A cavity, which is essentially a hole in the tooth, results from tooth decay caused by the acid produced by oral bacteria feeding on sugars and starches. This process breaks down the tooth’s hard outer layer, the enamel, and the softer dentin beneath it. Since decay is progressive and will not stop on its own, prompt professional treatment is necessary to prevent the infection from spreading and causing more extensive damage to the tooth’s structure.
Detecting the Need for Repair
The diagnostic process begins with a thorough visual inspection using a small mirror and a specialized instrument to check the tooth surfaces for signs of decay, such as softness or stickiness. This physical examination helps the dentist locate visible pits, fissures, or discoloration. However, much of the decay that requires repair is not immediately visible.
To confirm the presence and full extent of a lesion, dental radiographs are routinely used, particularly for decay between the teeth or under existing restorations. Bitewing X-rays, taken regularly during checkups, are effective for revealing interproximal decay. These images allow the dentist to accurately determine how deep the decay has penetrated the tooth structure.
The Standard Cavity Filling Procedure
Once decay is confirmed, the standard procedure begins with preparing the tooth. The dentist first applies a topical numbing gel, followed by a local anesthetic injection to ensure the area is completely numb. This anesthetic blocks nerve signals, preventing any sensation of pain during the removal of the decayed material.
The next phase involves removing the decayed tooth structure using a dental handpiece, commonly known as a drill. The dentist carefully removes the soft, infected material while preserving as much of the surrounding healthy enamel and dentin as possible. A slower-speed drill or specialized abrasive instruments may be used when working closer to the inner layers of the tooth.
After all the decay has been removed, the remaining space is cleaned and shaped to ensure the filling material will bond securely. For composite resin fillings, the tooth surface is treated with a mild acid gel, or etchant, which creates microscopic pores in the enamel. This is followed by the application of a bonding agent, a liquid resin that flows into these pores.
The chosen restorative material is then placed into the prepared space, often in small layers. Each layer of composite resin is hardened, or cured, using a high-intensity blue light, which sets the material and bonds it to the tooth structure. Finally, the dentist shapes the filling to match the natural contours of the tooth. The bite is checked and adjusted using articulating paper to ensure proper alignment. The filling is then polished to create a smooth, finished surface.
When the Cavity is Severe
Root Canal Therapy
If the decay progresses beyond the dentin, it can reach the pulp, the soft tissue core of the tooth containing nerves and blood vessels. When the pulp becomes irreversibly inflamed or infected, a standard filling is insufficient. The dentist will then recommend a root canal procedure, also known as endodontic therapy.
During a root canal, the dentist removes all the infected tissue from the canals inside the tooth’s roots. The cleaned space is disinfected, shaped, and permanently filled with a biocompatible material, typically gutta-percha, and sealed. Since the tooth often loses internal structure, it is usually restored with a dental crown to protect it from fracture.
Indirect Restorations (Inlays and Onlays)
Where decay is too large for a simple filling but has not reached the pulp, the remaining tooth structure may be too weak for a traditional filling. For these large preparations, the dentist may opt for an indirect restoration, such as an inlay or an onlay. These custom-made restorations are fabricated outside the mouth, typically from porcelain or gold, and then cemented onto the tooth to restore its original shape and strength.
Choosing the Right Filling Material
Composite Resin
The selection of the restorative material depends on the cavity’s size, location, required force resistance, and aesthetic concerns. Composite resin is the most frequently used material today, consisting of a blend of plastic and fine glass particles. It is popular because it can be shade-matched to the natural color of the tooth, offering an aesthetic result. Composite resin bonds directly to the tooth structure, requiring less removal of healthy material.
Dental Amalgam
Dental amalgam is an alloy of metals, including silver, tin, copper, and liquid mercury. Amalgam is known for its exceptional durability, cost-effectiveness, and ability to withstand heavy chewing forces, often lasting 10 to 15 years or more. However, its metallic appearance makes it less desirable for visible areas, and it requires slightly more tooth preparation than composite materials.
Gold
Gold restorations are typically used for inlays and onlays due to their superior strength and longevity, often lasting over 20 years. Gold does not corrode and wears similarly to natural tooth enamel, making it highly compatible with the mouth’s environment. While extremely durable, gold is the most expensive material and is rarely chosen for aesthetic reasons.