A cavity, also known as dental caries, is a hole or structural defect in a tooth that results from the progressive breakdown of the enamel. This damage is caused by acids produced by bacteria in the mouth. A true, established cavity—a physical hole that has breached the tooth’s surface—cannot disappear or heal on its own. However, the initial stage of tooth decay, a “pre-cavity” lesion that has only weakened the enamel, can often be reversed by natural biological processes and improved oral care.
Understanding Tooth Decay: The Demineralization Process
Tooth decay begins with demineralization, the loss of minerals from the tooth’s hard structure. Enamel, the outermost layer, is composed of calcium and phosphate ions. Bacteria in the mouth feed on sugars and starches, converting these carbohydrates into acids.
When the acidity level in the mouth drops below a pH of about 5.5, these acids dissolve the calcium and phosphate from the enamel, weakening the tooth. This mineral loss is the first sign of decay and often appears as a chalky white spot on the tooth surface. This white spot indicates a porous area where the enamel has been softened but has not yet broken through.
The constant presence of plaque ensures a continuous acid attack on the enamel. If the acid exposure is frequent and prolonged, mineral loss outpaces the tooth’s natural ability to repair itself. This ongoing chemical erosion eventually leads to a physical breakdown of the enamel structure.
How Early Lesions Can Reverse: The Power of Remineralization
The demineralization process can be counteracted by a natural repair mechanism called remineralization. This process deposits lost calcium and phosphate ions back into the weakened enamel structure. This natural restoration hardens the softened enamel and can reverse early white-spot lesions.
Saliva plays a central role in this repair because it acts as a reservoir for calcium and phosphate ions and helps neutralize the harmful acids produced by bacteria. When the oral pH returns to a neutral level, saliva allows these minerals to flow back into the porous enamel.
Fluoride greatly enhances this repair process. When present, fluoride incorporates itself into the damaged enamel, creating fluorapatite. This new crystalline structure is more resistant to acid attacks than the original enamel.
Using fluoride products helps tip the balance in favor of remineralization, strengthening the tooth surface and stopping decay progression. Reducing the consumption of sugary and acidic foods is also necessary, as it limits the fuel source for acid-producing bacteria, giving the repair process the time it needs to work.
When Decay Becomes a True Cavity Requiring Intervention
The point of no return occurs when demineralization progresses past surface softening and causes a structural breach. Once the acid completely erodes the enamel and creates a physical hole, the damage cannot be repaired naturally. This is when an early lesion transitions into a true cavity.
The decay progresses much faster once it penetrates the underlying dentin, the layer beneath the enamel. Dentin is softer and less mineralized than enamel, allowing the acid and bacteria to spread rapidly. The tooth is structurally compromised.
Professional intervention is necessary to remove the infected tissue and restore the tooth’s structure, preventing bacteria from reaching the innermost pulp chamber. Standard treatment involves a filling, where a dentist removes the decayed material and replaces the lost structure with a restorative material.
If the decay is left untreated and reaches the pulp, it can cause severe pain and may require more intensive procedures, such as a root canal or tooth extraction.