Effect of different bleaching methods on stained composites

This study aims to examine the whitening effect of three different bleaching methods on three different stained composite resins. Forty discs (5 mm diameter × 2 mm thick) from each tested material (ESTHET.X HD micro-matrix Restorative, Dentsply, Paradigm Nano-Hybrid Universal-Restorative, 3M/ESPE, and Artiste Nano-Composite, Pentron-Clinical) were made. The 40 discs of each tested material were immersed in coffee, 3 h a day for 21 days in order to be stained and then divided into four subgroups (n=10): non-bleached subgroup (color changes examined immediately after staining); bleached using Crest 3D-White Whitestrips Advanced Vivid (30 min once a day for 14 days); bleached using Colgate Visible White (30 min once a day for 14 days) and bleached using Pola Paint (30 min twice a day for 14 days). Between bleaching periods, specimens were immersed in artificial saliva. Specimens were tested for quantitative color changes using Quanta Environmental Scanning Electron Microscope. Data was statistically analyzed using three-way analysis of variance (ANOVA) and Tukey's post-hoc test (P≤0.05). Pola Paint did not bleach stained samples effectively as it showed the highest mean color change value (117.47 pixel). Meanwhile, Colgate gel and Crest Strips showed better bleaching and no significant difference was found between them (112.59 and 113.04 pixel, respectively). No significant difference was found between the three tested composites. The result showed that the three tested composites performed similar under the test conditions. The use of Colgate bleaching gel and the Crest 3D-White Strips could effectively eliminate the discoloration that resulted from staining of the tested materials. Key words: Bleaching, nano-composite, staining.