Auschill 2012.

Methods	Title: randomised clinical trial of the efficacy, tolerability, and long‐term colour stability of 2 bleaching techniques: 18‐month follow‐up Trial design: 2‐cell, parallel, examiner‐blinded, randomised controlled trial Location: Albert‐Ludwigs‐University, Freiburg, Germany Language: English Number of centres: 1 Recruitment period: not reported Funding source: Colgate Palmolive
Participants	Participants: 18 to 56 years old, mean age: 33.08 years Total number: 30 Inclusion criteria: maxillary central incisor with A3 or darker shade free of restorations no prior bleaching Exclusion criteria: fixed orthodontic appliance tooth hypersensitivity Number randomised: 30 Method of randomisation: a computer‐based randomisation Method of allocation concealment: not reported Method of blinding: personal examiner blinding done by coding which was only known to statistician Number evaluated: 28. 2 dropouts at follow‐up
Interventions	Total number of intervention groups: 2 Tray group: 5% hydrogen peroxide Strip group: 5.3% hydrogen peroxide Duration of treatment: 14 days
Outcomes	Improvement in tooth shade Vita shade guide: ranked from lightest B1 (1) to darkest C4 (16); mean score for anterior teeth was calculated Adverse effects. Patient recorded: mild, moderate and severe Patient acceptance, gingival irritation, sensitivity VAS scale: 0 (best acceptance) to 10 (no acceptance)
Notes	Sample size calculation: not reported Adverse effects: sensitivity Key conclusions of the study authors: "Both bleaching techniques (the tray technique with 5.0% hydrogen peroxide and the strip technique with 5.3% hydrogen peroxide) demonstrated similar success. Although a significant relapse in tooth shade was observed over an 18‐month post bleaching period, treated teeth were still significantly lighter compared to baseline. Adverse effects were minimal and reversible. Patient acceptance was statistically significantly higher in the tray group compared with the strip group" Correspondence required: no Contact: Dr Thorsten M Auschill; auschill@med.uni‐marburg.de
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "A computer‐based randomisation scheme (generated before starting the study) allocated patients…"
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote: "2‐cell, parallel, examiner‐blinded, randomised controlled trial." However, method is not mentioned
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "..examiners, who were blinded to the treatment modality and period, subjectively measured.. Personal blinding done by coding which was only known to statistician"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "2 had to be classified as dropouts for that single visit. Thus, 28 subjects were available at the 18‐month follow‐up" Comment: as each group had 14 participants each we considered it as low risk according to Higgins 2011 Section 8.5.d. Missing outcome data balanced in numbers across intervention groups
Selective reporting (reporting bias)	Low risk	All outcomes described were reported. Conclusions are in accordance with the results
Other bias	Low risk	None