ALMOST on a daily basis, patients come to see me because they are experiencing what they describe as an ‘edging’ or ‘shocking’ when they eat or drink anything sweet or sour, or when the food is hot or cold, or even with simply brushing. If you suffer from this, then you are among the approximately 60,000 Guyanese adults who suffer from dentin hypersensivity.

Dentin is mineralized tissue transected from the pulp chamber (at the centre of the tooth) to the enamel, or cementum, by minute tubules. Within the tubules are protoplasmic projections (‘tentacles’ of cells), with the cell body itself being located in the pulp chamber. Stimulating these cells emits only one sensation: Pain.

There are currently four hypotheses of pain transmission through dentin, of which the hydrodynamic theory is the most widely accepted. According to this theory, the movement of fluids within the dentin and pulp stimulates the nerves, causing pain. All external stimuli translate into hydrodynamic changes that alter the pulp equilibrium and elicit pain. So, even contact with air can result in pain.

Pain can be caused by mechanical, chemical, thermal (temperature) or bacterial stimuli. Stimulation sources may include: Toothbrushing, digital (finger) probing; dessication (a blast of air); acids; sweet; sour; hot and cold products; and acid products from plaque bacteria.

There are varied predisposing factors to dentinal hypersensitivity, but to no single cause. The tooth becomes sensitive after enamel loss or root surface exposure. Enamel loss follows mechanical wear (biting surface wear), neck abrasion or possibly tooth flexure after grinding, which fractures enamel rods chemical erosion (acid foods or stomach regurgitation), gingival   recession (retracting gums) and subsequent tooth root exposure allow more rapid and extensive exposure of dentinal tubules because the cementum layer overlying the root surface is thin and easily removed.

The many causes of gingival retraction include normal aging, chronic periodontal disease, abnormal tooth position in the dental arch, periodontal surgery, incorrect tooth brushing habits and root preparation for crowns. All of the precipitating factors allow the exposure of dental tubules, which create the condition for dentin hypersensitivity.

Treatment modalities fall into two main categories: Chemical and physical. All available treatments work to differing degrees, depending on the treatment and severity of the patient’s hypersensivity. Pain is extremely subjective, so that effective treatment often depends on the individual’s pain threshold. Some desensitizing agents can be used at home; others require a visit to the dentist.

Chemical desensitizing agents can be sub-classified by their action: Antiflammatory, protein precipitating, and tubule blocking. Corticosteroids, one of the many groups of chemical agents, have been used topically for their anti-inflammatory effects, but are not particularly effective.

The second group of chemical agents, the protein precipitants, includes silver nitrate and zinc chloride. Silver nitrate was widely used in the past. Unfortunately, both substances cause teeth to stain permanently, and are harmful to gums and pulp. Strontium chloride and formaldehyde (in Sensodyne toothpaste) belong to the group of agents that precipitate proteins within the tubule. I usually recommend this form of treatment as the initial therapeutic strategy. If this is not effective, then there are other options. Other drugs used to treat the condition include, calcium hydroxide, fluoride, and sodium citrate. Patients may also be treated with composites (fillings), resins varnishes, sealants, soft tissue grafts, glass ionmer cements and laser sealing of the tubules.