Dentin hypersensitivity (abbreviated to DH, or DHS, and also termed sensitive dentin, dentin sensitivity, cervical sensitivity, and cervical hypersensitivity) is dental pain which is sharp in character and of short duration, arising from exposed dentin surfaces in response to stimuli, typically thermal, evaporative, tactile, osmotic, chemical or electrical; and which cannot be ascribed to any other dental disease.
A degree of dentin sensitivity is normal, but pain is not usually experienced in everyday activities like drinking a cooled drink. Therefore, although the terms dentin sensitivity and sensitive dentin are used interchangeably to refer to dental hypersensitivity, the latter term is the most accurate.
The pain is sharp and sudden, in response to an external stimulus. The most common trigger is cold, with 75% of people with hypersensitivity reporting pain upon application of a cold stimulus. Other types of stimuli may also trigger pain in dentin hypersensitivity, including:
Thermal – hot and cold drinks and foods, cold air, coolant water jet from a dental instrument.
Electrical – electric pulp testers.
Mechanical–tactile – dental probe during dental examination, periodontal scaling and root planing, toothbrushing.
Osmotic – hypertonic solutions such as sugars.
Evaporation – air blast from a dental instrument.
Chemical – acids, e.g. dietary, gastric, acid etch during dental treatments.
The frequency and severity with which the pain occurs are variable.
Cross section of a tooth. Non-dentin layer is covered by enamel or cementum and gingiva.
An odontoblast cell showing odontoblast process (not in proportion – in reality this process is far longer than the body of the cell).
The main cause of DH is gingival recession (receding gums) with exposure of root surfaces, loss of the cementum layer and smear layer, and tooth wear. Receding gums can be a sign of long-term trauma from excessive or forceful toothbrushing, or brushing with an abrasive toothpaste (dental abrasion), or a sign of chronic periodontitis (gum disease). Other less common causes are acid erosion (e.g. related to gastroesophageal reflux disease, bulimia or excessive consumption of acidic foods and drinks), and periodontal root planing. Dental bleaching is another known cause of hypersensitivity. Other causes include smoking tobacco, which can wear down enamel and gum tissue, cracked teeth or grinding of teeth (bruxism).
Dentine contains many thousands of microscopic tubular structures that radiate outwards from the pulp; these dentinal tubules are typically 0.5–2 micrometres in diameter. Changes in the flow of the plasma-like biological fluid present in the dentinal tubules can trigger mechanoreceptors present on nerves located at the pulpal aspect, thereby eliciting a pain response. This hydrodynamic flow can be increased by cold, air pressure, drying, sugar, sour (dehydrating chemicals), or forces acting onto the tooth. Hot or cold food or drinks, and physical pressure are typical triggers in those individuals with teeth sensitivity.
Most experts on this topic state that the pain of DH is in reality a normal, physiologic response of the nerves in a healthy, non-inflamed dental pulp in the situation where the insulating layers of gingiva and cementum have been lost; i.e., dentin hypersensitivity is not a true form of allodynia or hyperalgesia. To contradict this view, not all exposed dentin surfaces cause DH. Others suggest that due to the presence of patent dentinal tubules in areas of hypersensitive dentin, there may be increased irritation to the pulp, causing a degree of reversible inflammation.