One of the barriers to patients bleaching their teeth is sensitivity. Many of them have experienced it, or at least heard about it and are concerned. The sensitivity that people experience during a bleaching procedures come in two varieties. Variety number one is the generalized sensitivity that occurs like an exaggerated version of root sensitivity, called dentin hypersensitivity . The second type are the “zingers’ that occur during in office procedures. Dentin Hypersensitivity and it’s cause are understood, and can occur with many different forms of stimulus. The fluid movement in the dentinal tubules is increased, creating a pull or tension in the pulpal tissue, which we experience as “sensitivity”. Normally the dentinal tubules are sealed with a smear plug. When this smear plug is removed the hydraulic conductance ) ability for tubular fluid movement) increases as much as 32 fold.
The oxygenation phase of all bleaching systems effectively removes the smear plugs that prevent dentinal tubule fluid movement. This loss of the smear plug increases the potential for tubular fluid movement. Now add to this that the more acidic or anhydrous the bleaching gel, the more it creates tubular fluid movement. Manufacturers prefer acidic and anhydrous formulas of bleaching gel because the have a longer shelf life and do not require refrigeration. If you are looking for a bleaching product that will cause less sensitivity, ask about the pH, and get something closer to neutral, that has to be refrigerated. Lastly, we all know that the higher the percentage of active ingredient the more patients report sensitivity. The carbamide peroxide breaks down into Hydrogen peroxide in the mouth. Hydrogen ions increase the acidity and therefore the tubular fluid movement. The second type of sensitivity is what we call “zingers”. These sharp intense pains seems to occur in the smaller teeth like incisors and cuspids. The current theory is that hydrogen peroxide enters the pulp. It is broken down by Catalase into water and oxygen. This oxygen creates a sharp spike in intrapulpal pressure resulting in the intense pain we call a zinger. One thing to note is that the use of lights and lasers have been shown to enhance the discomfort and sensitivity patients experience.
In the next post we will look at ways to minimize bleaching sensitivity and help our patients get the smile they desire.