Is it true that tooth decay can be contracted through a kiss?

There is concern that tooth decay, the most common dental disease, can be contracted through kissing. We decided to check whether such fear is justified by scientific data.

About this opportunity regularly report Media - as in materials about dental health and articlesdedicated to kisses. With significant reservations about the risk of contracting tooth decay during a kiss they tell and specialists in articles on the websites of dental clinics and professional blogs. However, some clinics publish this statement is without qualification or almost without them. And in a number of publications it is even stated the opposite - Kissing can protect against tooth decay.

Caries is pathological process, which is accompanied by the destruction of hard tooth tissues. It begins with demineralization of the inorganic part of the enamel under the influence of acids secreted by oral bacteria. At this stage, a chalk stain forms - the enamel changes color, but remains smooth. As tooth decay progresses, the enamel is destroyed, leading to the formation of a cavity. If the process does not stop, it can spread to the pulp (tissue containing blood vessels and nerve fibers) and even to the periodontium (tissue surrounding and holding the tooth in the socket). 

Main cause caries development - prolonged exposure of the tooth to acids formed by bacteria in the oral cavity during the breakdown of carbohydrates. In other words, we are talking about the coincidence of three factors at once:

• inadequate oral hygiene, due to which acids act on the tooth longer;
• a diet high in carbohydrates, particularly sucrose. What harms your teeth the most is regular snacking on such foods or dessert at the end of a meal. From a hygienic point of view, it would be optimal to eat dessert first, then the main course, and after that a vegetable salad;
• activity of cariogenic bacteria - acid-forming streptococci, in in particular Streptococcus mutans, Lactobacilli and a number of others, and, on the contrary, weak colonization of the oral cavity by anti-caries flora (recent scientific discoveries showthat there is a strain of streptococcus that counteracts the formation of caries).

Kissing, accordingly, has nothing to do with hygiene or diet. The only factor of the three listed that they can influence is the microflora of the oral cavity. Therefore, in order for caries to be transmitted from one person to another through a kiss during the exchange of biological fluids, the previously clean oral cavity must become infected with cariogenic bacteria. They really contained in saliva and can be transmitted along with it from one organism to another.

However, according to statistics, such bacteria colonize the oral cavity long before a person reaches a certain age and begins to practice kissing with the exchange of biological fluids. In the USA, for example, in 2011–2016, caries was in 23.3% of children aged two to five years. By age nine, more than half of children in the United States encountered with caries on milk or permanent teeth. In Russia the picture is even more depressing: the prevalence of caries is 12.2% among one-year-old children, 27.7% among two-year-olds, 57.7% among three-year-olds, 64.2% among four-year-olds, 78.3% among five-year-olds, 85.4% among six-year-olds.

The fact is that even before the age of kissing with the exchange of biological fluids, the child finds himself in many other situations in which infection occurs. Adultscaring for a baby, determine the temperature of the food or taste the food with the same cutlery that is used to feed the child, lick a pacifier or pacifier, give the child a taste of food that has already been bitten, etc. The transmission of cariogenic bacteria can even occur due to the contact of the toothbrushes of an adult and a child. Moreover, microparticles of saliva with cariogenic bacteria can get on the child's food even when an adult blows on it to cool it. Transmission is also possible through kissing, for example, a child’s fingers or feet - particles of saliva with bacteria remain on the skin, and then the baby licks his fingers and becomes infected with cariogenic bacteria. In addition, the overwhelming majority of children are not able to properly monitor oral hygiene. Finally, carbohydrate-rich foods are a favorite among most children. All this creates ideal conditions for the development of caries even at the stage of milk teeth. Therefore, by the age of the first kiss, almost any person is already infected with cariogenic bacteria. You should also not lose sight of various contacts between children, which create the possibility of transmitting bacteria from a sick child to a healthy one - using the same cutlery, dishes, eating shared food, licking toys, etc. 

Meta-analysis of studies on ways in which children become infected with cariogenic bacteria showedthat the main transmitter of such pathogens is the mother, and infection itself occurs during the first months and years of life. Some of the included studies demonstrated up to 100% matching of bacterial genotypes in the mouths of mothers and children. This is why it is so important, firstly, to protect the child from contact with adult microflora, and secondly, to monitor the oral health of all adults caring for small children.

Thus, in theory, through a kiss with the exchange of biological fluids, it is possible to become infected with caries, but in practice, it is extremely difficult to imagine a person who, by the age of the first kiss, would not have acquired these bacteria in another way. Despite the fact that the proportion of adults with absolutely healthy teeth is extremely small (according to data According to the US Centers for Disease Control and Prevention, up to 97% of Americans suffer from caries), the mere presence of cariogenic bacteria in the oral cavity does not necessarily mean the presence of diseased teeth, that is, the development of caries. Firstly, careful oral care and adherence to an anti-cariogenic diet ensure that pathogenic flora, although present, does not have a destructive effect on the teeth. Secondly, already mentioned anti-caries bacteria, on the one hand, slow down the growth of cariogenic bacteria and prevent them from creating a biofilm (the same dental plaque), on the other hand, they neutralize acids that are formed as a result of the breakdown of carbohydrates and destroy enamel. These two factors together may be the reason that a person with pathogenic microflora in the mouth does not necessarily suffer from tooth decay. In this case, a kiss will probably not have an undesirable effect: “good” bacteria will also fight “harmful” ones, few dangerous acids will be formed due to a suitable diet, some of these compounds will be neutralized, and the rest will be removed during regular hygiene. Finally, it cannot be ruled out probability active immune response - although bacteria enter the oral cavity, the recipient’s immunity will destroy them and no infection will occur. Conversely, in situations of immunosuppression or in pathological conditions that reduce saliva production, the likelihood that foreign bacteria will “take root” is higher.

Currently, several research centers are developing vaccines against caries. Scientists are considering options for populating the oral cavity with safe genetically modified organisms that will compete with cariogenic ones, pick up a protein that will force your own immunity to attack and destroy pathogenic microorganisms, and are trying Using a DNA vaccine, modify dental plaque so that it ceases to be a breeding ground for bacteria. However, so far all projects are in the development stage, tested mainly on animals and have not been introduced into widespread practice.

Therefore, for now, all that can be done to protect against tooth decay is to monitor oral hygiene and avoid excessive consumption of carbohydrates. It is quite pointless to refuse kisses - the vast majority of people have cariogenic bacteria, and infection with them does not yet lead to the development of dental disease. In addition, microflora, even transferred from one mouth to another, can be destroyed by the immune system.

Cover image: Image by summerstock from Pixabay

Misconception

What do our verdicts mean?