How Probiotics Prevent Tooth Decay: The case of Lactobacillus paracasei

Tamara Scepano
4 min readSep 30, 2020


Our mouths are home to over 700 types of bacterial species. Although bacteria are often described as dangerous, most of the bacteria found in our mouths are beneficial as they help remove harmful pathogens and aid in metabolizing nutrients. The microbiota, which is the collection of all bacteria and living cells in one area, is comprised of many dynamic relationships which help regulate the metabolic, hormonal and immunological responses of the host. A change in the natural microbiota could cause an imbalance to the hosts’ systems leading to tissue damage and disease. Due to the importance of maintaining a healthy microbiota, researchers have found that adding trace amounts of “mediator bacteria” can help regulate the microbiota. These “mediator bacteria” are called probiotics.

By definition, a probiotic is any living microorganism which causes a health benefit to the host. Although the mechanisms behind each probiotic differs, the overall goal of all probiotics is to regulate and maintain a healthy balance of bacteria in the body. The Lactobacillus probiotics help maintain a healthy oral cavity by out-competing pathogenic bacteria, meaning they take over the space, nutrients and other resources that the pathogenic bacteria would otherwise need for survival. Studies have shown that when increased amounts of Lactobacillus were present in the mouth, the growth of certain pathogenic bacteria was reduced. These findings hinted at a relationship between Lactobacillus and the development of tooth decay. However, the question then became which type of Lactobacillus is responsible for the prevention of tooth decay and how?

Recently, there has been a lot of speculation regarding the probiotic Lactobacillus paracasei and its ability to prevent tooth decay. L. paracasei is of particular interest as it has very few side effects, namely bloating and intestinal gas, and is commonly used in the fermentation process of many dairy products such as cheeses and yogurts, making it readily available for consumer.

Probiotics like L. paracasei can be found in many dairy products. Photo credits

Tooth decay, better known as caries, is caused by many factors, making it multifactorial, but its primarily cause is frequent sugar consumption. Some bacteria, such as the Streptococcus mutans, cause caries by metabolizing sugars and producing acid as a by-product. The acid demineralizes the tooth’s enamel, stripping it of its minerals, leading to the formation of caries. Thus, by controlling the presence of these bacteria, caries can be suppressed.

Teanpaisan et. al., looked at how L. paracasei impacted the presence of caries. The researchers had participants split into two groups, one of which was given a probiotic and the other a placebo. Both groups drank powdered milk either with a placebo or with the L. paracasei probiotic once a day for six months. Oral exams were done before the study, after six months and after 12 months to assess the long-term effects of the L. paracasei on the microbiota and the presence of caries. The researchers found that the probiotic group had fewer S. mutans in their oral microbiota and in turn fewer caries than the placebo group. Teanpaisan et al. believes that the antibacterial properties of L. paracasei prevented the S. mutans from adhering to teeth making them incapable of sticking around in the microbiota. Interestingly, they found that the number of S. mutans was lowest at the 12-month mark — 6 months after the probiotic group stopped drinking the powdered milk. The researchers believed that this is because it takes some time for the L. paracasei to fully colonized the microbiota. However, once colonized, the L. paracasei can multiply and survive for a long time in the mouth as it is the ideal environment, both in temperature and pH, for the species. Other studies have mimicked these results and claimed that daily consumption of the probiotic is needed in order for the bacteria to be properly introduced into the microbiota. Therefore, in order to gain the full caries-preventing benefits of L. paracasei, long-term and frequent use of the probiotic must be used.

Due to its ability in aiding the prevention of caries, some researchers have questioned if taking a probiotic is more effective than traditional methods, such as toothbrushing and eating a low-sugar diet, to prevent tooth decay. Corqueiro et al. found that although L. paracasei regulated the spread of S. mutants, it was less effective than traditional methods in preventing caries. These results are thought to be due to the mechanism as to which the probiotic regulates bacteria. L. paracasei regulates S. mutans by out-competing the bacteria for attachment onto the tooth’s surface. However, L. paracasei is not as effective at preventing the colonisation of other bacteria which have alternative mechanisms for attachment. As caries are a multifactorial disease, controlling the colonization of one bacteria is not enough to eliminate the risk of caries. Corqueiro et al. concluded that probiotics should be looked at as an additional step in caries prevention alongside traditional techniques.

Although consuming probiotics alone won’t prevent caries, consuming foods that contain them would still be beneficial in the prevention of tooth decay. As L. paracasei is commonly found in dairy products, which are a strong source of calcium and other important minerals in enamel remineralization, long-term and regular consumption could help with the maintenance of teeth and help maintain a healthy oral cavity as long as traditional methods are still being utilized.