Costa 2012.

Methods	Title: comparison of 2 at‐home whitening products of similar peroxide concentration and different delivery methods Trial design: randomised, single‐blinded, split‐mouth design Location: not reported Language: English Number of centres: 1 Recruitment period: not reported Funding source: Ultradent
Participants	Participants: 21 to 75 years old Total number: 25 Inclusion criteria: be at least 18 years old willing to sign a consent form willing to return for post‐whitening evaluation presence of all 6 maxillary teeth equal or darker than 1M2 VITA bleached guide in the value have no maxillary anterior teeth with more than 1/6 of the facial surface covered with a restoration Exclusion criteria: history of any medical disease that may interfere with the study or require special consideration presence of gross pathology use of tobacco products during previous 30 days current or previous use of whitening agent Loë and Silness 29 gingival score > 1.0 pregnant or lactating women tetracycline‐stained teeth Number randomised: 25 Method of randomisation: not reported Method of allocation concealment: not reported Method of blinding: not reported Number evaluated: 24
Interventions	Total number of intervention groups: 2 35% carbamide peroxide 14% hydrogen peroxide Duration of treatment: 2 weeks
Outcomes	Improvement in tooth shade: a*. b* and L were recorded. Whitening benefit was represented by negative b (yellowness reduction), and positive ΔL (increasing lightness) Sensitivity: VAS scale: 1 no pain, 10 severe pain
Notes	Sample size calculation: not reported Adverse effects: sensitivity Health‐related quality of life: not reported Key conclusions of the study authors: "There was no significant difference in tooth colour change between carbamide peroxide and hydrogen peroxide at either time point. By the end of the study no participants reported tooth and gingival sensitivity. Participants preferred CP over HP" Contact: Dr D Costa; dacostaj@ohsu.edu
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "randomised, single‐blinded, split‐mouth design clinical study." However, method is not reported
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote: "randomised, single‐blinded, split‐mouth design clinical study." However, method is not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: "randomised, single‐blinded, split‐mouth design clinical study." However, method is not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "A total of 25 participants enrolled and 24 completed the study" 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 described were reported. Conclusions are in accordance with the results
Other bias	Low risk	None