Aim: To investigate penetration of two external bleaching agents into the pulp chamber of teeth restored with three brands of composite resin. Methodology: Forty eight maxillary central incisors were equally divided into two groups and treated with In-Office Bleaching and Home Bleaching. Each group was equally subdivided into one control and three experimental groups according to composite resin used to restore class V preparations, either Filtek Z 350 or Filtek Supreme or Tetric EvoCeram. Teeth were sectioned 3 mm apical to the cemento-enamel junction. Acetate buffer was placed in the pulp chamber and the bleaching agents were applied for 30 min at 37°C. The buffer solution was removed and transferred to a glass tube where Leuco crystal violet and Horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined spectrophotometrically at 596 nm to be used to determine the amount of hydrogen peroxide penetrated to the pulp chamber. Data were submitted to ANOVA and Pairwise statistical comparisons. Results: A amounts of hydrogen peroxide found in the pulp chamber of Home bleaching group (WHITEsmile® HOME BLEACHING) were significantly lower when compared to In-Office bleaching group (WHITEsmile® POWER BLEACHING). Restored teeth held significantly higher hydrogen peroxide concentrations in the pulp chamber than intact teeth in both In-office and Home bleaching (p=0.001). Furthermore, teeth restored with nanofill composite resin (Filtek Z 350, Filtek Supreme XT) had higher mean values of H2O2 penetration than teeth restored with nanohybrid composite resin (Tetric EvoCeram). Conclusions: Within the limitations of this study, the following can be concluded, all teeth submitted to bleaching presented peroxide penetration into the pulp chamber and the restored teeth presented. higher peroxide penetration than the intact teeth in all experimental situations. Using Home bleaching technique, peroxide penetration into the pulp chamber of teeth restored with composite resin depended on the type of restorative material used.