Secondary caries is a new area of decay that forms at the border or underneath an existing dental filling. This decay is a frequent reason why dental restorations, such as fillings, eventually need replacement. It develops at the interface between the tooth structure and the restorative material. Understanding this process helps manage long-term oral health and maintain previous dental work.
How Secondary Caries Develops
Secondary caries often begins with microleakage, which involves the development of microscopic gaps between the dental restoration and the natural tooth structure. Changes in temperature from eating and drinking, along with chewing, can cause the filling material and tooth to expand and contract at different rates, creating these openings.
Once these gaps form, they allow seepage of saliva, bacteria, and microscopic food particles into the interface. This creates a sheltered environment where oral bacteria, similar to those that cause primary cavities, thrive and produce acids. These acids then dissolve the tooth enamel and dentin beneath or around the existing filling, leading to new decay. The edges, or margins, of fillings are vulnerable to this process because they can be challenging to clean effectively with a toothbrush and floss.
Identifying Secondary Caries
Dentists use several methods to detect secondary caries, as this decay can be hidden. A visual examination is often the first step, where the dentist looks for discoloration, such as a grayish or brownish tint, or defects around the existing filling. They may also use a dental explorer, a small, pointed instrument, to feel for softness, stickiness, or irregular changes in texture at the filling’s edge. While tactile assessment can be useful, its accuracy can be limited.
Dental X-rays are important for diagnosing secondary caries, especially when decay is not visible on the tooth surface. These images can reveal radiolucent (darker) areas underneath or adjacent to the existing restoration, indicating mineral loss. Bitewing radiographs are useful for detecting proximal lesions, which are those between teeth, as they provide a clear view of these areas. Combining visual, tactile, and radiographic assessments helps dentists form a comprehensive picture.
Repairing a Tooth with Secondary Caries
When secondary caries is identified, treatment involves removing the decay and placing a new restoration. The procedure begins with the dentist numbing the affected area to ensure patient comfort. Once numb, the old dental filling is carefully removed, along with all the newly decayed tooth structure. This step is thorough, as any remaining decay could compromise the success of the new restoration.
After the decayed material is cleaned out, the tooth cavity is prepared to receive the new filling material. The choice of restorative material, such as composite resin or amalgam, depends on factors like the tooth’s location and the extent of removed decay. If secondary caries is extensive and has weakened a significant portion of the tooth, a dental crown may be recommended instead of another filling. A crown encases the entire outer surface of the tooth, providing greater strength and protection against future damage.
Preventing Future Decay Around Restorations
Preventing secondary caries centers on consistent oral hygiene practices. Brushing teeth at least twice daily with fluoride toothpaste helps remove plaque and food particles, especially around existing fillings. Daily flossing or using an interdental cleaner is important to clean spaces between teeth and along the margins of restorations where a toothbrush may not reach effectively.
Regular dental check-ups are an important part of prevention, allowing dentists to detect early signs of decay or issues with existing restorations. During these visits, professional cleanings remove plaque and tartar that can accumulate around fillings. A balanced diet that limits sugary and acidic foods and beverages reduces the overall risk of tooth decay, including secondary caries. Choosing tooth-healthy foods like crunchy fruits, vegetables, and dairy products also promotes oral health.