["Power bleaching" with the KTP laser].

The most important constituent of the bleaching process is the hydrogen peroxyde. The bleaching effect is the result of a change in the chemical structure of organic molecules in the teeth. Different bleaching techniques are described on the basis of the concentration of the hydrogen peroxyde used and on the basis of the different methods of application. It has been demonstrated that a faster change in colour can be obtained when bleaching is performed in combination with a light source i.e. power bleaching aiming for a more in depth change of colour. Different investigations have demonstrated that negative effects associated with bleaching agents are seen earlier when light sources have been used as accelerators. So, light activation may not lead to 'heating of the pulp'. Different types of laser bleaching have been described, though, not all of them will lead to the desired result. There is only one exception at present and this is the KTP-laser bleaching with the Smart Bleach gel. The specific laser-tissue interaction is the result of different activation processes of the hydrogen peroxyde in the gel: as a result of the interaction with the laser a photocatalytic effect is induced (i.e. the activation of the gel by means of light--this is also referred to as a photochemical reaction), a limited photothermal effect (light absorption may result in a certain heating of the gel). The light activated gel also has an alkaline pH, which favours the ionisation of the hydrogen peroxyde into perhydroxyl ions (these are the most reactive free radicals). It is also possible to directly cut the tetracycline molecules (a good absorption of light by the tetracycline molecules at 532 nm). This will result in better decolouration of tetracycline stained teeth. This last process is described as direct photobleaching. It also needs to be emphasized that bleaching with a laser can only be performed by a dentist who has acquired a substantial knowledge on laser-tissue interaction and laser physics, and who follows accurately the requested bleaching procedure. Furthermore, whatever the opinion might be, tooth bleaching is a medical dental procedure on biologic tissues and hence this procedure can only by dentists.