Teeth sensitivity (dentin hypersensitivity) is characterized by short, sharp pain caused from exposed teeth in response to stimuli, typically thermal (hot and cold), evaporation (cold air), tactile, osmotic or chemical (sweet or sour foods).
Though teeth sensitivity can affect individuals of any age, it is more common in the age group of 30-40 years. Relatively more women are affected than men. The most affected teeth are canines and premolars of both the upper and lower arches equally.
Exposed dentin is the basic cause of sensitive teeth
To know clearly the causes of sensitivity, we should know the structure of tooth. Tooth consists of upper visible crown region and lower invisible root region inside the gum. A layer of enamel protects the crown region and cementum protects the root region.
At the center is the region called pulp having soft tissues, blood vessels and nerves. In between the outer enamel/cementum layer and inner pulp is another layer called dentin. Dentin consists of microscopic dentinal tubules and integrally connected to pulp.
The physiological reaction in either dentin or pulp affects the other. Odontoblasts are the major cell components of dentin and pulp. The extensions of odontoblasts called odontoblastic processes extend through the entire thickness of dentin from pulp to enamel and also occupy the dentinal tubules.
Inside the dentinal tubules odontoblastic processes are surrounded by dentinal fluid which accounts for nearly 20% of dentin volume. Dentinal fluid is formed from pulp blood supply and is the communication medium between the outer regions of the dentin and pulp.
Teeth sensitivity is due to fluid movement and fluid force inside dentinal tubules. Not all exposed dentin cause sensitive teeth. There are wider dentinal tubules with no smear layers or thinner smear layers in sensitive dentin when compared to non-sensitive dentin.
Pain or sensitivity perception is by the activation of dentinal nerve fibers (A-fibres) present on the pulpal wall. The stimuli activating these nerves are, rapid outward flow caused by capillary forces, contraction and outward flow due to cold and hydrodynamic flow caused by sweetness and sourness.
Causes leading to dentin exposure and sensitive teeth
The erosion of enamel and exposure of dentin may be due to a number of causes. Once the protective enamel or cementum are damaged pressure, temperature and other stimuli cause the teeth to become sensitive.
Poor oral hygiene
Poor oral hygiene causes food decay in the mouth and causes plaque and tartar formation on the teeth leading to caries, cavities, gum recession and dentin exposure.
Faulty tooth brushing
Brushing too hard erodes enamel and exposes dentin. Vigorous brushing, excessive forces and use of hard-bristled brush can erode the enamel and cause recession of gum tissue, exposing the underlying dentin .
Cracked or chipped teeth
Cracking and chipping of teeth exposes the dentin and causes bacterial infections.
Diseases of gum and teeth
Certain inflammations and diseases of gum like pyorrhea, gingivitis and periodontal diseases may cause sensitivity by exposing and damaging the dentin.
Acidic foods like pickles, yogurt, sour tasting fruits and carbonated soft drinks can cause enamel erosion and expose the dentin. Some teeth whitening products and pastes and some mouthwashes can be acidic in nature and erode enamel. Exposure to stomach acids may occur in gastroesophageal reflux disease (GERD) and cause enamel erosion.
Causes of teeth attrition
Attrition due to grinding of teeth affects teeth structure, initially affecting the enamel and then the underlying dentin. Once past the enamel, attrition can quickly destroy the softer dentin. The most common cause of attrition is bruxism. Normal functional actions like biting and chewing do not erode enamel.
Routine clinical procedures
Clinical procedures like cleaning, crown placement, filling, root canal treatment, orthodontics or restoration can cause temporary sensitivity which may last for 4-5 weeks.
Recent trends in management of teeth sensitivity
Foremost thing in the management of sensitivity is good oral hygiene. A soft bristled brush with a small head must be used to keep the gums healthy and prevent gums from recession.
Brushing must be done in a small circular movement for each tooth without excessive use of force covering all the surfaces of the tooth. Highly abrasive tooth powder or pastes should not be used.
The sensitivity will persist unless the exposed open tubular apertures are sealed by a smear layer or any other sealant. In the management of sensitivity, the method used should not cause pain or irritation, should not stain the teeth and should be easy in application.
At-home treatments including desensitizing pastes, gels and chewing gums containing fluoride, strontium chloride, potassium citrate or potassium nitrate, have been found effective in the control of sensitivity.
In-office sensitivity treatments at a clinic include sealants, fillings over the exposed roots and applying fluoride varnishes, sodium monofluorophosphate, fluorosilicates, sodium fluoride, stannous fluoride, potassium oxalate, conventional dentin bonding agents (DBA), hydroxyethyl methacrylate (HEMA), bioglass, calcium silicate cement, lasers, casein phosphopeptide or amorphous calcium phosphate.
By removing the etiological factors and causes and with proper treatment, occurrence and recurrence of sensitivity of teeth can be even prevented.
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Human tooth diagram
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Image author: KDS4444 (K. D. Schroeder)
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1.Miglani S, Aggarwal V, Ahuja B. Dentin hypersensitivity: Recent trends in management. J Conserv Dent 2010;13:218-24
2.Brännström M. Etiology of dentin hypersensitivity. Proc Finn Dent Soc. 1992;88 Suppl 1:7-13.
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