An interproximal cavity, or a cavity between two teeth, presents a unique challenge because the decay is hidden and the tooth’s natural shape must be perfectly recreated. Unlike a simple surface filling, this procedure requires specialized tools and techniques to access the area without damaging the adjacent tooth. The complexity arises from the need to restore the exact contact point between the teeth, ensuring the final filling functions naturally. This detailed process prevents future issues like food trapping and recurrent decay.
Preparing the Cavity Site
The process begins with ensuring patient comfort, typically by administering a local anesthetic to numb the area. Isolation of the affected tooth is achieved using a rubber dam or cotton rolls, which prevents moisture from saliva or blood from contaminating the prepared tooth surface, ensuring the filling material bonds correctly.
To reach the decay, which is nestled against the neighboring tooth, the dentist must carefully access the lesion, usually by drilling through the top (occlusal) or side surface of the tooth. This access is created with precision, often using a high-speed dental handpiece to remove the outer enamel. The goal is to remove all decayed material, which is softer and discolored, while preserving as much healthy tooth structure as possible.
Once the decay is exposed, specialized instruments are used to clean out the infected dentin and shape the inner walls of the tooth. This shaping process, known as creating the “preparation,” ensures the final filling material will be securely held within the tooth. The dentist defines the margins of the cavity and removes any unsupported enamel to create a stable foundation for the restoration.
Rebuilding the Missing Tooth Wall
The space between the teeth, where the original tooth wall was lost to decay, must be temporarily replaced before the filling material can be introduced. This is accomplished using a matrix system, which acts as a mold for the new filling and helps define the final contour of the tooth. A common system involves a thin metal or plastic matrix band that wraps around the tooth.
A small, triangular wedge, often made of wood or plastic, is then inserted into the gum line area below the matrix band. The wedge serves a dual purpose: it presses the matrix band tightly against the prepared tooth margin to seal the bottom edge and prevent the filling material from leaking out, which could create a rough overhang. Simultaneously, the wedge provides a slight separation of the two adjacent teeth, pushing them apart by a fraction of a millimeter.
This minor separation compensates for the thickness of the matrix band itself. When the matrix system is removed after the filling material has been placed and hardened, the teeth naturally spring back together. This action ensures the new filling material forms a tight, natural contact point with the adjacent tooth. If a proper contact point is not achieved, the resulting “open contact” allows food to become packed between the teeth, increasing the risk of gum irritation and new decay.
Specialized sectional matrix systems, which use smaller, curved matrix bands held in place by a tension ring, are often preferred for composite resin fillings. They more effectively recreate the natural curve and anatomy of the tooth. These systems provide the necessary separation and close adaptation to ensure the final restoration integrates seamlessly. The geometry of the matrix and wedge system is the most differentiating part of filling an interproximal cavity.
Placing and Finalizing the Restoration
With the matrix and wedge in place, the dentist prepares the cleaned tooth surface for bonding by applying an acidic etching gel followed by a liquid bonding agent. The etching gel creates microscopic roughness on the enamel, allowing the bonding agent to penetrate and form a strong link between the tooth structure and the composite resin. The bonding agent is then cured with a specialized light to activate the adhesive properties.
The tooth-colored composite resin is placed into the prepared cavity in small layers, or increments, which helps ensure the material cures completely and minimizes polymerization shrinkage. Each layer is hardened individually using a curing light, which emits a high-intensity blue light that initiates the chemical reaction in the resin. The material is molded against the matrix band to replicate the tooth’s original shape and contour.
Once the final layer is cured, the matrix band and wedge are removed, revealing the newly formed tooth wall. The dentist then uses fine burs and abrasive discs to contour the filling, smoothing rough edges and ensuring the filling matches the adjacent tooth surfaces. The occlusion, or the way the upper and lower teeth meet, is checked using articulating paper, which leaves colored marks on high spots.
These high spots are adjusted until the bite feels comfortable and natural, ensuring the new filling does not interfere with chewing. A final polish with progressively finer materials is applied to create a smooth, stain-resistant surface. Some patients may experience temporary sensitivity to hot or cold after the procedure, but this typically resolves within a few days to weeks as the tooth recovers.