Shim 2022.

Study characteristics
Methods	3‐arm parallel RCT
Participants	Number recruited: 75 (group 1 30; group 2 20; group 3 25); 46 attended 3‐month visit (group 1 16; group 2 16; group 3 14) and those participants were analysed Sex (M:F): 18:29 (group 1: 9M, 7F; group 2: 4M, 12F; group 3: 5M, 9F) Median age (IQR): group 1: 16.5 (15.3); group 2: 15.8 (13.6); group 3: 15.2 (13.6) Inclusion criteria: completion of comprehensive orthodontic treatment; Class I molar and canine relationship based on Andrew’s criteria for finishing; need for a fixed retainer on the mandibular anterior teeth assessed before debonding Exclusion criteria: refusal to participate in the study and conditions contraindicating fixed retainers, including poor oral hygiene and pathology Setting: orthodontic clinic of Saint Louis University, Saint Louis, Missouri, USA
Interventions	3 types of lower fixed retainers: Group 1: CAD/CAM multistrand stainless steel wire (Dentaflex wires, Dentaurum GmbH & Co., Ispringen, Germany) Group 2: lab‐based (lab) retainer, same type of wire as the CAD/CAM group, but manually bent Group 3: chairside (traditional) rectangular chain stainless steel (Ortho‐FlexTech, Reliance, Itasca, Ill)
Outcomes	Stability: LII and intercanine width changes Failure rate: complete or partial detachment were considered failures Time points: 3 and 6 months
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Well‐informed randomisation process generation. A simple software‐generated randomisation was performed by a statistician not involved in the study.
Allocation concealment (selection bias)	Low risk	The sequence generator was contacted by phone for group assignment after determining patient eligibility for enrolment.
Blinding of outcome assessment (detection bias) All outcomes	High risk	"The principal investigator and the clinicians bonding the fixed retainers could not be blinded regarding the assignment of patients to groups in the clinical setting. Upon data analysis, patients’ records were encrypted to minimize observer and measurement bias." It is likely to be influenced by lack of blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups
Selective reporting (reporting bias)	Unclear risk	The present study was not registered. Insufficient information to permit judgement. The published report includes the main primary outcomes.
Other bias	Low risk	The study appears to be free of other sources of bias.