Nathoo 2002.

Methods	Title: efficacy of novel, non‐tray paint on 18% carbamide peroxide gel Trial design: double‐blinded, parallel‐group, randomised trial Location: Colgate Palmolive Research Centre, USA Language: English Number of centres: 1 Recruitment period: not reported Funding source: Colgate Palmolive
Participants	Participants: 18 to 58 years old. Mean age 39.79 years Total number: 80 Inclusion criteria: A3 shade or darker Exclusion criteria: orthodontic treatment restoration or crowns Number randomised: not reported Method of randomisation: method not reported Method of allocation concealment: method not reported Method of blinding: non‐removable white packing with patient identification number Number evaluated: 77
Interventions	Total number of intervention groups: 2 18% carbamide peroxide paint‐on gel Placebo Duration of treatment: 21 days
Outcomes	Change in tooth shade Vita shade guide arranged base on lightness: 1 lightest (C1) to 16 darkest (B4)
Notes	Sample size calculation: not reported Adverse effects: not reported Health‐related quality of life: not reported Key conclusions of the study authors: "Study showed that subjects' teeth in the liquid whitening gel‐treated group exhibited an overall improvement and a 3.5‐shade difference compared with teeth in the placebo gel group. No soft tissue adverse reaction were reported" Contact: Saleem A Nathoo, Colgate Palmolive Research Centre, Piscataway, New Jersey, USA
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Qualifying subjects were then stratified... and randomly assigned within strata to one of the study treatment groups.." However, the method by which randomisation was done is not mentioned in the article
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "For blinding, all products were overwrapped with a non‐removable white label containing a unique subject identification number"
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	Number of patients randomised were 80. However, there were 3 dropouts. Quote: "Subjects who did not complete the study dropped out for reasons unrelated to the use of the treatments or adverse events" 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 adequately. Conclusion conforms to results
Other bias	Low risk	None