Myers 2003.

Methods	Title: clinical evaluation of a 3% hydrogen peroxide tooth whitening gel Trial design: double‐blinded, placebo‐controlled, randomised trial Location: School of Dentistry, Medical College of Georgia, Augusta, Georgia, USA Language: English Number of centres: 1 Recruitment period: not reported Funding source: Applied Dental Sciences
Participants	Participants: age not reported Total number: 65 Inclusion criteria: 21 years of age and above A3 or darker on vita shade guide Exclusion criteria: persons with significant medical problems or needing antibiotic premedication pregnant or nursing women persons with active dental caries or periodontal disease persons with a history of vital bleaching tetracycline staining Number randomised: 65 Method of randomisation: randomisation table by statistician Method of allocation concealment: syringes were labelled with the participant number. A single labelled syringe of gel was retained from each participant's box for later testing if needed Method of blinding: not reported Number evaluated: 65
Interventions	Total number of intervention groups: 2 3% hydrogen peroxide Nightguard gel Placebo Duration of treatment: 2 weeks
Outcomes	Colour change: Vita shade guide arranged base on lightness: 1 lightest (C1) to 16 darkest (B4) Dental sensitivity Irritation to tongue, gingiva, and throat
Notes	Sample size calculation: not reported Adverse effects: sensitivity in tongue and gingiva, dental sensitivity to hot and cold Health‐related quality of life: not reported Key conclusions of the study authors: "Patient‐applied NGVB with a 3% hydrogen peroxide gel for 30 minutes 3 times a day for 2 weeks was effective in whitening teeth an average of 4.2 Vita shade tabs. The lightening effect was maintained at 6 months, and the side effects with this agent were similar to other whitening agents. The use of this material could be considered for patients who cannot comply with the regimen" Contact: Michael L Myers, Department of Oral Rehabilitation, School of Dentistry, Medical College of Georgia, Augusta, Georgia 3091 USA; mmyers@mail.mcg.edu
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "A randomisation table was prepared by the lead statistician (CMR), who also maintained participant identification numbers used throughout the study"
Allocation concealment (selection bias)	Low risk	Quote: "A randomisation table was prepared by the lead statistician (CMR), who also maintained participant identification numbers used throughout the study..... The outside of the box and the individual syringes were labelled with the paticipant number"
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Double‐blinded study but method of blinding not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Double‐blinded study but method of blinding not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts reported
Selective reporting (reporting bias)	Low risk	All outcomes described were reported. Conclusions are in accordance with the results
Other bias	Low risk	None