Effectiveness of Probiotics in Managing Oral Halitosis: A Systematic Review of Randomized Controlled Trials.

Aim: Halitosis, characterized by volatile sulfur compound (VSC) production, is a prevalent oral health concern affecting 31.8% of the global population. Conventional treatments such as chlorhexidine-based mouthwashes offer temporary relief, but probiotics have emerged as a promising biological therapy by modulating oral microbiota. We aimed to systematically evaluate the efficacy of probiotic monotherapy in reducing halitosis-related VSC levels and organoleptic test (OLT) scores in randomized controlled trials (RCTs).

Materials and methods: A comprehensive database search (PubMed, Scopus, ClinicalTrials.gov, and gray literature) was conducted following PRISMA guidelines. The review protocol was prospectively registered with the Open Science Framework (OSF). Only RCTs comparing probiotics to placebo in systemically and periodontally healthy adults were included. Primary outcomes were changes in VSC levels and OLT scores, assessed using halimeters, Oral Chroma devices, or OLT evaluation. Risk of bias was assessed using the Cochrane RoB 2 tool.

Results: Six RCTs (n = 360 participants) met the inclusion criteria. Five studies demonstrated significant VSC reduction after probiotic intervention (P < 0.05). Three studies reported OLT score improvements, particularly with Streptococcus salivarius K12 and Weissella cibaria. Four studies confirmed microbiome alterations, with the effects of probiotics persisting post-treatment. No serious adverse effects were reported.

Conclusion: Probiotics significantly reduce VSC levels, improve OLT scores, and modulate the growth of oral microbiota. However, the heterogeneity of studies and limited long-term follow-up hinder clinical translation. Larger, standardized trials are essential for establishing the clinical efficacy. Probiotics present a safe adjunct therapy for halitosis management. Future research should focus on longitudinal studies, specific strain efficacy, and microbiome-targeted interventions.