Xu 2007.
| Methods | Title: randomised clinical trial comparing whitening strips, paint‐on gel and negative control Trial design: randomised, examiner‐blinded, placebo‐controlled study Location: Shanghai Second Medical University, Shanghai, China Language: English Number of centres: 1 Recruitment period: not reported Funding source: Procter & Gamble |
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| Participants | Participants: 18 to 45 years old. Mean age 21.85 years. 92% females. Total number: 52 Inclusion criteria: not reported Exclusion criteria: not reported Number randomised: 52 Method of randomisation: not reported Method of allocation concealment: not reported Method of blinding: similar kits Number evaluated: 49 |
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| Interventions | Total number of intervention groups: 3 Whitening strips 6% hydrogen peroxide (n = 18), Paint‐on gel 5.8% hydrogen peroxide (n = 17; 2 dropouts) Negative control (water rinse) (n = 17; 1 dropout) Duration of treatment: 8 days for whitening strip, 15 days for gel and water rinse |
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| Outcomes | Change in tooth colour ΔL, a*, b* values were recorded. Increase in ΔL and reduction in b* indicates whitening of tooth |
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| Notes | Sample size calculation: not reported Adverse effects: mild sensitivity in strip group Health‐related quality of life: not reported Key conclusions of the study authors: "Despite similarities in starting concentration (6% hydrogen peroxide), the strip and paint‐on gel differed significantly on improvement in yellowness, brightness, and redness, as well as overall colour improvement. These differences were achieved with one‐half the treatment duration (7 versus 14 days) for strips compared to the paint‐on gel. Since only 1 of the products used a barrier, differences in residence time of the peroxide gel under a strip versus the barrier‐free paint‐on gel may have contributed to the relative clinical response of these 2 peroxide‐containing products" Contact: Dr Xu, xuxiao@smmail.cn |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | Quote: "subjects were randomly assigned to peroxide whitening strips (the positive control), paint‐on peroxide whitening gel, or water (the negative control)." However, method of randomisation is not mentioned |
| Allocation concealment (selection bias) | Unclear risk | Not mentioned |
| Blinding of participants and personnel (performance bias) All outcomes | Low risk | Quote: "Subjects were provided an identically appearing kit box labelled only with the unique subject number" |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | Not mentioned |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | Quote: "All 18 subjects in the strip group completed the research, while 2 subjects in the paint‐on group and 1 subject in the water rinse group failed to complete 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 |