A cavity (dental caries) is tooth decay caused by acid-producing bacteria that erode the tooth structure. Decay begins when plaque converts sugars into acid, slowly dissolving the minerals in the tooth’s outer layer. If this erosion is not addressed, the structure will not repair itself and the bacterial infection advances. A dental filling removes the decayed material and seals the tooth, preventing the infection from spreading further. Delaying this simple procedure transforms a localized issue into a severe internal infection with consequences that extend beyond the mouth.
Progression Through Enamel and Dentin
The initial stage of decay occurs in the enamel, the hardest substance in the human body. At this point, the cavity is often asymptomatic, appearing only as a white or chalky spot where minerals have been lost. If caught early enough, a small lesion in the enamel can sometimes be reversed with professional fluoride treatments and improved hygiene practices, which promote remineralization of the surface.
Once the decay penetrates the enamel and reaches the underlying dentin, the progression accelerates significantly. Dentin is softer than enamel and contains microscopic tubes connecting to the tooth’s nerve center. When exposed, these tubules allow external stimuli to travel inward, leading to sensitivity, particularly to hot, cold, or sweet substances. This sensitivity is often transient, subsiding quickly after the stimulus is removed.
The decay at this stage is considered moderate, and a standard dental filling remains the most common treatment. The filling removes the infected dentin and restores the tooth’s structure, stopping the bacterial invasion.
The Onset of Pulp Infection
If the decay is left untreated through the dentin layer, the bacterial infection will eventually reach the dental pulp, the soft tissue at the center of the tooth. The pulp contains nerves, blood vessels, and connective tissue, making it the living core of the tooth. When bacteria invade this area, it causes a severe inflammation known as irreversible pulpitis.
The symptoms change dramatically from transient sensitivity to a more intense and persistent pain that can be spontaneous, throbbing, or aching. This discomfort often lingers long after exposure to hot or cold temperatures, and it can be severe enough to disrupt sleep. The constant presence of bacteria and inflammation causes the pulp tissue to become necrotic, meaning it dies.
This death of the pulp tissue is a turning point, as the infection is no longer localized to the hard tooth structure but is now inside the tooth’s root canal system. Although the tooth may temporarily stop hurting once the nerve dies, the infection remains and begins to travel down the root. This phase necessitates a major change in treatment because a simple filling can no longer resolve the issue.
Advanced Consequences and Treatment Changes
Once the infection moves past the pulp and exits the tip of the tooth root, it begins to form a dental abscess, a pocket of pus in the surrounding jawbone. This localized infection can cause severe pain, facial swelling, and a pimple-like bump on the gums that may drain pus. An untreated abscess represents a serious health threat, as the infection can spread beyond the tooth structure and into the surrounding tissues and bone.
The infection may travel through the facial spaces, potentially leading to conditions like cellulitis, a serious bacterial skin infection that causes widespread swelling. In rare but severe cases, the bacteria can enter the bloodstream, causing a life-threatening systemic infection such as sepsis. Furthermore, the chronic infection can cause the jawbone supporting the tooth to slowly dissolve, leading to tooth instability and, ultimately, tooth loss.
The required treatment at this advanced stage shifts from a routine, single-visit filling to a complex procedure. To save the tooth, root canal therapy is necessary, which involves removing the infected pulp and sealing the root canal system. If the tooth structure is too compromised, or the infection has caused too much bone loss, the tooth may be deemed non-restorable, requiring a surgical extraction. These advanced procedures are significantly more time-consuming, involve multiple appointments, and carry a substantially higher financial burden than addressing the initial cavity.