Abstract: Objective To compare the effectiveness of two different bleaching operation modes regarding the degree of bleaching and changes of color parameters. Methods 12 patients were treated with two bleaching operation modes, including three continuous sessions in one treatment and oneday interval between two sessions. Maxillary central incisor color was registered during each session and 1 week after completing the treatment by a dental colorimeter, registering parameters L*, a*, b*, color difference values, and whiteness values. Results For both bleaching operation modes, increase in L* values and decrease in b* values were found after bleaching. There was no significant difference in the color difference values after bleaching between bleaching operation mode A and B. Both bleaching operation modes showed a significant change in whiteness values after bleaching. Especially, whiteness values increased after each session for bleaching operation mode B. Conclusion Both bleaching operation modes can result in increase in brightness and blue shift in healthy central upper incisors when performing heating thermostat teeth bleaching.

Key words: tooth bleaching, heating, color parameter, bleaching protocol