Strong teeth are even more vital to health now that average lifespans are stretched in old age. With regular check-ups, cleanings, flossing, and fluoride treatments, we try to protect our teeth. But it is not enough. Dental caries, commonly known as cavities, pose a mounting global health concern with increasing prevalence.
Much research confirms that caries are related to the microbial imbalance of dental plaque biofilms. For several decades, probiotics have been studied as a means to prevent caries by inhibiting the growth of cariogenic bacteria and the formation of biofilm.
This blog will explore the current state of the evidence as well as the clinical potential of probiotics in caries prevention.
Dental Caries, in brief
Global Burden of Disease Study 2021 reported a global prevalence of 2.03 billion caries in permanent teeth, indicating a considerable threat to health.
Dental caries destroy the hard tissues of the teeth, leading to oral pain and tooth loss. They are primarily caused by acidic byproducts from the fermentation of carbohydrates by microbes.
Oral biofilms (microbial communities embedded in an extracellular matrix on mucosal and dental surfaces) teem with microbes, some beneficial, others harmless, and still others with pathogenic potential. Within this framework, dietary sugars are metabolized to lactic acid leading to a dysbiotic and acidic environment, which promotes the initiation of caries by demineralization. Sucrose, a refined carbohydrate (known as table sugar) that is also abundant in processed foods, is the chief culprit among fermentable sugars.
The main pathogen responsible for the initiation of caries is Streptococcus mutans (S. mutans), a bacterium that can both produce acid and thrive in acidic conditions. Streptococcus sobrinus is another cariogenic bacterium in this group. In addition, lactobacilli and other bacteria are associated with caries progression.
Accordingly, current prevention of caries includes limiting pathogen growth through diet modifications, oral hygiene practices, and stimulation of saliva and fluoride.
Probiotics and dental caries, potential mechanisms
Probiotics may exert beneficial effects against oral pathogens in multiple ways.
The primary mechanisms include:
Modulation of host’s defense: Probiotics can modulate innate and adaptive immunity; modify cell proliferation and apoptosis; and reduce mucosal permeability.
Destruction or inhibition of pathogens: Probiotics produce antimicrobial substances such as lactic acid, hydrogen peroxide, and bacteriocins, which can immediately affect pathogen viability.
Competitive exclusion: Probiotic bacteria may attach more securely to the oral tissues than pathogens, competing for adhesion surfaces and in the process creating a new biofilm. In addition, probiotics can compete with pathogens for essential nutrients.
Probiotics and cariogenic pathogens
According to research, probiotics may impact oral health by competing with harmful bacteria in the mouth.
S. mutans
Many studies have concluded that the use of probiotics can reduce cariogenic S. Mutans CFU counts during the time they are used.
A meta-analysis of 50 clinical trials observed a reduction of S. mutans with bifidobacteria the most significant contributor to this effect. An increase in lactobacilli (of which some may be cariogenic) colonization was also observed due to the use of probiotic strains of the same genus.
A systematic review published a year later also concluded that the use of probiotics can reduce S. mutans CFU counts.
For example, one study showed that after the addition of probiotics, lactic acid bacteria strongly inhibit the growth of oral Streptococcus, and Lactobacillus might inhibit the formation of oral biofilms by reducing glucan production and the antibacterial activity of S. mutans.
The effects of probiotics on pathogenic bacteria in biofilms are multiple and vary according to probiotic strain.
Probiotics and dental caries
Whereas many studies have confirmed that probiotics have a role in mitigating risk factors (such as pathogen reduction and other mechanisms of action detailed above), fewer clinical studies have addressed the effect of probiotics on dental caries as a primary outcome. Some studies found no significant changes in caries prevalence while others observed a lower caries risk. The commonly tested probiotics against dental caries belong to Lactobacillus and Bifidobacterium species. Others include Bacillus, Saccharomyces, and Streptococcus.
One study of 179 infants concluded that early intervention with Lacticaseibacillus paracasei did not affect the frequency of dental caries at nine-year follow-up.
When another team of researchers evaluated a strain of Limosilactobacillus reuteri, given to children daily in the first year of life, reduced caries prevalence was observed in their primary dentition at nine years of age.
A 2021 systematic review and meta-analysis of studies using Bifidobacterium observed no significant difference in caries incidence in deciduous teeth from that in placebo groups.
However, a 2023 systematic review and meta-analysis of 17 trials concluded that probiotics could effectively prevent dental caries in preschool children, of which Lacticaseibacillus rhamnosus was more effective than other bacteria in preventing dental caries.
Researchers also explored the combination of probiotics with fluoride and discovered a lower caries incidence in the intervention group.
Nonetheless, it is important to note that while probiotics can potentially offer certain benefits in averting dental caries, they also come with certain limitations. For instance, an excess of certain probiotics like Lactobacillus and Bifidobacterium can potentially heighten the risk of developing caries.
Effector strains
A promising addition to the caries prevention toolbox is genetically modified “effector strains” of cariogenic bacteria which may act as probiotics. Effector strains candisplacecariogenic bacteria such as S. mutans by producing ammonia and also helping to maintain optimum pH.
Mode of delivery
Dairy products are commonly used to administer probiotics due to their enamel-protective and anti-cariogenic properties. However, alternative methods such as capsules, liquid forms, straws or tablets, drops, lozenges, sweetened cakes, and ice creams have been proposed as probiotic administration agents, particularly for individuals allergic to dairy components. Some of these delivery formats may be better suited for oral benefits (such as lozenges and foods) than others (e.g. capsules or straws).
Takeaway
Dental caries remain a significant public health issue. Ample evidence supports the use of probiotics in reducing cariogenic pathogens such as S. mutans, which is a primary causative role in dental caries. Probiotics may also lower risk through other mechanisms including bolstering immune responses. Some studies observed a reduction in dental caries but others did not. Though probiotics show promise in reducing caries incidence, more research on optimum strains, dose, and format of administration is needed.
Key references
Amargianitakis, Markos, et al. “Probiotics, Prebiotics, Synbiotics and Dental Caries. New Perspectives, Suggestions, and Patient Coaching Approach for a Cavity-Free Mouth.” Applied Sciences, vol. 11, no. 12, June 2021, p. 5472. Crossref, https://doi.org/10.3390/app11125472.
Campana, Raffaella et al. “Strain-specific probiotic properties of lactic acid bacteria and their interference with human intestinal pathogens invasion.” Gut pathogens vol. 9 12. 6 Mar. 2017, doi:10.1186/s13099-017-0162-4
Do, Thuy et al. “Oral biofilms: molecular analysis, challenges, and future prospects in dental diagnostics.” Clinical, cosmetic and investigational dentistry vol. 5 11-9. 28 Feb. 2013, doi:10.2147/CCIDE.S31005
Gruner, Deborah et al. “Probiotics for managing caries and periodontitis: Systematic review and meta-analysis.” Journal of dentistry vol. 48 (2016): 16-25. doi:10.1016/j.jdent.2016.03.002
Hao, Siyuan et al. “Effectiveness and safety of Bifidobacterium in preventing dental caries: a systematic review and meta-analysis.” Acta odontologica Scandinavica vol. 79,8 (2021): 613-622. doi:10.1080/00016357.2021.1921259
Hasslöf, P et al. “Early intervention with probiotic Lactobacillus paracasei F19 has no long-term effect on caries experience.” Caries research vol. 47,6 (2013): 559-65. doi:10.1159/000350524
Lee, Sung-Hoon, and Young-Jae Kim. “A comparative study of the effect of probiotics on cariogenic biofilm model for preventing dental caries.” Archives of microbiology vol. 196,8 (2014): 601-9. doi:10.1007/s00203-014-0998-7
Li, J W et al. “A Novel Competence Pathway in the Oral Pathogen Streptococcus sobrinus.” Journal of dental research vol. 100,5 (2021): 542-548. doi:10.1177/0022034520979150
Meng, Nan et al. “Effects of probiotics on preventing caries in preschool children: a systematic review and meta-analysis.” The Journal of clinical pediatric dentistry vol. 47,2 (2023): 85-100. doi:10.22514/jocpd.2023.014
Meng, Nan et al. “Effects of probiotics on preventing caries in preschool children: a systematic review and meta-analysis.” The Journal of clinical pediatric dentistry vol. 47,2 (2023): 85-100. doi:10.22514/jocpd.2023.014
Paes Leme, A F et al. “The role of sucrose in cariogenic dental biofilm formation–new insight.” Journal of dental research vol. 85,10 (2006): 878-87. doi:10.1177/154405910608501002
Piwat, S et al. “An assessment of adhesion, aggregation and surface charges of Lactobacillus strains derived from the human oral cavity.” Letters in applied microbiology vol. 61,1 (2015): 98-105. doi:10.1111/lam.12434
Seminario-Amez, M et al. “Probiotics and oral health: A systematic review.” Medicina oral, patologia oral y cirugia bucal vol. 22,3 e282-e288. 1 May. 2017, doi:10.4317/medoral.21494
Sivamaruthi, Bhagavathi Sundaram et al. “A Review of the Role of Probiotic Supplementation in Dental Caries.” Probiotics and antimicrobial proteins vol. 12,4 (2020): 1300-1309. doi:10.1007/s12602-020-09652-9
Stecksén-Blicks, C et al. “Effect of long-term consumption of milk supplemented with probiotic lactobacilli and fluoride on dental caries and general health in preschool children: a cluster-randomized study.” Caries research vol. 43,5 (2009): 374-81. doi:10.1159/000235581
Stensson, M et al. “Oral administration of Lactobacillus reuteri during the first year of life reduces caries prevalence in the primary dentition at 9 years of age.” Caries research vol. 48,2 (2014): 111-7. doi:10.1159/000354412
Twetman, Svante. “Are we ready for caries prevention through bacteriotherapy?” Brazilian oral research vol. 26 Suppl 1 (2012): 64-70. doi:10.1590/s1806-83242012000700010
Zhu, Yimei et al. “Association of polymicrobial interactions with dental caries development and prevention.” Frontiers in microbiology vol. 14 1162380. 18 May. 2023, doi:10.3389/fmicb.2023.1162380
Also see: Probiotics Take Oral Exams , an earlier blog from IPA