A dental cavity, formally known as dental caries, is permanent damage to the tooth’s hard surface caused by acid-producing bacteria. This breakdown of tooth structure eventually results in a hole. While decay can affect any part of the tooth, its location determines its classification. This article focuses on the characteristics, development, and treatment of surface cavities.
What Defines a Surface Cavity
A surface cavity is a form of tooth decay that develops on the smooth, flat sides of the teeth, distinguishing it from decay in the deep grooves or pits of the chewing surfaces. Dentists often refer to this as a smooth surface cavity. These cavities are typically found on the sides of the teeth, close to the gumline, or between adjacent teeth, an area known as the interproximal surface.
Plaque, a sticky film of bacteria, is less likely to accumulate here compared to rougher chewing surfaces. However, plaque can still adhere to these areas if they are not effectively cleaned by a toothbrush. This type of cavity tends to be slow-growing because the enamel on the smooth sides of the tooth is dense and resistant to rapid acid erosion.
Interproximal decay poses a particular challenge because these lesions are difficult to see visually during a routine check-up. They often develop in people who do not regularly use dental floss. Because of their hidden location, interproximal cavities can progress significantly before they cause any symptoms.
How Surface Cavities Develop
The process of decay begins with the interaction between oral bacteria and dietary sugars and starches. Bacteria, such as Streptococcus mutans, metabolize these carbohydrates, producing acidic byproducts that lower the pH level in the mouth. This acidic environment causes the enamel, the hardest substance in the body, to lose its mineral content, a process termed demineralization.
During the earliest stage, a small, subsurface loss of minerals occurs, often appearing as a white or chalky spot on the tooth surface. This initial lesion is not yet a physical hole and is sometimes reversible. The tooth constantly cycles through demineralization and remineralization, where minerals from saliva and fluoride are reincorporated into the enamel structure.
A cavity forms when mineral loss consistently exceeds mineral gain. If the acid attack continues, the weak, demineralized enamel eventually collapses, creating a breach that allows bacteria to penetrate deeper. Once the decay progresses through the enamel and reaches the underlying dentin, the process accelerates because dentin is softer and less mineralized.
Because these lesions form on smooth surfaces, the decay often takes longer to break through the dense outer enamel layer, providing a longer window for intervention compared to pit and fissure decay. However, once the enamel is perforated, the cavity rapidly expands within the dentin toward the pulp, where the tooth’s nerves and blood vessels are located.
Diagnosis and Repair Methods
The detection of a surface cavity relies on professional techniques, as many lesions are not visible to the naked eye. A dentist performs a visual examination, often using an explorer tool to check for surface roughness or stickiness. For early decay, the visual assessment focuses on identifying white spots, which are signs of initial demineralization.
X-rays, specifically bitewing radiographs, are important for diagnosing cavities between the teeth, where direct inspection is impossible. These images show demineralized areas as dark spots, indicating mineral loss. Advanced digital tools, such as near-infrared light transillumination (NILT), can also detect early interproximal lesions without ionizing radiation.
Treatment depends on the stage of the decay. If the lesion is still in the early, non-cavitated white spot stage, the dentist may opt for non-invasive treatments. These involve monitoring the lesion and applying professional-strength fluoride varnish or prescription toothpastes to promote remineralization.
If the decay has progressed to form an actual hole, a restorative procedure is required to prevent further spread. The dentist removes the decayed material and cleans the area before placing a dental filling. Fillings, commonly made of composite resin or silver amalgam, restore the tooth’s function; for very large cavities, a full crown may be necessary to protect the remaining structure.
Stopping Cavities Before They Start
Preventing surface cavities relies heavily on consistent oral hygiene practices that disrupt the bacterial plaque biofilm. Because these lesions frequently occur between the teeth, daily flossing is highly effective for removing trapped plaque that a toothbrush cannot reach. Flossing should be performed with a gentle, sawing motion to clean the interproximal surfaces and along the gumline.
Proper brushing technique is also essential, focusing on the smooth surfaces and the area where the tooth meets the gum. Using a fluoride-containing toothpaste strengthens the enamel, making it more resistant to acid erosion and encouraging remineralization. Prescription-strength fluoride products may be recommended for individuals at a higher risk of decay.
Dietary adjustments play a large part in prevention by limiting the fuel source for acid-producing bacteria. Reducing the intake of sugary and starchy foods and minimizing the frequency of snacking limits the time teeth are exposed to acid attacks. Chewing xylitol-containing gum after meals can also help, as xylitol inhibits the growth of S. mutans and stimulates saliva flow, which naturally neutralizes acid.
Regular professional check-ups and cleanings allow the dental team to remove hardened plaque (calculus) and monitor any early signs of demineralization. Early detection, especially with the aid of X-rays for interproximal areas, ensures that decay is caught when it is still reversible or requires minimally invasive treatment.