Dentin Hypersensitivity: Patient Considerations, Etiologies, and Treatment Issues from an Endodontic Viewpoint

One of the more challenging problems to deal with in dentistry is to maintain teeth in symptom-free function over the life of the patient. Over time through normal wear, function, and maintenance, some teeth create a “sensitivity” problem for the patient to a point where the patient is alerted to teeth that give them a shooting sensation, a tingling sensation, sometimes a painful sensation, or at times just a different feeling during normal daily activities. The teeth may or may not be painful, depending on the patient’s perception, pain threshold, and emotional and physical factors.⁵² Yet they grab the patient’s attention when they ingest certain foods or liquids, chew, brush their teeth, and even just take in a cool breath. For the patient, the quality of life, defined in this case as a pain-free oral cavity, has been altered.

In some cases, the patient can identify the problem tooth and go directly to the sensitive part of it; in other situations, the problem is not focused and rather vague but very real. Daily, these patients are referred for an endodontic evaluation or are sent to have root canal treatment. In most circumstances, root canal treatment is unwarranted, but the patient feels that their dentist does not know what to do about the sensitivity that is present and has been for a period of time. A root canal procedure will certainly solve the problem. This is the quick fix and unfortunately occurs in many private-practice settings. However, the real question is whether this degree of treatment is truly indicated and in the best interest of the patient. In the bigger picture, the patient needs a diagnosis and treatment plan to maintain the vitality of the dental pulp in a particular tooth or teeth and if possible to restore symptom-free function.²⁰ This approach to the problem is neglected or simply cast aside when even more extensive insults to the tooth in the form of a crown or root canal treatment and crown are offered. This is the antithesis to problem solving and turns dental treatment planning and treatment into nothing more than a technical trade that provides an identified service for a fee. Such “care” is driven by business models that dictate the need to treat with high-end services to be profitable, as opposed to managing patients’ problems in a preventive manner that maintains both tooth integrity and symptom-free function whenever possible. In dental practices that are run as managed profit centers, an investigative, compassionate, and caring approach may not be a priority that ensures the bottom line of fiscal solvency.

Tooth hypersensitivity, or more frequently identified as dentin hypersensitivity, is defined as a short pain arising from exposed dentin in response to stimuli. Typically, thermal, evaporative, tactile, osmotic, or chemical stimuli produce responses which cannot be ascribed to any other form of dental defect or disease^3,26 (except for incipient, undiagnosed, or unidentified caries). Mostly, the sensations dissipate quickly and completely when the stimulus is removed. While many theories have been proposed for this problem (see Recommended Additional Readings at the end of this chapter), the most likely is a change in fluid flow with the dentinal tubules that excites neural endings at the pulpal-dentin interface (classic hydrodynamic theory).^3,19,29,62 The size and patency of the dentinal tubules also have a direct bearing on the degree of sensitivity.⁴¹ Essential to patient management in these situations is (1) an understanding of what causes dentin hypersensitivity, (2) a thorough clinical assessment and identification of the etiologic factors, and (3) a diagnosis and reasonable treatment plan.¹³ Common etiologies for this malady have been identified as:

The two most common etiologies have been identified as gingival recession and attrition,⁹ but this should not bias the clinician. Exhaustive evaluation of the patient’s problem is warranted because different patient populations may present with a much wider range of etiologic factors. For example, recession or tooth wear that may be identified as etiologies may in themselves be caused by acid diets and irregular or excessive tooth-brushing habits.² Moreover, the overwhelming consumer craze for teeth whitening has contributed greatly to dentin hypersensitivity.³⁹

With the first etiology, a simple evaluation using a fiberoptics (transillumination),^47,72 biting tests, and magnification²³ can determine the extent of the problem and a possible solution (see Chapters 1, 3, and 4). In the second situation, simple desensitization procedures are indicated.^7,45,46,59 With etiologic factors 3 through 6, simple restorative procedures and possible changes in oral home-care practices would be advised. In the last scenario, vital bleaching, desensitization would seem to be the treatment of choice.^20,37,39 Without supporting data and a diagnosis to indicate that root canal treatment is warranted, the patient should not be subjected to needless procedures.²⁰ A final procedure that may in time serve to provide rapid and lasting desensitization for the patient is the use of lasers. There has been limited success thus far, but their use to block the permeability of dentinal tubules on a predictable basis seems both reasonable and attainable⁶⁷ (see Recommended Additional Reading).

Desensitization techniques and minimally invasive procedures to eliminate the patient’s hypersensitivity would seem to be the treatments of choice to manage the patient’s chief complaint in these situations. This approach goes hand in hand with the initial phases of vital pulp therapy. Many clinicians may not identify this approach to management as being within the scope of endodontics, because too often endodontics and the everyday use of the term are erroneously equated only with root canal treatment. Treatment modalities for vital pulp therapy do fall within the scope of endodontics and should be considered first before doing a root canal procedure.³³

Directives for Considering Vital Pulp Therapy

It is a reasonable goal of endodontic research to seek diagnostic and treatment methods that more predictably determine the status of the dental pulp and preserve the vitality of the pulp under all conditions, especially when the vital pulp has exposed. Preserving pulpal vitality would have several advantages. The current techniques of vital pulp capping or pulpotomy are much less complicated and time consuming than root canal procedures. From a public health perspective, reduction of the number of teeth requiring root canal treatment would lessen the economic burden of dental care and increase tooth retention.^42,49 In the lower-income sectors of the economy on a global basis, the choice of a root canal procedure is currently not a viable option.

Are Vital Treatment Procedures Viable Options in Contemporary Dentistry?

Yes, pulp capping can play a major role in pulp and tooth retention. Recent studies have provided a great insight into the pulpal responses to irritants (see Recommended Readings). Early, careful intervention to eliminate the etiologies for pulpal disease and prevent further damage to the pulp generally yields a positive outcome.⁵⁴ Research confirms the inherent capability of the dental pulp to heal, but at this point—with the currently available imprecise methods of pulpal assessment, variations in operative techniques, and variety of pulp treatment materials—there are limitations to an ideal response.

When challenged by irritants, the pulp has an amazing capacity to form a hard, reparative tissue, sometimes in the form of its original tissue, tubular dentin (Fig. 7-1), and sometimes in the form of a gnarled, irregular or irritational dentin (Fig. 7-2, A). The nature and intensity of the insult and the host’s response will usually determine the nature of the reparative tissue. The pulp tries to stand its ground, so to speak, by forming a calciotraumatic line to block the ingress of both bacterial toxins and bacteria themselves (see Fig. 7-2, B).

FIGURE 7-1 Normal tubular dentin showing mineralized, unmineralized, and partially mineralized dentin.

FIGURE 7-2 A, Gnarled dentin in apposition to normal dentin. B, Gnarled, irregular, irritational dentin (left) with evidence of the calciotraumatic line. Note normal dentin (right) and bacteria that have penetrated the tubules.

Ideally, the clinician should strive to prevent a pulpal exposure, especially under optimal conditions when there are no signs or symptoms of pulpal pathosis. A step-wise approach to caries excavation known as an indirect pulp cap is one possible treatment option that may prevent an exposure and allow for remineralization of the affected dentin or stimulate the formation of dentinal sclerosis and irritational dentin.^18,54,73 Unfortunately, there is no correlation between symptoms and the degree to which the pulp may be affected by the invasion of caries. The extent to which bacteria may have invaded the pulp cannot be determined preoperatively. Nevertheless, the pulp possesses some capability to respond favorably even in the presence of bacteria (Fig. 7-3).

FIGURE 7-3 Irregular, irritational dentin (left), presence of the calciotraumatic line, and bacteria in the tubules. Note how some of the bacteria have passed through the calciotraumatic line into tubules that formed with the irritational dentin.

When signs or symptoms are not of consideration and an exposure occurs, the visual appearance of the exposure (Fig. 7-4, A) and the amount of hemorrhage (see Fig. 7-4, B) must be assessed. Small exposures would have a better prognosis than large or multiple exposures. A small amount of hemorrhage is normal and will usually slow with sterile water, saline, or sodium hypochlorite lavage.^60,71 The use of chlorhexidine has also been shown to be effective in these situations.⁶⁰ Care must be taken to not probe into the exposure or otherwise mechanically irritate the pulp. The preparation should be kept moist because desiccation is a strong irritant to the vital pulp.⁶⁹ If the hemorrhage is profuse, the prognosis for maintaining pulpal vitality by pulp capping is poor. The use of strong hemostatic agents such as ferric sulfate or racemic epinephrine should not be used; the infusion of strong chemicals into the blood clot that forms may be deleterious to the pulp.⁶⁹

FIGURE 7-4 A, Mechanical exposure of a presumed normal pulp with no hemorrhage or exudates. B, Carious exposure of a pulp with hemorrhagic exudates.

When Is Treatment of the Vital Pulp Preferable to Root Canal Treatment?

Possibly the most important indication for vital treatment procedures is in the case of pulpal exposures on teeth with incomplete root formation. In these cases, preservation of pulpal vitality is an essential objective for all exposures—whether traumatic, mechanical, or carious—to permit normal apexogenesis. Removal of the pulp immediately eliminates the possibility of further root development, leaving the root canal with an open apex and the root itself with thin dentinal walls that cannot undergo thickening, owing to loss of the radicular pulp. Root canal procedures in teeth with open, immature apices are more complicated, more time consuming, and less predictable in terms of outcome. Teeth with large-diameter canals and thin-walled roots are more prone to fractures of all types.⁵,²⁷,²⁸,⁷²

Fortunately, the pulps of teeth with immature root formation have a more generous blood supply than teeth with fully formed roots and apical closure. As a consequence, they are more tolerant of injury and exposure to microorganisms. Vital treatment procedures are far more likely to succeed in teeth with open, immature apical development than in teeth with mature root formation. With these factors in mind, vital techniques should be considered even when symptoms of pulpitis are present.

PROBLEM SOLVING

Problem

A 9-year-old male was brought to the dentist with a fractured maxillary right central incisor. The tooth had symptoms of irreversible pulpitis. There were prolonged pain reactions to cold, and the patient had experienced episodes of moderate spontaneous pain relieved by over-the-counter analgesics. The parent related that the tooth was fractured in a playground accident at school a month earlier. There had been little pain initially, and because of the Christmas holidays, no treatment was sought. Clinical examination indicated a complete midcoronal horizontal fracture with exposure of the coronal pulp. The periapical film indicated that the tooth had an open, immature apex and the apical periodontal ligament space was widened 2 to 3 mm more coronally than what would be typical of a normal physiologic apical formation (Fig. 7-5, A).

FIGURE 7-5 A, Traumatic fracture of a maxillary right central incisor in a 9-year-old boy. The tooth was examined approximately 1 month after the accident and was symptomatic of irreversible pulpitis. B, Postoperative radiograph of Cvek pulpotomy with calcium hydroxide. C, One-year reevaluation radiograph. The tooth responded normally to pulp testing, and the apex was closed.

Solution

Although the symptoms and radiographic appearance of the periapical tissues suggested an irreversible pulpitis, the potential problems associated with root canal treatment of the open apex highlighted the need to consider a form of vital therapy. A direct pulp cap (partial pulpotomy, also known as the Cvek technique), was performed with calcium hydroxide,²⁵ in which a sterile high-speed diamond bur is used under copious water irrigation to surgically excise the inflamed pulp tissue. The excision is considered complete when the pulp stump no longer bleeds profusely. The intent is to remove the contaminated, degenerating tissue and create a new surgical wound that will respond favorably to the placement of calcium hydroxide. The pulp cap was covered and sealed with an amalgam restoration (see Fig. 7-5, B). Postoperatively, the symptoms gradually resolved. Sensibility testing in the subsequent months indicated a return to normal pulpal responses. One year later, a reevaluation radiograph indicated normal physiologic completion of apical formation (see Fig. 7-5, C). Root canal treatment was then completed in preparation for a post-retained restoration.

Discussion

This case was treated more than 30 years ago with materials available at the time, which were limited. Fortunately, the choice of materials has improved, and the prognosis for pulpal healing has improved as well. Nevertheless, the preoperative conditions were no different than many cases today, so this case illustrates the reparative potential of pulp tissue in teeth that exhibit immature root development. Had this treatment approach failed, apexification (techniques for nonvital pulps) would have been indicated (see Chapter 13), which 30 years ago would have consisted of multiple applications of calcium hydroxide over an 18- to 24-month period of time.²⁸

There is growing evidence that vital pulp treatment is effective for carious exposures on permanent teeth. Clinicians must remember that a carious exposure does not necessarily imply that bacteria actually reached the dental pulp. Often the demineralized front of dentin that contains bacterial byproducts has reached the pulp, but not the bacteria themselves. Studies have found that with techniques to be described, both direct pulp caps and coronal pulpotomies can preserve pulpal vitality with a very high degree of predictability.^11,17,32,33 Although the majority of patients in these studies were in the 10- to 13-year age range, one study included cases with patients as old as 45.¹⁷ These findings open up new and exciting avenues of research. With currently available materials and the potential of more new developments, vital therapy in many cases of carious exposure may be a viable and predictable treatment option in the future.²⁴

When Is Root Canal Treatment Preferable to Vital Pulp Treatment Procedures?

Preoperative pulp sensibility testing would be appropriate for teeth with large carious lesions, but some teeth may respond positively to tests and still have localized intrapulpal inflammation and tissue degeneration. Factors that have been cited as indications for pulpectomy are uncontrollable hemorrhage from the exposure site,⁵¹ purulent exudates emanating from the exposure site, and complete lack of bleeding. Purulent exudate (Fig. 7-6) would indicate an intrapulpal abscess for which no evidence exists that suggests a positive outcome for either pulp capping or pulpotomy. Similarly, if the exposure site is pale yellow and without hemorrhage or exudates of any type, the pulp may already be partially necrotic.

FIGURE 7-6 Exposure of a pulp with an intrapulp/>

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