Ferrari 2004.

Methods	Title: clinical trial evaluating the peroxide concentration response of whitening strips over 28 days Trial design: randomised, double‐blinded, parallel‐group clinical study Location: private practice, Italy Language: English Number of centres: 1 Recruitment period: not reported Funding source: Procter & Gamble and Fiji
Participants	Participants: not reported Total number: 37 Inclusion criteria: not reported Exclusion criteria: not Reported Number randomised: 37 Method of randomisation: not reported Method of allocation concealment: not reported Method of blinding: similar packing Number evaluated: only 34 completed the study among them only 32 – day 7, 29 ‐ day 14, 28 – day 28 were present
Interventions	Total number of intervention groups: 3 1.8% hydrogen peroxide strips 3.3% hydrogen peroxide strips 5.3% hydrogen peroxide strips Duration of treatment: 28 days
Outcomes	Improvement in tooth shade Tooth whitening was characterized by decreased b* (reduction in yellowness) and increased ΔL* (increased brightness)
Notes	Sample size calculation: not reported Adverse effects: oral irritation Health‐related quality of life: not reported Key conclusions of the study authors: "Hydrogen peroxide at concentrations ranging from 1.8%‐5.3% resulted in significant colour improvement versus baseline as early as Day 7. There was a concentration‐response for reduction in yellowness (delta b*) and lightness improvement (deltaL*) at all time points, favouring the higher concentrations. While the concentration‐whitening relationship approached a linear response at Day 7, continued treatment resulted in incremental colour improvement. All 3 peroxide concentrations were well tolerated, and no subjects discontinued early due to a treatment‐related adverse event" Correspondence required: yes: number of participants per group is not reported, authors have been mailed requesting these data Contact: Marco Ferrari, Piazza Attias 19, Livorno 57120, Italy, ferrarimar@unisi.it