Tooth sensitivity, or dentin hypersensitivity, is a sharp, temporary pain occurring in response to external triggers like cold air, hot liquids, or sweet foods. While a cavity is a cause of sensitivity, this sudden discomfort does not automatically signal tooth decay. Many other dental conditions can lead to this painful sensation, often involving the exposure of the tooth’s inner layer.
The Physiological Mechanism of Sensitivity
The tooth structure has three main layers: the hard outer enamel, the softer inner dentin, and the central pulp containing the nerve. Enamel protects the dentin, which is honeycombed with millions of microscopic tubes called dentinal tubules. These tubules extend from the outer dentin surface inward to the nerve-rich pulp chamber.
When the protective enamel layer is worn away or the gum tissue recedes, the dentin and its tubules become exposed. The hydrodynamic theory explains the resulting pain. External stimuli, such as temperature changes or air movement, cause the fluid within the exposed dentinal tubules to rapidly shift.
This fluid movement stimulates mechanoreceptors on the nerves near the pulp, which interprets the signal as a sudden, sharp pain. The pain is transient, stopping almost immediately after the stimulus is removed, which is characteristic of this process.
Primary Causes Beyond Tooth Decay
Sensitivity frequently occurs due to factors other than bacterial decay, all of which lead to dentin exposure. Gum recession is a prevalent cause, where gum tissue pulls away from the tooth, uncovering the root surface. The root is normally covered by cementum, which is softer than enamel and easily worn away, leaving the underlying dentin exposed.
Enamel erosion results from regular exposure to high levels of acid, often from dietary sources like citrus fruits, carbonated drinks, or wine. Acids chemically dissolve the enamel structure, thinning the protective layer. Gastroesophageal reflux disease (GERD), which brings stomach acid into the mouth, is another source of chemical erosion.
Aggressive toothbrushing, known as abrasion, can wear down the enamel and cause gum recession. Using a hard-bristled brush or applying too much force physically strips away the enamel over time, especially near the gum line. This mechanical wear exposes the sensitive dentin layer.
Microscopic cracks or chips in the tooth structure, which may not be visible, can provide a pathway for external stimuli to reach the dentin and pulp. These cracks are often caused by teeth grinding or clenching (bruxism), which puts excessive stress on the enamel. Short-term sensitivity is also common following recent dental procedures like a new filling, crown placement, or professional cleaning. This post-procedure pain is temporary, resulting from pulp inflammation that subsides as the tooth heals.
Professional Diagnosis and Clinical Treatment Options
A dentist must accurately diagnose the source of the sensitivity, as treatment depends entirely on the underlying cause. The diagnostic process involves a visual examination and probing to check for decay, gum recession, or cracks. Radiographs (X-rays) are used to look for evidence of deep decay, bone loss, or abscesses.
The dentist may also perform a thermal or tactile test, applying a cold stimulus or lightly touching the sensitive area to pinpoint the location and type of pain response. If the sensitivity is non-decay related, several clinical treatments can provide relief.
In-office desensitizing agents, such as fluoride varnishes or prescription-strength gels, are applied to the exposed dentin. These substances strengthen the enamel and physically seal the dentinal tubules to block fluid movement. For significant gum recession, the dentist may apply a dental bonding resin or a sealant to create a protective layer over the sensitive surface. In severe cases where the nerve is inflamed or infected, a root canal procedure may be necessary to remove the damaged nerve tissue and eliminate the pain.
Managing Sensitivity Through Home Care and Prevention
For sensitivity not caused by decay, simple changes to daily routines can provide relief. The most common home treatment is the use of specialized desensitizing toothpastes. These products contain active ingredients like potassium nitrate, which calms the nerve’s pain response, or stannous fluoride, which physically blocks the openings of the dentinal tubules.
It takes several weeks of regular, twice-daily use for these toothpastes to be effective. Proper brushing technique is important for prevention, requiring a soft-bristled toothbrush and gentle, circular movements. Brushing too hard or using a medium- or hard-bristled brush can further damage enamel and exacerbate gum recession.
Reducing the intake of acidic foods and beverages helps prevent further enamel erosion. When consuming acidic drinks, using a straw can limit contact with the tooth surfaces. If teeth grinding is the suspected cause, wearing a nightguard can protect the teeth from mechanical forces that wear down enamel.