Salehi 2013.

Methods	2‐arm parallel randomised controlled trial
Participants	Numbers recruited: 142 (83 females and 59 males) Mean (± SD) age: Group 1: 18.1 ± 5.23 years and Group 2: 18.2 ± 4.81 years Inclusion criteria: people treated with standard edgewise fixed appliances and: good oral hygiene healthy periodontium no previous bonded retainer Exclusion criteria: deep overbite traumatic parafunctional habits such as bruxism and clenching Setting: clinic of 1 operator in Iran, participants paid for treatment
Interventions	Comparison: polyethylene ribbon retainer vs. multistrand retainer Group 1: polyethylene ribbon retainer ('Ribbond') was cut to the correct length, pre‐treated with adhesive bis‐GMA sealant and the bonded with 'Heliosite' orthodontic composite resin Group 2: multistrand retainer was 0.0175" passive multistrand wire Both types were bonded to all teeth, canine to canine in the lower arch Both retainers bonded under rubber dam with Heliosite composite resin using Fluoro Bond adhesive bis‐GMA sealant
Outcomes	Outcome relevant to review: survival of retainers Retainer assessed as failed if it debonded from tooth or fractured Survival reported using failure rates of retainers over 18 months
Notes	No assessment of stability, adverse effects on health or patient satisfaction
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random table number table used
Allocation concealment (selection bias)	Unclear risk	No concealment described. Authors contacted to clarify this, but no reply received
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Authors noted that the statistician analysing the data was blinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	Drop‐outs clearly reported and not included in final analysis
Selective reporting (reporting bias)	Low risk	No evidence or suggestion of selective reporting
Other bias	Low risk	No other suggestions of bias noted