A caries lesion is the physical damage to a tooth caused by dental caries, more commonly known as tooth decay. This disease leads to the breakdown of the hard tissues of the teeth. To understand this, one can think of dental caries as the process that creates a pothole, while the caries lesion is the pothole itself.
The Process of Tooth Decay
The formation of a caries lesion begins with a shift in the mouth’s natural balance. Your teeth constantly experience cycles of demineralization, the loss of minerals, and remineralization, the regaining of minerals. This dynamic is influenced by the bacteria in your mouth and your diet. Specific bacteria, such as Streptococcus mutans, thrive on the sugars and fermentable carbohydrates you eat.
As these bacteria metabolize sugars, they produce acids, primarily lactic acid. This acid lowers the pH at the tooth’s surface, and when it drops below a certain point (around 5.5), the demineralization process accelerates. During this phase, calcium and phosphate ions are leached from the tooth’s hard, outer layer, called enamel.
Between meals or sugar exposures, your saliva works to neutralize these acids and redeposit minerals back onto the tooth surface, a process aided by fluoride. When acid attacks are too frequent or prolonged, demineralization outpaces remineralization. This net loss of mineral content eventually weakens the tooth structure, leading to the development of a caries lesion.
Stages and Classification of Lesions
The development of a caries lesion occurs in distinct stages. The earliest sign is an “incipient” or “initial” lesion, which appears as a “white spot” on the tooth enamel. This chalky area indicates subsurface demineralization, but the enamel surface itself is still intact. At this stage, the process is reversible with proper intervention.
If demineralization continues, the lesion progresses to a moderate stage. The enamel surface breaks down, creating a visible cavity or hole. The decay has breached the outer enamel but has not yet reached the deeper layers of the tooth. This is the point where a simple restoration, or filling, is required.
An advanced or severe lesion occurs when the decay penetrates through the enamel and into the underlying dentin. Dentin is softer and more porous than enamel, which allows the decay to spread more rapidly. Once the lesion reaches the pulp—the innermost part of the tooth containing nerves and blood vessels—it can cause significant pain and sensitivity. Lesions are also classified by their location, such as on chewing surfaces, the smooth sides of the teeth, or on exposed root surfaces.
Professional Diagnosis and Identification
Identifying caries lesions, especially in their early stages, requires a professional examination. During a dental check-up, a dentist or hygienist performs a visual and tactile inspection using a mirror and a dental explorer. This inspection checks for softened or discolored areas on the tooth surfaces to detect cavities and surface changes.
Dental radiographs, or X-rays, play an important part in diagnosis. Bitewing X-rays are particularly effective at revealing interproximal caries, which are lesions that form between the teeth and are often impossible to see with the naked eye. On a radiograph, decay appears as a darker area because the demineralized tooth structure is less dense.
Newer technologies also assist in detecting lesions at their earliest, most reversible stages. Devices using fluorescence, such as laser fluorescence detectors, can identify changes in the tooth’s mineral content before a cavity is visible. These tools measure the light reflected from the tooth, with healthy enamel fluorescing differently than a demineralized area, allowing for early intervention.
Management and Treatment Approaches
The treatment for a caries lesion is directly related to its stage of progression. For incipient lesions, where the enamel is still intact, non-invasive approaches are preferred. The goal is to halt the decay and encourage remineralization. This can be achieved through professional fluoride treatments, prescription-strength fluoride toothpaste, and dietary adjustments to reduce sugar intake.
When a lesion has created a cavity in the enamel, a restoration is necessary. This procedure involves the dentist removing the decayed portion of the tooth and placing a filling. Materials like composite resin or amalgam are used to restore the tooth’s shape and function, preventing the decay from advancing.
For severe lesions that have reached the dentin and are affecting the pulp, more extensive treatments are required. A root canal may be needed to remove the infected pulp, after which the tooth is often covered with a crown to protect it. In the most advanced cases where the tooth structure is too compromised to be saved, extraction may be the only option.