A comprehensive review of the application of probiotics and postbiotics in oral health

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TL;DR

This narrative review examines the role of probiotics and postbiotics in oral health, finding that strains such as Lactobacillus, Bifidobacterium, and Streptococcus can significantly reduce cariogenic bacteria like Streptococcus mutans and improve periodontal outcomes. The authors propose postbiotics (non-viable bacterial metabolites) as a safer, more stable alternative to live probiotics for preventing and managing oral diseases including dental caries, periodontitis, halitosis, and oral Candida infections. The clinical significance lies in offering bacteriotherapy as a cost-effective preventive strategy to complement traditional oral care, though more human trials are needed to confirm long-term efficacy.

Full summary

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**Background:** Oral diseases affect approximately half the global population, with 2.4 billion people suffering from permanent tooth decay and 532 million children affected by primary tooth decay. Oral healthcare costs are substantial, consuming about 5% of total health expenditure in high-income countries. Dental caries is a multifactorial disease involving cariogenic diet, poor oral hygiene, high counts of cariogenic bacteria (notably Streptococcus mutans), dental plaque, inadequate saliva flow, and insufficient fluoride exposure. The oral microbiome, comprising bacteria such as Actinobacteria, Proteobacteria, Fusobacteria, Bacteroidetes, and Firmicutes (constituting 80-95% of the total oral microbiome), plays a crucial role in health and disease. Dysbiosis—disruption of the normal microbial balance—is a key step in oral disease development. While S. mutans is considered the primary cariogenic species, evidence shows that 10-15% of active caries cases do not involve S. mutans, with species like Scardovia wiggsiae detected in about 40% of children with active caries who lacked S. mutans. Probiotics (live microorganisms conferring health benefits when administered in adequate amounts) and postbiotics (non-viable bacterial metabolites or cell components) have emerged as potential preventive and therapeutic agents.

**Methods:** This is a narrative review synthesizing evidence from in vitro studies, in vivo animal studies, and human clinical trials examining the effects of various probiotic strains and postbiotic compounds on oral health outcomes. The review covers studies on Lactobacillus, Bifidobacterium, Streptococcus, and other genera, evaluating their impact on dental caries, periodontal disease, halitosis, and oral Candida infections. The authors also discuss the mechanisms of action, including competitive adhesion, production of antimicrobial compounds (bacteriocins, organic acids, hydrogen peroxide, fatty acids), and immune modulation.

**Key Results:** The review reports that 69% of Lactobacillus strains tested could inhibit S. mutans growth, and 82% could inhibit Porphyromonas gingivalis. Multiple human studies demonstrated significant reductions in salivary S. mutans counts following probiotic consumption. For example, Jindal et al. (2011) reported a statistically significant decrease (p<0.001) in S. mutans after 14 days of probiotic ingestion in children. Cannon et al. (2013) found significant reductions in both S. mutans and Lactobacilli counts in children aged 6-12 years after 28 days of L. reuteri lozenges. In a 7-month study of 571 children aged 1-6 years, L. rhamnosus GG in milk reduced the risk of decay. Teanpaisan et al. (2015) reported that in a high-caries-risk group, new caries was reduced 4.5-fold after 6 months of L. paracasei SD1 consumption. For Bifidobacteria, results were more mixed: some studies showed significant S. mutans reduction (e.g., Nagarajappa et al., 2015; p<0.05), while others found no significant effect. Notably, Zhai et al. (2009) found Bifidobacterium in 47.5% of patients with severe early childhood caries versus 0% in healthy children, raising concerns about potential cariogenicity. For periodontal disease, L. reuteri consumption decreased gum bleeding and inflammation, reduced levels of P. gingivalis, P. intermedia, and Aggregatibacter actinomycetemcomitans, and decreased concentrations of IL-17, IL-1β, and TNF-α in gingival crevicular fluid. For halitosis, Weissella cibaria reduced H₂S by 48.2% and CH₃SH by 59.4%, while S. salivarius K12 maintained reduced volatile sulfur compound levels for at least 2 weeks. For oral Candida, probiotic cheese containing L. rhamnosus GG decreased C. albicans abundance by 75% in elderly subjects. Postbiotics—including bacteriocins, organic acids, fatty acids, and hydrogen peroxide—are proposed as safer alternatives with advantages including a safe profile, long shelf life (up to 5 years), no toxic effects, standardization, and easier transportation.

**Clinical Implications:** The evidence supports probiotics as a promising adjunctive strategy for preventing and managing oral diseases, particularly dental caries and periodontitis. Probiotics may reduce the need for antibiotics in periodontal treatment, helping to decrease antibiotic resistance. However, the authors caution that Lactobacillus species themselves produce acids and have been associated with caries progression in some studies, though most evidence suggests controlled probiotic consumption does not initiate caries. Postbiotics offer a potentially safer alternative, especially for immunocompromised individuals, as they eliminate risks associated with live bacteria including transmission of antibiotic resistance genes and the need for cold chain storage. The review emphasizes that more animal studies and human clinical trials are needed, particularly for postbiotics from different probiotic species, to definitively establish their efficacy and determine whether the acids produced by probiotics differ in cariogenic potential from those produced by pathogenic bacteria.