Dental caries, commonly known as a cavity or tooth decay, is not contagious like a cold or flu; you cannot “catch” the physical hole in the tooth. However, dental caries is a transmissible bacterial infection that leads to the decay of the tooth structure over time. The specific bacteria responsible for initiating this process can be transferred from one person to another, primarily through saliva. While the damage itself is not spread, the infectious agents that cause it are.
The Science of Transmission
The decay process begins when specific types of bacteria in the mouth metabolize sugars from food and drink, producing acid as a byproduct. This acid slowly dissolves the mineral content of the tooth enamel, a process called demineralization, which eventually results in the formation of a cavity. The main culprits in this process are the mutans streptococci, most notably Streptococcus mutans, along with some Lactobacillus species.
The transfer of these bacteria occurs when saliva is shared, with the most significant risk being vertical transmission from a primary caregiver to an infant. Infants are born without Streptococcus mutans in their mouths and must acquire the bacteria to colonize the oral environment. Acquisition usually occurs during the “window of infectivity,” generally between 6 and 30 months of age. This timeframe is vulnerable because it coincides with the eruption of primary teeth, which provide the hard surfaces necessary for the bacteria to adhere and form stable colonies. High levels of these bacteria in a caregiver’s saliva increase the likelihood of transmission to the child.
Common Routes of Bacterial Sharing
The most common ways cavity-causing bacteria are transferred involve everyday behaviors that result in the exchange of saliva. Vertical transmission, the passing of bacteria from a parent or caregiver to a child, is the most frequently studied route. The risk of transmission is not limited to parents, as older siblings or other children can also facilitate horizontal transmission through behaviors like sharing drinks or food.
Common routes of transfer include:
- Cleaning a dropped pacifier by placing it in the caregiver’s mouth before giving it back to the infant.
- Sharing eating utensils, which transfers bacteria directly from the user’s mouth to the spoon or fork.
- Testing a baby’s food temperature or flavor by putting the feeding spoon in one’s own mouth before offering it to the child.
- Frequent direct physical contact, such as kissing a child directly on the mouth, which transfers a high bacterial load.
Reducing the Risk of Spread
Minimizing the risk of bacterial transmission centers on reducing the overall bacterial load in the caregiver’s mouth and avoiding saliva-sharing behaviors.
Caregivers should practice strict oral hygiene, which involves brushing twice daily with fluoride toothpaste and flossing once a day to remove plaque and reduce the number of Streptococcus mutans. Dentists may also recommend therapeutic antibacterial mouthwashes for caregivers with high levels of decay activity to suppress bacterial counts. Professional dental care is equally important; regular checkups and early treatment of any existing cavities in the caregiver will lower their bacterial reservoir.
Avoiding specific saliva-sharing behaviors is a direct action that prevents transfer to a child. Caregivers should refrain from using their own mouth to clean objects like pacifiers or using their own spoon to taste a child’s food.
A diet that reduces the bacteria’s food source is an effective preventative measure, as S. mutans thrives on fermentable carbohydrates. Limiting the frequency of sugary or acidic snacks and drinks for the entire family creates an environment less hospitable to the acid-producing bacteria. For children, the application of dental sealants to the chewing surfaces of molars can provide a protective barrier against decay, even if the bacteria are present.