This study was performed to compare the power bleaching effect of various bleaching systems on temperature rise and color changes of anterior teeth at different time periods. Eight products with hydrogen peroxide concentrations ranging from 25% to 40% were evaluated. The treatment contact time varied from 30 to 45min according to the manufacturer’s instructions. Sixty four extracted human anterior teeth were selected. The crowns of all teeth were sectioned in the mesiodistal direction with a cutting machine under water irrigation to facilitate the access to the pulp chamber for the temperature measurements. The specimens were stained with a standardized tea solution method. The teeth were then divided into eight groups (n = 8) according to the bleaching regimes used.Group1: Opalescence Xtr Boost chemically activated bleaching system, Group 2: Easy White ®Ready chemically activated system used as universal material, Group 3: Zoom advanced power dental bleaching system (lamp and gel) based on ultraviolet activation. Group4:BEYONDTM whitening system (BEYONDTM whitening accelerator and Gel) based on halogen activation, Group 5: white smile light whitening system (White smile power whitening gel and lamp2) based on LED activation, Group 6: Easy White ®Ready (universal material) exposed to ultraviolet light (Zoom AP light), Group 7: Easy White ®Ready (universal material) exposed to LED light (White smile Power whitening lamp and Group 8: Easy White ®Ready (universal material)exposed to halogen light (BEYONDTM whitening accelerator). Color measurements were done by Vitapan classic shade guide (visual method) and spectrophotometer (instrumental method) before, immediately, one day and one week after bleaching for all experimental groups. Digital thermocouple thermometer was used to determine intra-pulpal temperature changes for all experimental groups. The temperatures were measured; before treatment (T0), immediately after the bleach application and before light exposure (T1), during activation of the bleaching agent (T2), and after bleach activation (T3). Then the collected data were analysed statistically by Kruskal-Wallis test, a nonparametric test, equivalent to the analysis of variance (ANOVA) followed by Mann-Whitney U test. Friedman’s test was used to study the temperature changes after different applications and different time periods, followed by Wilcoxon signed-rank test. The results of the present study indicated that all in-office tooth whitening systems were effective in tooth whitening. Although the shade guide evaluation did not exhibit any differences among the bleaching treatment groups, spectrophotometer readings showed different findings among the tested groups when evaluated immediately. Furthermore, there was no significant statistical difference between the eight experimental groups over the one week period of observation. The use of light did not demonstrate any benefit over the chemically activated tooth whitening system after a one week examination. The one week post bleaching evaluation demonstrated a significant rebound for all groups. In general, the in-office power bleaching showed an increase in the intra-pulpal temperature. The universal bleaching agent coupled with the zoom lamp (UV light) and the zoom whitening system group resulted in the significantly highest temperature rise (5.78±1.260C and 3.86±0.670C respectively).The white smile system and the universal bleaching agent coupled with the LED light showed significantly lower mean temperature rise (1.99±0.530C and 1.60± 0.79 0C respectively).The Beyond whitening system and the universal bleaching agent coupled with halogen induced lower pulp chamber temperature rise (1.08± 0.57 0C and 1.00±0.23 0C respectively). Less temperature rise has been observed when using each light source with its recommended kit except for LED light source (white smile lamp), which showed the statistically significantly lower temperature rise when using with universal bleaching agent. The results revealed that the third application of light showed the highest rise in intra-pulpal temperature for all the bleaching systems. Maximum increase in temperature of 8.36±2.08 °C on average was observed for universal bleaching agent when activated with zoom lamp (UV). Conclusions Under the limitations of this in vitro study, the following conclusions could be drawn: 1. Chemical bleaching systems have the same whitening effect as photo-activated bleaching type but with minimum intra-pulpal temperature rise. 2. Visual color evaluation method is not as precise as objective color evaluation by spectrophotometer. 3. Bleaching efficacy and tooth temperature changes were affected significantly by the interaction between the type of light source and bleaching material used. 4. All bleaching systems used showed rebound in color change values one week post bleaching. 5. Halogen light (Beyond lamp) produced the least temperature rise in the pulp chamberwhile, Zoom whitening lamp raises the temperature inside the pulp chamber to levels that could cause severe pulpal damage. 6. The Whitening gel, which contains nano-fillers (SiO2), produces the desired aesthetic result faster with minimum temperature rise compared to other bleaching materials.