A cavity (dental caries) is the progressive destruction of tooth structure caused by acids produced by oral bacteria. These bacteria feed on sugars and starches, forming plaque that erodes the tooth’s hard outer layer, the enamel. While small cavities are easily treatable with a simple filling, ignoring the issue allows the decay to tunnel deeper, leading to increasingly severe complications. An untreated cavity moves from a localized dental problem to one that can affect the entire body.
Dentin Exposure and Increased Sensitivity
The enamel is the hardest substance in the human body, but once bacterial acid breaches this protective layer, the decay accelerates dramatically. The infection then reaches the dentin, the softer layer immediately beneath the enamel. Dentin contains millions of microscopic tunnels, called dentinal tubules, that lead directly toward the tooth’s central pulp chamber.
This structural change causes discomfort, marking the first real signs of trouble. The open tubules allow external stimuli to quickly reach the inner nerve tissue, causing sharp, noticeable sensitivity. Common triggers include hot or cold foods, beverages, or sugary sweets. At this stage, the decay is still largely reversible with a standard dental filling, which removes the infected dentin and seals the area.
Deep Infection and Irreversible Pulp Damage
If the decay is ignored, bacteria continue their advance through the dentinal tubules, eventually penetrating the dental pulp. The pulp is the soft core of the tooth, containing the nerves, blood vessels, and connective tissue. Once bacteria invade this inner chamber, they cause a severe inflammatory response known as pulpitis.
The inflammation is trapped within the rigid walls of the tooth, leading to a painful buildup of pressure that compresses the nerves. This stage is characterized by intense, throbbing, constant pain that may spontaneously occur. The damage progresses to irreversible damage, meaning the pulp tissue dies (necrosis). The temporary disappearance of pain may mistakenly feel like resolution, but it simply means the nerve has died while the infection continues to spread deeper into the tooth’s root.
Localized Abscess Formation and Jawbone Impact
Once the pulp tissue has died, the infection travels down the root canal to the tip of the tooth root. This results in a periapical abscess, a localized pocket of pus that forms in the surrounding bone and gum tissue. The abscess can cause visible symptoms such as swelling in the gum, face, or jaw, and sometimes a persistent bad taste if the pus is draining.
If left untreated, the chronic infection can erode the bone surrounding the tooth root, a condition known as osteomyelitis. This process weakens the jawbone structure and can lead to the loosening and eventual loss of the affected tooth.
Spread of Infection to General Health
The most severe consequences occur when the infection breaks out of the localized abscess and spreads to other parts of the head, neck, and body. The bacteria can travel through the soft tissues of the face and neck, potentially causing cellulitis, a spreading skin and soft tissue infection. A particularly dangerous form is Ludwig’s angina, a rapidly advancing infection on the floor of the mouth that can cause swelling significant enough to obstruct the airway, creating a life-threatening emergency.
In rare instances, the bacteria may travel through the bloodstream, leading to complications like cavernous sinus thrombosis, a blood clot in the brain that carries a high mortality rate. The risk of sepsis is also present, a life-threatening condition where the body’s response to the infection triggers a widespread inflammatory reaction. Sepsis can lead to organ damage, shock, and death.