Davidovitch 1997.

Study characteristics
Methods	Setting: Medical College of Virginia, USA, postgraduate orthodontic clinic Design: parallel (2 arms) No. of centres: 1 Study duration: 6 months
Participants	Inclusion criteria: "(1) white ethnicity, (2) 3 to 8 mm mandibular arch length deficiency, (3) presence of the mandibular deciduous second molars, and (4) Class I, Division 2 malocclusion" Exclusion criteria: not reported Participant sampling: N = 34 selected Group 1 (n = 16): sex and mean age of group not reported Group 2 (n = 18): sex and mean age of group not reported Overall age reported across both groups: 7.9‐13.1 years (mean = 10.2 years) Sex: not reported Dropouts: not reported
Interventions	Orthodontic intervention group: fixed appliances and auxiliaries Lip bumper versus no active treatment (observation)
Outcomes	Crowding, arch length, lower incisors to mandible, lower molars to mandible
Notes	Funding source not cited
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Unclear 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	Not specifically reported whether lip bumper removed for impressions or radiographs
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Dropouts not reported
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	Unclear risk	There was a large difference between tomographic and lateral ceph measurements Quote: "Tomographic data (‐6.31° ± 1.28°) showed approximately twice the angulation change as that measured from lateral cephalometric radiographs (‐3.38° ± 3.67°). The average change in molar angulation of experimental versus control subjects was found to be statistically significant when observed tomographically (p < 0.02)".