Dental hypersensitivity

INTRODUCTION
Dental hypersensitivity is a major problem. The pain and discomfort from this problem negatively affect the patient’s ability to practice oral hygiene. As a result, plaque builds up and the teeth and periodontal apparatus become damaged.
The following article reviews some of the common treatments for dental hypersensitivity (DHS) and gives a straightforward approach to treating DHS. It reviews some of the proposed theories for how DHS is caused and several treatments currently available on the market. It also reviews key issues to cover with a patient when DHS is found and treatment is started.

BACKGROUND
Proposed Mechanisms Resulting in Dental Hypersensitivity
There are currently 3 proposed mechanisms resulting in dental sensitivity.Under the first mechanism, nerve endings (nociceptors) located throughout the dentin are stimulated, resulting in sensitivity. Under the second mechanism, odontoblasts that are either chemically and or electrically related to nerves become stimulated, thus generating sensitivity. The third and most widely accepted mechanism is referred to as the hydrodynamic mechanism. Under this proposed mechanism, when stimulus is applied to dentin, it produces a displacement of the contents of dentinal tubules. This displacement then excites mechanosensitive nerve endings near the pulpal end of the tubules. Under this mechanism theory, the fluid within dentinal tubules obeys the laws of fluid movement, ie, stimuli cause movement of the fluid in the dentinal tubules that in turn causes stimulation of intradental nerves and a perception of pain. It is important to understand the mechanism of hypersensitivity to properly treat one’s patients.

Multifactorial Causes for Dental Hypersensitivity
Before dentists decide to treat patients with DHS, they must first explain very carefully that DHS rarely is caused by just one thing. It is important for patients to understand that most DHS conditions have a multifactorial etiology. A clear understanding of this will help patients understand that DHS may not have a quick fix. In many cases, DHS requires several small treatment steps to resolve. One of the most important factors is diet. Giving patients a clear understanding of how diet affects DHS and how changing it can improve DHS is very important. Microscopic studies have shown that when dentine is exposed for 5 minutes to fluids like red and white wine, citrus fruit juices, apple juice and yogurt, they remove the smear layer and open up dentinal tubules. The loss of the smear layer is known to enhance dental hypersensitivity. One good tip is to tell patients not to brush right after ingesting acidic food or drink. A small sip of water after ingesting acidic food or drink will go a long way in helping DHS. Another important factor is brushing. Show your patients how to brush properly and recommend they change their toothbrush every 3 months, as that also will go a long way in reducing DHS.

Effects of Dentin Exposure
Once dentin is exposed, it increases the likelihood of DHS. Dentin exposure is caused by recession or enamel loss. If the DHS is caused by recession alone, it is best treated by a connective tissue graft provided that the recession falls into a Miller’s Class I or II lesion. A Miller Class I lesion has recession above the mucogingival junction (MJC), with no bone loss. A Miller Class II lesion also has no bone loss, but the recession is beyond the MJC. If a dentist is presented with either of these types of recession, along with DHS, the condition can predictably be treated by a connective tissue graft. By contrast, it is difficult to explain to a patient when one of these types of lesions is treated by a restoration that may then become an untreatable endodontic lesion that leads to extraction of the tooth.
Miller Class III or IV lesions both involve bone loss along with recession. In those instances, a connective tissue graft may be needed to gain attached tissue. However, attempting to treat recession and DHS simultaneously is likely to be ineffective due to the bone loss. As a result, the dentist must look at alternate ways to treat the DHS.

Over-the-Counter Treatment Options
Unless there is an obvious etiology requiring immediate treatment, it may be preferable to have the patient try an over-the-counter (OTC) product for 2 to 4 weeks to treat the DHS. Specialized toothpaste or mouthrinses are a couple of good OTC options. However, it is important to understand how these products work because a patient will often ask the dentist to explain how these alleviate DHS. Toothpaste or mouthrinse that contains strontium salts and fluorides claim to treat DHS by occluding dentinal tubules. There are even some OTC toothpastes that contain formaldehyde, which supposedly destroys vital elements within the tubules. Currently, most desensitizing toothpastes contain a potassium salt; such as potassium nitrate, potassium chloride, or potassium citrate. Toothpastes that contain these substances are thought to treat DHS by diffusing along dentinal tubules and decreasing the excitability of intradental nerves by altering their membrane potential. One important concept that a dentist must understand is that these toothpaste or mouthrinse additives must be able to perform in such a manner that they overcome hydrostatic pressure. When an additive is moving within the tubules, hydrostatic pressure is preventing more additive from entering the tubules.8 This may be one reason that additive-enriched toothpastes or mouthrinses have limitations in treating DHS. Notwithstanding, some patients may experience DHS relief from using such OTC products, if only because of the “Hawthorne effect” and their psychological belief that the products should work.
A 2-week follow-up visit is recommended after a patient has tried an OTC product to treat DHS. If the patient experiences improvement in DHS, continued use of the OTC product is recommended, along with a subsequent 4-week follow-up visit to assess whether the patient has experienced any additional benefit from continued use of the OTC product.

In-Office Topical Application Options
If the patient does not experience marked improvement in DHS from the use of OTC agents, a topical application product is a suggested next step. In order to assess which topical application is appropriate for any given patient, the dentist must first determine whether the patient is missing any dentin. If dentin is missing, then topical applications containing dentin adhesive products such as varnish or bonding agents can be used. These types of applications can often produce immediate results; however, a potential downside is that they can be easily removed, thereby undermining their effectiveness. Moreover, such applications have limited effectiveness when no dentin is missing, as they do not easily adhere to enamel. Often, such topical agents are incorrectly prescribed or misused because the practitioner has no understanding of their limitations.
There are other topical products that can be applied to an exposed root to treat DHS. These products range from resins to glass ionomer cements. Resins seal exposed dentinal tubules and provide an immediate blockage of pain-producing stimuli to pulpal nerves. Glass-ionomer cements are hydrophilic and can also block pain-producing stimuli.

An Extended Contact Varnish Versus Conventional Fluoride Varnishes
An example of another professionally applied topical product that can provide some versatility in treating DHS is the light-cured extended contact varnish designed for site-specific application. One such product, Vanish XT (3M ESPE), is composed of resin-modified ionomer material that releases fluoride, calcium, and phosphate. According to the manufacturer, the product acts by filling dentin tubules, thereby blocking DHS pain and, once it is applied, it releases more fluoride than conventional fluoride varnish; doing so every time the patient brushes.