Across 3 RCTs, 1 reported a beneficial large effect on probing depth reduction, while 2 reported neutral effects (small reductions not statistically significant vs. placebo). The predominant effect is neutral, with small effect sizes in the neutral studies. The only beneficial study used 1×10⁹ CFU/day for 8 weeks in patients with periodontitis or gingivitis; the two neutral studies lasted 6 months in diabetic patients with periodontitis. Evidence is limited and inconclusive.
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. Additionally, the only beneficial study used a shorter duration (8 weeks) and a different population (non-diabetic) compared to the neutral studies (6 months, diabetic patients), suggesting possible population- or duration-dependent effects.
PD improved by 35.8% (4.92 ± 1.13 vs 3.12 ± 0.37 mm, p 0.05)
At 6 months, both groups showed statistically significant reductions in the primary outcome (mean probing depth), with reductions of 0.9 mm in the probiotic group and 0.8 mm in the placebo group, with no significant differences between them.
At #PD ≥ 7 mm, SI + Probi had a more frequent number of sites (p = 0.03) compared to SI + Placebo only at baseline.