Irvine 2004.

Study characteristics
Methods	Setting: Royal Bournemouth Hospital Design: parallel (2 arms) No. of centres: 1 Study duration: 6 months
Participants	Inclusion criteria: "A malocclusion requiring the extraction of all first premolars, no previous orthodontic treatment, lateral cephalometric radiographs to have been taken of the patient within the previous 12 months at the start of treatment." Exclusion criteria: not reported Participant sampling: N = 71 selected Group 1 (n = 30): 12 male, 18 female (mean age of 13.6 ± 1.5 years) Group 2 (n = 32): 14 male, 18 female (mean age of 13.8 ± 1.5 years) Sex: 26 male, 36 female Dropouts:   Group 1 = 3 withdrew, 2 lost to follow‐up Group 2 = 4 withdrew Total = 9
Interventions	Orthodontic intervention: fixed appliances and auxiliaries Lacebacks with fixed appliances versus fixed appliances only
Outcomes	Crowding, arch length
Notes	Funding source not cited
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Adequate method of randomisation
Allocation concealment (selection bias)	Unclear risk	Unclear if allocation sequence concealed from those assigning patients to participant groups
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not possible to blind participants and personnel due to the different interventions used
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Unclear if assessors were blinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	Dropouts reported
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	High risk	Unclear who/how many examiners took the measurements and intra/inter‐rater reliability not reported