Tooth decay is a common infectious disease process that affects the hard structures of the teeth. This damage occurs when specific oral bacteria consume sugars and produce acid, which gradually dissolves the protective tooth enamel. The term “spread” applies to two distinct scenarios: the progression of damage within the mouth and the transmission of the responsible bacteria to another person. Understanding both is necessary to protect oral health.
How Tooth Decay Progresses Within a Single Tooth
The process of tooth decay begins with demineralization, where the acid produced by bacteria strips away the mineral content of the enamel. This initial stage often appears as a small, white, chalky spot on the tooth surface. At this point, the process may still be reversed with proper care and fluoride application. If the acid attack continues, the damage progresses to form a cavity, or a noticeable hole, penetrating through the enamel layer.
Once the decay breaches the enamel, it reaches the underlying dentin, a softer and more porous material. Because dentin contains microscopic tubules leading directly to the tooth’s nerve center, the pulp, decay accelerates significantly. The bacteria and acid spread more rapidly sideways and deeper into the tooth structure, often leading to increased sensitivity or pain. If left unchecked, the infection will eventually reach the pulp chamber, causing inflammation and potentially leading to a painful abscess at the root tip.
Spread of Decay Between Adjacent Teeth
Decay does not “jump” from one tooth to another, but the same acidic, bacteria-rich environment affects multiple teeth simultaneously, especially in proximal spaces. These interproximal surfaces, where two teeth touch, are difficult for a toothbrush to reach, creating a sheltered area where plaque and acid accumulate undisturbed. When decay begins on the side of one tooth, the neighboring tooth is exposed to the shared environment, often resulting in mirror-image decay. Poor flossing habits are a significant risk factor, as flossing is the primary way to disrupt the bacterial biofilm in these tight spaces. Furthermore, the collapse of a decayed tooth can create a larger area for food to become lodged, fueling bacteria affecting the adjacent surface.
Transmission of Cavity-Causing Bacteria
While tooth decay itself is not contagious like a virus, the specific bacteria responsible for the disease are transmissible between individuals. The primary culprits are Streptococcus mutans and Lactobacilli species, which thrive in the oral environment. This transmission, often called “vertical transmission,” most commonly occurs from a primary caregiver to an infant. The transfer happens through saliva contact, using activities like sharing eating utensils or cleaning a pacifier by mouth. Delaying the acquisition of these bacteria until after a child’s second birthday may reduce the lifetime risk of developing dental caries.
Stopping the Progression and Spread
Stopping the progression of decay within a tooth requires professional intervention. This usually involves a dental filling, which removes the infected material and seals the cavity. For damage only at the initial demineralization stage, high-concentration fluoride treatments can help remineralize and strengthen the enamel. Once decay has advanced into the dentin, a filling is necessary to halt the infection before it reaches the pulp and necessitates a root canal.
Preventing the spread to adjacent teeth and the transmission of bacteria involves improved hygiene, diet, and behavior. Daily flossing is necessary to remove plaque and bacteria from the proximal surfaces inaccessible to a toothbrush. Reducing the frequency of sugar and carbohydrate intake limits the fuel source for Streptococcus mutans and Lactobacilli to produce acid. To prevent transmission to children, caregivers should avoid sharing saliva-contaminated items and actively manage their own oral health.