In vitro evaluation of the effectiveness of bleaching agents activated by KTP and Nd:YAG laser.

Abstract

To compare two different laser sources, a KTP laser with a wavelength of 532 nm and a Nd:YAG laser with a wavelength of 1064 nm, to investigate the relation between laser source and bleaching gel during laser irradiation. Extracted human teeth were stained and randomly divided into six groups. Two in-office bleaching gels, Beyond and Opalescence Boost, were applied to stained teeth and then irradiated at either 532 nm or 1064 nm. The temperature change of pulp chamber was measured. The color change (ΔE*) was evaluated at the following time points: immediately after bleaching, 7, 14 and 30 days after the end of bleaching. Boost irradiated by KTP laser showed the higher temperature increase when compared with Beyond irradiated KTP and Nd:YAG. Boost irradiated by Nd:YAG presented lower temperature increase than by KTP. All groups showed a certain color change. After bleaching, Nd:YAG laser irradiation did not increase the ΔE* value significantly compared with gels without laser (p > 0.05). At each time point, Boost activated by KTP laser showed higher ΔE* value compared with other groups (p < 0.05), but decreased significantly 15 days after the end of bleaching. The other groups showed a relatively small change in ΔE* value after 30 days (p > 0.05). KTP laser achieved better results than the Nd:YAG laser regarding tooth color change when associated with the Opalescence Boost bleaching gels.