Clinical significance of hypersensitivityDentinal hypersensitivity, while neither life threatening nor a serious dental problem, can be a particularly
uncomfortable and unpleasant sensation for patients and can dictate types of foods and drinks ingested.
Patients may describe the condition as dull or sharp, vague or specific and intermittent or constant. Teet causing such symptoms are rarely considered to be as seriously affected as those affected by caries, endodontic problems or periodontal disease, however, the condition is nonetheless of sufficient concern to warrant appropriate and proper management. In most instances the condition can be managed by patients through appropriate home care using properly prescribed over the- counter products. These features of the condition negate, in the majority of cases, the need for expensive and lengthy professional care. Notwithstanding the above, the condition still requires an appropriate differential diagnosis since carious exposure of dentine surfaces, inflamed pulps or cracked cusps can produce symptoms similar to cervical dentinal hypersensitivity.
Treatment for hypersensitivity
There is a surprisingly large number of treatment options for managing dentinal hypersensitivity. Chemical or physical agents are used to either desensitize the nerve or cover the exposed dentinal tubules. The most common form of management is the placement of a topically applied agent applied either by a dental professional or by the patient at home. All currently available treatments appear to work.
Several criteria are recognized as constituting an ideal desensitizing agent. These include not irritating the pulp, being relatively painless to apply, easily applied, rapid action, permanently effective and should not discolour the teeth.20 Overall, patient responses are very subjective and thus treatment results are largely dependent upon the individual’s pain threshold.
Role of dental plaque
While there are many factors which can contribute to dentine hypersensitivity, plaque accumulation has often been cited as an important factor.23 Plaque accumulation on root surfaces may lead to demineralization of tooth structures which could be associated with patency of dentinal tubule orifices.23 It has been reported that patients who maintain good levels of plaque control are less likely to report dentine hypersensitivity.24 On the other hand, patients who have significant proportions of their root surfaces covered with dental plaque report more problems with dentine hypersensitivity.
Despite these findings, the influence of plaque on dentine hypersensitivity remains controversial. Interestingly, many patients with gingival recession have minimal plaque deposits yet still complain of sensitivity.
Nerve desensitization
Potassium nitrate
A number of studies have reported the efficacy of potassium nitrate for managing dentinal hypersensitivity.
While the Hodosh study was the first to report that potassium nitrate was a “superior desensitizer” this study was not well controlled and it was not until the studies of Tarbet et al that good evidence for the efficacy of potassium nitrate in managing dentinal hypersensitivity was demonstrated.
These controlled studies demonstrated that potassium nitrate at a concentration of 5% in a low abrasive toothpaste was able to desensitize dentine for up to four weeks compared to a control paste. Potassium nitrate in bioadhesive gels at 5% and 10% has also been shown to be effective in reducing dentinal hypersensitivity. Importantly, it has been shown that potassium nitrate does not induce any pulpal changes.
Despite these encouraging findings it is interesting to note that a recent Cochrane Database Systematic
Review failed to find strong evidence supporting the efficacy of potassium nitrate toothpaste for dentine
hypersensitivity.34 Nonetheless, this review did report that the differences which were noted were statistically significant in favour of treatment with potassium nitrate toothpaste.
The mechanism of action of potassium nitrate is largely unknown, although an oxidizing effect or blocking of tubules by crystallization has been proposed28 but not proven. The effect of potassium nitrate on dentinal fluid flow has been reported to be minimal even at a 30% concentration.35 A more likely explanation is that the potassium ions are the active component and that potassium nitrate reduces dentinal sensory nerve activity due to the depolarizing activity of the K+ ion,36 although this proposal has never been confirmed in intact human teeth
Anti-inflammatory agents
Corticosteroids
Anti-inflammatory agents such as corticosteroids have been proposed for use to manage dentine hypersensitivity. However, trials have not found them to be particularly useful.22 While it is presumed that these agents may induce mineralization leading to tubule occlusion, this view has yet to be validated38 and the validity of using such agents has been questioned.
Covering or plugging dentinal tubules
Calcium hydroxide
Several studies have reported on the effectiveness of calcium hydroxide in managing dentinal hypersensitivity. Its mode of action has been proposed to be via occlusion of dentinal tubules through the binding of loose protein radicals by calcium ions42 and increasing mineralization of the exposed dentine. Although immediately effective, the action of calcium hydroxide diminishes rapidly requiring multiple applications to maintain its effect.19 A negative feature of calcium hydroxide is its reported irritation of gingival tissues.
Casein phosphopeptides
A relatively new product on the market composed of casein phosphopeptides has been used for the management of dentinal hyperersensitivity. Despite a number of anecdotal case reports on various websites, to date there are no published studies reporting the efficacy of this material for dentinal hyperersensitivity.
Sodium fluoride
Many clinical studies have shown that treatment of exposed root surfaces with fluoride toothpaste and concentrated fluoride solutions is very efficient in managing dentinal hypersensitivity.43-45 The improvement
appears to be due to an increase in the resistance of dentine to acid decalcification as well as to precipitations in the exposed dentinal tubules. Tal et al.46 suggested that the probable desensitizing effects of fluoride are related to precipitated fluoride compounds mechanically blocking exposed dentinal tubules or fluoride within the tubules blocking transmission of stimuli.
Sodium monofluorophosphate
Toothpastes containing sodium monofluorophosphate have been shown to be effective in managing dentinal hypersensitivity.47,48 The mechanism of action of sodium monofluorophosphate is unclear.21 It does not appear to act by occluding dentinal tubules since scanning electronmicroscopic studies have failed to demonstrate any visual changes to the dentine surface treated with sodium monofluorophosphate.21 Any tubule occlusion which might occur does not appear to be permanent.
Stannous fluoride
Stannous fluoride in either an aqueous solution or in glycerine gelled with carboxymethyl cellulose is
effective in controlling dentinal hypersensitivity.50 The mode of action appears to be through the induction of a high mineral content which creates a calcific barrier blocking the tubular openings on the dentine surface.Alternatively, stannous fluoride may precipitate on the
dentine surface leading to occlusion of the exposed dentinal tubules.
Fluoride iontophoresis
Iontophoresis is the process of influencing ionic motion by an electric current and has been used as a desensitizing procedure in conjunction with sodium fluoride.42 Studies report that there is an immediate reduction in sensitivity after treatment with iontophoresis, but the symptoms gradually return over the ensuing six months.52 This method has enjoyed some popularity but more controlled studies are required.
Formaldehyde or glutaraldehyde
Claims have been made that formaldehyde and glutaraldehyde, through their ability to precipitate salivary proteins in dentinal tubules, can be used to manage dentinal
hypersensitivity. However, this effect
has been questioned since various formulations have been found to have little or no effect on dentinal hypersensitivity.Given that these agents are very strong tissue fixatives, they should be used with extreme
caution to ensure they do not come in contact with the vital gingival tissues.
Dentine sealers
Resins and adhesives
Sealing of dentinal tubules with resins and adhesives has been advocated for many years as a means of managing dentinal hypersensitivity.55 In general, results have been good but problems arise when the adhesive breaks away resulting in exposure of the tubules. This technique is generally reserved for cases of specific and localized dentinal hypersensitivity rather than generalized
dentinal pain.
Lasers
Both the Nd:YAG and CO2 lasers have been studied for their use in managing dentinal hypersensitivity. Both applications rely on their ability to occlude the dentinal tubules. The Nd:YAG laser has been used in conjunction with sodium fluoride varnish with encouraging results showing up to 90 per cent of the dentinal tubules being occluded through use of this combined therapy.56 CO2 laser irradiation and stannous fluoride gel has also been shown to be effective for inducing tubule occlusion for up to six months after treatment.57,58 While still largely experimental, this technique requires further scientific investigation before it becomes a clinically acceptable means of treatment.
Combination of desensitizing agents and fluoride
Because some effective desensitizing dentifrices (such as those containing potassium nitrate) were not fluoridated, people requiring relief from dentinal sensitivity and protection against dental caries needed to use both desensitizing and fluoridated dentifrices. As a result a number of well-controlled clinical studies have been carried out to determine the efficacy of potassium nitrate as a desensitizing agent in dentifrices containing fluoride.As early as 1992, the United States Food and Drug Administration granted Category 1 status to combination 5% potassium nitrate:fluoride dentifrices, indicating they were not only safe but also effective.
Restorative materials
The use of restorative materials is generally an invasive solution to the problem of hypersensitivity. Commonly used materials include composite resins and glass ionomer restorations. Generally this approach is reserved for situations where there has been significant prior loss of cervical tooth structure or as a last resort for a tooth which does not respond to other less invasive desensitizing protocols.
Periodontal surgery
There are numerous soft tissue grafting procedures which can be carried out to cover exposed root surfaces including lateral sliding grafts, free gingival grafts, connective tissue grafts and coronally repositioned flaps. While these procedures may cover exposed dentinal tubules, some are not very predictable in terms of their efficacy in root surface coverage. Soft tissue grafting for localized recession defects requires careful planning and an understanding of the anatomical defect to be treated. In general, soft tissue grafting for the management of sensitivity is not regarded as a very predictable treatment strategy.
Safety of commonly used at home desensitizing agents
Most “at home” desensitizing agents are generally restricted to dentifrices and mouthrinses containing one or a combination of the agents discussed above. Of these, the most common “active ingredients” are potassium nitrate, stannous fluoride, sodium fluoride, sodium monofluorophosphate and strontium chloride.For all products which are currently on the market as over-the-counter products extensive toxicity testing has already been carried out by the manufacturers and has been reviewed by various regulatory bodies to ensure both safety and efficacy. Although there is only minimal evidence to demonstrate superiority of one desensitizing agent over another, there is ample evidence that desensitizing toothpastes do provide benefit to the patients suffering from dentinal hypersensitivity. As a general rule, all well performed clinical studies published in the literature report safety assessments of the products under study.60 Moreover, in recent times, studies carried out within universities require the approval of a human ethics committee prior to commencement. All such committees require safety issues of products under investigation to be reported as part of the routine experimental protocol. Safety measures for toothpastes generally include adverse event data to elicit complaints/symptoms of the subjects at each examination time point and by evaluating changes in medical history and concomitant medications. All adverse reactions are recorded, listing the date of onset, duration, frequency, maximum intensity, seriousness, action taken and outcome. In addition, the oral soft tissues and perioral area should always be visually examined to evaluate effects that could be manifested as a tissue response to an irritant, soft tissue pathology or other clinically meaningful deviations from the normal. It is of particular note here that there are very few (if any) reports of adverse reactions to dentifrices containing the desensitizing agents listed above (Table 2). A Medline search (concluded December 2005) failed to find any citations regarding adverse reactions, toxicity or safety problems with strontium chloride or potassium nitrate. Only a few citations were found for fluoride formulations and these involved predominantly children. Since dentinal hypersensitivity is considered to be a response to a localized condition within individual teeth and is not indicative of, or related to, any known
systemic condition, management of dentinal hypersensitivity is not considered to mask or impact on any other systemic conditions which a patient might have.
There is no literature to support the concept that dentinal hypersensitivity is anything other than a well-localized dental problem. Finally, one of the most effective treatments for the majority of patients is simple daily plaque removal. Daily plaque removal over time allows demineralization of the dentinal tubules from salivary minerals and can alleviate much of the discomfort caused by exposed dentine. The use of an additional aid, such as a dentifrice containing additional agents which might expedite (or at least encourage) improved oral hygiene and daily plaque removal, is not considered harmful to either the tooth, the surrounding soft tissues, or the whole body.
CONCLUSION
Dentinal hypersensitivity is a relatively common and significant dental problem which can be successfully managed by a very wide variety of procedures, agents and formulations applied locally, either “in office” or “at home”. It is clear that some products appear to be more effective than others. For those products developed for self application at home, potassium nitrate, stannous fluoride, sodium fluoride, sodium monofluorophosphate and strontium chloride have all been extensively studied and shown to be not only safe to use but of benefit to individuals suffering from dentinal hypersensitivity.
has been questioned since various formulations have been found to have little or no effect on dentinal hypersensitivity.Given that these agents are very strong tissue fixatives, they should be used with extreme
caution to ensure they do not come in contact with the vital gingival tissues.
Dentine sealers
Resins and adhesives
Sealing of dentinal tubules with resins and adhesives has been advocated for many years as a means of managing dentinal hypersensitivity.55 In general, results have been good but problems arise when the adhesive breaks away resulting in exposure of the tubules. This technique is generally reserved for cases of specific and localized dentinal hypersensitivity rather than generalized
dentinal pain.
Lasers
Both the Nd:YAG and CO2 lasers have been studied for their use in managing dentinal hypersensitivity. Both applications rely on their ability to occlude the dentinal tubules. The Nd:YAG laser has been used in conjunction with sodium fluoride varnish with encouraging results showing up to 90 per cent of the dentinal tubules being occluded through use of this combined therapy.56 CO2 laser irradiation and stannous fluoride gel has also been shown to be effective for inducing tubule occlusion for up to six months after treatment.57,58 While still largely experimental, this technique requires further scientific investigation before it becomes a clinically acceptable means of treatment.
Combination of desensitizing agents and fluoride
Because some effective desensitizing dentifrices (such as those containing potassium nitrate) were not fluoridated, people requiring relief from dentinal sensitivity and protection against dental caries needed to use both desensitizing and fluoridated dentifrices. As a result a number of well-controlled clinical studies have been carried out to determine the efficacy of potassium nitrate as a desensitizing agent in dentifrices containing fluoride.As early as 1992, the United States Food and Drug Administration granted Category 1 status to combination 5% potassium nitrate:fluoride dentifrices, indicating they were not only safe but also effective.
Restorative materials
The use of restorative materials is generally an invasive solution to the problem of hypersensitivity. Commonly used materials include composite resins and glass ionomer restorations. Generally this approach is reserved for situations where there has been significant prior loss of cervical tooth structure or as a last resort for a tooth which does not respond to other less invasive desensitizing protocols.
Periodontal surgery
There are numerous soft tissue grafting procedures which can be carried out to cover exposed root surfaces including lateral sliding grafts, free gingival grafts, connective tissue grafts and coronally repositioned flaps. While these procedures may cover exposed dentinal tubules, some are not very predictable in terms of their efficacy in root surface coverage. Soft tissue grafting for localized recession defects requires careful planning and an understanding of the anatomical defect to be treated. In general, soft tissue grafting for the management of sensitivity is not regarded as a very predictable treatment strategy.
Safety of commonly used at home desensitizing agents
Most “at home” desensitizing agents are generally restricted to dentifrices and mouthrinses containing one or a combination of the agents discussed above. Of these, the most common “active ingredients” are potassium nitrate, stannous fluoride, sodium fluoride, sodium monofluorophosphate and strontium chloride.For all products which are currently on the market as over-the-counter products extensive toxicity testing has already been carried out by the manufacturers and has been reviewed by various regulatory bodies to ensure both safety and efficacy. Although there is only minimal evidence to demonstrate superiority of one desensitizing agent over another, there is ample evidence that desensitizing toothpastes do provide benefit to the patients suffering from dentinal hypersensitivity. As a general rule, all well performed clinical studies published in the literature report safety assessments of the products under study.60 Moreover, in recent times, studies carried out within universities require the approval of a human ethics committee prior to commencement. All such committees require safety issues of products under investigation to be reported as part of the routine experimental protocol. Safety measures for toothpastes generally include adverse event data to elicit complaints/symptoms of the subjects at each examination time point and by evaluating changes in medical history and concomitant medications. All adverse reactions are recorded, listing the date of onset, duration, frequency, maximum intensity, seriousness, action taken and outcome. In addition, the oral soft tissues and perioral area should always be visually examined to evaluate effects that could be manifested as a tissue response to an irritant, soft tissue pathology or other clinically meaningful deviations from the normal. It is of particular note here that there are very few (if any) reports of adverse reactions to dentifrices containing the desensitizing agents listed above (Table 2). A Medline search (concluded December 2005) failed to find any citations regarding adverse reactions, toxicity or safety problems with strontium chloride or potassium nitrate. Only a few citations were found for fluoride formulations and these involved predominantly children. Since dentinal hypersensitivity is considered to be a response to a localized condition within individual teeth and is not indicative of, or related to, any known
systemic condition, management of dentinal hypersensitivity is not considered to mask or impact on any other systemic conditions which a patient might have.
There is no literature to support the concept that dentinal hypersensitivity is anything other than a well-localized dental problem. Finally, one of the most effective treatments for the majority of patients is simple daily plaque removal. Daily plaque removal over time allows demineralization of the dentinal tubules from salivary minerals and can alleviate much of the discomfort caused by exposed dentine. The use of an additional aid, such as a dentifrice containing additional agents which might expedite (or at least encourage) improved oral hygiene and daily plaque removal, is not considered harmful to either the tooth, the surrounding soft tissues, or the whole body.
CONCLUSION
Dentinal hypersensitivity is a relatively common and significant dental problem which can be successfully managed by a very wide variety of procedures, agents and formulations applied locally, either “in office” or “at home”. It is clear that some products appear to be more effective than others. For those products developed for self application at home, potassium nitrate, stannous fluoride, sodium fluoride, sodium monofluorophosphate and strontium chloride have all been extensively studied and shown to be not only safe to use but of benefit to individuals suffering from dentinal hypersensitivity.
