prospective and twelve were retrospective studies.

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3.2.

Quality assessment

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3.2.1.

RCT studies

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The methodological quality of the nine included RCTs assessed on the basis of the Cochrane risk of bias tool21 is shown in Fig. 2.

Identification

Records identified through database searching (n = 1162)

Records remaining after title screening (n = 301)

Additional records identified through other sources (n = 8) 8 identified studies after hand searching

Eligibility

Screening

Records after duplicates removed (n = 308) 1 duplicate removed

Records screened (n = 145)

Full-text articles assessed for eligibility (n = 38)

Studies included in qualitative synthesis (n = 27)

Included

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Records excluded (n = 163) 162 not satisfying inclusion criteria

Records excluded (n = 107) 107 not satisfying inclusion criteria

Full-text articles excluded, with reasons (n = 11) 6 review/opinion articles 3 studies assessing post-retention changes, not failure rate 1 study implementing costminimization analysis 1 study investigating settling and discrepancy index

Studies included in quantitative synthesis (n = 2)

Fig. 1 – Study flow diagram. Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 1 – Characteristics of included studies ordered by study design and date. Author Study title Study design

Observation period (months)

Rose E26 (2002) Clinical comparison of a multistranded wire and a direct bonded polyethylene ribbon- reinforced resin composite used for gingival retention RCT

24

Sto¨rmann I18 (2002)

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Participants

20 patients (8 female, 12 male) Inclusion criteria: healthy periodontal condition, good oral hygiene, compliance, no previous bonded retainer on lingual side of mandibular incisors

A prospective randomised study of different retainer types RCT

Mean age: 22.4  9.7 years 103 patients (98 included) Inclusion criteria: faultless periodontal status Age: 13–17 years

Interventions

- Polyethylene woven ribbon; mandible: all 6; n = 10 - Multistranded steel wire; 0.0175 in.; mandible: all 6; n = 10

Outcome

Retainer loosening

Composite: Heliosit Orthodontic (LC)

Bond failure - Coaxial stainless steel 0.0215 in.; mandible: all 6; n = 36 - Coaxial stainless steel 0.0195 in.; mandible: all 6; n = 30 - Prefabricated; mandible: only canines; n = 32 Composite: Heliosit Orthodontic (LC) or Concise (CC)

Tacken MP20 (2010)

24

Glass fibre reinforced versus multistranded bonded orthodontic retainers: a 2 year prospective multi-centre study RCT

184 patients (90 male, 94 female; 169 analysed) Inclusion criteria: good general health, correct dental alignment, a Class I relationship with an overbite/overjet between 1 and 3 mm, need for permanent orthodontic retention in the upper and lower anterior segments. Mean age: 14 years

- Glass fibre reinforced (GFR500); mean age: 14.8  1.3; maxilla: lateral incisor to lateral incisor (n = 45); mandible: all 6 (n = 45)

Bond failure, retainer fracture

- Glass fibre reinforced (GFR1000); mean age: 14.6  2.7; maxilla: lateral incisor to lateral incisor (n = 48); mandible: all 6 (n = 48) - 6-stranded coaxial wire, 0.0215 in.; mean age: 15  1.3; maxilla: lateral incisor to lateral incisor (n = 91); mandible: all 6 (n = 91) Composite: Excite and Tetric Flow (LC)

Scribante A25 (2011) Efficacy of esthetic retainers: Clinical comparison between multistranded wires and direct-bond glass fibrereinforced composite splints RCT

12

34 patients (9 male, 25 female) Inclusion criteria: correct dental alignment, need for permanent orthodontic retention in the lower anterior segments, no occlusal interferences

- Multistranded Stainless steel; 0.0175 in.; mandible: all 6, n = 17 - Polyethylene ribbonreinforced resin composite; mandible: all 6; n = 15

Bond failure

Composite: Transbond XT (LC)

Mean age: 14.3 years

Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 1 (Continued ) Author Study title Study design Bolla E19 (2012)

Observation period (months) 72

Failure evaluation after a 6year retention period; A comparison between glass fibre reinforced (GFR) and multistranded bonded retainers RCT

Pandis N23 (2013)

85 patients (29 male, 56 female) Mean age: male, 23.7 years; female, 21.9 years

26.3 (median)

18

Comparison of survival time between two types of orthodontic fixed retainer: a prospective randomised clinical trial RCT

220 patients

- Tru-Chrome multistranded wire; 0.022 in.; mandible: all 6; n = 110; Reliance (CC) - Tru-Chrome multistranded wire; 0.022 in.; mandible: all 6; n = 110; Flow Tain (LC)

Age: median: 16 years; range, 12–47 years 142 patients (59 male, 83 female) Inclusion criteria: good oral hygiene, healthy periodontal condition, and no previous bonded retainer

Indirect vs. direct bonding of mandibular fixed retainers in orthodontic patients. A single-centre randomised controlled trial comparing placement time and failure over a 6-month period RCT

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- Glass fibre reinforced; maxilla: all incisors (n = 14); mandible: all 6 (n = 34) - Multistranded wire, 0.0175 in.; maxilla: all incisors (n = 18); mandible: all 6 (n = 32) Composite: ENA bond LC primer and flowable composite (LC)

Age: 14–28 years Bovali E49 (2014)

Interventions

Inclusion criteria: good oral hygiene, periodontal health, mean crowding 3.1 mm and 2.2 mm for maxilla and mandible respectively, absence of dental agenesis, anomalies, enamel declassification, white spots on the lingual surfaces, postorthodontic treatment Class I relationship with overbite and overjet between 1 and 3 mm, non-extraction treatment

Inclusion criteria: no active caries, restorations, fractures on the mandibular anterior teeth, or periodontal disease; and adequate oral hygiene.

Survival of bonded lingual retainers with chemical or photo polymerisation over a 2-year period: a singlecentre, randomised controlled clinical trial RCT

Salehi P24 (2013)

Participants

60 patients (at 6 month follow-up) Inclusion criteria: presence of 4 mandibular incisors and 2 mandibular canines, no active caries, restorations, fractures or periodontal disease. Mean age: 19.8 years (direct bonding), 17.2 years (indirect bonding)

Outcome

Bond failure, retainer fracture

Bond failure

Composite: Reliance (CC) and Flow Tain (LC)

- Polyethylene woven ribbon; maxilla and mandible: all 6; mean age: 18.1  5.23 years; n = 68 - Flexible spiral wire; 0.0175 in.; maxilla and mandible: all 6; mean age: 18.2  4.81 years; n = 74 Composite: Fluoro Bond (sealant) and Heliosit Orthodontic (LC) - Multistranded steel wire 0.0215 in.; mandible: all 6; n = 29; direct bonding

Bond failure

Retainer failure

- Multistranded steel wire 0.0215 in.; mandible: all 6; n = 31; indirect bonding Composite: direct bonding, Transbond LR (LC); indirect bonding, Maximum Cure A and B (CC)

Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 1 (Continued ) Author Study title Study design Sfondrini MF47 (2014) Clinical evaluation of bond failures and survival between mandibular canine-to-canine retainers made of flexible spiral wire and fibre-reinforced composite RCT Zachrisson BU28 (1977)

Observation period (months) 12

Participants

87 patients (52 female, 35 male) Inclusion criteria: required a lower arch fixed retainer

Interventions

- Glass fibre reinforced; mandible: all 6; n = 40 - Multistranded wire; 0.0175 in.; mandible: all 6; n = 47

Outcome

Bond failure

Composite: Transbond XT (LC) Average age: 24 years (14–62 years)

12

43 patients Inclusion criteria: not mentioned

Clinical experience with direct-bonded orthodontic retainers Prospective

- Heat-treated and polished blue Elgiloy; 0.036 in. or 0.032 in.; mandible: only canines; held with finger during placement; n = 22

Retainer loosening

Age: 14–17 years - Heat-treated and polished blue Elgiloy; 0.036 in. or 0.032 in.; mandible: only canines; ligated during placement; n = 21 Composite: Concise (CC)

Lee RT29 (1981)

36

46 patients

36

Inclusion criteria: cases following upper and lower fixed appliance therapy where a long period of lower incisor retention was considered advisable 49 patients

The lower incisor bonded retainer in clinical practice: a three-year study. Prospective Artun J32 (1997)

Inclusion criteria: not applied

A 3-year follow-up study of various types of orthodontic canine-tocanine retainers Prospective

- Round stainless steel; 0.7 mm; n = 33

Retainer loosening

- Flat rectangular ribbon arch; 0.015 in.  0.036 in.; n = 13 mandible: only canines (n = 40); mandible: only laterals (n = 6) - Thick plain wire; 0.032 in.; mandible: only canines; n = 11

Bond failure

- Thick spiral wire; 0.032 in.; mandible: only canines; n = 13 - Thin, flexible spiral wire; 0.0205 in.; mandible: all 6; n = 11 - Removable retainers; n = 14

Al-Nimri K30 (2009) Gingival health and relapse tendency: a prospective study of two types of lower fixed retainers Prospective

at least 12

62 patients (44 female, 18 male) Inclusion criteria: completed treatment, required fixed retention for the lower anterior segment

Composite: Concise (CC) - Round, stainless steel; 0.036 in.; mandible: only canines; mean age: 20.23  3.8; n = 31

Retainer fracture

- Multistranded wire; 0.015 in.; mandible: all 6; mean age: 19.97  4.2; n = 31 Composite: Filtek P60 restorative (LC)

310 Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 1 (Continued ) Author Study title Study design Ardeshna AP27 (2011)

Observation period (months) max 24

Participants

51 patients Inclusion criteria: good oral hygiene

Clinical evaluation of fibrereinforced- plastic bonded orthodontic retainers Prospective

All ages

Interventions

- Maxilla: fibre-reinforced-thermoplastic - FRP formula A; 0.53; n = 1 - FRP formula A; 1.02 mm; n = 1 - FRP formula B; 0.53 mm; n = 6 - FRP formula B; 1.02 mm; n = 8

Outcome

Retainer failure

- Mandible: fibre-reinforced-thermoplastic – FRP formula A; 0.53 mm; n = 15 - FRP formula A; 1.02 mm; n = 6 - FRP formula B; 0.53 mm; n = 10 - FRP formula B; 1.02 mm; n = 29

Taner T31 (2011)

6

A prospective clinical evaluation of mandibular lingual retainer survival Prospective

Dahl EH35 (1991)

66 patients (52 female, 14 male) Inclusion criteria: not applied

Composite: Phase II (CC) - 8-braided flattened stainless steel; 0.022 in.  0.016 in.; mandible: all 6; direct bonding; mean age: 15.96  3.21; n = 32

Bond failure

- 8-braided flattened stainless steel; 0.022 in.  0.016 in.; mandible: all 6; indirect bonding; mean age: 19.44  6.79; n = 34

72

142 patients

36

Inclusion criteria: not applied

Long-term experience with direct-bonded lingual retainers Retrospective

Mean age: 28.5 years and 31.2 years

Composite: Transbond LR (LC) - 3-stranded spiral wire; 0.0195 in. or 0.0215 in.; mean age: 28.5; maxilla: usually all incisors (n = 41); mandible: usually all 6 (n = 14); both (n = 15)

Bond failure, retainer fracture

- 5-stranded spiral wire; 0.0215 in.; mean age: 31.2; maxilla: usually all incisors (n = 55); mandible: usually all 6 (n = 8); both (n = 9) Composite: Concise (CC) Andren A36 (1998) A clinical evaluation of long term retention with bonded retainers made from multistrand wires Retrospective

At least 60

103 patients (81 female, 22 male) Inclusion criteria: not applied Mean age: 35, range 16–68 years

- 0.0175 in. Dentaflex; maxilla and/or mandible: all 6; n = 33 - 0.015 in. Wildcat; maxilla and/ or mandible: all 6; n = 32 - 0.0175 in. Wildcat; maxilla and/or mandible: all 6; n = 20 - 0.0195 in. Wildcat; maxilla and/or mandible: all 6; n = 15

Bond failure, retainer fracture

Composite: concise (CC) and saga sealant

310 Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 1 (Continued ) Author Study title Study design Lumsden KW37 (1999)

Observation period (months) 6–48

Participants

178 patients Inclusion criteria: not applied

Breakage incidence with direct- bonded lingual retainers Retrospective

Interventions

- Co-axial wire; 0.18 in.; all 6, maxilla: n = 18, mandible: n = 122

Outcome

Bond failure, retainer fracture

Composite: Rely-A-Bond Mean age: 15.5 years - Co-axial wire; 0.18 in.; all 6, maxilla: n = 4, mandible: n = 56 Composite: Helioprogress

Segner D38 (2000)

Not reported

549 patients Inclusion criteria: at least 1 bonded retainer placed after completion of active orthodontic treatment

Bonded retainers–clinical reliability Retrospective

Average age: 23.3 years

- Multistranded stainless steel wire; 0.0175 in.; maxilla: bonded from 1-1 until 4-4; n = 135

Bond failure, retainer fracture

- Multistranded stainless steel wire; 0.0175 in.; mandible: bonded from 1-1 until 4-4; n = 414 Composite: Durafil flow (LC)

Cerny R39 (2007)

48

Inclusion criteria: not applied

The reliability of bonded lingual retainers Retrospective

Zachrisson BU17 (2007)

1156 patients

- Round stainless steel heat treated; 0.018 in.; maxilla and mandible: all 6

Retainer failure

Composite: OrthoSolo (primer), Z100 restorative (LC)

Mean: 50.4, range: 12–120

1081 patients Inclusion criteria: not applied

Long- term experience with direct-bonded retainers: Update and clinical advice Retrospective

- Gold coated wire; 0.030 in.; mandible: only canines; n = 381

Retainer failure

- Gold coated wire; 0.0215 in.; mandible: all 6; n = 191 - Gold coated wire; 0.0215 in.; maxilla: all incisors; n = 323 - Gold coated wire; 0.0215 in.; maxilla: all 6; n = 186 Composite: Concise (CC), Transbond LR (LC)

Booth FA40 (2008) Twenty-year follow-up of patients with permanently bonded mandibular canineto-canine retainers Retrospective

Median: 300, range: 240–348

45 patients Inclusion criteria: not applied

- Stainless steel wire; 0.025 in.; mandible: only canines; n = 45

Retainer failure

Composite: Orthomite

310 Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 1 (Continued ) Author Study title Study design Lie Sam Foek DJ41 (2008)

Observation period (months) Mean: 19.1  7.2, median: 19.9 (IQR 15.2–23.7)

Survival of flexible, braided, bonded stainless steel lingual retainers: a historic cohort study Retrospective

Participants

277 patients (162 female, 115 male) Inclusion criteria: finished their orthodontic treatment with fixed appliances and having received a bonded retainer between December 2002 and May 2006.

Interventions

- Flexible, braided, rectangular; stainless steel wire; 0.022 in.  0.016 in.; mandible: all 6; n = 277

Outcome

Retainer failure

Composite: Heliobond and Tetric Flow (LC)

Median age: females, 14.8 years; males, 15.3 years Renkema AM34 (2008)

60

Bond failure rates for Vloop vs. straight wire lingual retainers Retrospective

- Stainless steel; 0.0215 in.  0.027 in.; mandible: only canines; n = 235

Retainer failure

- Multistranded stainless steel; 0.0175 in.; straight wire; maxilla and mandible: all incisors or all 6; age: 9–60 years (mode: 15); n = 153

Bond failure

Inclusion criteria: treated with full fixed appliances, lingual retainer bonded only to the mandibular canines with the same wire dimensions (0.0215 in.  0.027 in. stainless steel rounded rectangular wire), both mandibular permanent canines present before treatment, no spacing in the mandibular anterior region before and after treatment, no retreatment, dental casts were available before treatment (Ts), after treatment (T0), at least 2 years after treatment (T2), and at least 5 years after treatment (T5).

Effectiveness of lingual retainers bonded to the canines in preventing mandibular incisor relapse Retrospective

Lee KD42 (2009)

235 patients (139 female, 96 male)

6

Mean age: 15.6  2.7 years 300 retainers Inclusion criteria: not applied

- Black Australian stainless steel; 0.016 in.; V-loop design; maxilla and mandible: all incisors or all 6; age: 9–58 (mode: 14); n = 147 Composite: Transbond LR (LC)

310 311 312

313 314 315 Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 1 (Continued ) Author Study title Study design Scheibe K43 (2010)

Observation period (months) 30  19.5

Lower bonded retainers: Survival and failure rates particularly considering operator experience Retrospective

Renkema AM33 (2011)

Interventions

Participants

1062 patients (601 female, 461 male)

- CrNi steel; 0.6 mm; mandible: only canines; n = 824

Inclusion criteria: treated with a multibracket appliance, bonded a lower fixed retainer, completed active orthodontic treatment between 1995 and 2006.

- Twistflex; 0.18 in.; mandible: all 6; n = 227

Long-term effectiveness of canine-to-canine bonded flexible spiral wire lingual retainers Retrospective

Retainer failure

- Other; mandible: involving various teeth; n = 11

Age: 15.7  4 years 221 patients (75 female, 146 male)

60

Outcome

- Flexible spiral wire (3-strand heat treated); 0.0195 in. twist; mandible: all 6; n = 221

Bond failure

Inclusion criteria: treated with full fixed appliances, received a mandibular lingual retainer (0.0195-in., 3-strand, heat-treated twist wire, Wildcat, GAC International, Bohemia, NY), bonded to all 6 mandibular anterior teeth, dental casts and intraoral photographs were available before treatment (Ts), after treatment (T0), at least 2 years after treatment (T2), and at least 5 years after treatment (T5). Mean age: 16.3  4.2 years

*

310 311 312 313 314 315 316

LC indicates light-curing material whereas CC indicates chemical-curing material ** all 6 indicates bonding to 33,32,31,41,42,43

Only three studies23,24,49 demonstrated adequate randomisation, allocation concealment and blinding of outcome assessors and these studies were classified as low risk of bias.23,24,49 Two of the nine included studies20,26 demonstrated unclear randomisation, although one study20 claimed to involve randomisation using paper sheets after personal communication with the author. Allocation

concealment was unclear.20 Blinding of the clinicians and patients was not always possible due to the nature of the interventions. Losses to follow up were appropriately described and there was no evidence of selective outcome reporting. Thus, these studies were classified at unclear risk of bias. In the last four studies,18,19,25,47 no information was reported regarding allocation concealment and blinding

Table 2 – Quality assessment for included prospective studies. Author Zachrisson BU28 (1977) Lee RT29 (1981) Al-Nimri K30 (2009) Ardeshna AP27 (2011) Artun J32 (1997) Taner T31 (2011)

Inclusion criteria explicitly described

Adjusting for confounders

Description of potential biases

Blinding of the assessor

Reporting of drop outs

Reporting of follow up

Risk of Bias

No – unclear risk (partially reported) No – unclear risk (partially reported) No – unclear risk (partially reported) Yes – Low Risk

No – Risk No – Risk No – Risk No – Risk No – Risk No – Risk

No – Unclear Risk (not reported) No – Unclear Risk (not reported) No – Unclear Risk (not reported) No – Unclear Risk (not reported) Yes – Low Risk

No – Unclear Risk (not feasible) No – Unclear Risk (not reported) No – Unclear Risk (not reported) No – Unclear Risk (not feasible) No – Unclear Risk (not reported) No – Unclear Risk (not reported)

Yes – Low Risk No – High Risk Unclear Risk (not reported) No – High Risk No – High Risk Yes – Low Risk

Yes – Risk Yes – Risk Yes – Risk Yes – Risk Yes – Risk Yes – Risk

Low

High

Low

High

Low

High

Low

High

Low

High

Low

High

No – unclear risk (partially reported) No – unclear risk (partially reported)

High High High High High High

No – Unclear Risk (not reported)

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317 318 319 320 321 322 323

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Fig. 2 – Risk of bias summary for included RCTs: the plus sign indicates low risk of bias; the circle with question mark indicates unclear risk of bias; the minus sign indicates high risk of bias.

324 325 326

of participants, therapists or outcome assessors. Based on the aforementioned points, those studies were rated at high risk of bias.

327 328 329 330 331 332 333 334 335 336

3.2.2.

quality assessment, those studies were classified as high risk of bias, as well.

337 338

3.3.

339

Retrospective studies

Prospective studies

Six prospective studies were identified but none was rated at low risk of bias, since no study met the necessary criteria outlined by the Cochrane Handbook (Table 2). No study reported adjustment for confounders. One study27 described the inclusion criteria explicitly and reported follow up, but did not report on drop-outs. Thus, it was rated at high risk of bias. Finally, in five studies28–32 the inclusion criteria were only partially reported. In three studies29,30,32 no drop outs were reported. Based on the

Twelve retrospective studies were identified. The quality assessment of each study was valued according to the predetermined criteria of Bondemark et al.22 The studies were graded with a score of A, B, or C (Table 3). Five studies33–35,37,42 met all criteria of acquiring B grade, and regarded, thus, as moderate value of evidence. The rest seven studies17,36,38–41,43 received a grade C, considered, therefore, as low value of evidence. Only one of them reported the existence of diagnostic reliability tests.33 Five

Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

340 341 342 343 344 345 346 347 348

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Table 3 – Quality assessment for retrospective studies according to the criteria of Bondemark et al. (2007). Author

Defined control group

Defined diagnosis and end points

Dahl EH35 (1991) Andren A36 (1998) Lumsden KW37 (1999) Segner D38 (2000) Cerny R39 (2007) Zachrisson BU17 (2007) Booth FA40 (2008) Lie Sam Foek DJ41 (2008) Renkema AM34 (2008) Lee KD42 (2009) Scheibe K43 (2010) Renkema AM33 (2011)

Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes

Yes Yes Yes Yes Yes Partially Yes Yes Yes Yes Yes Yes

349 350

studies36,38,40,41,43 failed to report both diagnostic reliability and reproducibility tests.

351

3.4.

352 353 354 355 356 357 358 359 360 361 362 363 364 365 366

Substantial differences in the interventions, participants, and outcomes among studies were observed. Thus, quantitative analysis was only feasible between polyehtylene woven ribbon versus multistranded wire retainers. Moreover, some variations with respect to the type of retainer, the number of participants and the observation period within the studies included in the meta-analysis were also evident. What should be taken into consideration is that metaanalyses of studies that are at high risk of bias may be seriously misleading. If bias exists in some of the included studies, meta-analysis may compound the errors, and yield a ‘wrong’ result that may be interpreted as credible. Hence only one meta-analysis which included one study at unclear risk of bias: the study of Rose26 and one at low risk of bias: the study of Salehi was implemented.24

367

3.5.

368 369 370 371 372 373 374 375 376 377 378

Diagnostic reliability tests

Reproducibility tests described

Not Not Not Not Not Not Not Not Not Not Not Yes

Yes Not Yes Not Yes Yes Not Not Yes Yes Yes Yes

reported reported reported reported reported reported reported reported reported reported reported

reported reported

reported reported

Grade B C B C C C C C B B C B

indicated no statistically significant difference in the risk of failure between the treatment groups (RR: 1.74; 95% CI: 0.45, 6.73; p = 0.42). The degree of heterogeneity between studies was found to be high (I2 = 55%) (Fig. 3). Statistical analysis of publication bias was not indicated, because fewer than 10 studies were included in the quantitative synthesis. The assessment of the quality of evidence on the specific metaanalysis revealed that the level of the existing evidence was of low quality. These findings suggest that further research is (very) likely to have an important impact on our confidence in the estimate of effect and may change the estimate (Fig. 4).

379 380 381 382 383 384 385 386 387 388 389

3.5.2.

In order to proceed to the qualitative analysis, the 25 studies were divided into 5 groups according to the material of the retainer. The aforementioned categorisation did not derive from any established methodological background, but was implemented for readership’s lucidity. Moreover, outcome measures are described as failure rate on the majority of the papers although they imply risk of failure since the factor time is not included (risk of failure = failure/n). Thus, the outcomes will be described as risk of failure instead on failure rate (Table 4).

390 391 392 393 394 395 396 397 398 399 400

3.5.1. Comparison: polyehtylene woven ribbon vs. 0.0175 in. multistranded wire retainers

3.6.

401

Two trials could be mathematically combined for this comparison.24,26 The mandibular retainers compared were polyethylene ribbon retainers (Ribbond, Seattle, USA) and 0.0175 in. multistranded stainless steel wire (Respond, Ormco, USA). All retainers were bonded with the same light-cured adhesive (Heliosit, Vivadent, Liechtenstein). The duration of the studies was 1824 and 2426 months. The outcome measured was retainer failures, including breakage, detachment and bond failure incidents. The random-effects meta-analysis

The risk of failure for glass-fibre reinforced retainers ranged from 11 to 71%. Due to the properties of this type of retainers, all adjacent anterior teeth (canine to canine or lateral to lateral) are bonded. In the first study,19 which was an RCT, bonding was done with a light-cured orthodontic adhesive combined with a light-cured flowable resin-composite. The risk of bond failure was 21.4% when retainers were bonded from lateral incisor to lateral incisor in the maxilla and 11.8%

Quantitative synthesis of included studies

Effects of interventions

Qualitative synthesis of the included studies

Glass fibre reinforced retainers

Fig. 3 – Random-effects meta-analysis of polyethylene ribbon vs. multistranded wire bond failures. Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

402 403 404 405 406 407 408 409

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Fig. 4 – Assessment of quality of evidence on meta-analysis of polyethylene ribbon vs multistranded wire bond failures.

410 411 412 413 414 415 416 417 418 419 420

when bonded from canine to canine in the mandible. Moreover, fracture was estimated as 7.1% and 8.8% respectively. Glass-fibre retainers were placed likewise in the second study,20 which was also an RCT. Retainers were bonded from lateral to lateral at the upper jaw and from canine to canine at the lower jaw. A light-cured material was used, combined with a light-cured flowable resin-composite. The overall risk of failure was 51%. In another prospective study,27 which indicated high risk of bias, bonding was accomplished with a chemically-cured orthodontic material. Mean survival time was estimated at 7.7 months.

421

3.7.

422 423 424 425 426 427 428 429 430 431 432 433

Retainers fabricated with round Cr–Ni wire were used in a single retrospective study rated as low quality of evidence.43 The 0.6 mm wire was bonded only to the mandibular canines and the reported bond failure was 34.9%. In 2007, Zachrisson et al.17 published a study on Au-coated retainer wires bonded either with a light-cured or with a chemically-cured orthodontic adhesive. For the upper arch, the observed risk of failure was 6.2% when bonding was applied from lateral incisor to lateral incisor. However, when the retainers were bonded to all six anterior teeth, the risk of failure tripled to 21.5%. In the lower arch, bonding only to canines (3.5% failure) provided better results than bonding to all six teeth (5.3% failure).

434

3.8.

435 436 437 438

In a prospective study Zachrisson28 (1977) observed 5/43 (11.6%) failures for mandibular retainers made from a Cobased alloy and bonded to all anterior teeth with a chemicallycured adhesive over a mean period of 15.7 months.

439

3.9.

440 441 442

In one prospective study rated as unclear value of evidence, Artun32 observed bond failure of 20.8% in retainers bonded with a chemically-cured orthodontic material, only to the

Cr–Ni retainers

Blue Elgiloy retainers

Stainless steel retainers

mandibular canines. In two other prospective studies of low value of evidence, Al-Nimri30 bonded stainless steel alloy retainers with a light-cured adhesive only to the mandibular canines and reported a fracture risk of 13%, whereas Lee RT29 bonded stainless steel retainers only to the mandibular canines or laterals, and reported that 9 out of 46 retainers failed (19.7%). Three retrospective studies were identified. Lee KD42 bonded stainless steel retainers to four or six maxillary or mandibular anterior teeth with a light-cured material and recorded bond failure risk of 14.3%. Cerny39 bonded stainless steel retainers to all six maxillary or mandibular anterior teeth with a light-cured material and recorded bond failure risk of 9%. Finally, Booth40 bonded stainless steel retainers only to mandibular canines with a light-cured bonding agent and concluded that 17 out of 45 retainers were in need of repair (37.7% failure).

443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459

3.10.

460

Multistranded retainers

Several studies have used multistranded wires for fixed retention. When using light-cured adhesives to bond retainers to all six anterior teeth of the mandible, bond failure ranged from 8.8 to 46%.20,23 Bolla19 mentioned detachments of 22.2%, when retainers were placed from lateral incisor to lateral incisor in the maxilla, and 15.6% when placed in all six anterior mandibular teeth. A study rated at low value of evidence reported bond failures of both maxillary and mandibular retainers of 12.4%.42 Lie Sam41 indicated retainer failure of 31.4% and Al-Nimri30 of 29% for mandibular retainers. Finally, Taner31 and Bovali49 by introducing two different methods of mandibular 3-3 retainer application (direct and indirect) found no significant differences in favour of any technique.

461 462 463 464 465 466 467 468 469 470 471 472 473

4.

474

Discussion

To minimise or prohibit relapse of orthodontic treatment, almost every patient is given some type of retainer. Recent

Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 4 – Outcomes and interventions of studies included in the qualitative synthesis ordered by study design and date. Author/observation period Sto¨rmann I18 (2002) RCT 24 mo.

Interventions

- Coaxial stainless steel 0.0215 in.; mandible: all 6; n = 36 - Coaxial stainless steel 0.0195 in.; mandible: all 6; n = 30 - Prefabricated; mandible: only canines; n = 32

Events (total)

18/36

Risk ratio

0.0215 coaxial SS/0.0195 coaxial SS: 1.5

10/30 6/32

95% confidence intervals [0.82,2.74] [0.74,4.29]

0.0195 coaxial SS/ prefabricated: 1.78

[1.21,5.89]

0.0215 coaxial SS/ prefabricated: 2.67 Tacken MP20 (2010) RCT 24 mo.

- Glass fibre reinforced (GFR500); maxilla: lateral incisor to lateral incisor (n = 45), mandible: all 6 (n = 45) - Glass fibre reinforced (GFR1000); maxilla: lateral incisor to lateral incisor (n = 48); mandible: all 6 (n = 48) - 6-stranded coaxial wire 0.0215 in.; maxilla: lateral incisor to lateral incisor (n = 91); mandible: all 6 (n = 91)

Scribante A25 (2011) RCT 12 mo. Bolla E19 (2012) RCT 72 mo.

Pandis N23 (2013) RCT

- Multistranded Stainless steel; 0.0175 in.; mandible: all 6; n = 17 - Polyethylene ribbon-reinforced resin composite; mandible: all 6; n = 15 - Glass fibre reinforced; maxilla: all incisors (n = 14); mandible: all 6 (n = 34) - Multistranded wire, 0.0175 in.; maxilla: all incisors (n = 18); mandible: all 6 (n = 32)

GFR500 Maxilla 23/45 Mandible 21/45 GFR1000 Maxilla 25/48 Mandible 25/48 Multistranded Maxilla 13/91 Mandible 8/91

The unit of analysis was the tooth with no details of failure at the patient level Maxilla 4/14 Mandible 7/34 Maxilla 7/18 Mandible 10/32

- Tru-Chrome multistranded wire; 0.022 in.; mandible: all 6; n = 110; Reliance (CC) - Tru-Chrome multistranded wire; 0.022 in.; mandible: all 6; n = 110; Flow Tain (LC)

47/110

Bovali E49 (2014) RCT

- Multistranded steel wire 0.0215 in.; mandible: all 6; n = 29; direct bonding

7/29

6 mo.

- Multistranded steel wire 0.0215 in.; mandible: all 6; n = 31; indirect bonding - Glass fibre reinforced; mandible: all 6; n = 40 - Multistranded wire; 0.0175 in.; mandible: all 6; n = 47

26.5 mo.

Sfondrini MF47 (2014) RCT

Maxilla GFR500/multi: 3.58 GFR1000/multi: 3.65 GFR1000/GFR500: 1.02

[2.01,6.38] [2.06,6.46] [0.69,1.51]

Mandible GFR500/multi: 5.31 GFR1000/multi: 5.92 GFR1000/GFR500: 1.12

[2.55,11.04] [2.90,12.11] [0.74,1.69]

Not applicable

Not applicable

Maxilla: Glass fibre/ multistranded 0.0175: 0.73

[0.27,2.02]

Mandible: Glass fibre/ multistranded 0.0175: 1.52 Light cure/Chemical cure: 1.17

[0.66,3.50]

[0.88,1.56]

55/110

Indirect bonding/direct bonding: 1.34

[0.59,3.04]

Multistranded 0.0175/ Glass fibre: 1.64

[1.01,2.68]

10/31

14/40 27/47

12 mo.

477

478 Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 4 (Continued ) Author/observation period Zachrisson BU28 (1977) Prospective

Interventions - Heat-treated and polished blue Elgiloy; 0.036 in. or 0.032 in.; mandible: only canines; held with finger during placement; n = 22

Events (total) 3/22

Risk ratio

95% confidence intervals

Held with finger/ligated technique: 1.43

[0.27,7.73]

Only total failures were given: 9/46 (19.6%)

No data for intergroup comparisons provided



1/11

Thick spiral wire 0.032/ thick plain wire 0.032: 3.38

[0.44,26.00]

Thick spiral wire 0.032/ thin flexible 0.0205: 1.13

[0.37,24.58]

2/21

12 mo. - Heat-treated and polished blue Elgiloy; 0.036 in. or 0.032 in.; mandible: only canines; ligated during placement; n = 21 Lee RT29 (1981) Prospective

- Round stainless steel; 0.7 mm; mandible: only canines or only laterals; n = 33

36 mo.

- Flat rectangular ribbon arch; 0.015 in.  0.036 in.; mandible: only canines or only laterals; n = 13

Artun J32 (1997) Prospective

- Thick plain wire; 0.032 in., mandible: only canines; n = 11

36 mo.

4/13 - Thick spiral wire; 0.032 in.; mandible: only canines; n = 13

3/11

- Thin, flexible spiral wire; 0.0205 in.; mandible: all 6; n = 11

Al-Nimri K30 (2009) Prospective

- Round, stainless steel; 0.036 in.; mandible: only canines; n = 31

[0.32,3.99]

Thin flexible 0.0205/ thick plain wire 0.032: 3.00 4/31

Mulistranded 0.015/ Round SS 0.036: 2.25

[0.77,6.54]

Maxilla/mandible: 0.76

[0.59,0.99]

Direct bonding/indirect bonding: 1.59

[0.84,3.02]

9/31

12 mo.

- Multistranded wire; 0.015 in.; mandible: all 6; mean; n = 31

Ardeshna AP27 (2011) Prospective

- Fibre-reinforced-thermoplastic FRP formula A and B; 0.53 and 1.02 mm; maxilla: all 6; n = 60

34 mo.

- Fibre-reinforced-thermoplastic FRP formula A and B; 0.53 and 1.02 mm; mandible: all 6; n = 16

Taner T31 (2011) Prospective

- 8-braided flattened stainless steel; 0.022 in.  0.016 in.; mandible: all 6; direct bonding; n = 32

40/60 14/16

15/32 10/34

6 mo. - 8-braided flattened stainless steel; 0.022 in.  0.016 in.; mandible: all 6; indirect bonding; n = 34

477

478 Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 4 (Continued ) Author/observation period Dahl EH35 (1991) Retrospective 72 mo.

Interventions - 3-stranded spiral wire; 0.0195 in. or 0.0215 in.; maxilla: usually all incisors (n = 41); mandible: usually all 6 (n = 14); both (n = 15)

36 mo.

- 5-stranded spiral wire; 0,0215 in.; maxilla: usually all incisors (n = 55), mandible: usually all 6 (n = 8); both (n = 9)

Andren A36 (1998) Retrospective

- 0.0175 in. Dentaflex; maxilla and/ or mandible: all 6; n = 33 - 0.015 in. Wildcat; maxilla and/or mandible: all 6; n = 32 - 0.0175 in. Wildcat; maxilla and/or mandible: all 6; n = 20 - 0.0195 in. Wildcat; maxilla and/or mandible: all 6; n = 15

60 mo.

Events (total) Maxilla: 27/56 Mandible: 6/29 Maxilla: 7/64 Mandible: 1/17

11/33

Risk ratio Maxilla 3-stranded/5-stranded: 4.41

0/15

[2.08,9.33] [0.46,26.80]

Mandible: 3-stranded/5-stranded: 3.52

0.0175 Dentaflex/0.015 Wildcat: 1.19

9/32 2/20

95% confidence intervals

[0.57,2.47] [0.82,13.52]

Dentaflex/ 0.0175Wildcat: 3.33 Dentaflex/0.0195 Wildcat: 10.82

[0.68,172.45] [0.68,11.71] [0.57,148.55]

Wildcat/0.0175Wildcat: 2.81

[0.20,73.95]

Wildcat/0.0195Wildcat: 9.21 0.0175Wildcat/ 0.0195Wildcat: 3.81 Lumsden KW37 (1999) Retrospective

- Co-axial wire; 0.18 in.; all 6; maxilla: n = 18; mandible: n = 122; Rely-A-Bond

Rely-A-Bond Upper: 7/18 Lower: 27/122

Maxilla Helioprogress/Rely-ABond: 1.93

6–48 mo.

- Co-axial wire; 0.18 in.; all 6; maxilla: n = 4; mandible: n = 56: Helioprogress

Helioprogress Upper: 3/4 Lower: 13/56

Mandible Helioprogress/Rely-ABond: 1.05

Segner D38 (2000) Retrospective

- Multistranded stainless steel wire; 0.0175 in.; maxilla: from 1-1 until 4-4; n = 135

No relevant data provided

No data for intergroup comparisons provided

Not reported

- Multistranded stainless steel wire; 0.0175 in.; mandible: from 1-1 until 4-4; n = 414

Cerny R39 (2007) Retrospective

- Round stainless steel heat treated; 0.018 in.; maxilla and mandible: all 6

Approx. 145/1156 (12.6%)

No data for intergroup comparisons provided

14/381

Mandible: 0.0215 in. gold coated, all 6/0.030 in. gold coated, only canines: 1.53

[0.86,4.33] [0.59,1.88]



48 mo.

Zachrisson BU17 (2007) Retrospective Mean: 50.4 mo.

- Gold coated wire; 0.030 in.; mandible: only canines; n = 381 - Gold coated wire; 0.0215 in.; mandible: all 6; n = 191 - Gold coated wire; 0.0215 in.; maxilla: all incisors; n = 323

10/191 20/323 40/186

- Gold coated wire; 0.0215 in.; maxilla: all 6; n = 186

[0.69,3.44] [2.09,5.76]

Maxilla: 0.0215 in. gold coated, all 6/0.0215 in. gold coated, all incisors: 3.47

477

478 Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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Table 4 (Continued ) Author/observation period Booth FA40 (2008) Retrospective

Interventions

Events (total)

Risk ratio

95% confidence intervals

- Stainless steel wire; 0.025 in.; mandible: only canines; n = 45

17/45 (38%)

Not applicable



- Flexible braided rectangular stainless steel wire; 0.022 in.  0.016 in.; mandible: all 6; n = 277

87/277 (31.4%)

Not applicable



- Stainless steel; 0.0215 in.  0.027 in.; mandible: only canines; n = 235

48/235 (20.4%)

Not applicable



- Multistranded stainless steel; 0.0175 in.; straight wire; maxilla and mandible: all incisors or all 6; n = 153

19/153

0.016 austr/0.0175 multistranded: 1.15

[0.65,2.05]

262/824

All 6/only canines: 1.43

[1.20,1.70]

103/227

Other/all 6: 1.10

[0.58,2.08]

6/11

Other/only canines: 1.57

[0.84,2.95]

70/221(31.7%)

Not applicable



Median: 300 mo.

Lie Sam Foek DJ41 (2008) Retrospective Median: 19.9 mo.

Renkema AM34 (2008) Retrospective 60 mo.

Lee KD42 (2009) Retrospective

21/147

6 mo. - Black Australian wire stainless steel; 0.016 in.; V-loop design; maxilla and mandible: all incisors or all 6; n = 147

Scheibe K43 (2010) Retrospective 30  19.5 mo.

- CrNi steel; 0.6 mm; mandible: only canines; n = 824 - Twistflex; 0.18 in.; mandible: all 6; n = 227 Other; mandible: involving various teeth; n = 10

Renkema AM33 (2011) Retrospective

- Flexible spiral wire (3-strand heat treated); 0.0195 in. twist; mandible: all 6; n = 221

60 mo. All 6 indicates bonding to 33,32,31,41,42,43.

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surveys have shown a variety of retainer protocols based on the orthodontist’s preferences.44,45 These have shown that Hawley retainer and fixed lingual retainers remain the most frequently used, with the later most commonly used in the mandibular arch.48 The range of fixed retainers has expanded and preliminary designs typically involving large-diameter stainless steel round wires bonded to the canines have evolved, to narrower, braided, or coaxial round wires of various compositions and resilience, bonded to all mandibular anterior teeth. The aim of the present review was to systematically search the relevant literature to assess lingual retainer failures and to identify factors that influence the risk of failure. Significant differences considering participants,

interventions and outcomes were noted in the included studies. Although, all studies dealt with orthodontic retention after orthodontic treatment, intrinsic differences regarding interventions and the time points of outcome assessment were observed. Therefore, due to the great heterogeneity, only a few studies could be combined mathematically and the results of the majority of the included studies were presented using qualitative synthesis. Glass-fibre reinforced retainers, demonstrated a wider range of bond failures (11.819–71%27) than polyethylene ribbon (50%24,26). Although the characteristics of the bonding material (i.e. orthodontic adhesive or restorative composite, conventional or low viscosity, chemically- or light-cured) and the attachment mode (all 6 or only canines) may affect the risk of

Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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failure, there are several other factors directly related to the retainer material, not identified in most studies. For example, it is interesting to note that glass-fibre reinforced retainers have significantly lower bond failures in the study of Bolla et al.19 and Sfondrini et al.47 were silanisation before bonding was implemented. Thus the need of silanisation in order to strengthen the resin/fibre interface could be an important bond failure predictor in this type of retainers. Moreover, several commercially available glass-fibres are pre-impregnated with uncured resin, whereas others are not. On the other hand, some polyethylene fibres are surface treated to enhance the resin/fibre interface (i.e. plasma treatment etc). Moreover, the retainer dimensions, texture and number of layers may dramatically modify the performance of the main retainer as they may increase the retainer modulus and fracture toughness. Therefore, it is very difficult to assign a positive treatment effect to a specific type of fibre reinforced material in the absence of this information. Retainers made of conventional wires (round Cr–Ni,43 Cobased,28 Au-plated17) exhibited risk of failure ranging from 3.5%17 to 31.9%,43 with the highest values observed at the upper jaw. Finally, the popular categories of stainless steel and multistranded retainers, manifested failure ranging from 939 to 38%40 for the former, and from 1220 to 50%23 for the latter, when bonded with light-cured adhesives. Based on the meta-analysis of the present study, no difference was observed between multistranded and polyethylene ribbon retainers. It should, however, be pointed that this result was generated by combining only two relatively small trials and one them was characterised as unclear risk of bias. The relatively lower failures of metal wires may be assigned to the increased stiffness of the material, especially the stainless steel, providing increased toughness to the complex vectors of the functional forces. Recent developments in the field of resin adhesion to metals may further increase the bonding capacity of resin composites to these appliances. For example, metal sandblasting with powders capable of tribochemically coating metal surfaces, may increase the interfacial strength as it has long been documented for prosthodontic alloys.50 Alternatively, simpler chairside treatments by priming metal surfaces with phosphate or carboxylic functionalised resin monomers may increase interfacial strength and prevent ‘‘loosening’’ of metal-resin interfaces.51 Such primers are routinely used for bonding to dental alloys and ceramics. Chemically-cured (mix or no-mix systems) and lightcured resin composites are commonly used for bonding retainers to enamel. From the reviewed studies a slight difference between light-cured and chemically-cured bonding systems was observed, in favour of the former. Out of 22 comparisons tested in 16 studies with light-cured materials, bond failures varied from 9%39 up to 51%.20 Meanwhile, out of 9 comparisons tested in 8 studies employing chemically-cured materials, failures ranged from 7.8%35 up to 71%.27 Nevertheless, the advantages of light-curing (curing on command, fast setting, better monomer conversion, less oxygen inhibition) seem to facilitate the bonding protocols of the retainers, considering that the majority of resin composite viscosities are available excessively in light-cured versions.

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As far as the glass fibre retainers are concerned, failures obtained from 4 studies occurred from 28.6%19 up to 87.5%27 for the maxilla and from 20.6%19 up to 66.6%27 for the mandible, respectively. A greater failure risk was observed in the upper jaw, a finding that may be attributed to the occlusion contacts obtained with the antagonists. Glass fibre retainers treated with silane primers resulted in the lowest failures,19,47 apparently due to enhanced bonding at the glassresin interface mediated by the silane. As far as the multistranded retainers are concerned, failures in the upper jaw ranged from 10.9%35 up to 48.2%,35 whereas in the lower jaw failures extended from 5.9%35 up to 57.4%47 when using round wires. A tendency of failure decrease with increasing wire diameter was noted, although an actual correlation may not exist. Moreover, failures with placement of rectangular retainers in the mandible ranged from 20.4%34 up to 31.4%.41 Regarding the influence of direct vs. indirect bonding procedures of mandibular retainers on the failure rates, no statistically significant difference was reported in two studies.31,49 Finally, stainless steel wires failures of 6.2% and 21.5% were reported when bonding gold-coated retainers of the same diameter to four maxillary incisors and to all upper anterior teeth respectively.17 The failures, though, seem to drop to 3.5%17 and 5.3%18 in the mandible. Finally, in regards to the number of bonded teeth, in 25 comparisons reported in 18 studies, with retainers attached to every single tooth (usually canine to canine), bond failures from 5.3%17 up to 71%27 were reported. In 10 comparisons presented in 9 studies, with retainers bonded only to canines, bond failures ranged from 3.5% to 37.7%.17,40 Despite the fact that valid comparison cannot be made between these groups, due to great population diversity, bonding only to canines seems to prevent multiple focal points of internal stresses developed when bonding retainers to all teeth. In a recent study,46 regarding the type of retainers used in Switzerland, the most predominant factors concerning the choice of retainers among Swiss orthodontists were the amount of crowding and patients’ motivation. No agreement concerning the optimal type of wire was reported. Fixed retention was without doubt the first choice for the orthodontist apart from cases treated with extractions and maxillary expansion were a combination of fixed and removable retainers was preferred. Overall, two main categories of fixed retainers, fibres and multistranded wires are most popular in modern clinical practice. Although being remarkably esthetic, the former is susceptible to a higher risk of failures. Further studies should be undertaken to show whether the recent developments in chemical bonding to fibre and metal surfaces can improve the clinical performance of the fibre-reinforced and metal fixed orthodontic retainers. An urgent need for high quality RCTs in orthodontic retention is required in the following areas:

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 to compare different types of retainer materials and mainly the popular categories of stainless steel and multistranded wires;  to compare bond failure and similar outcomes when retainers are bonded to a different number of teeth (canines only, all 6, all incisors – in the maxilla);

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Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

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 to introduce and evaluate new bonding protocols incorporating surface modification of retainers for enhanced bonding with resin composites.

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Despite the numerous studies dealing with parameters of fixed retention in orthodontics there is a lack of evidence on the selection of the optimal protocol and materials for fixed orthodontic retention.

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Funding

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No funding was obtained for this review.

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Conflict of interest

640 641

The authors declare no conflict of interest on relevant bonding materials.

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Appendix 1

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5.

Conclusion

Search strategy for MEDLINE via Pubmed (Search ran on 30.01.2013 und updated 15.06.2014) #1 (orthodont*[Title/Abstract]) AND retainer* [Title/Abstract] #2 (orthodont*[Title/Abstract]) AND retention [Title/Abstract] #3 orthodontic retention[MeSH Major Topic] #4 (#2) AND bond*[Title/Abstract] #5 (#1) AND bond*[Title/Abstract] #6 (bond[Title/Abstract]) AND failure*[Title/Abstract] #7 (#1) AND #6 #8 (#2) AND #6 #9 ((orthodont*[Title/Abstract]) AND wire*[Title/Abstract]) AND retention*[Title/Abstract] #10 ((orthodont*[Title/Abstract]) AND wire* [Title/Abstract]) AND retention*[Title/Abstract] Filters: Randomised Controlled Trial #11 (#1) AND bond*[Title/Abstract] Filters: Randomised Controlled Trial #12 (#2) AND bond*[Title/Abstract] Filters: Randomised Controlled Trial #13 (orthodont*[Title/Abstract]) AND stabil*[Title/Abstract] Filters: Randomised Controlled Trial #14 (orthodont*[Title/Abstract]) AND stabil*[Title/Abstract] #15 (#14) AND bond*[Title/Abstract] #16 (#1) AND wire*[Title/Abstract] #17 (#2) AND wire*[Title/Abstract]

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Q4

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Please cite this article in press as: Iliadi A, et al. Failure of fixed orthodontic retainers: A systematic review. Journal of Dentistry (2015), http:// dx.doi.org/10.1016/j.jdent.2015.05.002

Failure of fixed orthodontic retainers: A systematic review.

To evaluate the risk of failure of fixed orthodontic retention protocols...
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