Dental fillings are the most common dental prosthetics. They are used to restore small-to-moderate decayed or damaged areas of a tooth. They are frequently recommended as a restoration option for dental caries (cavities). A cavity occurs when oral bacteria secretes an acid that eats away the surface and eventually the interior of a tooth. Small cavities may cause little pain, or they may lead to tooth sensitivity in the area where the enamel is damaged. Larger cavities weaken the tooth structure and may contribute to fracturing or cracking over time. At this point, dental fillings may or may not be sufficient to restore a tooth. Severely affected teeth may require extensive restoration with a crown, bridge or implant.
Additional Uses for Dental Fillings
When a cavity penetrates into the center of the tooth (where the pulp is located), bacteria may enter and create a very painful abscess (infection). A root canal is the standard treatment for this dental infection. Dental fillings are sometimes used for restoration of the center and surface of the tooth after a root canal (a full crown is another option). A filling may also be a possible treatment option for small fractures or to correct the biting and chewing surfaces of teeth to improve function. In general, fillings are most successful over the long term if dental damage or decay is addressed early.
History of Dental Fillings in the United States
Dental fillings were in common use in dental practices by the mid 1800s. However, the materials had not yet been standardized. Dentists experimented with a very wide variety of materials trying to find the right mix of durability and malleability to correct cavities. Some of the materials used included:
- Common metals such as lead and tin
- Precious metals (gold, silver, platinum)
- Amalgams (various mixtures of metals such as tin, silver, mercury, lead, aluminum and bismuth)
- Temporary filling materials such as gutta-percha (rubber) and various minerals such as quartz
Most of these materials could be placed directly in the cavity and then molded into shape inside the tooth. Some metal mixtures had to be heated either before being poured into the tooth or with heated instruments inserted into the tooth after placing the filling. By the late 1800s, metal amalgam made of mercury, silver, tin, copper and other metals such as zinc became the standard for dental fillings. This amalgam is an inexpensive filling and easy to work with, delivering longer lasting results than many other materials investigated during the early days of dentistry. This type of amalgam, with some minor adjustments, remains one of the most common filling materials used today (especially for back teeth).
Other Dental Fillings
The desire for a mercury-free dental filling option and for fillings that are more aesthetically pleasing has led to the development of many modern alternatives in the last 50 years or so. These include:
- Tooth-colored resin (a mix of acrylic and glass)
- Tooth-colored polymers (resin or glass)
- Porcelain (used in onlays and inlays)
- Gold alloy
These materials each have their own benefits and drawbacks. All of them are more challenging to place than metal amalgam dental fillings, and some are significantly more expensive.
Treatment Overview for Dental Fillings
For all dental fillings, the first step is to numb the area. This is done with a local anesthetic. Some patients choose nitrous oxide for sedation as well since the treatment can be uncomfortable. A rubber dam or a bite block may be inserted into the patient’s mouth to keep the mouth open and the treatment area dry. Next, the dentist identifies and removes the decayed tooth tissue. Some dentists use a combination of high-speed and low-speed drills while others use a laser or a stream of forced air and an abrasive powder during this process.
Patients may find lasers and air abrasion more comfortable than traditional dental drills since they don’t produce a vibrating sensation. However, the type of equipment used depends on the location and extent of the cavity, whether there are already other fillings in the tooth and the type of material being used for the new filling. For example, a dentist might use a laser to begin the removal process and finish up with a traditional drill. Air abrasion tools are only used when a composite resin filling is being installed. After the tooth is drilled, the hollowed out area is cleaned to remove any bits of debris and bacteria.
Placement of Metal Dental Fillings
For deep cavities, a sealant may be layered onto the tooth before the filling is inserted. This reduces the risk of sensitivity in the tooth root. Next, the metal filling is placed. A traditional amalgam filling is made up of a carefully measured blend of metals that are mixed together on-site and pressed down into the tooth cavity so that it fits tightly. Then, the blob of metal is shaped to ensure that the biting surface is the correct height. A wedge and stainless steel band may be used to help shape and position amalgam correctly when a cavity between teeth (where the side of one tooth touches another) is being filled. These shaping devices are removed once the amalgam is installed. The metal surface is finished and polished as a final step.
Placement of Composite Dental Fillings
The dentist prepares the surface to be filled with a mild acid to etch the tooth tissue and help the filling attach more firmly. A layer of bonding adhesive is applied first followed by a layer of composite resin that has been carefully matched to the patient’s existing tooth color. The composite resin is painted or squirted into the hollowed out area in layers. Each layer is dried with a laser lamp to harden it. A clear band and wedge may be used for cavities between teeth. Once the cavity is completely filled, any excess resin is removed and the surface is finished and polished to create a natural-looking result.
After Dental Filling Placement
The local anesthetic used in dental filling treatment wears off soon after the procedure. Mild tooth and gum sensitivity may persist for several days after treatment. Salt water rinses may help ease these symptoms. Patients should avoid chewing on a metal amalgam filling for the first 24 hours after placement.
Composite resin fillings are ready for normal use once full feeling has returned to the mouth. A metal filling will be visible in the mouth (that’s one reason they are usually placed in molars rather than front teeth). A tooth-colored resin filling shouldn’t be noticeable.
While dental fillings may halt the progress of the current cavity, they do not prevent future cavities from forming. Patients must take steps to improve their oral hygiene to prevent the development of more cavities. Fillings are often long lasting (they may stay in place for more than a decade). However, they will generally require replacement at some point.