Aim: The aim of this randomized placebo-controlled clinical trial was to evaluate the effects of Lactobacillus reuteri-containing probiotic lozenges as an adjunct to scaling and root planing (SRP).

Methods: Thirty chronic periodontitis patients were recruited and monitored clinically and microbiologically at baseline, 3, 6, 9 and 12 weeks after therapy. All patients received one-stage full-mouth disinfection and randomly assigned over a test (SRP + probiotic, n = 15) or control (SRP + placebo, n = 15) group. The lozenges were used two times a day for 12 weeks.

Results: At week 12, all clinical parameters were significantly reduced in both groups, while there was significantly more pocket depth reduction (p < 0.05) and attachment gain (p < 0.05) in moderate and deep pockets; more Porphyromonas gingivalis reduction was observed in the SRP + probiotic group.

Conclusions: The results indicate that oral administration of L. reuteri lozenges could be a useful adjunct to SRP in chronic periodontitis.