Law 2000.

Methods	RCT Parallel design
Participants	Location: USA Orthodontic patients undergoing separator placement, N = 63 (including Group B) Setting: Department of Orthodontics Group A: 10 male, 12 female; mean age (years) 13.4 (SD 1.7) Group C: 9 male, 13 female; mean age (years) 13.1 (SD 1.8)
Interventions	Group A: 400 mg ibuprofen 1 hour preoperatively (and placebo immediately after the appointment) (N = 22) Group C: placebo 1 hour preoperatively (and placebo immediately after the appointment) (N = 22) All oral
Outcomes	Incidence and severity of pain at different time intervals postoperatively, using a visual analogue scale
Notes	We did not report Group B as this group only received postoperative painkillers
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Participants "randomly assigned"
Allocation concealment (selection bias)	Unclear risk	Method of allocation concealment not reported
Blinding (performance bias and detection bias) All outcomes	Low risk	Investigator, clinician and participants were blinded to the treatment
Incomplete outcome data (attrition bias) All outcomes	High risk	111 participants consented, but 28 of these did not receive separators at next appointment, and 17 participants forgot to take pretreatment dose before appointment. Trial authors did not include 3 more participants for unspecified reasons. It was unclear from the paper which groups participants were lost from
Selective reporting (reporting bias)	Low risk	All expected outcomes reported
Other bias	Low risk	None apparent