Systematic Review Evaluates Clinical Outcomes of Probiotics as an Adjunct to Periodontal Therapy

Probiotics are live microorganisms that may confer health benefits when administered in adequate amounts and when the appropriate genus, species, subspecies, or strain is used (alone or in combination). In the past, they have been used in treating various systemic and gastrointestinal conditions. In oral health, probiotics may shift the subgingival microflora toward a healthier, eubiotic state by competing with periodontopathogens for nutrients and preventing pathogen adhesion by regulating gingival or crevicular fluid secretion. Additionally, they may contribute to immunomodulation by increasing anti-inflammatory cytokine production, producing antimicrobial agents, modulating cell proliferation and apoptosis, and modulating subgingival pH.¹

The current gold standard for managing periodontitis is mechanical biofilm control, specifically nonsurgical periodontal therapy (NSPT). Adjunctive antimicrobial therapies have been proposed to further reduce bacterial load in patients who do not respond well to NSPT alone. The most common antimicrobial adjuncts are local and systemic antibiotics, antimicrobial photodynamic therapy, and probiotic therapy.¹ However, among these, probiotic therapy remains absent from formal clinical practice guidelines as an adjunct to NSPT for managing chronic periodontitis.²

Although prior systematic reviews have evaluated probiotics as an adjunct to periodontal therapy, evidence remains inconclusive because of methodological inconsistencies, small sample sizes, and brief follow-up periods. To address these gaps and provide nuance, researchers conducted a systematic review and meta-analysis to provide updated, robust clinical insight into outcomes with adjunctive probiotic use.¹

The Study

This systematic review and meta-analysis utilized only randomized controlled trials published in the last 10 years, with searches conducted on March 20, 2024. To be included, trials must evaluate different probiotics as adjunctive treatment for gingivitis or periodontitis. After retrieval and eligibility screening, a total of 24 randomized controlled trials with 951 participants across probiotic and placebo groups were included. Of the selected articles, 10 focused on gingivitis and 14 on periodontitis.¹

The clinical parameters evaluated included biofilm index, bleeding on probing (BOP), and probing pocket depth (PPD). The researchers grouped findings by disease type (gingivitis or periodontitis) and follow-up duration to test the null hypothesis that adjunctive probiotic therapy does not differ significantly from control or placebo treatments in clinical outcomes.¹

The Results

The results showed clinical differences by underlying disease. In gingivitis studies, adjunctive probiotic use reduced biofilm index, BOP, and PPD compared with controls, but these differences were not statistically significant. The statistical findings translate into varied clinical relevance, as the results suggest these parameters could decrease or increase with adjunctive probiotic use.¹

Conversely, in patients with periodontitis, the probiotic group showed statistically significant reductions in both biofilm index and BOP with very minor-to-moderate clinical improvement. Although PPD were also lower in the probiotic group, the overall difference was not statistically or clinically significant.¹

Considering the long- and short-term clinical effects of adjunctive probiotics on periodontal parameters, the findings suggest that the observed improvements may depend on which probiotic is used and may attenuate or improve over time.¹ Only two long-term trials evaluating the efficacy of a single probiotic (Limosilactobacillus reuteri) were included. These trials reported that adjunctive probiotic groups showed statistically greater reductions in BOP, PPD, and biofilm index at 52 weeks, but the placebo group also showed statistically significant improvements in these parameters. Nonetheless, clinical and biochemical improvements were greater in the probiotic groups.^1,3,4

Shorter-term studies (4 to 12 weeks) frequently observed no significant clinical differences between probiotic and placebo groups. When clinical parameters improved (BOP and PPD), the effects were significant primarily in the short term (≤12 weeks). Biofilm index reductions were observed at longer follow-up durations (exceeding 8 weeks), suggesting biofilm prevention develops over time.¹

Specific strains like Bifidobacterium animalis subsp. lactis HN019 were used in 2 trials, both of which reported reduced PPD in the probiotic group compared with placebo. Another trial using a combination of Lactobacillus brevis and L. plantarum showed less improvement than a trial that used L. reuteri, decreasing BOP but impeding healing at sites with PPD greater than 4 mm. Notably, variability in PPD outcomes was associated with baseline pocket severity and species selection, with Bifidobacterium showing greater depth reductions in deep pockets (>6 mm) than Lactobacillus or Streptococcus species.¹

Overall, the results show no clinical improvement in patients with gingivitis and only minor effects on the biofilm index and BOP. This may reflect moderate variability across studies, likely due to differences in treatment protocols, operator experience, and outcome-measurement techniques.¹

Limitations

The authors warn that these findings should be interpreted cautiously because of multiple limitations. Language bias is a potential limitation, as the review included only English-language publications. However, the researchers attempted to mitigate this risk by completing a thorough grey literature search. Additionally, the overall certainty of evidence was rated low because all periodontal parameter measures had a serious risk of bias. Most concerning, the results were too uncertain to rule out whether adjunctive probiotics are beneficial or potentially harmful.¹

Furthermore, short follow-up periods across many included trials may limit the applicability of the findings, as long-term results could differ. The included periodontitis studies utilized different case definitions to classify disease. These diagnostic inconsistencies create inherent clinical variability that limits direct cross-study comparison. The meta-analysis focused strictly on clinical metrics and omitted microbiological and immunological parameters, leaving these effects unexplored. Finally, attentional bias (participant habit changes prompted by trial enrollment) cannot be ruled out.¹

Conclusion

This systematic review and meta-analysis found statistically significant improvements in specific periodontal parameters with select adjunctive probiotic use. However, this study aimed to provide clinicians with insight and highlight the distinction between statistical significance and clinical relevance. Some periodontal parameter improvements were statistically significant but had only very minor to modest clinical effects. However, because study designs, follow-up durations, and treatment protocols varied, the clinical relevance of these findings remains uncertain.¹

This systematic review and meta-analysis further supports the need for standardized, high-quality, long-term trials to determine the true effectiveness and long-term benefits of adjunctive probiotics while ruling out potential harm. Future studies should also focus on optimizing treatment protocols, patient-centered outcomes, and establishing clearer clinical guidelines for adjunctive probiotic use for patients with periodontitis.¹

Before you leave, check out the Today’s RDH self-study CE courses. All courses are peer-reviewed and non-sponsored to focus solely on high-quality education. Click here now.

Listen to the Today’s RDH Dental Hygiene Podcast Below:

References

1. Benavides-Reyes, C., Cabello, I., Magán-Fernández, A., et al. Clinical Effects of Probiotics on the Treatment of Gingivitis and Periodontitis: A Systematic Review and Meta-analysis. BMC Oral Health. 2025; 25(1): 490. https://pmc.ncbi.nlm.nih.gov/articles/PMC11971800/
2. Smiley, C.J., Tracy, S.L., Abt, E., et al. Evidence-Based Clinical Practice Guideline on the Nonsurgical Treatment of Chronic Periodontitis by Means of Scaling and Root Planing With or Without Adjuncts. J Am Dent Assoc. 2015; 146(7): 525-535. https://jada.ada.org/article/S0002-8177(15)00334-7/fulltext
3. İnce, G., Gürsoy, H., İpçi, ŞD., et al. Clinical and Biochemical Evaluation of Lozenges Containing Lactobacillus reuteri as an Adjunct to Non-Surgical Periodontal Therapy in Chronic Periodontitis. J Periodontol. 2015; 86(6): 746-754. https://pubmed.ncbi.nlm.nih.gov/25741580/
4. Tekce, M., Ince, G., Gürsoy, H., et al. Clinical and Microbiological Effects of Probiotic Lozenges in the Treatment of Chronic Periodontitis: A 1-Year Follow-Up Study. J Clin Periodontol. 2015; 42(4): 363-372. https://pubmed.ncbi.nlm.nih.gov/25728888/