Evaluate clinically and microbiologically the effect of the oral probiotic Lactobacillus reuteri Prodentis (PerioBalance®, Sunstar, Switzerland) on implants with mucositis or periimplantitis, as a coadjuvant treatment of mechanical therapy.

A total of 44 patients, 22 with mucositis and 22 with periimplantitis, were randomly assigned to either the control or the test group, so that 11 patients received placebo and 11 probiotic treatment. After the baseline clinical, radiological and microbiological examination, and once the study group was randomly assigned (probiotic or placebo), supragingival prophylaxis was performed in the mucositis group and subgingival mechanical therapy in the periimplantitis group. Then they get a container with 30 probiotic or placebo tablets and instructions on how and when to take them. At 30 and 90 days after beginning the treatment, a clinical, radiological and microbiological examination was performed.

Inclusion Criteria:

• adult patients with general good health,
• non-smokers,
• history of mild or moderate chronic periodontitis
• at least one dental implant with probing pocket depth ≥4mm together with bleeding on probing and/or suppuration, and a fixed prosthetic restoration in function for at least 12 months,
• compliance with the periodontal maintenance program,
• accessibility during all the study period and receptiveness and ability to fulfill with the protocol.

Exclusion Criteria:

• pregnant or lactating women,
• patients who required prophylaxis of bacterial endocarditis or had taken local or systemic antibiotic, anti-inflammatory, antiseptic or probiotic therapy in the previous 3 months,
• subjects who had received surgical periodontal treatment in the last 6 months,
• uncontrolled periodontal disease,
• previous or current history of alcoholism or smoking,
• treatment with bisphosphonates, neurologic deficiencies, systemic diseases such as immunodeficiencies or uncontrolled diabetes, rheumatoid, hepatic, renal, cardiovascular or infectious pathologies, radiotherapy, chemotherapy, use of any medication which can affect at periodontal level,
• lack of patient cooperation (failure to follow the treatment instructions and/or failure to attend visits),
• implants with mobility and/or radiographic bone loss ≥ 5mm and/or ≥ 50% of implant length.

The patients, the clinical examiner, the laboratory technician and the statistician did not know the content of the containers (probiotic or placebo).