Hypersensitivity exposed

A variety of solutions are available following diagnosis

by Dawn Kasper, RDH

Our 21st century lifestyles have many benefits, but also have many consequences — dentinal hypersensitivity being one of them. As dentistry has progressed to the point of bringing diseases of infectious origin — caries, and periodontal disease — under control, a new set of conditions and problems are emerging, including exposed dentin.

What causes dentin to become exposed? Patients and clinicians alike have been investigating this question for years (and most likely will continue to do so well into the future). As technology and products advance, our actions to our teeth and gingival tissue continue to have negative consequences, the most prevalent being pain and discomfort. Changes in our diets further complicate the problem with acid erosion playing a large part, as well as gingival recession. Both of these conditions lead to exposed dentin which has been found to be the most common symptom in the initiation of dentinal hypersensitivity.

Often referred to as the “common cold of dentistry,” it is a common oral condition that affects many patients, yet few bring it to the attention of their dental hygienist or dentist. Sufferers do not always realize they have developed coping strategies to minimize the discomfort. They may also feel the problem is not serious enough to warrant concern or even worse, they might fear this pain could be a sign of something more serious. Without knowledge of an existing problem, dental professionals might not be screening for this condition.

Where do we go from here?

Recently, the World Health Organization has defined dental erosion as “the progressive irreversible loss of dental hard tissue that is chemically etched away from the tooth surface by extrinsic and/or intrinsic acids by a process that does not involve bacteria.” Dentinal hypersensitivity has been defined as a sharp, sudden, painful reaction when the teeth are exposed to hot, cold, chemical, mechanical, touch or osmotic (sweet or salt) stimuli and cannot be attributed to any other form of dental pathology or defect. In its simplest definition, it can be described as a short, sharp pain from exposed dentin in response to stimuli. In order to exhibit a response to stimuli, the tubules would have to be open both at the dentin surface as well as the pulpal surface of the tooth.

Theories

Most frequently observed on premolars, dentinal hypersensitivity occurs when tubules at the exposed dentin surface lead to sharp pain when exposed to a stimulus or trigger. Common triggers include hot or cold air, acidic, sweet or sugary foods or beverages, tooth brushing, and many dental procedures including tooth whitening.

The dentinal tubule is the portal through which stimuli gain access to the pulp. The odontoblasts and associated nerve fibers are able to detect dentinal fluid movement. Very little appears to be required to disturb and move odontoblasts and their associated pulpal nerve fiber endings into the proximal ends of the dentinal tubules.

Throughout the years, several theories have been cited to explain the mechanism involved in sensitivity, including the transducer theory, the modulation theory, the “gate” control and vibration theory, and the hydrodynamic theory. The latter (hydrodynamic theory was developed in the 1950s and based on two decades of research) is the most widely accepted explanation of the cause of tooth sensitivity. It concludes that when the fluids within the dentinal tubules are subjected to temperature changes or physical osmotic changes, the movement stimulates a nerve receptor sensitive to pressure, which leads to the transmission of pain. The most important variable affecting the fluid flow in dentin is the radius of the tubules. If the radius is reduced by one-half, the fluid flow within the tubules falls to one-sixteenth of its original rate. Consequently, the creation of a layer of obturation of the tubule can greatly increase the effectiveness of the treatment of this malady.

Making a diagnosis

Discovering the reason for tubules to be exposed or open should be assessed. A comprehensive examination will ultimately rule out other underlying conditions for which sensitivity is a symptom such as cracked teeth, fractured restorations, chipped teeth, dental caries, gingival inflammation, post-restorative sensitivity, bruxism, clenching, marginal leakage, and pulpitis. A thorough examination including medical and social history, lifestyle, medications, supplements, dietary habits, and oral hygiene self-care is essential for the dental professional to make a definitive diagnosis. It is important to allow the patient to assist in the diagnosis by identifying the pain-inciting stimuli, as well as describing the type of pain and location involved.

The most commonly cited reason for exposed dentinal tubules is gingiva recession — reduction of the height of the marginal gingival to a location apical to the CEJ (predisposing factor). Recessed areas may become sensitive due to the loss of cementum or enamel, ultimately exposing dentin, which is then prone to abrasion, erosion, and hypersensitivity from exposure of open tubules to the oral environment. Chronic exposure to bacterial plaque, toothbrush abrasion, and gingival laceration from oral habits such as toothpick use, excessive flossing, crown preparation, inadequate attached gingiva, gingival loss secondary to disease or surgery, normal aging, abnormal tooth position in the dental arch, and periodontal surgery are some, but not all causes of gingival recession.

Clinicians should routinely check for dentinal hypersensitivity to avoid underdiagnosis. A thorough assessment should include history of pain, complete medical history, thorough exam, X-rays, probing depths, recession measurements, diet, percussion testing, bite stress test, thermal tests, assessment of occlusion, and sensitivity reported by the patient.

The impact of enamel loss and tooth wear on the occurrence of sensitivity cannot be underestimated. Erosion, abrasion, and attrition seldom occur in isolation. Generally a pH of 5.5 or lower is capable of softening the surface of enamel within only a few minutes, leaving it vulnerable to physical abrasive forces leading to irreplaceable loss and tooth wear. Once enamel is lost, the exposed dentin is subject to wear and chemical erosion from acid attacks. Dentin may be demineralized at pH levels as high as 6.5 and remineralizes very poorly.

Saliva may play a critical role in naturally reducing dentinal hypersensitivity. Saliva supplies calcium and phosphate, which can enter open dentin tubules and, over time, block the tubules from external stimuli. Insufficient saliva, hyposalivation, is a risk factor for dental caries and tooth demineralization and may exacerbate sensitivity. Dry mouth (xerostomia) is a side effect of over 500 prescription and OTC medications. These factors all need to be considered in arriving at a differential diagnosis.

Treatment options

With a definitive diagnosis of dentinal hypersensitivity, a treatment plan can be formulated, and recommendations can be made to the patient. However, it can be challenging for both the patient and the health-care provider, as it is difficult to measure or compare different patients’ pain, and it is difficult for patients to change the habits that initially caused the problem. Hypersensitivity can resolve without treatment or may require several weeks of desensitizing agents before improvement is seen. The two principal treatment options are:

• Plug the dentinal tubules, thus preventing fluid flow.
• Desensitize the nerve, making it less responsive to stimulation.

To date, no single agent or form of treatment has been found effective for all patients. Solutions, however, have been tried with varying degrees of success. Professional interventions range from applying fluoride varnish to promoting remineralization to more aggressive, low-level laser treatments that occlude or fuse the tubules (the goal). Home care recommendations include professionally endorsed desensitizing toothpaste with active agents:

• Potassium salts (nitrate, chloride, and citrate) interfere with transmission of stimuli by depolarizing the nerve surrounding the odontoblasts.
• Strontium salts (chloride or acetate) penetrate and occlude the tubules, thereby stopping flow of fluid.
• Sodium citrate and various fluoride compounds act as barriers to dentinal tubules, preventing fluid movement and thereby reducing sensitivity.

Other recommendations proven to be effective in the management of dentinal hypersensitivity are prescribed depending on the severity of the condition.

• Calcium compounds like casein phosphopeptide-amor-phous calcium phosphate (CPP-ACP) occlude dentinal tubules and can be administered at home via custom tray, toothbrush or finger application.
• Use of a custom tray filled with dentifrice containing potassium nitrate increases medicament-tooth contact time, thus increasing effectiveness.
• Iontophoresis delivers a low voltage charge of sodium fluoride into the dentin.
• Methacrylic polymers, which are applied as a base or composite restoration.
• Sodium fluoride varnishes that are painted on the tooth surface and set in presence of moisture.

There are many products to consider for treating sensitivity based on the individual patient’s needs. These professional products include but are not limited to: GC America’s MI Paste and MI Paste Plus, Colgate’s Sensitive Pro-Relief, Sunstar Butler’s Protect Desensitizing Paste, SDI’s Soothe, Preventech’s Dayli, Discus Dental’s Relief ACP, Heraeus Kulzer’s Gluma, Sultan Healthcare’s ReNew, and Omnii Pharmaceutical’s SootheRx.

Other suggestions include modifications of home care including tooth brushing to control plaque buildup and reduce toothbrush abrasion, caries-control measures with fluoride rinses, diet counseling, and proper brushing and flossing. The recommendation of an electric or battery-operated toothbrush to reduce abrasion, plaque accumulation and massage the gingival tissues would be an excellent addition to a home-care routine. Dental professionals recommend the rotating-oscillating brush technologies as beneficial and proven effective with both Philips Sonicare and Oral-B offering the most options.

More recently, dentifrices have been introduced containing combinations of desensitizing agents, fluorides, anti-calculus and/or whitening ingredients to provide multiple therapeutic and cosmetic benefits. Sensitive toothpastes often recommended include: GSK’s Sensodyne, Colgate’s Sensitive, Butler’s Sensitive, Crest’s Sensitivity, Aquafresh’s Sensitive, Discus Dental’s BreathRx , Oral-B Rembrandt’s Sensitive, Dentsply’s Nupro NUsolutions, Arm & Hammer’s Sensitive, Biotene’s Sensitive, Tom’s of Maine’s Natural Sensitive, Dr. Collins’s Restore, Oravive’s Oravive and The Natural Dentist’s Toothpastes. In making treatment recommendations, it is important to have an understanding of the clinical data that support the product’s efficacy and safety.

Dentinal hypersensitivity is a chronic problem that plagues many patients and is consistently underdiagnosed. A comprehensive assessment is essential, as is appropriate treatment to decrease the dentinal flow and relieve discomfort. The majority of cases begin with gingival recession and tooth erosion. Once the tubules are exposed, the patient will experience pain. Differential diagnosis is critically important, followed by a clinically appropriate management plan that also addresses any predisposing conditions. Minimally invasive, inexpensive, and effective options should be tried first. The initial treatment choice should be to either plug the dentinal tubules or to desensitize the nerve.

Consideration should be given to the use of in-office desensitizing agents or the use of fluoride varnishes. Professional as well as over-the-counter treatment options to eliminate the sensitivity should be presented to the patient with the product of choice based on the scientific evidence supporting each active ingredient and the patient’s preference for products that will fit most easily into his or her oral hygiene regimen. Planned follow-up to monitor treatment and reduction in pain also should be included as part of the recommendation. Forming an alliance to create an individualized approach to treating dentinal hypersensitivity will increase patient compliance during treatment, resulting in enhanced outcomes without patient discomfort.

Dawn Kasper, RDH, has been a practicing dental hygienist for three decades. She is president of Trusted Success Consulting, providing practice management services for dental practices, and speaks on numerous topics, specializing in pain management, dentinal hypersensitivity, salivary testing, and optimizing whitening options. Dawn has authored several published articles and is a product evaluator for Dental Products Shopper. She also works as an independent consultant in the corporate arena. Dawn has been an active member of the American Dental Hygienists’ Association, the American Academy of Dental Hygiene, the American Dental Education Association, and many other professional associations. She is a member of the KOL Speaker Program for Sunstar/Butler and sits on many professional panels. She can be contacted at [email protected].

Factual Information

Dentinal hypersensitivity:

• It affects more than 40 million people in the United States annually, impacting one in five adults.
• It is most common between 30 and 40 years old, and it is experienced by women at a younger age than men.
• Patients with periodontal diseases are particularly high risk — between 72% and 98%.
• “Hyper” sensitivity means painful response to stimuli not normally associated with pain.
• Response to stimuli varies from person to person due to differences in pain tolerance, environmental factors, and emotional state.

Dentin

• It is composed of hydroxyapatite mineral and organic components.
• It is formed by the odontoblasts during tooth development.
• It is differentiated from other mineralized tissues in the body, because it contains thousands of tubules which run perpendicular to the pulp chamber.
• The tubules are formed as the odontoblasts migrate away from the dentinoenamel junction during dentin formation.
• The tubules contain the odontoblastic process as well as fluid surrounding the process.
• It is normally covered by enamel or cementum.
• The gingival margin seals the teeth as they erupt, leaving only the coronal portion exposed in the oral cavity and the root portion protected from the external environment.
• To be considered hypersensitive, it must be exposed, and the exposed tubules must be open to the pulp.

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Causes of Dentinal Hypersensitivity

• Gingival recession, 47.1%
• Abrasion, 24.9%
• Abfraction, 16.6%
• Caries, 6.2%
• Erosion, 3.1%
• Other causes, 1.9%

References

1. Jacobsen PL, Bruce G. Clinical dentin hypersensitivity: understanding the causes and prescribing a treatment. The Journal of Contemporary Dental Practice 2.1 Winter Issue 2001; 1-8.
2. Barrow SL. Dentin hypersensitivity — an overview. The Journal of Professional Excellence, Dimensions of Dental Hygiene, June 2006; 4(6):28, 30 http://www.dimensionsofdentalhygiene.com/print.asp?id=852.
3. Walters P. Dentinal hypersensitivity: a review. The Journal of Contemporary Dental Practice 6.2 Spring Issue, May 15, 2005; 110-112,115.
4. Stefanou LB. Brighter, whiter, ouch: treating whitening induced dentin hypersensitivity. The Journal of Professional Excellence, Dimensions of Dental Hygiene, June 2007; 5(6):24, 26. http://www.dimensionsofdental-hygiene.com/ddhright.aspx?id=1156.
5. Marvin K. Bright, white and sensitive: an overview of tooth whitening and dentin hypersensitivity. Dentistry Today.com; May 2008. http://www.dentistrytoday.net/ME2/Segments/Publications/Print.asp?Module=Publications::Article&Id=C2C6E8D21EBD4128A403EE18C9F1FE81.
6. Caceci T. Digestive system: oral cavity. Education: VetMed 8054 Veterinary Histology, Exercise 17; http://images.google.com/imgres?imgurl=http://education.vetmed.vt.edu/curriculum/vm8054/labs/Lab17/IMA
7. Strassler H, Drisko C, Alexander D. Dentin hypersensitivity: its inter-relationship to gingival recession and acid erosion. Supplement to Inside Dentistry; June 2008; 4(6):2,3,5,8.

Useful Diagnostic Tools

• Air/water syringe
• Dental explorer (touch)
• Percussion testing
• Bite stress test
• Thermal tests (ice)
• Assessment of occlusion

Potential Risk Factors

• Excessive dietary acids
  Citrus juices
  Citrus fruits
  Carbonated drinks
  Wines
  Ciders
  Energy drinks
  Toothbrush abrasion
• Chemical erosion
• Thin enamel
• Gingival recession
• Exposed dentin
• Eating disorders