Gerlach 2004e.

Methods	Title: placebo‐controlled clinical trial evaluating a 10% hydrogen peroxide whitening strip Trial design: randomised, double‐blinded, placebo‐controlled trial Location: University of Florida, USA Language: English Number of centres: 1 Recruitment period: not reported Funding source: Procter & Gamble
Participants	Participants: 18 to 50 years old. Mean age: 38.8 years Total number: 39 Inclusion criteria: no history of bleaching no restorations no orthodontic brackets no tooth sensitivity Exclusion criteria: not reported Number randomised: 39 Method of randomisation: not reported Method of allocation concealment: not reported Method of blinding: similar white foil packing with unique ID Number evaluated: 34. 2 dropouts on 8th day of evaluation and 3 for all parts of study
Interventions	Total number of intervention groups: 2 10% hydrogen peroxide whitening strips Placebo Duration of treatment: 7 days
Outcomes	Improvement in tooth colour b*: decreased b* indicates reduced yellowness ΔL: increased ΔL is increased brightness
Notes	Sample size calculation: not reported Adverse effects: oral irritation and tooth sensitivity Health‐related quality of life: not reported Key conclusions of the study authors: "Statistically significant tooth whitening was evident after 3 days' treatment with 10% hydrogen peroxide whitening strips, and colour improved with continued usage over 7 days" Contact: Dr Robert W Gerlach; gerlach.rw@pg.com
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "A randomised double‐blinded, placebo‐controlled clinical trial was conducted... Groups were randomly assigned to treatment based on age and baseline tooth colour." No further details are given
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "Each strip was packaged in an individual white foil pouch, with the subject identification number... Strips were over packaged in a kit box,.."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "3 subjects (1 in the 10% group and 2 in placebo group) failed all or pat of the day 8 evaluation" Comment: plausible effect size (difference in means) among missing outcomes not enough to have a clinically relevant impact on observed effect size
Selective reporting (reporting bias)	Low risk	All outcomes mentioned are reported. Conclusions are in accordance with the results
Other bias	Low risk	None