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Sensitive Issues

Dec. 1, 2000
Historical evidence clearly reveals that the teeth of man have been hurting for thousands of years. For the most part, dental pain in the past was of pulpal origin, typically as a result of decay leading to periapical pathology - and the inevitable dental abscess. With the decline in caries and the retention of teeth long into old age, the problems associated with teeth and, in particular, exposed dentin indicate that hypersensitivity is likely to be a major cause of dental pain in the future. T

The management of dentinal hypersensitivity relies on careful diagnosis and elimination

of factors that cause pain, such as overly enthusiastic brushing, diet, or plaque control.

Juliana J. Kim, BSDH, MS, and

Iain A. Pretty, BDS, MSc

Historical evidence clearly reveals that the teeth of man have been hurting for thousands of years. For the most part, dental pain in the past was of pulpal origin, typically as a result of decay leading to periapical pathology - and the inevitable dental abscess. With the decline in caries and the retention of teeth long into old age, the problems associated with teeth and, in particular, exposed dentin indicate that hypersensitivity is likely to be a major cause of dental pain in the future. The hygienist`s role in the recognition and management of dentin hypersensitivity is crucial to the comprehensive care of the patient.

The nature of dentin hypersensitivity has been debated for many years. It is frequently encountered and yet is poorly understood and often left untreated. This article provides the reader with a scientific background of the condition, its diagnosis, treatment, and some of the products that have been developed for both at-home and in-office treatment.

The science of hypersensitivity

Many readers are familiar with "hydrodynamic theory." Gysi in 1900 stated, "The dentinal tubules contain fluid or semi-fluid materials, and their walls are relatively rigid. Peripheral stimuli are transmitted to the pulp surface by movements of this column of semi-fluid material within the tubules." This theory has been further supported by the work of Brännström, and is now widely accepted.

Several biological factors can reduce the fluid movement that occurs in the dentinal tubules due to hydrodynamic stimuli:

* The smear layer contains very small particles of dentin - a mineral and organic matrix covering the exposed surface of dentin - which block the orifices of the tubules.

* Salivary proteins can also obstruct the tubular openings.

* The production of reparative (or secondary dentin) in response to chronic irritation. This type of dentin is less permeable than the primary form and serves to insulate the pulp from irritating stimuli via hydrodynamic forces.

* Sclerotic dentin or intratubular dentin occurs as a result of aging or in response to attrition. Intratubular dentin is deposited in the lumen of the dentinal tubule, thus reducing the radius of the tubule or obliterating it entirely. If this progresses to the adjacent dentinal tubules, the net result is the reduction of permeability of the dentin, rendering it less sensitive than nonsclerotic dentin.

* The deposition and accumulation of calculus acts as a barrier and protects the dentin from external stimuli.

Dentin that is exposed to the oral environment is susceptible to hypersensitivity. The exposure of dentin usually occurs due to a loss of gingival attachment as a result of recession, followed by abrasion of the root cementum.

This process can occur due to periodontal disease, orthodontics, jaw surgery, toothbrush abrasion, or periodontal instrumentation.

However, it should be noted that not all exposed dentin is sensitive. Provided that the dentinal tubules are open and the stimuli sufficient, it is the fluid movement within the dentinal tubules which causes the sensory nerve fibers to initiate the pain response.

The exposure of dentin that results in hypersensitivity is most common in the buccal cervical regions of teeth. The facial prominence of canine and premolar roots can make such teeth susceptible to toothbrush abrasion and gingival recession - as well as, of course, hypersensitivity.

Dentin hypersensitivity can also occur lingually, palatally, and occlusally, although this is rare. Tooth position and number can also affect dentin hypersensitivity. Addy reported that the dominant factor for distribution of hypersensitivity was the side of the mouth. In a group of 92 patients, 86 were right-handed, and recession was greater and hypersensitivity more common and severe on the left side of the mouth.

Of interest to the hygienist is the dentin hypersensitivity that often accompanies periodontal treatments, particularly root planning. Teeth whose root surfaces were covered by gingiva, cementum, plaque, or calculus are suddenly exposed to the oral environment. Such teeth often experience hypersensitivity, and patients will often complain afterwards. Indeed, teeth that are extensively root-planed may lack cementum around their entire cervical third. These teeth are especially prone to sensitivity, leading to the phenomenon known as iatrogenic root sensitivity.


Dentin hypersensitivity may be defined as pain arising from exposed dentin, typically in res-ponse to chemical, thermal, tactile, or osmotic stimuli that cannot be explained as arising from any other form of dental defect or pathology. A diagnosis of hypersensitivity should only be reached following the consideration of a careful medical and dental history and a thorough clinical and radiographical examination.

Difficulties may arise when one or more conditions providing similar clinical findings co-exist. Hence, a differential diagnosis that rules out caries, fractures, leaking restorations, periapical pathology, and trauma is pivotal in the treatment of dentinal hypersensitivity.

The patient`s ability to effectively locate the source of pain from hypersensitivity may differentiate it from pulpal or dentinal pain. With the latter symptoms, the patient`s description of location can be vague.

The characteristics of the pain associated with hypersensitivity is pain that is initiated by changes in temperature and can worsen with sweet and sour stimuli. The intensity of the pain is usually mild to moderate and can be replicated by scratching the exposed dentin or application of air. The pain is of an acute nature, but is usually described as acute episodes of a chronic condition. The chronic nature of the condition ends following the repair of the enamel or cementum defect either by chemical or restorative techniques. The radiographic appearance of the tooth should suggest an absence of periapical pathology.


The initial step in the treatment of sites that respond to stimuli is the elimination or control of etiological factors. Overly enthusiastic brushing, an acidic diet, and inadequate plaque control are some factors that contribute to tooth pain. They must be rectified in order to resolve the hypersensitivity. Subsequently, the use of at-home desensitizing agents, application of professional products, or retreatment should be implemented as necessary.

o Self-applied desensitizing agents - Current at-home desensitizing agents contain fluorides and/or potassium nitrate as their active ingredient. These agents are in the form of dentifrices or gels. The fluoride products are available in various concentrations and are believed to help with root desensitization. However, it must be noted that fluorides have been approved by the FDA for preventing caries, but not reducing hypersensitivity.

The desensitizing dentifrices on the market currently contain 5 percent potassium nitrate, which blocks repolarization of sensory nerve endings in the pulp. The intradental nerves are hyperpolarized by the raising of extracellular potassium ion concentration. The sustained hyperpolarized state reduces nerve excitation and the nerves become insensitive to further stimulation. As a result, the pain response to thermal and tactile stimuli is reduced. However, frequent and regular use of the dentifrice is necessary to avoid the recurrence of sensitivity. Table I lists the at-home desensitizing products currently available on the market.

In terms of clinical studies supporting effectiveness of dentifrices, it is important to consider the patient`s perception of pain relief (a subjective assessment), as well as the thermal and tactile responses. The thermal and tactile measures do not reflect every day sensitivity well. A good desensitizer will always demonstrate significant reductions in patients` perceived pain; lack of this data may indicate a lack of effectiveness in the real world as opposed to the laboratory findings. When recommending desensitizing dentifrices, hygienists should evaluate the studies that measure patients` perceptions of pain relief. Not all studies include this important criteria when making claims about the effectiveness of a desensitizing dentifrice.

* Professionally-applied desensitizing agents - Using a desensitizing dentifrice twice a day may be appropriate for patients with slight or mild hypersensitivity, but ineffective for patients with more severe hypersensitivity.

When sites of hypersensitivity are unresponsive to the at-home desensitizing products, professionally-applied desensitizing agents are indicated. These in-office treatments include fluoride compounds, strontium chloride, oxalates, and hydroxyethyl methacrylate (see Table II). These agents act to occlude the dentinal tubules. Professionally-applied fluorides in the form of varnishes are high in concentration and are believed to narrow the radius of the dentinal tubules by the remineralization and deposition of crystals into the dentinal tubules. These agents are applied directly to the exposed root surface to occlude the dentinal tubule.

* Restorative treatment - In many severe cases of hypersensitivity, a loss of tooth structure will require restorative treatment. This involves the placement of composite or glass ionomer materials at the tooth defect. In more severe cases, endodontic treatment and, perhaps, tooth removal is warranted. It is important to diagnose and treat dentinal hypersensitivity early in order to prevent the need for more extensive dental treatment.

Understanding the etiology of dentinal hypersensitivity is critical in making a correct differential diagnosis. Once the diagnosis is made and the causative factors of hypersensitivity are discussed with the patient, a treatment plan can be developed to resolve patient discomfort. Most patients experiencing dentinal hypersensitivity can be treated with patient-applied desensitizing dentifrices. However, if the sensitivity persists, professionally-applied tubule occluding desensitizing agents can be used to reduce the sensitivity.

All too often, the hygienist`s primary focus is the removal of calculus. As a result, other conditions are overlooked and neglected. The key in managing dentinal hypersensitivity is to perform a thorough intraoral exam and incorporate desensitization measures into the preventive and maintenance care plans for each patient. Hygienists have a critical role in the management of dentinal hypersensitivity. This includes staying informed of current research and new products, selecting treatments that meet the patient`s needs, and educating the patient for effective self-care habits.

Juliana J. Kim, BSDH, MS, is the manager of dental hygiene affairs at the Block Drug Corporation in Jersey City, N.J. Iain A. Pretty, BDS, MSc, is a dentist at the department of clinical dental sciences at University of Liverpool.

References available upon request.

Who is suffering?

The incidence of dentinal hypersensitivity appears to peak in the third decade of life, and root sensitivity develops by the fifth decade. The frequency of the condition is approximately one in six people who have one or more teeth affected. Other studies have suggested an incidence of 8 to 30 percent of dentate individuals. Such differences can be attributed to different diagnostic criteria.

Despite the fact that dentinal exposure increases with age (especially through gingival recession), there is a reduced prevalence of hypersensitivity in the older age group. This is thought to reflect the changes in dentin and pulp that occur in older teeth, such as dentin sclerosis, the addition of secondary dentin, and pulpal fibrosis. All of these changes are likely to retard the hydrodynamic transmission of stimuli from the surface of the dentin to the pulp.

Further epidemiological data is not available for hypersensitivity. A possible exception is a slight but statistically insignificant difference between males and females, where females appear to suffer from it slightly more than males. Data regarding racial, social, cultural, and occupational influences of sensitivity have not been investigated.

Individuals who are most at risk for dentinal hypersensitivity include:

- People who exhibit gingival recession from oral hygiene habits

- People who have frenal defects

- Overly enthusiastic brushers

- Consumers of high acidic foods and drinks, such as citrus fruits and some carbonated beverages

- Bulimics who - through acid regurgitation - have eroded the palatal surfaces of their teeth, leaving them more prone to exposed dentin

- People who experience xerostomia (dry mouth) either through side effects caused by pharmaceutical agents, aging, or radiation therapy.

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