A dental cavity, or dental caries, represents permanent damage to the hard surface of a tooth, resulting in a tiny opening or hole. This destruction occurs when bacteria convert sugars and carbohydrates into acids, which erode the tooth’s protective outer layer, the enamel. If left untreated, this erosion progresses into the softer inner dentin, accelerating the decay and potentially leading to pain or infection. The goal of a restorative dental procedure is to halt the progression of this disease by completely removing the infected material and sealing the tooth with a filling to restore its original shape and function.
Preparing the Area for Treatment
The process of repairing a cavity begins with a thorough assessment, often confirmed by visual examination or dental X-rays. A primary step involves administering a local anesthetic, such as lidocaine, to numb the tooth and surrounding gum tissue, which blocks pain signals and prevents discomfort during the decay removal. This often starts with a topical numbing gel applied to the injection site.
Once the area is numb, the tooth must be isolated from the rest of the mouth to maintain a dry, clean surface, a requirement for successful bonding of most modern filling materials. Dentists typically achieve this isolation using a dental dam, a thin sheet of rubber placed around the affected tooth, or by placing cotton rolls to absorb saliva and moisture.
The Physical Removal of Decayed Tissue
With the tooth isolated and the area anesthetized, the dentist proceeds to the precise physical removal of the carious tissue. The main instrument for this task is the dental handpiece, commonly referred to as a drill, which rotates small cutting tools called burrs at extremely high speeds. The burrs, manufactured from materials like tungsten carbide or diamond grit, are selected based on the tooth structure being cut.
The technique involves using the high-speed handpiece with a diamond or carbide burr to quickly cut through the hard outer enamel to access the softer, infected dentin underneath. Once the decay is exposed, the dentist shifts to a lower-speed burr or specialized polymer burrs to carefully remove only the soft, infected dentin while preserving the healthy, firmer tooth structure beneath. This selective removal avoids unnecessary removal of sound tissue and prevents exposure of the tooth’s sensitive pulp chamber. The physical removal process is complete when the cavity margins are clean, defined, and completely free of infected material, creating a stable foundation for the restoration.
Filling and Restoring the Tooth Structure
After the decay is fully removed, the prepared surface must be conditioned to ensure a lasting bond with the restorative material. For composite resin fillings, this involves the application of a mild acid gel, typically phosphoric acid, to the enamel and sometimes the dentin.
This process, known as etching, creates microscopic pores and a rough surface texture, which is rinsed away to leave a “frosted” appearance. Following the etching, a bonding agent, which is a liquid resin, is applied to penetrate these microscopic pores and create a chemical link with the tooth structure.
The chosen filling material is then applied in small increments, or layers. For composite resins, each layer is hardened with a high-intensity blue light, a process called light-curing, which rapidly sets the material. The dentist then meticulously shapes and contours the filling to match the tooth’s natural anatomy and bite before a final polish is applied to ensure a smooth, functional, and aesthetic restoration.
Less Invasive Methods of Cavity Removal
For smaller or shallower areas of decay, dentists can employ techniques that minimize the use of the traditional high-speed handpiece, offering a gentler alternative. One such technique is air abrasion, which uses a device to direct a high-pressure stream of fine abrasive particles, such as aluminum oxide, at the decayed area. This method essentially functions as a tiny sandblaster, effectively removing the decayed material with minimal heat or vibration and often without the need for local anesthesia.
Dental lasers represent another minimally invasive option, using specific wavelengths of light energy to precisely vaporize the decayed tooth structure. Lasers like the Er:YAG type can ablate the carious tissue with high control, preserving more healthy tooth material and reducing the noise and vibration that can cause anxiety for some patients. Both air abrasion and laser removal are generally reserved for smaller lesions and offer the advantage of conserving more of the natural tooth structure compared to traditional mechanical methods.