Interproximal decay, commonly known as a cavity between teeth, occurs on the surfaces where two adjacent teeth touch. These cavities are particularly challenging because they develop below the contact point, an area nearly impossible for a patient to see during a self-examination. This shielded location allows the decay to progress silently, often without causing pain or other noticeable symptoms until it has advanced significantly.
The Early Visual Clues
The actual decay begins beneath the enamel surface, making visual identification difficult. The earliest visible change a person might notice is not a hole, but a subtle alteration in the tooth’s appearance near the gum line. This can manifest as a small, faint white or chalky spot, which indicates the initial demineralization of the enamel.
If the decay is allowed to progress further, it may eventually become visible as a dark shadow. This shadow is not the cavity itself, but rather the internal deterioration of the dentin layer showing through the translucent enamel. This gray or dark coloration is typically seen only when the decay is extensive enough to reach the outer edge of the tooth.
In advanced cases, the decay may break through the enamel, creating a brown or black spot or a noticeable pit near where the teeth meet. At this stage, the structural integrity of the tooth is compromised, and the decay is often far past its initial formation. For decay that is truly hidden between the teeth, visual identification by the patient is generally unreliable.
Recognizing Non-Visual Indicators
Because interproximal cavities are difficult to see, physical sensations are often the first alert that decay is present. A common indicator is a heightened sensitivity, particularly a brief, sharp “zing” when consuming cold drinks, hot foods, or sugary treats. This sensitivity suggests that the decay has eroded the enamel and is now affecting the underlying dentin, the softer layer closer to the tooth’s nerve.
Issues with flossing can also serve as a localized warning sign of a problem between two specific teeth. If the dental floss consistently shreds, frays, or catches in the same spot, it may be snagging on a rough edge or a small break in the enamel caused by the developing cavity. A persistent, localized foul taste or chronic bad breath may also signal interproximal decay.
This unpleasant odor or taste occurs because food debris and bacteria become trapped in the small space created by the decay, and the normal flow of saliva cannot wash them away. Additionally, some people experience mild, localized discomfort or a strange pressure when biting or chewing, especially on harder foods. This is a sign that the tooth structure is weakening under the force of mastication.
How Dentists Confirm Hidden Decay
Because interproximal decay is visually shielded, professional diagnostic methods are routinely used to confirm its presence. The most accurate and frequently used tool is the bite-wing X-ray, which provides an image of the crowns of the upper and lower back teeth in a single view. These images are necessary because X-rays can penetrate the hard enamel and dentin, revealing the internal structure that is otherwise hidden.
On a bite-wing X-ray, the decay appears as a dark shadow or notch, often triangular in shape, located just below the point where the teeth touch. Healthy enamel and dentin are dense and appear white or gray on the image, while the decayed, less dense area appears darker, or radiolucent. Dentists grade the severity of the cavity based on how far this shadow has extended into the tooth layers.
During a clinical examination, the dentist uses a small mirror to inspect visible surfaces and may employ a dental explorer. This thin, pointed instrument checks for changes in enamel texture, such as soft or sticky spots that indicate a loss of mineral content. Advanced tools, such as transillumination devices or laser fluorescence units, may also be used to shine light through the tooth or measure structural changes.