Hypersensitivity Basics

Dentin hypersensitivity is among the most common oral health conditions affecting patients today.1 However, it rarely is the primary reason for an office visit. Defined as a short, sharp pain arising from exposed dentin in response to stimuli,² prevalence data show that up to 50% of the general population suffers from the condition, yet dental professionals do not routinely address it.¹ Also with the growing frequency of tooth whitening procedures, whitening-related sensitivity is a common problem. Up to 75% of tooth whitening patients may experience dentin hypersensitivity.¹

Dental hygienists play an important role in identifying and managing dentin hypersensitivity. With our experience in prevention, hygienists should be questioning patients about sensitivity at each visit instead of waiting for patients to complain of pain. A patient’s history of whitening treatment and whether he or she is considering it in the future should also be discussed. Then, treatment should begin with the least invasive and least expensive option—over-the-counter toothpaste designed to address sensitivity.

WHAT IS DENTIN HYPERSENSITIVITY?

By understanding how dentin hypersensitivity occurs, dental hygienists can then explain to patients why they may be experiencing pain or discomfort.

The hydrodynamic theory is the most commonly accepted scientific explanation for dentin hypersensitivity. It is based on the concept that fluid within the dentinal tubules can flow in either an inward or outward direction, depending on pressure differences in the surrounding tissue. A stimulus that makes contact with a tooth surface where there is exposed dentin in addition to patent (also know as open) dentinal tubules causes fluid to flow and alter direction. This fluid flow within the tubules serves as a medium to excite intradental nerves, which is perceived as pain by the patient. Foods or beverages that are hot, cold, sweet, or sour, as well as cold air or an explorer touch, are common stimuli or triggers of dentin hypersensitivity.  The stimuli that elicits the pain of dentin hypersensitivity is typically thermal, evaporative, tactile, osmotic, or chemical in nature, and cannot be attributed to any other defect or pathology.²

PREVALENCE

Dentin hypersensitivity typically occurs in people between the ages of 20 and 50, while the highest incidence exists between the pages of 30 and 40.³ This younger age group also has higher rates of undergoing tooth whitening procedures.

In addition to age, gender may play a role. Research has shown that dentin hypersensitivity occurs slightly more frequently in women than men. A global survey conducted in 2002 suggests that 42% of women in North America suffer from the condition, compared to 31% of men.4  Patients undergoing periodontal treatment also have higher rates of dentin hypersensitivity.5

Dentin hypersensitivity also affects certain teeth at different rates. Sensitivity most commonly involves canines and first premolars followed by incisors, second premolars, and molars.⁶ Sensitivity is most often experienced on the facial surfaces of teeth at the cervical margins.⁷

Natural desensitization may decrease sensitivity over time. These natural causing desensitizers, also known as dentin sclerosis, appear on radiographs, as an increase in calcification. This process can be caused by caries or attrition and may be associated with elderly patients. The progression of increased mineralization may cause the tubules to become obstructed, thereby interrupting an impulse that causes pain.⁸

CONTRIBUTING FACTORS

A number of different factors and conditions can contribute to dentin hypersensitivity. Gingival recession and loss of enamel and/or cementum caused by abfraction or abrasion are among the most common factors. Abfraction is caused by cervical tooth flexure. Abrasion can be caused by overly aggressive tooth brushing or flossing, eating coarse foods, or other tooth trauma such as frequent use of toothpicks. Interestingly, women tend to practice more aggressive oral care habits, which may be one reason for the higher frequency of dentin hypersensitivity in women. As many as 72% to 98% of periodontal patients experience dentin hypersensitivity.⁴  Gingival recession and exposed dentin result from the disease process and treatment like pocket elimination surgery. Over instrumentation of root surfaces during scaling and rootplaning leaves a smear layer but the action of the scaler may also force bacteria into the dentinal tubules, which may cause an inflammatory response within the pulp.⁹ Erosion is an additional contributor, and can result from the low pH of saliva after ingesting acidic foods and beverages, as well as stomach acid resulting from conditions like gastric reflux.

IDENTIFYING DENTIN HYPERSENSITIVITY

Many patients don’t tell their dental professional that they are suffering from dentin hypersensitivity. One reason may be because patients are afraid they have a more serious condition that requires extensive treatment. Patients often do not realize that simple and effective solutions are available to treat their pain.

Many patients change their behavior to avoid the pain of dentin hypersensitivity. They may wait for hot beverages to cool before drinking or avoid putting ice in drinks. Patients also may avoid brushing sensitive areas. This can result in an excessive amount of plaque build-up and potentially lead to gingivitis and/or adult periodontitis. By engaging patients in a dialogue about sensitivity and asking about these potential triggers, dental hygienists can more easily identify patients who are suffering.

Questions to ask at each patient visit:

1. Do you avoid specific foods or beverages that cause tooth sensitivity or pain?
2. Do you experience discomfort from hot, cold, sweet, or sour foods or beverages?
3. Have you recently undergone a whitening treatment?
4. If so, did you discontinue or interrupt treatment because of sensitivity?
5. Are you considering whitening treatment in the future?

Once a patient’s current status for dentin hypersensitivity is identified, a thorough clinical examination is necessary to rule out other conditions, which include dental caries, cracked tooth syndrome, sinusitis, open or defective margins, bruxism, and endodontic problems.

MANAGING DENTIN HYPERSENSITIVITY

Dental hygienists should initiate intervention strategies by educating patients about proper brushing and oral care techniques to prevent further exposure of dentin, as well as recommending the elimination of excessive dietary acids found in beverages such as soda or wine and acidic foods like yogurt. Acidic foods and beverages can cause acid erosion as well as surface softening, which leaves tooth surfaces highly susceptible to tissue loss.^10,11 If patients must consume dietary acids, then the dental hygienist should instruct the patient to do so separate from toothbrushing times. There is evidence that brushing with a toothpaste creates a smear layer that will occlude the dentinal tubules for a short time. But toothbrushing before and after exposure to dietary acids opens dentinal tubules.¹²  Therefore, toothbrushing should not precede or follow exposure to acid, but should be separate from mealtimes.¹²

Treatment recommendations for dentin hypersensitivity should begin with the most conservative options, as they can be as effective as more expensive in-office treatments.¹³ Over-the-counter toothpastes designed to treat sensitivity should be the first plan of action. Anti-hypersensitivity toothpastes containing 5% potassium nitrate are an effective, at-home treatment option for dentin hypersensitivity. Toothpastes containing 5% potassium nitrate act by depolarizing the nerves located at the dentin-pulpal interface. Potassium ions in the toothpaste penetrate the length of the dentin tubules and prevent repolarization of sensory nerve endings. This interrupts transmission of the pain-causing nerve impulses that are normally associated with dentin hypersensitivity, therefore reducing the patient’s pain.¹⁴ Patients using a desensitizing toothpaste with 5% potassium nitrate typically experience sensitivity relief within 14 days.¹⁴  Patients should brush twice daily and continue use of the desensitizing toothpaste indefinitely for long-term relief. Antihypersensitivitytoothpastes are safe to use for an extended period of time and contain fluoride in addition to potassium nitrate.

Some patients may require a more enhanced treatment combined with the useo f an anti-hypersensitivity toothpaste. Common in-office treatments for dentin hypersensitivity include topical agents such as fluorides, protein precipitates, oxalates,and HEMA compounds. These work by blocking open dentinal tubules from the stimulus. However, these interventions may not provide long-term relief as they can be brushed off over time. Other, more assertive in-office treatments include restorations,such as glass ionomer cements or resins.

MANAGING SENSITIVITY IN PATIENTS USING WHITENING AGENTS

Tooth whitening is a common cause of hypersensitivity, occurring when the chemical by-products of carbamide and hydrogen peroxide used in whitening treatment pass through the enamel and dentin and into the pulp.¹⁴ Many whitening patients experience sensitivity that is so severe they suspend their treatment.¹⁴

In whitening treatments, the ratio of carbamide peroxide to hydrogen peroxide is typically 3:1. For example, a 10% solution of carbamide peroxide is roughly 3% hydroge nperoxide, the remaining 7% is urea.¹⁵

To reduce the potential for sensitivity, dental professionals may recommend that whitening patients use a desensitizing toothpaste for 2 weeks prior to beginning whitening treatment, as well as throughout the duration of their treatment. Recommending this protocol may help reduce the number of patients who discontinue whitening treatment due to whitening-related sensitivity.

CONCLUSION

Dentin hypersensitivity is a highly under reported and under-diagnosed condition. Dental hygienists can play a key role in the identification and management of the condition by inquiring about sensitivity at each patient visit. Recommending the use of desensitizing toothpastes as the first line of treatment is a simple and effective at-home treatment option. Dental hygienists also should ask patients if they are undergoing whitening treatment or planning to do so in the future. By addressing this common side effect prior to whitening, patients maybe come more comfortable and satisfied with their treatment overall, and less likely to discontinue treatment due to sensitivity.

REFERENCES

1. Kielbassa A. Dentine Hypersensitivity: Simple steps for everyday diagnosis and management. Int Dent J. 2002;52:394-396.
2. Addy M. Etiology and clinical implications of dentine hypersensitivity. Dent Clin North Am. 1990;34:503-514.
3. Gillam DG, Aris A, Bulman JS, Newman HN, Ley F. Dentine hypersensitivity in subjects recruited for clinical trials: clinical evaluation, prevalence and intra-oral distribution. J Oral Rehabil. 2002:29:226-231.
4. Addy M. Dentine hypersensitivity: New perspectives on an old problem. Int Dent J. 2002;52:375-376.
5. Chabanski MB, Gillam DG, Bulman JS, Newman HN. Clinical evaluation of cervical dentine sensitivity in a population of patients referred to a specialist periodontology department: a pilot study. J Oral Rehabil.1997;24(9):666-672.
6. Ong G, Strahan D. Effect of a desensitizing dentifrice on dentinal hypersensitivity. Endod Dent Traumatol.1989;5:213-218.
7. Graf H, Galasse R. Morbidity, prevalence and intraoral distribution of hypersensitive teeth. J Dent Res.1977;56(special issue a):162.
8. Mitchell S. Dentinal sensitivity. In: Daniel S, Harfst S, eds. Mosby’s Dental Hygiene: Concepts, Cases and Competencies. Philadelphia: Mosby; 2002:429-439.
9. Drisko C. Dentine hypersensitivity—dental hygiene andperiodontal considerations. Int Dent J. 2002;52:385-393.
10. Schweizer-Hirt CM, Schait A, Schmid R, Imfeld T, Lutz F,Muhlemann HR. [Erosion and abrasion of the dental enamel.Experimental Study]. SSO Schweiz Monatsschr Zahnheilkd. 1978;88:497-529.
11. Eisenburger M, Hughes J, West NX, Jandt KD, Addy M.Ultrasonication as a method to study enamel demineralization during acid erosion. Caries Res. 2000;34:289-294.
12. McAndrew R, Kourkouta S. Effects of toothbrushing prior and/or subsequent to dietary acid application on smear layer formation and the patency of dentinal tubules:a n SEM study. J Periodontol. 1995;66:448-448.
13. Canadian Advisory Board on Dentin Hypersensitivity.Consensus-based recommendations for the diagnosis and management of dentin hypersensitivity. J Canadian Dent Assoc. 2003;69:222-226.
14. Haywood VB. Dentine hypersensitivity: bleaching and restorative considerations for successful management. Int Dent J. 2002;52:376-385.
15. Haywood VB. Current status of nightguard vital bleaching. Compend Contin Educ Dent Suppl.2000:21(8):S10-S17.

From Dimensions of Dental Hygiene. March 2005;3(3):32, 34-35.