A cavity (dental caries) represents a hole in the tooth structure that forms when bacteria on the tooth surface produce acids that erode the protective layers. The process is progressive, beginning with the demineralization of the hard outer enamel and continuing inward through the softer tissues beneath. Since this bacterial invasion cannot be stopped or reversed by the body’s natural defenses alone, an untreated cavity will always worsen over time. Understanding the chronological phases of this decay is important for recognizing why prompt intervention is necessary to preserve the tooth and overall health.
Worsening Pain and Increased Sensitivity
The first significant discomfort begins when the decay penetrates the enamel and reaches the dentin, the layer directly beneath the outer shell. Dentin is softer than enamel and contains millions of microscopic channels called dentinal tubules. These tubules extend inward, leading directly toward the tooth’s nerve center.
When the dentin becomes exposed through the cavity, these fluid-filled tubules transmit external stimuli to the pulp. This causes a characteristic sharp, short-lived pain often triggered by changes in temperature, such as consuming hot or cold foods and drinks. Sweet foods can also provoke this painful sensitivity because the sugar creates a temporary osmotic pressure change in the tubular fluid. The pain at this stage is usually intermittent and resolves quickly once the stimulus is removed.
Infection Reaches the Tooth Pulp
If the decay is still ignored, the bacteria eventually tunnel through the dentin and reach the pulp, the tooth’s innermost chamber that houses the blood vessels, connective tissue, and nerves. The bacteria entering this space trigger a severe inflammatory response, a condition known as pulpitis. Because the pulp is enclosed within the rigid walls of the tooth, the swelling has nowhere to expand, leading to intense pressure on the nerve.
At this stage, the pain transforms from a sharp, momentary twinge into a severe, continuous, and throbbing ache that can be spontaneous and may even wake a person from sleep. The infection causes irreversible pulpitis, meaning the pulp tissue cannot recover. This overwhelming infection leads to the death of the nerve and blood vessels, a process called pulp necrosis. Paradoxically, once the nerve dies, the excruciating pain may temporarily subside, giving a false impression that the problem has resolved, but the infection remains and continues to spread beyond the confines of the tooth.
Abscess Development and Jawbone Erosion
Following the death of the pulp, the infection travels down the tooth’s root canal and exits at the root tip (apex) into the surrounding jawbone. The body’s immune system attempts to contain this spreading bacteria by forming a localized pocket of pus, resulting in a periapical abscess. This localized collection of infected material causes inflammation and swelling in the surrounding tissues.
A dental abscess can cause noticeable symptoms like swelling in the face or jaw, fever, and tenderness in the lymph nodes of the neck. Sometimes, the infection creates a small channel (fistula) through the bone and gum tissue, appearing as a pimple-like bump that releases pus into the mouth. The chronic infection and accompanying inflammatory response cause the gradual destruction and erosion of the supporting jawbone, a process known as alveolar bone loss. This loss of bone is a direct result of the immune system releasing chemicals and enzymes that break down the bone tissue near the infection site.
Spreading Infection and Systemic Health Risks
If a dental abscess is left untreated, the infection can breach the confines of the jawbone and spread into the deep fascial spaces of the head and neck. This can lead to Ludwig’s Angina, a severe infection of the floor of the mouth that causes rapid swelling and can obstruct the airway. The infection can also enter the bloodstream, leading to sepsis, a life-threatening condition where the body damages its own tissues and organs.
In rare cases, bacteria can travel from the face to the brain, potentially causing a brain abscess or cavernous sinus thrombosis (a blood clot in a major sinus). The chronic infection can also contribute to systemic health issues, including an increased risk of cardiovascular problems like endocarditis. These systemic complications require immediate, often intensive, emergency medical intervention.