Interproximal cavities, commonly known as cavities between teeth, are a frequent but often unseen form of dental decay. Unlike cavities that form on chewing surfaces, these develop in the narrow spaces where two adjacent teeth meet. Their location makes them challenging to spot during routine at-home inspection, often allowing the decay to advance silently. Because the decay begins beneath the external surface of the enamel, understanding the subtle indicators and specialized detection methods is key to preventing significant dental damage.
Identifying Interproximal Cavities: Signs and Symptoms
Since interproximal cavities hide between teeth, patients rarely see the decay until it is quite advanced. Subtle sensory and tactile changes are often the first warnings. You might notice localized sensitivity to temperature, such as a sharp twinge when consuming hot coffee or ice water, or an uncomfortable sensation when eating sugary foods. This sensitivity indicates that the protective enamel layer has been breached, exposing the underlying dentin.
A common tactile sign is when dental floss repeatedly snags, shreds, or breaks in one specific spot. This is often due to the floss catching on a rough edge created by the early decay process breaking down the enamel surface. Another indicator is if food seems to get trapped in the same spot more frequently than before. This packing of food can result from the decay creating a small void or disrupting the normal, tight contact between the teeth.
In later stages, you may experience persistent discomfort or sharp pain when biting or chewing, suggesting the decay has progressed deeply into the tooth structure. Occasionally, a grayish or brown discoloration may become visible near the gum line, but this visual cue usually only appears once the decay is extensive. Bad breath or a persistent unpleasant taste can also be a sign, as the hidden decay traps bacteria and debris that release foul odors.
Why Decay Thrives Between Teeth
Decay thrives in the interproximal space due to the unique environment created by the close proximity of two teeth. This area, known as the contact point, is shielded from the cleansing action of a toothbrush and the abrasive forces of chewing. Plaque, a sticky film of bacteria and food particles, easily accumulates and remains undisturbed in this tight crevice.
The bacteria within this trapped plaque consume residual sugars from the diet and produce acid as a metabolic byproduct. This acid then attacks the enamel surface where the two teeth touch, initiating a process called demineralization. Unlike the rest of the tooth surface, the interproximal area does not benefit significantly from the neutralizing effects of saliva flow, which normally helps wash away acids and buffer the mouth’s pH.
The decay process often starts just below the enamel surface at the contact point, tunneling inward. Once the decay breaches the outer enamel, it rapidly spreads through the softer underlying layer of dentin. Furthermore, a cavity starting on one tooth can easily spread to the adjacent tooth because both surfaces are exposed to the same acid attack and high concentration of decay-causing bacteria.
How Dentists Locate Hidden Cavities
Because these cavities are almost impossible to see during a standard visual examination, dentists rely on specialized diagnostic tools. The most effective method for detecting interproximal decay is the use of bitewing X-rays. These specific radiographs are taken with the patient biting down on a film holder, which provides a detailed, side-by-side view of the crowns of the back teeth.
The X-ray image reveals the decay as a darker, radiolucent area, indicating mineral loss within the tooth structure. This allows the dentist to see the decay that has started beneath the intact surface of the contact point. Without bitewing X-rays, interproximal cavities often go undetected until they are large enough to cause pain or collapse the enamel surface.
Other diagnostic aids may be used to confirm or supplement the X-ray findings. Transillumination involves shining a bright fiber-optic light through the teeth; decay appears as a dark shadow because the demineralized area does not transmit light effectively. Dentists may also use a dental explorer, or probe, to gently assess the tooth surface for soft spots, but this is typically reserved for areas where the decay has progressed enough to break through the enamel.
Treatment Options and Prevention Strategies
Treatment for an interproximal cavity depends on how far the decay has progressed. For decay confined to the enamel, a dentist may recommend a minimally invasive approach, such as applying a highly concentrated fluoride varnish to encourage remineralization. However, if the decay has reached the dentin, the standard treatment is a dental filling.
This procedure involves the dentist accessing the decay, usually by drilling through the biting surface or the side of the tooth, to remove the infected material. The resulting void is then restored with a filling material, typically a composite resin that matches the natural tooth color. For very large cavities that have severely compromised the tooth structure, a full or partial crown may be necessary to restore function and protect the remaining tooth.
Preventing interproximal cavities focuses on disrupting the plaque accumulation in the tight spaces that toothbrushes cannot reach. Daily flossing or the use of interdental brushes is the most effective preventive measure, as it physically removes the bacterial plaque from between the teeth. Using fluoride products, such as fluoride toothpaste and mouth rinses, also helps, as fluoride strengthens the enamel and makes it more resistant to acid attacks.