Peroxide dental bleaching via laser microchannels and tooth color measurements.

The aim of this study was to use microchannels drilled by an Er:YAG laser into a human tooth through the enamel into the dentin for direct injection of hydrogen peroxide (HP) to produce a minimally invasive, rapid, tooth bleaching effect. The experiments were conducted in vitro. Five microchannels with a diameter of ?200???m and a depth of ?2??mm were drilled through the palatal side of a human tooth crown using the microbeam of an Er:YAG-laser with a wavelength of 2.94???m. After injection of an aqueous solution of 31%-HP through the microchannels, the tooth color was evaluated using a VITA shade guide and International Commission on Illumination L*ab color parameters. A tooth model used for the evaluation of the distribution of HP concentration was created and the amount of HP which can be injected into tooth dentin to bleach it safely was estimated. Injection of 1.5±0.1??mm3 of 31%-HP into the tooth led to noticeable bleaching within 3 h and significant improvement of tooth color within 24 h.