Are probiotics effective as an adjunct to periodontal therapy?

The evidence suggests probiotics offer modest but inconsistent clinical benefits as an adjunct to non-surgical periodontal therapy (NSPT). Several meta-analyses report statistically significant reductions in probing pocket depth (PPD) and gains in clinical attachment level (CAL) compared to NSPT alone, particularly at 3 and 12 months of follow-up ^[1][2], and significant reductions in plaque index and bleeding on probing have also been demonstrated in periodontitis patients ^[3]. However, the magnitude and durability of these benefits vary considerably across studies, with one well-designed randomised controlled trial finding no statistically significant additional clinical benefit over NSPT alone ^[4], and another meta-analysis noting CAL gains were significant in the short and medium term but not long term ^[5].

The strain, form, frequency, and duration of probiotic administration appear to influence outcomes. L. reuteri delivered as lozenges twice daily was associated with the most consistently favourable results for PPD reduction ^[5], and sensitivity analyses suggest greater benefit in patients with more severe baseline disease (mean PPD ≥5 mm) ^[1]. At a microbiological level, adjunctive probiotics - particularly L. reuteri used as a single strain - appear to reduce counts of key periodontopathogens such as Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola in subgingival plaque ^[6]. When compared directly to antibiotics, probiotics showed comparable PPD and CAL reductions, though antibiotics were more effective for plaque and gingival indices, and a combination of both outperformed either alone ^[7].

Overall, high heterogeneity across trials and limited immunological and microbiological data mean that current evidence is insufficient to issue firm clinical recommendations, and further standardised, high-quality RCTs are needed ^[1][3].