To compare two home-based over-the-counter (OTC) bleaching tray products with similar hydrogen peroxide (HP) concentrations with respect to tooth lightening efficacy and potential to induce negative side effects in tobacco- and non-tobacco users as well as degree of satisfaction with product handling. The HP concentrations were near the regulation limit for bleaching products of 6% set by the European Union in 2011.

The study was performed to assess the risk of at-home and in-office bleaching procedures, and to recognise potential predictors for side effects.
Bleaching treatment, irrespective of method, caused a high prevalence of side effects