Am I really whitening? Tooth Dehydration and Laser Tooth Whitenin

Tooth dehydration is a common side effect with all teeth bleaching treatments. Once dehydrated, the teeth can look whiter. When rehydration happens (usually a few days), the dehydrated teeth relapse to a darker color. Knowing that teeth dehydrate during bleaching, one may wonder what the actual effects are of quick in-office laser teeth whitening. Could it be that there is no actual bleaching happening and that the teeth are just being dehydrated?

To better understand how a light source can dehydrate teeth its theory must be explained. When undergoing a laser teeth whitening procedure, the light hits the tooth at a very high intensity. The bleach on the surface of the tooth boils off into the air, which is the path of least resistance. Some bleach will infuse into the teeth and allow for some actual bleaching. As the light illuminates the tooth, darker colored parts of the tooth absorb the light rather than reflect it. This absorbed light is converted into heat energy. Areas of the tooth like the pulp chamber and dentin are the darkest so they heat up the most. This causes the tooth to heat up from the inside. As the tooth builds this uncontrollable internal heat, fluids in the pulp and dentin expand. This expansion pushes water out of the tooth through the protein matrix surrounding the enamel rods. 

Teeth are porous, so for the same reason they will allow bleach penetration, they will allow fluids out of the tooth. This dehydration as well as the overheating of the tooth is what causes the extreme pain that often is reported following light assisted bleaching procedures. This whole phenomenon is what makes using a light to bleach teeth ambiguous. The idea is to move bleach into the teeth for bleaching to occur. With the lights, all the "teeth fluids" could be moving out of the teeth. So bleach may have to go against the flow to get into the teeth. This could make for a very inefficient technique, as the bleach is always fighting against the current. The final result of this may be that the teeth lose water or dehydrate and appear whiter for a temporary time, usually around 72 hours. After that they began to recover and absorb water from the saliva, much like a sponge, and in so doing they turn dark again. 

The “Rod’s Deep Bleach” method acknowledges this theory as fact and in so doing, the method employs techniques to keep fluids in the teeth. TheMetaTray product also does this.