Dental decay, or dental caries, begins as a bacterial infection that slowly dissolves the hard structure of the tooth. A “rotten tooth” results from this infection progressing deep into the tooth’s layers. Decay is a progressive process that steadily worsens and will not heal on its own until treated by a dental professional. Ignoring this allows the infection to breach protective barriers, leading to severe localized damage and systemic health complications.
Progression from Cavity to Pulp Death
Untreated decay begins on the outermost layer of the tooth, the enamel. Bacteria in plaque produce acids that cause demineralization, initially appearing as a chalky white spot. If this early stage is not reversed, the enamel is penetrated, forming a cavity.
Once decay moves past the enamel, it quickly reaches the underlying dentin, a softer and more porous tissue. Dentin contains microscopic tubules that lead directly to the tooth’s core, which often causes sharp sensitivity to hot, cold, or sweet stimuli. The infection accelerates as it spreads through the dentin toward the central pulp chamber.
The central pulp is the living tissue of the tooth, containing nerves and blood vessels. When infection reaches this area, it causes inflammation known as pulpitis. As bacteria multiply, the pressure inside the rigid chamber cuts off the blood supply, leading to irreversible pulpitis. The final stage is pulp necrosis, where the nerves and blood vessels die entirely, often resulting in a temporary cessation of pain.
Formation of Dental Abscesses and Cysts
The death of the dental pulp allows bacteria to exit the tooth root and invade the surrounding bone and gum tissue. This invasion results in a periapical abscess, a localized pocket of pus that accumulates at the tip of the tooth root. This collection causes significant pressure, leading to the severe, throbbing pain associated with a toothache.
The body may attempt to relieve this pressure by creating a channel called a fistula, or a “gum boil,” through the bone and gum tissue. While pus drainage often relieves acute pain, the underlying infection remains active and continues to destroy the jawbone. A more dangerous consequence is cellulitis, where the infection diffuses through the soft tissues of the face and neck. This causes widespread, painful swelling that represents a significant localized emergency.
Spread of Infection Beyond the Mouth
If a localized dental infection is left untreated, it can disseminate into the bloodstream, posing a threat to distant organ systems.
Life-Threatening Airway Obstruction
One dangerous extension is Ludwig’s angina, a rapidly advancing form of cellulitis affecting the floor of the mouth and neck. The resulting severe swelling can push the tongue upward and backward, leading to a potentially fatal obstruction of the airway.
Spread to the Brain
The infection can also spread upward into the head through veins connecting the face to the brain area. This can cause cavernous sinus thrombosis, a rare but life-threatening condition where a blood clot forms in the cavernous sinus. This may lead to brain abscesses, meningitis, or stroke.
Systemic Complications
An untreated chronic infection acts as a continuous source of bacteria entering the bloodstream. This hematogenous spread can affect the heart, particularly in individuals with pre-existing heart valve conditions. Bacteria can colonize the heart valves, causing infective endocarditis. Furthermore, the uncontrolled spread of bacteria can overwhelm the immune response, leading to sepsis, which can result in organ failure or death.
Permanent Functional and Aesthetic Consequences
The end stage of untreated decay is the irreversible loss of the tooth, requiring extraction to resolve the infection. Once a tooth is removed, the jawbone that anchored the root no longer receives functional stimulation from chewing. This lack of stimulation initiates alveolar bone resorption, leading to a progressive loss of jawbone volume and density.
Bone loss can be rapid, often continuing indefinitely without intervention. This atrophy changes the structure of the face, resulting in a sunken appearance around the mouth and an older facial profile. The absence of teeth also severely impairs functional ability, making it difficult to chew and digest food properly.
Missing teeth disrupt the coordination required for clear speech, potentially resulting in impediments like lisping or slurring. The aesthetic and functional consequences of tooth loss often lead to a profound psychological impact, including a decline in self-esteem and social anxiety.