This clinical study was carried out to investigate and evaluate the effect of using a titanium dioxide photocatalyst in conjunction with different concentrations of hydrogen peroxide bleaching gels on the color change, tooth sensitivity and surface roughness of enamel.Seventy two patients were divided into three main groups, twenty four each, representing the three bleaching agent concentrations used, namely 32%, 9.5% and 6% concentrations of hydrogen peroxide. Each of the three groups was divided into two subgroups, twelve each, corresponding to whether the teeth will be pretreated with titanium dioxide or no. Each subgroup was further subdivided into two divisions, six each, representing the two times of application of the bleaching gels, namely (1 x 15) and (2 x 15) minutes, respectively. Each division was divided into two subdivisions, three each, relative to whether the bleached teeth will receive a remineralizing treatment or no. Color assessment was performed under standardized conditions using shade guide buttons, digital imaging and Easyshade Spectrophotometer. Tooth sensitivity was assessed using a questionnaire based thermal sensitivity test. Enamel surface roughness assessment was measured by means of epoxy resin replicas imaged under SEM and analyzed using a computer software. The data were analyzed using Independent-samples t-test of significance, Mann Whitney U test and ANOVA.The current study revealed a statistically significant change in both ∆E and Y values after bleaching with the 32% concentration of hydrogen peroxide in most of the groups tested, while the lower concentrations mostly lacked such effect in the adopted bleaching time. The increase in concentration and exposure time of the hydrogen peroxide gel was found to increase the bleaching effect. In some groups, the addition of the TIO2 photocatalyst leads to a significantly higher bleaching effect, especially when applied for two cycles. TIO2 pretreatment as well as post-bleaching remineralization appears to have significantly reduced the occurrence and intensity of tooth sensitivity, while the extended treatment time increased it. The 32% concentration of hydrogen peroxide bleaching gel caused a statistically non-significant increase in surface roughness. It was concluded that the TIO2 photocatalyst pretreatment seemed to be inconsistent in potentiating the bleaching effect of the different concentrations of hydrogen peroxide. Extended bleaching time and higher concentrations of the bleaching gel cause more tooth lightening, while all combinations seemed to be safe regarding their effect on the enamel surface roughness..