Cavities (Dental Caries)

What is a cavity?

Cavities are the result of bacterial infection of the hard structure of the teeth.  Cavities occur when bacterial plaque (an invisible, sticky film of bacteria) is allowed to accumulate on tooth surfaces.  The bacteria excrete acids as a by product of their metabolism, and these acids dissolve the extremely hard outer tooth layer, known as enamel.  Once the bacteria penetrate the outer enamel layer, they infect the inner hard tooth layer known as dentin (or ivory).  Bacteria continue to dissolve the dentin, spreading through the tooth and causing more damage as time passes.  

The technical term for this disease is dental caries.  Dental caries is an infection of the tooth which causes the teeth to soften, break, or crumble if the disease is left untreated.

In the earlier stages of the disease, most of the infection lies under the hard surface enamel of the tooth, within the hard tooth dentin.  Infected portions of the dentin are softened to a consistency similar to that of wet newspaper. Although only a tiny portion of the tooth surface is involved, there can be extensive involvement beneath the surface.  At this stage, before the tooth start to break or crumble, there may not be an actual hole, or cavity, in the tooth - even though its interior is soft and mushy. Dental caries which is not apparent to the naked eye is usually clearly quite clearly seen on dental radiographs (or "x-rays").

Dental caries is the second most common human disease.  (Only periodontal, or gum disease, is more common).  By comparison, both dental caries and periodontal disease are more common than the common cold.

Dental caries is a preventable disease.  If bacteria are not allowed to remain on the tooth surface, the disease can not occur.  The best means of removing bacterial plaque on the tooth surface is by brushing after eating, as well as before bedtime, in addition to the daily use of dental floss for cleaning areas the toothbrush can't reach.  Special preventive treatments include professional tooth cleaning and maintenance care, and the use of flourides to make teeth more resistant to attack by bacterial acids.

Spreading Infection from Untreated Cavities

Teeth with dental caries may allow infection to spread into the soft inner tissue of the tooth and tooth roots, known as the dental pulp.  The dental pulp is similar to gum tissue, but once it becomes infected it can not recover.  Infection of the dental pulp is a serious but treatable problem which can cause severe pain and may allow infection to spread into the jawbone or even beyond the mouth to the rest of the body.  Left untreated infections of dental origin can be fatal, though this is uncommon in developed nations. The treatment for an infected dental pulp is called endodontic treatment (or "root canal treatment").  

Cavities Resulting from Unsatisfactory Restorations

Dental caries may also begin in areas on the teeth which can't be reached by the toothbrush or dental floss.  The most common of these protected areas are broken down or unsatisfactory fillings, caps, or crowns with small defects in their fit to the tooth.  Bacteria readily colonize these tiny crevices and gaps between inadequately fitting restorative materials and the tooth structure.  This is why any tiny deficiencies in the ability of a cap, crown, bridge, or filling to seal the tooth surface from bacteria must be corrected by dental treatment.

Different Treatment Options for Cavities

The most common treatment for cavities is removal of the infected or weakened portions of the tooth, followed by placing a restoration (or "filling") to seal the damaged tooth from oral bacteria, replace lost tooth structure, and restore both form and function of the tooth. After removal of "decay" (infected enamel and dentin), a hole or cavity remains in the portion of the tooth that was infected before dental treatment.  If enough natural tooth structure remains, the tooth can be restored with a filling, if not a crown ("cap") might be unavoidable.

A variety of different restorations ("fillings") are available.  The different types are classified by the type of material used to make the restoration. These commonly include silver alloy, gold alloy, porcelain, combinations of metal and porcelain, non-precious metal alloys, composite resin bonding materials, and glass ionomer materials.  Each material has distinct advantages and disadvantages.  Your dentist carefully selects the best material to meet your individual needs, your health, and the needs of your tooth.