Dina Fazaeli - Department of Oral and Maxillofacial Medicine, School of Dentistry, North Khorasan University of Medical Sciences, Bojnūrd, Iran
Reza Mehrara - Department of Oral and Maxillofacial Medicine, School of Dentistry, North Khorasan University of Medical Sciences, Bojnūrd, Iran
Fatemeh Oroojalian - Department of Advanced Technologies, School of Medicine, North Khorasan University of Medical Sciences, Bojnūrd, Iran

Objective(s): In this study we evaluated the photocatalytic activity and dye degradation of blue light-activated and UV-activated carboxymethylcellulose gel containing titanium dioxide nanoparticles and compared with ۴۰% hydrogen peroxide bleaching effect to reach to a new strategy that has most efficiency with minimal side effects.Materials and Methods: The effective concentration of carboxymethylcellulose gel containing TiO۲ nanoparticles was determined. The color of the main samples was measured at first, after staining with coffee and after the bleaching process by colorimeter. E۱, E۲, E۳ were recorded and ΔE۱, ΔE۲ were calculated. Samples were divided into eight groups, each containing six. In three groups, the bleaching effect of CMC gel containing TiO۲ nanoparticles irradiated with UV-C was investigated after one, two, and three times exposure to the teeth. In the other three groups, the bleaching effect of CMC gel containing TiO۲ nanoparticles irradiated with light cure was investigated after one, two, and three times exposure to the teeth. The results were compared with two control groups CMC and H۲O۲.Results: The effective concentration of carboxymethylcellulose gel containing TiO۲ nanoparticles was ۲۰%. ΔE۲  result for H۲O۲ control group was ۶.۳۴ and for CMC control group was ۲.۵۴. The values of ΔE۲ in groups were exposed once, twice and three times to CMC gel containing TiO۲ nanoparticles that were activated by UV were ۳.۸۳, ۴.۱۹, ۴.۴۲ respectively and ΔE۲ results in groups were exposed once, twice and three times to CMC gel containing TiO۲ nanoparticles that were activated by blue-light were ۴.۴۵, ۵.۰۳, ۵.۵۵ respectively. Conclusion: The greatest value of ΔE۲ belonged to the bleached group with hydrogen peroxide gel with ΔE۲: ۶.۳۴ and after that related to the group activated three times with blue light with ΔE۲: ۵.۵۵.  All groups except the CMC control group showed ΔE۲ higher than ۳.۳. 

Blue light, Hydrogen peroxide, Titanium dioxide nanoparticles, Tooth bleaching, UV