An interproximal cavity is a form of tooth decay that develops specifically on the smooth side surfaces of a tooth, where it contacts an adjacent tooth. This area, known as the contact point, is challenging to clean thoroughly, making it highly susceptible to the accumulation of plaque and subsequent demineralization. Since these lesions occur in a tight space beneath the enamel surface, they are often hidden from view, presenting a unique challenge for both detection and restoration. Successfully addressing this type of decay, known in dentistry as a Class II restoration, requires specialized tools and techniques.
Identifying the Interproximal Cavity
Detecting decay between the teeth is difficult because the lesions are obscured by the surrounding tooth structure and cannot be seen during a standard visual examination. Dentists rely primarily on diagnostic imaging to identify these hidden areas of breakdown. The bitewing X-ray is the established method for visualizing the contact points between molars and premolars.
This specific type of X-ray captures a clear image of the crowns of the back teeth, revealing areas where the enamel has lost mineral density. On the image, a cavity appears as a dark or radiolucent area against the lighter, denser tooth structure. By the time a lesion is visible on a radiograph, it may have already progressed through the outer enamel layer and into the softer dentin beneath. A dental probe may be used after a clinical examination to gently confirm the location or size of the lesion.
Specialized Preparation and Isolation Techniques
Once the interproximal cavity is diagnosed, the dentist employs specific techniques to access and repair the decay without affecting the adjacent tooth. The first step involves isolating the treatment area, typically using a rubber dam, a thin sheet of material that fits over the tooth. This barrier prevents contamination from saliva and blood, which is necessary for the filling material to bond correctly, and also protects the patient from aspirating small instruments.
The next challenge is creating a temporary wall to rebuild the missing side of the tooth, which is achieved with a sectional matrix system. This system uses a thin, contoured metal or plastic band that is placed around the prepared tooth to act as the missing wall of the cavity. A wedge, often made of wood or plastic, is then inserted firmly at the gum line between the prepared tooth and the neighboring tooth.
The wedge serves two functions: it seals the base of the matrix band tightly against the tooth to prevent the filling material from leaking out, and it provides a slight separation between the teeth. This temporary separation, sometimes aided by a specialized ring placed over the wedge, compensates for the thickness of the matrix band. When the matrix and wedge are removed, the slight pressure from the adjacent tooth ensures the new filling creates a tight, natural contact point, preventing food from getting trapped after the procedure.
The Filling Process and Restoration
With the area isolated and the matrix system in place, the decay is removed using a high-speed dental handpiece to shape the tooth for the restorative material. The prepared surface is then treated with an etching gel, typically containing 30–40% phosphoric acid, for several seconds. This acid creates microscopic porosities in the enamel and dentin surfaces, which are rinsed away and lightly dried.
A liquid bonding agent is then applied to the conditioned tooth surface. This agent acts as a molecular bridge, forming a strong chemical link between the natural tooth structure and the composite filling material. The bonding agent is cured, or hardened, using a specialized high-intensity blue light, typically for 10 to 20 seconds.
The composite resin is then placed into the cavity in small incremental layers, usually no more than two millimeters thick. Placing the material in thin layers is necessary because the curing light can only penetrate a limited depth to fully harden the resin. Each layer is individually hardened with the specialized light before the next is applied, ensuring a complete and durable restoration against the matrix band. Finally, the matrix and wedge are removed, and the dentist sculpts and polishes the surface to ensure the filling matches the tooth’s natural anatomy and fits seamlessly within the patient’s bite.
Post-Procedure Expectations and Maintenance
Following the procedure, it is common to experience some temporary sensitivity in the restored tooth, particularly to cold temperatures or pressure when biting. This reaction typically subsides within a few days or weeks as the tooth recovers. The area around the gums may also feel slightly irritated due to the placement of the wedge and matrix system, but rinsing with warm salt water can help alleviate this localized soreness.
The new filling is set immediately, allowing patients to chew normally once the local anesthetic has completely worn off. Long-term maintenance requires meticulous oral hygiene, focusing on the contact point between the teeth. Resuming daily flossing is important to prevent recurrence, ensuring the floss reaches just beneath the gum line to clean the newly restored surface. Regular dental check-ups and subsequent bitewing X-rays are necessary to monitor the integrity of the restoration and detect any new decay early.