Flath 1987.

Study characteristics
Methods	Study design: parallel‐group randomized controlled trial Sample size: 28 Country: USA Setting: dental medical school Dates conducted: not reported Postoperative opioid used and delivery: none Pain score collection: patient self‐report Concurrent postoperative analgesics: not reported
Participants	Inclusion criteria Age 20‐80 years Non‐surgical endodontic therapy Exclusion criteria Root canal therapy complicated by sclerotic or bayonet‐shaped canals ASA 3, 4 or 5 Long‐term steroid or immunosuppressant therapy Pregnancy Recent administration of analgesics
Interventions	Group C (13 participants): 100 mg flurbiprofen 30 minutes before procedure and placebo 3 hours after surgery Group B (15 participants): placebo 30 minutes before procedure and 100 mg flurbiprofen 3 hours after surgery
Outcomes	Postoperative pain (0‐100 mm VAS and categorical rating scale at 3, 7 and 24 hours) Adverse events (gastrointestinal, central nervous and other during follow‐up)
Notes	Funding: 'The Upjohn Company provided no financial support for this study’ Declarations of interest: not reported Authors contacted: no Other: pain score data extracted from graph. Three‐hour data not included as this was when postoperative administration occurred. SD estimated. Pain score data only included symptomatic preoperative patients.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random draw of envelopes. Quote: "By random draw"
Allocation concealment (selection bias)	Unclear risk	No details regarding the envelopes
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐dummy placebo. Quote: "Placebos and the flurbiprofen (The Upjohn Co Kalamazoo, MI) were compounded into identical blue tablets".
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Likely blinded as patient self‐report and blinded intervention
Incomplete outcome data (attrition bias) All outcomes	Low risk	Only four dropouts, unlikely to cause bias. Quote: "...of the 120 patients enrolled in the study, 116 completed all phases".
Selective reporting (reporting bias)	Unclear risk	No protocol
Other bias	Low risk	Similar baseline characteristics. No industry funding