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Background.  The use of trayless at-home bleaching agents in darker teeth is raising some concerns due to their unknown efficacy. The purpose of this in vitro study was to evaluate the effect of tooth discolouration severity on the efficacy and colour stability of two different trayless at-home bleaching systems.  Methods.  Ninety enamel-dentin samples were divided into two groups: lighter tand darker teeth. The teeth in each group were further divided into three groups (n=15): (1) tray-based system with 10% carbamide peroxide (Opalescence Oh) (control group); (2) a tray applied whitening membrane with 10% hydrogen peroxide (Treswhite Supreme); and (3) a whitening pen with 22% carbamide peroxide (Hollywood Smiles). After bleaching, the teeth were stained for 9 days using red wine. Colour readings before bleaching treatment were determined using a dental spectrophotometer and were repeated 24 h after bleaching treatment and 24 h after staining process. Analysis of variance, Bonferroni and Dunnett C tests were used at 5% significance level.  Results.  No differences were observed between the bleaching efficacy of Treswhite Supreme and Opalescence Oh in the lighter teeth, while Opalescence Oh had the best bleaching efficacy in the darker teeth (p&lt;0.05). Hollywood Smiles had the worst bleaching efficay but the best color stability in both lighter and darker teeth (p&lt;0.05). No differences were observed between the color stability values of Treswhite Supreme and Opalescence Oh.  Conclusion.  This study suggested that both the tooth discolouration severity and the type of trayless system used affected the bleaching efficacy, whereas only the type of trayless system affected the color stability.

Effect of tooth discoloration severity on the efficacy and color stability of two different trayless at-home bleaching systems