Sensitive teeth, also known as dentin hypersensitivity, is a common malady that is experienced by almost 30% of the U.S. population at some point in their lives. It is a sharp, momentary pain felt by the teeth due to a variety of stimuli – from pressure changes, to temperature and electrical changes. Tooth sensitivity has a bi-modal distribution peaking initially between 20-30 year olds, and again in the 50 year olds.

Tooth sensitivity is very common in premolars and canines, whose facial surfaces near the cervical aspect are generally affected. The initial cause in majority of cases is gingival recession, which in turn can be caused by periodontal diseases, improper brushing or overzealous brushing of teeth, or some periodontal treatment.

Theory of sensitive teeth

There have been different theories explaining tooth sensitivity, the most widely accepted of which is the Hydrodynamic Theory of Martin Brannstrom. It proposes that there are areas of the dentin that are exposed to the external environment. Within the dentin are numerous fluid-containing microtubules or canals that lead to the nerve-rich and sensitive pulp. Changes in temperature, pressure, hydration status, and electrical or osmotic gradient cause movement of the fluid by capillary force. This then stimulates the nerves in the pulpal surface. This results in short, sharp stabbing pains.

According to this theory, pain transmission and sensation is directly proportional to the radius of the tubules, in that reduction of the tubular radius by half significantly reduces pain. Corollary to that, occlusion of the tubules or anything that stops the movement of the fluids inside the tubules will result to pain relief.

Risk factors associated with sensitive teeth

Practices that result to enamel damage and exposure of the dentin are all considered risk factors. Overzealous brushing, toothbrush abrasions, chemical erosions, and gingival recession all have the potential to expose the dentin. Excessive dietary intake of citrus fruits and juices, carbonated drinks, wines and ciders have also been cited as potential risk factors. Eating disorders and other medical problems, such as GERD, are also risk factors as then expose the enamel to undue concentrations of acid.

Tooth decay, dental fractures or cracks, and ill-fitting dentures and mouth guards can also predisposed to dentin exposure, and therefore tooth hypersensitivity.

Diagnosis of sensitive teeth

Diagnosis is made by visually examining the teeth and getting a detailed dietary history from the patient to identify possible causes of the tubules being exposed. A thorough oral examination is done to identify other dental conditions that could be the underlying cause for the symptom of dentin hypersensitivity (e.g. tooth decay and cavitation, microfractures and cracks, sealant failure, gingival infection). If found, these entities are managed first.

Treatments fr sensitive teeth

The patients’ thresholds for pain vary considerably and so pain response is difficult to assess objectively. But any tooth pain should be investigated properly to prevent further damage that otherwise is correctable.

Various treatments are available, depending on the degree of tooth sensitivity, the cause of the sensitivity, and the choice of the patient and dentist. The simplest modalities involve home application of fluoride, the use of high fluoride content toothpastes, and dentrifices, among which, the dentrifices are the most widely used owing to their effectivity, affordability, and ease of use. For the more advanced disease, invasive procedures such as surgery may be offered. Less invasive procedures include the application of desentisizers, whose main ingredients are:

• potassium nitrate
• stannuous fluoride
• strontium chloride

Potassium Nitrate (KNO3) ions in 5% concentration are believed to work by reducing nerve excitation. By bathing the nerve cells with high concentrations of potassium, the threshold potential is increased so that an impulse will not occur no matter how strong the stimulus. With no impulse elicited, no pain is felt. Some studies show that KNO3 can obliterate tubules, and hence obliterating any stimulus from the dentin surface. However, a meta-analysis has shown that KNO3 is better used with an osmotic agent, such as dimethylisosorbide (DMI), since the agent enhances the distribution of the KNO3 into the pulp. The microtubules have constrictions and tight junctions that may block or further slow down the transport of KNO3 alone. When DMI was added into the solution, there was significant improvement in the delivery, resulting in more rapid pain relief from tooth hypersensitivity. The resultant comfort was profound and lasting.

Stannous fluoride is known to have antibacterial actions that help reduce plaque formation, inhibit gingivitis and suppress bad breath caused by bacteria. Aside from these actions, stannous fluoride has been used for decades in the treatment of dentin hypersensitivity. It has been studied that stannous fluoride works by chemical precipitation of stannous ions, thereby occluding the dentinal microtubules and eliminating the pain stimulus. A 0.4% solution of stannous fluoride in gel or toothpaste dentrifice has been widely used for years and has shown effective therapeutic remedy for tooth sensitivity.

A limitation of stannous fluoride is tooth staining caused by its long-term used. However, a study done in 2006 added sodium hexametaphosphate (SHMP), calcium-seqeuestering agent with extrinsic whitening activity, to stannous fluoride to reduce the staining problem. The degree of tooth whitening was not discussed, however, it concluded that the addition of SHMP did not significantly reduce the activity and effectivity of stannous fluoride in relieving tooth hypersensitivity.

Strontium Chloride also works by blocking the dentin microtubules, thus stopping the transmission of the stimulus into the pulp. Usually in the form of effervescent mouthwash, it dispenses a 2-15% concentration of strontium ions by weight. In this aqueous solution, strontium ion is released and it strongly binds to the organic fraction of the teeth: dentin and cementum. It penetrates the depth of the dentin tubules and binds to the bicolloidal of the organic matrix, as such, an effective transmission blockade is effected.