Icy Response

When cold winds blow, are your patients afraid to smile? When they take a big lick from an ice cream cone, do they carefully curl up their tongues and funnel the icy stuff straight down the throat? You already know this, but these patients belong to a club that has at least 40 million members. Dentinal hypersensitivity is more common than the cold, more tenacious than crabgrass, and more annoying than telemarketing. It is the condition in which exposed dentin is sensitive to stimuli such as touc

Formulas in dental materials soothe dentinal hypersensitivity.

Cathy Hester Seckman, RDH

When cold winds blow, are your patients afraid to smile? When they take a big lick from an ice cream cone, do they carefully curl up their tongues and funnel the icy stuff straight down the throat? You already know this, but these patients belong to a club that has at least 40 million members. Dentinal hypersensitivity is more common than the cold, more tenacious than crabgrass, and more annoying than telemarketing. It is the condition in which exposed dentin is sensitive to stimuli such as touch, sweets, temperature change, or air. The dental profession has been treating sensitivity for 150 years with products such as calcium hydroxide, silver nitrate, sodium or stannous fluoride, strontium chloride, glutaraldehyde, and potassium nitrates.

Still, nearly 25 percent of Americans - possibly including you - suffer from dentinal hypersensitivity. Such sensitivity can cause a pain and fear cycle that results in a dental phobia. How often do you hear the story of the patient`s husband, or aunt, or father, who hasn`t been to a dentist in 13 years - because their teeth hurt? How often do you get a new patient who points to a canine or premolar and says, "Oh, please, don`t touch this one. I`ll jump right out of the chair." Because patients like this fear their sensitivity, they`re less likely to take care of their teeth or to let us take care of them.

"What can I do about my sensitive teeth?" might be the most frequent question you get from patients. Maybe you can recite the speech in your sleep, because you say it over and over and over again in the course of your job.

"Mrs. Smith, we`ve talked about your brushing habits. You don`t really have to scrub so hard. Brush down from the gum, not sideways. Use a lighter touch, throw away that hard toothbrush, and you`ll stop wearing grooves in your teeth."

"But I did go to a soft brush! And I`m using it the right way, I swear. But what can I do about the teeth that are already sensitive?"

That`s the real question. You can teach better brushing habits until you`re blue in the face, but it doesn`t mean patients will listen soon enough for it to help. You can recommend a sensitivity formula toothpaste, but some patients don`t like the taste. Some don`t like the price. Some say it doesn`t work for them. What can you tell them? What`s new in the sensitivity field?

First, you have to understand sensitivity. Think back to those college lectures on tooth anatomy. Normal dentin has no sensation itself, but is able to transfer tactile impressions, thermal changes, and chemical irritations to the pulp. The pulp chamber and pulpal tissue, remember, are connected to overlying dentin by millions of microscopic tubules. One square millimeter of dentin, for instance, can contain 30,000 tubules. In patients who complain of sensitivity, there are eight times as many open tubules visible by scanning electron microscope.

The most widely accepted explanation for dentin sensitivity is Martin Brannstrom`s hydrodynamic theory. It states that fluid in dentin tubules expands when it is exposed to heat and contracts when it is exposed to cold or touch. These actions change the pressure in the fluid, which then activates mechanoreceptor nerves close to the pulp. When the nerve receptors are activated, sodium and potassium ions change places, polarizing the nerves that cause the pain. In other words, when too many tubules are open, they become easy avenues for pain sensation.

Cementum, which is supposed to provide a natural occlusion of the tubules, is only 20-50 microns thick, and can be removed by curettes, power instruments, abrasive food or toothpaste, or by brushing too vigorously. Because tubules are larger and more numerous closer to the pulp chamber, a preparation cut for a large restoration allows a major opportunity for open tubules. Other causes of open dentinal tubules are acute or chronic trauma, gingival recession, or idiopathic cervical erosion. Erosion that is spontaneous or has an unknown or obscure cause can occur because of occlusal misalignment which produces tensile stress at the cervix of the tooth.

Eventually, of course, exposed dentin will naturally sclerose - a phenomenon of aging. Fluid movement will then stop and sensitivity will disappear. But that can take years to happen, and more cementum loss can occur in the meantime.

Dentinal hypersensitivity, once begun, can be a continuing problem. A patient who uses her toothbrush like a scrub brush in her 20s, bleaches her teeth in her 30s, then experiences gum recession in her 40s, will be looking to you, her hygienist, for answers.

One of the newer causes of tooth sensitivity is bleaching. Any bleaching gel that contacts exposed dentin can heighten sensitivity, either because the gel is cold or because of an improperly made tray. Ultradent, makers of Opalescence bleach, also markets sustained-release desensitizing gels that can be used in bleaching trays made with reservoirs. UltraEZ contains 3 percent potassium nitrate and .11 percent fluoride ion. Flor-Opal contains 1.1 percent neutral sodium fluoride.

Jennifer Barney, a market segment manager for Ultradent, reports the desensitizing gels - provided in a unit-dose syringe - make bleaching possible for greater numbers of people.

"Patients want whiter teeth," she says, "that`s the bottom line. And with our stand-alone desensitizing gel, the percentage of the population that has sensitivity can still bleach if they want to. When they use the gel in their tray for a couple of nights before bleaching, it helps a lot."

Fluoride varnishes are sometimes used in-office to treat hypersensitivity. First developed in Germany, they are also used in Europe and some parts of the United States as anticaries agents. Duraphat, made by Colgate-Palmolive, is a temporary varnish, applied with a brush, that sets when it comes in contact with saliva. A single application allows a 77 percent increase in enamel fluoride, forming a reservoir from which fluoride is slowly released. The yellowish varnish can be brushed away by the patient at the end of the day, but its effects are lasting.

Another product called Super Seal forms insoluble precipitates on enamel and dentin surfaces and within dentinal tubules to stop fluid flow.

Zarosen, made by Cetylite, uses strontium chloride applied with a brush to provide immediate relief from sensitivity. Again, the effects can last for weeks.

Gluma Desensitizer has been shown to be an effective topical agent, using a 2.5 percent glutaraldehyde fixative to react with amino groups and induce protein precipitation inside dentin tubules. The disadvantage of Gluma is that it can cause chemical burns and allergic reactions in soft tissue.

A new product on the market is D/Sense 2, made by Centrix. John Discko, executive vice president of Centrix, calls D/Sense 2 "the most successful product we`ve ever launched. It`s totally unique. Dentists who`ve tried it say it`s the best they`ve ever used."

D/Sense 2 is a two-step product that can be applied in minutes during a routine cleaning appointment. "It works by using inorganic salts," Discko explains. "You clean and dry the tooth surface, then brush on the Step 1 liquid. It`s a clear, colorless, odorless solution that contains potassium phosphate and potassium carbonate. When you brush it onto the dentin, it depolarizes the nerve endings, shutting down the pain. Then, with a clean brush, you apply Step 2 right on top. This one contains strontium chloride and calcium chloride salts. They immediately react on the tooth surface and crystallize into four insoluble salts which seal dentinal tubules. The remaining potassium salts also raise the pain threshold. The crystallization thickness is three microns.

"It`s 96 percent effective, hypoallergenic, and has at least six months of effectiveness. If you cover it with a crown or filling, it will last as long as the restoration does. It`s not a bonding agent, there`s no light activation, and it`s not a resin or varnish. It won`t wash or chip away, and it`s invisible."

It doesn`t cost the patient anything for you to fine-tune his or her brushing technique - or to recommend a sensitivity formula toothpaste. Maybe that`s all they`ll need. But in-office desensitizing treatments call for a charge. "Application of Desensitizing Medicaments" is a recognized procedure, and the ADA code is 09910. Cost for the treatment ranges from $40 in New England to $23 in the West North Central region of the United States, with a median fee of $29.

Whether the cause is cervical abrasion, gum recession, periodontal surgery, deep fillings or idiopathic erosion, hypersensitivity can be a serious problem for your patients - and one that deserves our best efforts to solve.

Cathy Hester Seckman, RDH, is a frequent contributor to RDH. She is based in Calcutta, Ohio.

References

- Dental Practice and Finance, National Fee Survey Data, 1998

- Collaert, B., Fischer, C., Dentine Hypersensitivity: A Review, 1991

- Hodosh, M., Hodosh, S., Hodosh, A., About Dentinal Hypersensitivity, Compend. Contin. Educ. Dent., Vol. XV, No. 5

- Beutlich Pharmaceuticals, Cause of Dentin Hypersensitivity in the Cervical Area

- Dental Therapeutic Digest, OTC Products, Toothpastes, Sensitive Teeth 2000

- Hafez, A., Cox, C., Definitive Desensitization of Dentin: The Prevention and Treatment of Postoperative Hypersensitivity

- Gaffar, A., Treating Hypersensitivity with Fluoride Varnishes, Compendium 1998

A paste that`s sensitive

Sensitivity formula toothpastes should be front-runners in the toothpaste wars in the coming years, because of the baby boomers. Analysts say the marketing of sensitivity formulas plays directly into a demographic trend since millions of Americans turn 50 each day, creating demand for the formulas.

Colgate-Palmolive predicted its new Sensitive line may generate $222 million in sales. According to Colgate`s market research, although nearly one fourth of American adults suffer from sensitive teeth, 40 percent don`t use a special toothpaste for the problem - yet.

The 2000 edition of Dental Digest lists 15 different over-the-counter toothpastes marketed specifically for sensitive teeth. Nearly all use potassium nitrate, which has been shown to reduce dentin sensitivity without causing pulpal changes. Increasing the extracellular potassium ion concentration has been shown to depolarize nerve fiber membranes and keep them from repolarizing.

Potassium nitrate is popular for at-home use for several reasons. It is safe and effective, does not discolor teeth or mucosa, does not burn or damage tissue, acts rapidly with long-term effects, and has a pleasant taste.

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