Dentin is the soft, porous tissue lying beneath the protective layers of tooth enamel and cementum, forming the bulk of a tooth’s structure. When this outer covering is lost, dentin becomes exposed, leading to dentin hypersensitivity. This exposure creates a direct pathway to the tooth’s nerve center, the pulp, which is why everyday activities can suddenly trigger sharp, intense pain.
The Structure and Sensation Pathway of Dentin
Dentin is not a solid mass but is permeated by millions of microscopic tunnels called dentinal tubules, which run from the outer surface inward toward the pulp chamber. Each tubule contains fluid and a small extension of the cells that form dentin, known as odontoblasts. These tubules act as a transmission line, connecting the tooth’s exterior to the sensitive nerves housed in the pulp.
The mechanism for how exposed dentin registers pain is primarily explained by the Hydrodynamic Theory. This widely accepted theory posits that external stimuli, such as cold air or sugary drinks, cause a rapid movement of the fluid within the open dentinal tubules. This fluid movement creates pressure changes inside the tubules that mechanically activate the sensory nerve endings in the pulp.
The nerve registers a painful signal, even though the stimulus is not directly touching the nerve. For instance, external stimuli cause fluid movement—either inward or outward—which excites the mechanoreceptors near the pulp. The degree of pain is directly related to the number and width of the exposed, open tubules.
Understanding Dentin Hypersensitivity
Dentin hypersensitivity is characterized by a specific type of pain. The sensation is sharp, sudden, and short-lived, lasting only as long as the external stimulus is present. This transient nature distinguishes it from the dull, lingering ache associated with a cavity or other deeper dental problems.
The pain can be triggered by a wide range of common factors that cause fluid movement in the exposed tubules. Common thermal triggers include sipping a cold drink, inhaling cold air, or consuming hot food. Chemical and osmotic stimuli are also frequent causes, such as eating sweet or acidic foods, which draw fluid out of the tubules.
Even simple mechanical or evaporative forces can provoke the sharp sensation, including the light touch of a toothbrush bristle or the quick evaporation caused by an air blast during a dental check-up. The sensitivity can significantly affect a person’s quality of life, making routine eating and drinking uncomfortable.
Common Causes of Dentin Exposure
Dentin exposure occurs when the two main protective layers, the hard enamel on the crown and the thinner cementum on the root, are compromised. One common cause is gum recession, where the gum tissue pulls back and exposes the root surface. Since cementum is much softer than enamel, it wears away quickly, leaving the dentin exposed.
Gum recession is often a consequence of aggressive toothbrushing, especially with a hard-bristled brush, or is linked to periodontal disease. Another primary cause is enamel erosion, which is the chemical loss of tooth structure due to acid exposure. This acid can come from frequent consumption of highly acidic foods and drinks or from intrinsic factors like stomach acid reflux (GERD).
Physical wear and tear also contribute to dentin exposure through processes like abrasion and attrition. Abrasion involves the wearing away of tooth structure by external objects, such as overly forceful brushing or using abrasive toothpaste. Attrition is the wear resulting from tooth-to-tooth contact, often seen in individuals who grind their teeth, a condition known as bruxism.
Managing Sensitivity and Protecting Dentin
Relief from dentin hypersensitivity often begins with changes in daily oral hygiene practices. Using a soft-bristled toothbrush and adopting a gentler technique can prevent further wear of the protective layers. Desensitizing toothpastes are an accessible at-home treatment that contains active ingredients to interrupt the pain signal.
Some desensitizing toothpastes utilize compounds like potassium nitrate, which works by diffusing along the tubules to decrease the excitability of the nerve fibers in the pulp. Other formulations, such as those containing stannous fluoride or arginine and calcium carbonate, work by physically blocking the open dentinal tubules. This occlusion prevents the fluid movement that triggers the pain response.
If at-home care does not provide sufficient relief, professional treatments are available from a dentist. In-office options include the application of high-concentration fluoride varnishes or gels, which help to block the tubules by forming mineral precipitates. Dentists can also apply bonding agents or resin materials to seal the exposed dentin surface. For severe gum recession causing root exposure, a surgical gum graft may be recommended to cover the exposed area and restore the natural protective barrier.