ESR investigation of ROS generated by H 2O 2 bleaching with TiO 2 coated HAp

Abstract

It is well known that clinical bleaching can be achieved with a solution of 30% hydrogen peroxide (H 2O 2) or H 2O 2/titanium dioxide (TiO 2) combination. This study examined the hypothesis that TiO 2 coated with hydroxyapatite (HAp-TiO 2) can generate reactive oxygen species (ROS). ROS are generated via photocatalysis using electron spin resonance (ESR). The bleaching properties of HAp-TiO 2 in the presence of H 2O 2 can be measured using hematoporphyrin litmus paper and extracted teeth. We demonstrate that superoxides (O 2• -) and hydroxyl radicals (HO•) can be generated through excitation of anatase TiO 2, rutile TiO 2, anatase HAp-TiO 2, and rutile HAp-TiO 2 in the presence of H 2O 2. The combination of R HAp-TiO 2 with H 2O 2 produced the highest level of HO• generation and the most marked bleaching effects of all the samples. The superior bleaching effects exhibited by R HAp-TiO 2 with H 2O 2 suggest that this combination may lead to novel methods for the clinical application of bleaching treatments.