A dental cavity (dental caries) is the destruction of tooth structure caused by acid produced by bacteria in the mouth. This decay is a progressive infectious disease that begins with the erosion of the hard outer surface of the tooth. Unlike most body injuries, a cavity cannot heal itself once the physical structure is compromised. The decay will continue to worsen until it is professionally removed and restored, making the consequences of inaction increasingly severe.
Progression from Enamel Decay to Dentin Sensitivity
The initial stage of decay targets the enamel, the hardest substance in the human body. Decay often presents as a small white or brown spot and is typically asymptomatic because the enamel contains no nerves. If detected early, the tooth may sometimes be remineralized, or a simple filling can stop the process.
Once the bacterial acid penetrates the enamel, it reaches the dentin, the layer immediately beneath. Dentin is softer and contains microscopic channels (tubules) that lead toward the tooth’s center where the nerve resides. Decay spreads much faster in this softer material.
The penetration into the dentin is typically when the first noticeable symptoms appear. Patients may experience a sharp sensitivity, particularly when consuming hot, cold, or sugary items. This occurs because stimuli travel through the exposed dentinal tubules to the internal nerve. At this stage, the decay is still localized and can usually be treated with a standard dental filling.
Severe Pain and Pulp Infection
If the decay is left untreated, it continues through the dentin until it reaches the pulp chamber, the innermost part of the tooth. The pulp contains the nerve tissue, blood vessels, and connective tissue. When bacteria infect this space, it causes inflammation of the pulp, known as pulpitis.
Because the pulp is encased in the rigid tooth structure, swelling creates immense pressure on the nerve. This results in severe, often chronic, throbbing pain that may be spontaneous or linger long after a stimulus is removed. This intense discomfort may even wake a person from sleep.
As the infection progresses, swelling compromises blood flow, causing the pulp tissue to die (pulp necrosis). While pain may temporarily subside once the nerve dies, the infection remains contained within the root canal system. Treatment at this stage is complex, often requiring a root canal procedure to remove the infected tissue and seal the canals.
Spread of Infection and Abscess Formation
If the infection is not cleared from the dead pulp, bacteria eventually exit the tip of the tooth root (the apex). This allows the infection to spread into the surrounding bone and gum tissue. The body’s immune system responds, resulting in a localized collection of pus known as a periapical dental abscess.
An abscess causes painful pressure, sometimes accompanied by localized swelling of the gum or cheek. Symptoms may include fever, swollen lymph nodes, and a persistent bad taste. Pressure may create a small channel (fistula) through the gum tissue to drain into the mouth, which temporarily relieves the pain.
This stage represents a dental emergency because the infection is no longer confined to the tooth. Treatment requires immediate drainage of the abscess and often antibiotics to control the acute infection. This must be followed by root canal therapy or extraction. Delaying treatment risks the infection spreading to adjacent spaces in the face and neck.
Broader Health Consequences and Tooth Loss
Chronic, untreated dental infection carries severe consequences that extend beyond the mouth, beginning with the irreversible loss of supporting bone structure. Bacteria from the abscess slowly destroy the alveolar bone surrounding the tooth root. This destruction leads to loosening of the tooth and, ultimately, the need for extraction. Tooth loss is often the final outcome of neglecting a cavity.
The infection can become systemic, posing a risk to general health. Bacteria from the abscess can enter the bloodstream (bacteremia) and travel to other parts of the body. While rare, this can lead to life-threatening conditions, such as facial cellulitis (a rapid, widespread infection of the soft tissues) or sepsis.
Chronic oral inflammation has also been linked to other systemic health issues. Studies suggest a connection between ongoing dental infections and an increased risk of cardiovascular problems, including endocarditis. Allowing a dental infection to persist places a continuous strain on the body’s immune system and increases the risk for serious, non-dental complications.