ProlacSan probiotic lozenges and gels contain L. plantarum and L. brevis strains with proven in vitro antimicrobial activity against P. gingivalis. In our study we aim to investigate proposed benefit of ProlacSan as adjunct to conventional initial periodontal treatment in a group (n = 40) of Grade III and IV periodontitis patients. Patients will be randomized in two groups receiving either probiotic (n = 20) or placebo (n = 20) after completion of nonsurgical treatment within 7 days. Before treatment and after three months, standard periodontal parameters will be measured by masked examiner and plaque samples harvested for cultivation of 9 most relevant periodontal pathogens. One lozenge per day of probiotic/placebo will be used during 3 months healing period. Primary outcome measures will be the number of persisting sites per patient that need additional surgical treatment defined as sites with probing depth > 4 mm and bleeding on probing.

Inclusion Criteria:

• periodontitis stage III or IV
• at least 20 teeth for evaluation
• besides solitary crowns, no other prosthodontic tooth replacements
• good systemic health
• smoking less than 10 cig/day

Exclusion Criteria:

• periodontal treatment lass than 1 year before inclusion
• antibiotic therapy in the last 6 months
• chronic systemic diseases with the impact on periodontium or healing process
• medication with the impact on periodontium or healing process

Placebo, masked evaluator