Frequency doubled neodymium:yttrium–aluminum–garnet and diode laser-activated power bleaching—pH, environmental scanning electron microscopy, and colorimetric in vitro evaluations

Corrosiveness of enamel surfaces of Smartbleach®, Opus White®, Opalescense Xtra Boost® and a gel containing titanium dioxide (TiO₂) particles, activated either by a frequency doubled neodymium: yttrium–aluminum–garnet (Nd:YAG) laser (532 nm) or a diode laser (810 nm) was evaluated by environmental scanning electron microscopy (ESEM). Changes in teeth color shades and the pH were also evaluated. Each bleaching agent was laser activated for 30 s and removed after 1 min or 10 min. This procedure was repeated up to four times, the bleaching agent receiving a maximum application time of 40 min, with total irradiation times of 0.5 min to 2 min of laser activation. The results of the pH measurements showed that only Smartbleach® was in the alkaline pH range, whereas the other three were acidic. The surface effects were unrelated to the pH of the bleaching agents. With the exception of Opus White®, no severe alterations on the enamel surface were detected. Although short application times were chosen, improved changes in brightness of up to ten steps on the Vitapan® classical shade guide were detected.