Different external bleaching procedures utilizing highly concentrated hydrogen peroxide formulations can be used for tooth bleaching and tooth whitening. Whitening is the removal of superficial discoloration of the teeth, whereas bleaching constitutes the removal of stains on and in tooth substance by means of oxygen radicals. Light can be used to enhance or accelerate the bleaching process. In most cases, the effect of light is limited to heating of the bleaching formulation and this process differs from rue photobleaching. Photobleaching or photodynamic bleaching is a process where light from a laser or non-coherent light source is used to drive molecular changes in light-sensitive compounds, and where the discoloration or bleaching of the teeth is caused as a result of the generation of reactive oxygen species. Secondly, it is also possible to photobleach colored organic compounds and especially those that are inherently resistant to the action of the oxygen free radicals. At present, true photobleaching can only be performed with the KTP laser (532 nm) in conjunction with a red colored highly concentrated hydrogen peroxide gel. Furthermore, it has also been demonstrated that the use of the KTP laser with the Smart Bleach system is safe: no intrapulpal temperature elevations beyond 5.5°C have been registered, and there is no risk of enamel microhardness decrease. KTP laser bleaching can be considered a noninvasive esthetic procedure, and hence is the least invasive procedure of what is called today minimally invasive dentistry.
Keywords: laser bleaching, laser tooth whitening, KTP laser, photobleaching, power bleaching, tetracyclines