By Rodney Ogrin, DDS

Does potassium nitrate belong in whitening gel? Is it safe to medicate all your whitening patients, and is KNO3 (potassium nitrate) an effective obtundent in whitening gel?

Sensodyne issues a warning on their KNO3 tooth paste that says: "If you accidentally swallow more than used for brushing, seek professional assistance, or contact a Poison Control Center im- mediately." A KNO3 bleaching gel patient can swallow 20 to 60 doses during treatment of two arches.

Desensitizing toothpaste is safely rinsed and expectorated after brushing. The KNO3 in whitening gels is swallowed. Whether a patient is in the small minority of patients who will even experience acute pulpal sensitivity, he/she should be medicated in a manner accepted by the FDA and that has been ADA safety tested and approved for certification as a drug. Having the patient use the KNO3 fluoride toothpaste for two weeks prior to and then during the course of whitening is the recommended method to maximize effectiveness and limit the risk of swallowing KNO3.

KNO3 works in toothpaste because it interferes with electric conductance on nerve endings. At the dendrites, a cascade of Na ions are released by the nerve fibers depolarizing the chemical-neural response along the nerve endings. The sensation of pain transmitting information (pain) via release of K ions interferes with receptors of Na ions resulting in lessening the sensation of pain. By applying a KNO3 flouride containing dentrifice 10-14 days before bleaching, fluoride will reduce the dentin tubule orifices. The KNO3 will assuage discomfort due to fluid imbalance (hydrostatic pressure change).

Brushing with a KNO3 fluoride tooth- paste (i.e. Synsodyne) has for years now proven effective in alleviating whitening sensitivity. This approach allows the KNO3/Fluoride to act palliatively without risk.

Is KNO3 in the whitening gel the magic bullet for sensitivity? "No one product has demonstrated superiority in sensitivity reduction of any significance," says Van Haywood, DMD.1 "Even materials that purport to decrease sensitivity - such as the new Nite White Excel 2 Z (Discus Dental) and Opalescence PF (Ultradent) - cause sensitivity in some patients," says Dr. Michael Miller of Reality Publishing.2

The bad news is that potassium nitrate in the bleaching gel isn't the answer. The good news is, carbamide peroxide sensitivity can be managed. See the RDH Corner.

1. Haywood V.B., "Current status and recommendations for dentist-prescribed, at-home tooth whitening." Contemporary Esthetics & Restorative Practice supplement, 3S1:2-9, 1999.

2. Staff interview, "Putting esthetic materials to the test," Dental Practice & Finance Esthetic Report, June 1999; 20:27

Reservoirs sounded like such a good idea at the time. But, when Clinical Research Associates released the results of their 1997 study of the major bleaching materials, all the products had expired approximately 70% of the active ingredient in the first hour.1 Dr. Matis' more recent study found a higher retention of the oxidizing agent studied. However, since the CRA study, most of the bleaching suppliers have been run- ning to short-term modality. So why would we continue to use reservoirs?

Reservoirs take unnecessary lab time and may not be in the best interest of our patients. Overnight/multiple-hours bleaching is just not user friendly, making reservoirs the baggage of an outdated bleaching modality.

As pointed out by Rella Christiansen of Clinical Research Associates last November at the Loma Linda University, "The State of the Art 2000" panel discussion, an independent CRA study has found no data to support the contention of reservoir effectiveness. An identical conclusion was reached in another clinical study concluding, "…there are no statistically significant differences in those teeth whitened with tray reservoirs versus teeth whitened without tray reservoirs."2 So, the evidence indicates the desired benefits are simply not realized.

Other researchers have known it for years. A Haywood 1997 article states: "There is no indication that the presence or absence of a reservoir-type spacer or similar foam insert has any effect on bleaching time." 3

I believe that reservoirs lack benefits because the extra oxidizing material doesn't reach the tooth surface. The additional material in the reservoir dissipates in the reservoir cavity instead of being absorbed into and activated inside the tooth.

The old-school method of reservoirs and overnight bleaching subject the patient to the swallowing of gel. The reservoirs provide more gel to be swallowed. Overnight bleaching then gives the patient a great deal more time to swallow the extra gel. Swallowing whitening gel is a questionable idea when the product contains KNO3.

With no reservoirs, nature's methods are left to work their Basic Science, and your patients are at lower risk. Van der Waal's forces create a seal between the tray and the tooth that holds the stent in place and helps resist saliva penetration (see figure 2 below). The minimal amount of gel is used. This way, regardless of how well the patient follows instructions, less gel is at risk of being swallowed. Dosage is .25 cc, the equivalent of 10 to 12 drops placed in the tooth indentations. Less gel equals less patient risk. Therefore, very little material is swallowed and the actual whitening process has the benefit of maximum oxidation per volume of gel. High concentration/short-session bleaching makes whitening teeth amenable to keeping bleaching as a bathroom modality. Put the gel in the tray, the tray onto the teeth, shower, dry, put on cosmetics/shave, take the tray out, expectorate, rinse, and voilá -- timeless patient compliance!

The repeatable data in Bleaching Science has ushered out overnight modality. We can leave the rest of the overnight reservoir baggage behind, simplify our lab work, and lower the risks for our patients.

With Reservoirs =

Without Reservoirs =

1. Clinical Research Associates Newsletter, Tooth bleaching, state-of-art '97, 21:4, 1:3
2. Bosma M, Bowman J, Dorfman W, and Soll K, Clinical evaluation of a tray fabrication design and effects
on vital tooth bleaching. Hill Top Research, Inc., Miamiville, OH; 1:3
3. Haywood V, Extended bleaching of tetracycline-stained teeth. Cont. Esth. & Rest. Practice, Sep. '97, 14:21