Innovations In Dentin Hypersensitivity: A Unique Oxalate-Based Strip Technology

Adriana Altuve, PhD; Paul A. Sagel, BSChE; and Robert W. Gerlach, DDS, MPH

Dentin hypersensitivity represents one of the most commonly occurring dental problems. Despite its prevalence, the condition is usually underdiagnosed and undertreated. Recently, a user-friendly technology involving an oxalate-based strip was developed for treatment of dentin hypersensitivity. This novel sensitivity strip affords some of the same conveniences seen with whitening strips, and like those strips, may allow direct professional application. Strip usage is similar irrespective of the setting (office or home), with a low total amount of an oxalate gel delivered continuously over a 10-minute period to occlude dentin tubules and reduce sensitivity. Real and transcending evidence (preclinical and clinical), including practice-based research, exists on the strip technology’s effects, which makes this supplement particularly relevant to the practicing professional.

Dentin hypersensitivity is defined as a brief, sharp pain elicited when dentin is exposed to thermal, tactile, osmotic, chemical, or evaporative stimuli, and which cannot be ascribed to any other form of dental defect or disease.¹ Sensitivity results from exposed dentin tubules, most often due to gingival recession and loss of cementum through erosion, abrasion, or other factors. The hydrodynamic theory is the most commonly accepted theory for dentin hypersensitivity; it purports that when exposed dentin tubules come into contact with a stimulus, fluid flow within the tubule activates nerve receptors of the pulp, which leads to pain.²

The prevalence of dentin hypersensitivity has been reported to range from 4% to 57%, depending on the type of population and research methods.^3,4 Interestingly, many patients do not consider dentin hypersensitivity to be a serious oral health problem and, therefore, do not seek a solution. As such, they may develop strong compensating behaviors related to eating habits as well as oral care practices. Extreme cases may include neglecting oral hygiene, noncompliance with oral care instruction, or, ultimately, avoiding dental visits; all of these behaviors lead to an increased risk of dental disease.⁵

Despite the fact that dentin hypersensitivity is a common clinical problem that has been extensively investigated over the years, the condition is underreported and underdiagnosed. Even though research has shown that 88% of dental professionals believe dentin hypersensitivity can affect patients’ quality of life, the majority of professionals do not routinely screen for sensitivity, impeding diagnosis.⁶ It is essentially a diagnosis of exclusion after examination for fractures, caries, or other conditions associated with painful symptoms.

When a diagnosis is made, treatment can be challenging because there is no recognized “gold standard” solution.⁷ Common therapies range from over-the-counter dentifrices to in-office options like fluoride varnishes and prophylaxis pastes. Most therapies work by either blocking neural transmission at the pulp level (ie, potassium nitrate) or sealing and occluding dentin tubules (ie, stannous fluoride, arginine). Product efficacy is dependent on the delivery system, ingredient, formulation, and other factors. Unfortunately, many treatments have a slow onset of relief and/or may require continued use.

Oxalates, which are organic substances found in plants, have been used for more than four decades to treat dentin hypersensitivity due to their ability to block dentin fluid flow by occlusion of dentin tubules.⁸ Laboratory and clinical investigations have demonstrated deposition of oxalate crystals in exposed tubules, showing a reduction in sensitivity pain when delivered by rinse, brush, or tray systems.^9-11 A well-known characteristic of oxalates that makes them a particularly effective treatment is the fact that they are relatively insoluble in acids. Unlike most other occluding agents, oxalate crystals are resistant to dissolution when they undergo common challenges like salivation, brushing, and dietary acid challenges.^12-14

The unique occlusive properties and durability of oxalates inspired the development of an oxalate technology via a strip delivery system for targeted and enduring relief of dentin sensitivity. The patented antisensitivity strips, marketed as Crest® Sensi-Stop™ Strips (Procter & Gamble, www.dentalcare.com), are coated with a 1.5% oxalate gel. This breakthrough innovation is based on the tooth whitening strip system introduced in 2000 as a novel approach to deliver hydrogen peroxide.¹⁵ Each thin, flexible polyethylene strip contains dipotassium oxalate desensitizing gel on one side and is designed to extend over the gingival margin (Figure 1 and Figure 2). The strips provide a unique delivery system for oxalate to remain in contact with exposed tubules for a 10-minute treatment period, enabling release of oxalate to the affected area. Contrary to most contemporary sensitivity treatments that provide slow onset or transient relief, research shows one to three strip applications provide immediate sensitivity relief that lasts for 1 month or longer.¹⁶

Application of the strip can be done easily by the patient. Following oral hygiene, the patient simply peels the oxalate strip off the backing strip, applies it to the sensitive site for 10 minutes, and then removes it (Figure 3 through Figure 6). If the patient has multiple sensitive sites that cannot be covered by a single strip, separate strips can be applied to each sensitive area. Most people experience relief after using one strip, but treatment can be repeated if needed allowing 1 day between uses. Product labeling advises patients to contact their dental professional if tooth sensitivity persists after three treatments.

The oxalate strips are indicated for adult patients (18 or over) who suffer from sensitivity associated with cold, heat, acids, or sweets. Contraindications include periodontal disease (eg, bleeding gums or loose teeth), a history of kidney stones, pregnancy or breastfeeding, or allergies to oxalate or any of the ingredients.

Numerous preclinical investigations and clinical trials, conducted at various sites among different populations, demonstrate the efficacy of this innovative oxalate-based technology. This supplement reviews results from a series of in vitro investigations, two randomized clinical trials, and a practice-based study. Key findings include the following:

• Hare and colleagues used an in vitro model to evaluate the immediate and long-lasting performance of the oxalate strip to occlude patent tubuli in human dentin.¹² After a single treatment, significant deposition of crystalline oxalate was observed in treated dentin and there was a quantitative reduction in hydraulic conductance, indicating reduced fluid flow. The oxalate crystal barrier was also shown to be only modestly impacted by a series of dissolution and mechanical challenges over a 30-day period.

• A separate in vitro investigation assessing hydraulic conductance and using scanning electron microscopy (SEM) compared the effectiveness of several popular over-the-counter antisensitivity product technologies: oxalate strip; oxalate rinse; arginine rinse; stannous fluoride dentifrice; strontium acetate dentifrice; arginine-calcium carbonate dentifrice; and calcium sodium phosphosilicate dentifrice.¹³ The oxalate-coated strip demonstrated markedly enhanced tubule occlusion (Figure 7) relative to the dentifrice and arginine rinse products tested. In addition, the oxalate strip was shown to reduce hydraulic conductance much more efficiently, ie, with fewer applications, than an oxalate rinse. Of the other products tested, the stannous fluoride dentifrice showed the highest occlusion under conditions simulating daily treatment and challenge conditions.

• A randomized controlled clinical trial described by Amini and colleagues evaluated the safety and efficacy of the oxalate strip versus a potassium nitrate dentifrice for twice-daily use (control group).¹⁶ After first treatment, only the oxalate strip group exhibited significant immediate sensitivity relief to both air and tactile stimulation. Response improved with repeated use, and both treatments demonstrated effectiveness over 30 days. Between-group comparisons showed greater sensitivity relief with strips versus the daily-use dentifrice. A majority of strip users had no measured air sensitivity at Day 30.

• Papas and colleagues evaluated the durable effects of oxalate strips on dentin hypersensitivity versus a professional oxalate acid potassium salt solution in a positively controlled trial.¹⁷ Test products were professionally administered at sensitive test sites per each manufacturer’s instructions. After 1 month, there were 84% to 86% reductions in clinically measured cool air sensitivity for each oxalate group. Use of oxalate strips yielded similar benefits as a professionally applied oxalate treatment.

• In practice-based research by Anderson and colleagues,¹⁸ the oxalate strip was applied to pre-identified sensitivity patients as a professional in-office treatment during a recall visit. Sensitivity assessments demonstrated that patients with cervical dentin hypersensitivity were easily identifiable, professional strip application was feasible at various tooth sites across both arches, and treatment resulted in both immediate and durable sensitivity effects over a 1-month period.

Given the prevalence of dentin hypersensitivity and the lack of an accepted standard intervention,⁷ the oxalate strip-based technology with a durable occlusive mechanism represents a unique treatment option that may be particularly amenable to the dental practice. One of the most obvious ways the treatment can be incorporated into the dental practice is as a pre-procedural application for patients who experience thermal or tactile sensitivity during routine dental procedures, such as a prophylaxis. The strip can be applied prior to the appointment by the patient at home, or in the office by the patient or dental professional. The rapid relief experienced by most patients allows for immediate in-office evaluation of pain response, which also aids in a differential diagnosis. Strips can also be recommended for home use between dental appointments, either as a single remedy or to supplement other therapies as part of a broader comprehensive treatment plan.

Providing an effective, durable sensitivity solution not only allows patients to once again enjoy many cold and hot foods and beverages they may have been avoiding, but it also has a positive impact on daily oral hygiene. Sensitivity relief can enable longer and more thorough brushing and flossing because patients no longer need to avoid sensitive sites for fear of pain. Furthermore, patients are no longer limited to using only a sensitivity dentifrice. They can choose from a plethora of options, such as dentifrice that reduces gingivitis or provides extrinsic whitening, to meet their oral health needs and desires. Collectively, these benefits contribute towards a better quality of life and improved oral health for the patient.

Clinical and laboratory investigations show a novel system, comprised of thin polyethylene strips coated with a 1.5% oxalate gel, provides immediate and durable relief for dentin hypersensitivity. Oxalate depositions occlude dentin tubules and demonstrate significant resistance to daily mechanical and acid challenges. Randomized clinical research shows oxalate strips provide faster and more enduring relief compared to a popular potassium nitrate dentifrice and comparable relief to a professionally applied oxalate treatment. Strips are also an effective option for in-office use with sensitivity patients as part of a recall visit. Collectively, the data show the oxalate-based strip system provides a novel, effective at-home or in-office solution for patients suffering from dentin hypersensitivity.

Adriana Altuve, PhD
Group Leader
Global Oral Care R&D
Procter & Gamble
Mason, Ohio

Paul A. Sagel, BSChE
Research Fellow
Global Oral Care R&D
Procter & Gamble
Mason, Ohio

Robert W. Gerlach, DDS, MPH
Research Fellow
Global Oral Care R&D
Procter & Gamble
Mason, Ohio

Figures and Images

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Figure 1

Fig 1. Oxalate-based polyethylene strip with specifications.

Figure 2

Fig 2. Marketed oxalate-based strip product.

Figure 3

Fig 3. Opening of strip product packaging.

Figure 4

Fig 4. The strip product after removal from package.

Figure 5

Fig 5. Removal of oxalate-based strip from the backing strip.

Figure 6

Fig 6. Application of the oxalate-based strip at sensitive site (courtesy of Chad J. Anderson, MS, DMD).

Figure 7

Fig 7. Close-up of dentin cross-section following three applications with the oxalate strip. The colored overlay, highlighting areas containing deposits of oxalate crystals, was obtained by combining the SEM image with EDS elemental maps for oxygen, calcium, carbon, and phosphorous.