Introduction The oral microbiota plays a fundamental role in maintaining both oral and systemic health, while dysbiosis contributes to diseases such as dental caries and periodontitis. Probiotics have gained attention as adjunctive strategies to restore microbial homeostasis. Heyndrickxia coagulans (formerly Bacillus coagulans) is a spore-forming, lactic acid-producing bacterium with documented antimicrobial, antioxidant, and immunomodulatory properties. Its resilience to environmental stressors and industrial processing makes it a promising probiotic candidate. This systematic review and meta-analysis aimed to evaluate the effects of H. coagulans on oral health outcomes.Methods A comprehensive search was performed across multiple databases up to September 2025 to identify randomized controlled trials (RCTs) and non-randomized studies assessing H. coagulans as a probiotic intervention for oral health. Data extraction followed PRISMA guidelines, and the risk of bias was evaluated using the RoB 2.0 and ROBINS-I tools. Meta-analysis was conducted using Stata SE® 18.5, with changes in salivary Streptococcus mutans levels as the primary outcome measure.Results Eight studies (seven RCTs and one NRSI) met the inclusion criteria. Most were conducted in India, Iran, and North Macedonia, with sample sizes ranging from 30 to 183 participants aged 5-73 years. Administration of H. coagulans, via chewable tablets, mouthwash, or food matrices, resulted in a significant reduction of salivary S. mutans counts in both children and adults compared with placebo or other probiotics. Meta-analysis of four studies demonstrated a pooled effect size of -0.99 (95%CI = -1.60/0.39; p < 0.01), although substantial heterogeneity was observed (I² = 98.2%). Additional studies reported improvements in Gingival Index, bleeding on probing, and clinical attachment levels among participants with gingivitis or periodontitis. No significant adverse events were reported.Conclusion H. coagulans appears to exert beneficial effects on oral health by reducing cariogenic bacterial load and improving periodontal parameters, supporting its potential use as an adjunct in caries prevention and gingival health maintenance. H. coagulans may favorably modulate the oral microbiota and contribute to overall oral health. However, further high-quality, large-scale clinical trials are needed to confirm these findings and define their therapeutic role in preventive oral care.
Cirio et al. (Wed,) studied this question.