2022-05-17
Dental caries, a common oral disease, is the most widespread disease worldwide, with a prevalence approaching 91% of the adult population. The imbalance of microbial ecology is the most important factor in its pathogenesis. In recent years, it has been found that probiotics possess the ability to displace cariogenic microorganisms and colonize the oral cavity, so they have great potential in the prevention of dental caries and become a new strategy for preventing dental caries.

The oral cavity constitutes a habitat for a wide variety of microorganisms. Many microorganisms colonize the surface of the oral mucosa and hard dental tissues. These microorganisms colonize together to form a complex "oral biofilm" or "dental plaque." In a healthy state, all of them are in a state of symbiosis with each other as much as with the host. When ingested sugar is absorbed by pathogenic bacteria (mostly Streptococcus mutans) on dental plaque and metabolized into acids, these acids can dissolve hard tooth tissue at this time, that is, demineralization; once the acid residue is removed, remineralization occurs. In low-frequency sugary diets, demineralization and remineralization are in balance; while in high-frequent high-sugar diets, the constant low-pH conditions exert predominate toward an acidogenic bacteria, and demineralize and remineralization of tooth surfaces imbalance, thus creating the occurrence of dental caries.

Based on the mechanism of dental caries, recent studies have found that probiotics can prevent caries by inhibiting the growth of cariogenic microorganisms and the formation of biofilms, including: (1) Probiotics can compete with cariogenic microorganisms for nutrition or colonization sites ; (2) symbiotic with cariogenic microorganisms and exert antibacterial effects; (3) probiotics can produce organic acids, hydrogen peroxide, bacteriocins, etc. to interfere with the metabolism of cariogenic microorganisms. The remaining anti-caries mechanisms include modulation of immunity, regulation of local pH, and increased salivary production. Probiotics reported in the literature to prevent dental caries include Lactobacillus rhamnosus GG (LGG), Lactobacillus reuteri, Lactobacillus salivarius and Lactobacillus paracasei, etc. In clinical research, a number of studies have confirmed that these probiotics can indeed effectively prevent the occurrence of dental caries. For example, Wattanarat et al. used milk powder as a carrier to supplement Lactobacillus paracasei SD1 (about 3.7 × 109 CFU/g). During the process of taking, the number of Streptococcus mutans (the main cariogenic microorganism) in saliva decreased significantly. After 6 months of cessation of intake, it was observed that the experimental group had a significant reduction in dental caries compared with the control group, but the number of Streptococcus mutans had increased to the baseline level. Rodríguez et al. included 261 healthy children and randomly divided them into 2 groups. The probiotic group was given milk containing Lactobacillus rhamnosus SP1 (about 1.5 × 109 CFU/g), and the control group was given pure milk. After 10 months, the average number of per child in the probiotic group (1.13) was significantly lower than that in the control group (1.75). Nishihara et al. asked subjects to ingest inactivated Lactobacillus salivarius CECT 5713 and found that from the 3rd day of involvement to the end of treatment, the level of Streptococcus mutans was significantly reduced, indicating that inactivated probiotics also have a probiotic effect.

Some clinical studies have shown that probiotics can indeed prevent the occurrence of dental caries without side effects, however, the safety of some people still needs attention, including premature infants, immunodeficiency people and the elderly. In order to ensure the safe use of probiotics, long-term in-depth research on the efficacy and safety of each strain is still required. However, knowledge about the mechanism of action of oral probiotics is still lacking. Further studies are needed to understand their interactions with host cells and the microbiome. At the same time, they should be used as a preventive method rather than as a caries therapy tool.

References:
  1. Markos Amargianitakis, Maria Antoniadou , Christos Rahiotis and Theodoros Varzakas. Probiotics, Prebiotics, Synbiotics and Dental Caries. New Perspectives, Suggestions, and Patient Coaching Approach for a Cavity-Free Mouth.Appl. Sci. 2021, 11, 5472. https://doi.org/10.3390/app11125472.
  2. Fu Zhuohui,Deng Jiaxin,Chen Yuan,Wang Yan. Research progress into probiotics for the prevention of dental caries.Journal of Prevention and Treatment for Stomatological Diseases Vol.27 No.9 p603~608 Sep. 2019 http://www.kqjbfz.com