Dental caries, commonly known as tooth decay or a cavity, is the breakdown of tooth structure caused by acid produced by bacteria in the mouth. This condition is highly prevalent, affecting people of all ages globally. Understanding the processes behind this condition is the first step toward effective prevention and treatment.
The Mechanism of Tooth Decay
The formation of tooth decay involves specific bacteria, fermentable carbohydrates, and the tooth’s mineral structure. The primary culprit is the acid-producing bacterium Streptococcus mutans, which colonizes dental surfaces. These bacteria thrive in dental plaque, a sticky biofilm that accumulates on the teeth.
When sugars and fermentable carbohydrates are consumed, S. mutans metabolize them rapidly. This results in the production of organic acids, primarily lactic acid, which significantly lowers the pH level within the plaque. Once the pH drops below a critical point (around 5.5 for enamel), the acids dissolve the tooth’s hard mineral component, a process called demineralization.
If this acidic attack is frequent and prolonged, the loss of minerals outpaces the natural repair process of remineralization, leading to a lesion. Decay begins in the outer layer of the tooth, the enamel, often appearing as a white spot. If left unchecked, the decay progresses through the enamel and into the softer dentin, where destruction accelerates. Finally, the decay can reach the pulp, which contains the nerves and blood vessels, leading to infection and severe pain.
Recognizing the Signs and Symptoms
While decay on the outer enamel may not cause immediate sensation, symptoms become noticeable as the lesion advances into the dentin. A common sign is heightened sensitivity to temperature changes, particularly when consuming hot or cold items. Patients may also experience sharp or throbbing pain when chewing, or a continuous toothache.
Visible indicators of decay include a small hole or pit in the tooth surface (the physical cavity). Discoloration is another sign, often presenting as a white, brown, or black spot. Dentists identify decay through visual inspection and diagnostic tools during a regular examination.
The dentist visually checks tooth surfaces for subtle changes like white spots or visible pits. They may use a gentle probe to check for softness or stickiness that suggests a compromised tooth structure. X-rays, specifically bitewing radiographs, are a routine diagnostic component, revealing decay hidden between teeth or under existing fillings.
Professional Treatment Options
Treatment for dental caries is guided by the severity and depth of the decay within the tooth structure. For the earliest stage of decay, characterized by white spots on the enamel, the process can sometimes be reversed with non-invasive methods. Professional fluoride treatments, applied as a gel, foam, or varnish, help the enamel remineralize and become more resistant to future acid attacks.
Once a physical cavity has formed, the standard treatment is a dental filling, which requires the removal of the decayed material. Two common materials are amalgam and composite resin. Amalgam (silver fillings) is known for strength and durability, often lasting 10 to 15 years, and is typically used for molars that bear heavy chewing forces.
Composite resin fillings are tooth-colored and bonded directly to the tooth, requiring less removal of healthy structure. While aesthetically pleasing, composite fillings may have a shorter lifespan (five to ten years) and are often more expensive than amalgam.
If the decay is extensive but the tooth is still restorable, a crown may be necessary to cover the entire tooth and protect it from fracture. For decay that has reached the pulp, causing infection, a root canal procedure is performed to remove the infected nerve and pulp tissue, saving the tooth from extraction.
Essential Prevention Methods
Effective prevention focuses on disrupting the cycle of bacterial acid production and strengthening the tooth’s enamel. A cornerstone of prevention is maintaining a diligent oral hygiene routine, including brushing for at least two minutes twice daily with a fluoride toothpaste. Proper technique involves holding a soft-bristled toothbrush at a 45-degree angle to the gums and using gentle, circular motions to clean all tooth surfaces, including the tongue.
Daily flossing is equally important, as it removes plaque and food debris from between the teeth and below the gum line, areas a toothbrush cannot reach. To floss effectively, use about 18 inches of floss, wrapping it into a “C” shape around each tooth and gently sliding it up and down.
Dietary changes play a significant role in prevention by limiting the fuel available to acid-producing bacteria. Reducing the consumption of sugar, acid, and sticky foods decreases the frequency of acid attacks on the enamel. Substituting regular sugar with sugar alcohols like xylitol can be beneficial because S. mutans cannot metabolize it, inhibiting acid production.
Fluoride works to strengthen the enamel by promoting remineralization. Sources include fluoridated water, toothpaste, and professional applications, which provide a high concentration of the mineral. Another preventive measure is the application of dental sealants, which are thin plastic coatings painted onto the chewing surfaces of the back teeth (molars). These sealants fill the deep grooves and pits where food particles and plaque commonly accumulate, creating a smooth barrier that blocks bacteria and prevents decay.