The Influence of Probiotics in Halitosis and Cariogenic Bacteria: A Systematic Review and Meta-Analysis

Background: The aim of this systematic review was to evaluate the therapeutic potential of probiotics in patients with halitosis and to assess whether probiotics can also be implemented as a preventative tool in oral health. Secondary objectives included the effect of probiotics on oral-health-related quality of life, as well as their safety. Materials and methods: An electronic literature search in Medline (PubMed), Scopus, Web of Science, and the Cochrane library was carried out for the identification and selection of relevant randomized controlled trials. Eligibility was based on inclusion criteria, which included RCTs published after 2013, and the outcome variables were volatile sulfur compound (VSC) levels, organoleptic scores, plaque, or saliva samples to assess cariogenic bacteria counts and/or pH levels. Results: Out of 192 identified records, 16 randomized controlled trials were included. Ten of those studied the effects of probiotics on halitosis and the other six analyzed the effect of probiotics on oral health parameters, such as cariogenic bacteria counts, pH levels, and salivary flow and quality. A total of 921 patients were evaluated. The risk of bias was assessed using the Cochrane risk-of-bias assessment tool version 2. Conclusions: Probiotics exhibit the potential for oral health management by reducing VSC levels, improving saliva quality, and enhancing oral-health-related quality of life. Combining probiotics with tongue scraping may sustain VSC reduction, while symbiotics show potential in reducing tongue coating. However, different bacterial strains have been used in the included studies; hence, the conclusions cannot be generalized, being one of the main limitations of this review. Future research should explore the probiotics' potential to persist in the oral cavity post-treatment and employ standardized methodologies for conclusive efficacy assessment.