Kau 2004.

Study characteristics
Methods	Setting: dental clinics in Italy, Germany, Wales Design: parallel (2 arms) No. of centres: 3 Study duration: 1 year, follow‐up 2 years
Participants	Inclusion criteria: "Caucasian children aged between 8 and 9 years old; crowding of the lower incisors greater than or equal to 6 mm, according to the irregularity index of Little (1975); Class I type occlusion as indicated by the molar relationship; the lower molars should have a good long‐term prognosis; overbite should be within normal limits". Exclusion criteria: not reported Participant sampling: N = 97 selected Group 1 (n = 55): sex and mean age of group not reported Group 2 (n = 42): sex and mean age of group not reported Age: "Caucasian children aged between 8 and 9 years old" (mean age and SD not reported) Sex: not reported Dropouts: 14
Interventions	Orthodontic intervention: extractions Extraction of lower deciduous canines versus no active treatment (control)
Outcomes	Crowding, arch length, lower incisors to mandible
Notes	Funding source: “This study was supported by a general research grant from the Wales Office of Research and Development for Health and Social Care.”
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Adequate method of randomisation Quote: "Simple randomization was the method of allocation treatment. A restricted randomization of allocation was used in blocks of 50 to ensure that equal numbers of patients were allocated to each of the treatment groups."
Allocation concealment (selection bias)	Low risk	Adequate method of allocation concealment Quote: "The random allocation was then concealed in envelopes labelled with the study identification number and held in a central place."
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	Low risk	Adequate blinding of assessors Quote: "Observer bias was reduced by ensuring that the examiner was blind to whether the patient had received an extraction or non‐extraction treatment."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Low dropout rate Quote: "53/55 (96%) extraction group; 30/42 (71%) non‐extraction group followed up; overall 83/97 (86%)"
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	Unclear risk	Unclear how many participants came from each centre and what the characteristics were of the participants from each centre