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
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
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
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
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
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