Gerlach 2005.

Methods	Title: clinical trial comparing 2 hydrogen peroxide tooth whitening systems: strips versus pre‐rinse Trial design: randomised, examiner‐blinded, parallel‐group trial Location: not reported Language: English Number of centres: 1 Recruitment period: not reported Funding source: Procter & Gamble
Participants	Participants: 29 to 58 years old. Mean age 39.8 years Total number: 28 Inclusion criteria: 4 maxillary anterior teeth no sensitivity Exclusion criteria: not reported Number randomised: 28 Method of randomisation: not reported Method of allocation concealment: not reported Method of blinding: not reported Number evaluated: 28
Interventions	Total number of intervention groups: 2 Mouthwash: 2% hydrogen peroxide Strip: 10% hydrogen peroxide Duration of treatment: 7 days
Outcomes	Improvement in tooth shade a*, b* and ΔL were recorded Whitening benefit was represented by negative b* (yellowness reduction), and positive ΔL (increasing lightness)
Notes	Sample size calculation: not reported Adverse effects: tooth sensitivity and oral irritation Health‐related quality of life: not reported Key conclusions of the study authors: "Relative to baseline, the whitening strip group experienced colour improvement at day 3, continuing through day 8. The pre‐rinse group did not show any significant change at day 3, and had a significant increase in yellowness at day 8. The strip group exhibiting significantly greater whitening at day 8. Both products were well tolerated, with no participants discontinuing treatment early as the result of an adverse event. In head‐to‐head testing, 7‐day use of the 10% hydrogen peroxide whitening strips resulted in significant tooth colour improvement relative to a barrier‐free 2% hydrogen peroxide pre‐brushing mouthrinse" Correspondence required: no Contact: Dr Geralch; geralch.rw@pg.com
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "...subjects were randomly assigned to 1 of 2 test groups." However, method of randomisation is not mentioned
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote: "Examiner‐blinded, parallel‐group, randomised controlled trial." However, method of blinding not mentioned
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: "Examiner‐blinded, parallel‐group, randomised controlled trial." However, method of blinding not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "All the participants completed all the visits and were evaluated"
Selective reporting (reporting bias)	Low risk	All outcomes described were reported. Conclusions are in accordance with the results
Other bias	Low risk	None