Smooth surface decay forms on the flat, vertical sides of the tooth rather than in the deep grooves of the chewing surface. These lateral surfaces include the buccal or lingual sides facing the cheek or tongue, the cervical third near the gumline, and the proximal surfaces where adjacent teeth touch. Identifying this decay is challenging because it is often visually hidden or presents with subtle color and texture changes that differ from the typical dark spot seen elsewhere.
How Cavities on the Side Appear
The first visual sign of smooth surface decay is often an opaque, chalky white patch known as a white spot lesion, rather than a dark hole. This appearance results from demineralization, where acid draws minerals out of the enamel structure, making the area porous. When decay begins near the gumline, this chalky white spot is subtle and is often only visible when the tooth surface is dried.
As the decay progresses, the compromised enamel structure absorbs stains, causing the lesion to darken. The color shifts from white to light yellow, then to brown, and eventually to black as the decay penetrates deeper. An advanced smooth surface cavity may also be felt as a distinct rough or sticky spot when running your tongue over the area.
Decay occurring between two teeth, known as proximal decay, is the most difficult to spot visually without professional help. Because the decay starts at the contact point, it is hidden by the adjacent tooth. In some cases, a large proximal cavity may cause the visible side of the tooth to appear shadowed or a faint gray, indicating the underlying breakdown of the tooth structure.
Recognizing the Physical Sensations
A developing cavity on the side of a tooth can trigger distinct sensory experiences, often before a visible change is apparent. The most common sensation is heightened sensitivity, especially when consuming cold beverages, sweet foods, or acidic items. This reaction occurs once the decay has broken through the tough outer enamel layer, exposing the softer, porous dentin underneath.
The dentin contains microscopic tubes that lead directly to the tooth’s nerve center. Exposure of the dentin allows external stimuli to trigger a sharp, temporary pain. When decay has advanced deeper, you may experience a mild ache or discomfort when biting down or chewing, signaling that the structural integrity of the tooth is compromised.
A mechanical indicator of proximal decay is dental floss catching, tearing, or shredding when pulled through a specific spot between two teeth. This snagging is caused by the floss encountering a rough edge or the sharp margin of a developing cavity. If the floss consistently tears in the same location, it suggests the presence of a defect or a hole in the side surface of the tooth.
Why These Specific Areas Are Vulnerable
Smooth surface decay forms differently than the decay found in the deep pits and fissures on the chewing surfaces. Plaque accumulation is the primary factor, thriving in areas that are difficult for saliva and toothbrush bristles to reach effectively. Two areas are especially susceptible: the cervical third and the proximal surfaces.
The cervical area, located near the gumline, is vulnerable because the enamel is naturally much thinner there than on the rest of the tooth. The enamel thickness can be as little as 0.3 to 0.4 millimeters near the gumline. This means the decay process reaches the softer dentin layer much quicker.
The proximal surfaces, where teeth touch, create a sheltered environment ideal for plaque stagnation. Since the toothbrush cannot penetrate this tight space, plaque sits undisturbed, constantly producing acid that demineralizes the enamel. This combination of an acid-producing biofilm and the mechanical difficulty of cleaning makes the interproximal area a frequent site for decay.
Seeking Professional Confirmation and Care
Because decay on the side of a tooth, particularly between teeth, is often hidden, professional diagnosis is necessary for confirmation and treatment. Dentists rely on Bitewing X-rays, which are specialized radiographs that capture a detailed view of the crowns of the back teeth and the spaces between them. These images can reveal interproximal decay as a dark shadow long before it becomes clinically visible.
Treatment options depend on the stage of the decay. If the lesion is detected early, while still a white spot and confined to the outer enamel, the decay can often be reversed through professional fluoride treatments and improved oral hygiene. This process, called remineralization, works to restore the mineral content of the compromised enamel.
Once a physical hole or cavitation has formed, a filling is required to remove the decayed material and restore the tooth’s structure. For prevention, place the toothbrush bristles at a 45-degree angle toward the gumline to clean the cervical area effectively. For the proximal surfaces, flossing must involve curving the floss into a C-shape around the side of each tooth to thoroughly clean the surface below the contact point.