Potassium Nitrate May Limit Bleaching-Related Sensitivity

Caroline Helwick

November 06, 2013

NEW ORLEANS, Louisiana — For the treatment of tooth sensitivity related to bleaching, application of potassium nitrate via various approaches is a highly effective treatment, researchers reported here at the American Dental Association (ADA) 2013 Annual Session.

"It's almost like putting a topical anesthetic on the tissue," said Van B. Haywood, DMD, professor in the Department of Oral Rehabilitation at the Georgia Regents University College of Dental Medicine in Augusta, who presented the work. "It reduces the excitability of the nerve and makes it almost numb," continued Dr. Hayward, who helped pioneer the Nightguard Vital Bleaching technique 15 years ago and is the author of the chairside guide for clinicians, Tooth Whitening: Indications and Outcomes of Nightguard Vital Bleaching.

In clinical trials, almost three quarters of patients who undergo bleaching in the office report sensitivity, he noted. Over-the-counter whitening strips are no less irritating; in fact, gingival irritation can be even greater with these strips because of the 9.5% concentration of peroxide and their acidic pH level of 5.5, he said.

Tooth sensitivity can be mechanical, resulting from pressure or poor fit with trays, or chemical (primarily reversible pulpitis). Gingival irritation mostly arises from ill-fitting trays but can also be chemical. The higher the concentration of bleach, the higher the risk. The flavoring of the bleach, rather than the bleach itself, can also be the irritant, he said, suggesting that mixed fruit and peppermint flavors are generally the least bothersome.

Bleaching Sensitivity

Early research revealed that sensitivity related to bleaching usually occurs in the first 2 weeks of treatment. The only significant predictors are inherent sensitivity (at baseline) and application of bleach more than once a day, Dr. Hayward and his team showed.

This is one reason he prefers carbamide peroxide over hydrogen peroxide. Carbamide peroxide releases 50% peroxide in 2 hours, followed by a slow decline; hydrogen peroxide releases 50% to 100% in 30 minutes or less, with a quick decline. With hydrogen peroxide applied several times a day, there is more "insult" to the pulp, he said, compared with the slow release of carbamide peroxide.

Treatment of Sensitivity

"You really can't get rid of sensitivity," Dr. Hayward noted. "You just have to find a way to deal with it."

Passive treatments include a reduction in the duration or frequency of bleaching, temporary interruption of the treatment, or cessation of the bleaching altogether. These options are generally not satisfactory for the patient, he said.

A more active approach during bleaching is more effective, thanks to the use of 3% to 5% potassium nitrate, he said. Potassium nitrate penetrates to the nerve to create a calming effect by affecting the transmission of nerve impulses. After the nerve depolarizes, it cannot repolarize.

Potassium nitrate can be purchased through dental suppliers for application via the bleaching tray; it is now an ingredient in at least 1 brand of whitening systems and is likely to become part of many more.

Tray System

Patients with bleaching trays can apply potassium nitrate to the tray and wear it for 10 to 30 minutes before bleaching, after bleaching, or as needed, "whenever the teeth hurt," he said. Patients can also alternate nights bleaching with nights using potassium nitrate. Just 10 to 30 minutes of potassium nitrate exposure will reduce sensitivity in 90% of patients, he said.

Dr. Hayward believes the tray system delivery is an excellent option for most patients. "This gives patients control of their sensitivity. They can take care of symptoms as soon as they occur, and the treatment can be used long-term. It is also cost-effective," he said.

Potassium nitrate 5% is the active ingredient in all desensitizing toothpastes (such as Sensodyne, GlaxoSmithKline), and therefore, it is a good initial option, Dr. Hayward said. When used as a toothpaste, however, the healing effect of potassium nitrate is delayed 2 to 4 weeks. When the toothpaste is applied via the tray, its effect is felt within 30 minutes. "Application technique is critical," he emphasized.

Tooth Brushing

"The problem with toothpaste is the inactive ingredient, which is sodium lauryl sulphate, which is what makes the toothpaste foam. It is associated with increased aphthous ulcers and gingival irritation, and it also removes the smear layer from dentin. So when there is sodium lauryl sulphate in the toothpaste, you are getting rid of the protective substance," Dr. Hayward pointed out.

There has been a need, therefore, for an over-the-counter product that does not contain sodium lauryl sulphate. This gap has just been filled by Rembrandt Classic (McNeil-PPC), which is marketed for canker sores, and by the newest option, Sensodyne Pronamel (GlaxoSmithKline), which also does not contain gluten.

He recommended that patients begin brushing with Sensodyne Pronamel 2 weeks before starting bleaching. In a controlled experiment in which patients brushed for 2 weeks with either a potassium nitrate–containing toothpaste or a toothpaste not containing potassium nitrate, those using potassium nitrate reported far less sensitivity once bleaching began. Patients who do not experience sensitivity early on are more likely to stick with the bleaching process, he added.

Professional Products

For patients who have a reaction to the contact of toothpaste with the gingivae, then a professional product can be used. One such product is UltraEZ (Ultradent), a desensitizing gel that includes potassium nitrate as well as fluoride in a syringe delivery system for application to the tray.

Dental companies are also now developing bleaching products that contain potassium nitrate. This may reduce the sensitivity caused by bleaching, as well as the effect of forces from the tray, and does not seem to negatively affect the bleaching.

General Rules

Dr. Hayward summarized his recommendation for managing patients with sensitivity related to bleaching as follows:

  • Use a low-concentration bleaching product, preferably 10% carbamide peroxide.

  • Use a desensitizing product or bleaching product that contains potassium nitrate (and fluoride).

  • Use potassium nitrate in the bleaching tray, as needed, for up to 30 minutes.

  • Minimize treatment contact time (although time to maximum whitening will be delayed).

  • Encourage patients to avoid acid beverages and to maintain good brushing habits.

"This is information we will all be able to apply to our practices," Mark D. Anderson, DDS, from Mid City Smiles in New Orleans, who moderated the session, told Medscape Medical News. "We see these patients at least once a month. Patients report sensitivity, and you see exposed areas and gum lines. You do have a lag effect with the desensitizing toothpastes, but we can now get products like UltraEZ, which Dr. Hayward mentioned, that you can apply to the tray prior [to] or after whitening, and these will help. It's very useful information for dentists."

Dr. Haywood reported financial relationships with Ultradent Products, Colgate Oral Pharmaceuticals, Discus Dental Co, Block Drug Co, Marion Laboratories, Proctor & Gamble, Dental Learning Systems, ArchTek Inc, GlaxoSmithKline, Shofu Inc, Johnson & Johnson, Quintessence International, Densply International, and Heraeus. Dr. Anderson has disclosed no relevant financial relationships.

American Dental Association (ADA) 2013 Annual Session. Presented November 2, 2013.

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