This a Randomized Controlled Clinical Trial comparing two techniques for the nonsurgical treatment of peri-implant mucositis. The main objective of the present randomized controlled clinical trial is to determine whether the application of a novel treatment strategy for peri-implant mucositis could lead to significantly improved clinical parameters as compared to standard treatment. Half of the patients receives treatment with manual instruments and chlorhexidine gel 1%, half receives treatment with submucosal biofilm removal by erythritol powder.

Inclusion Criteria:

• Subjects should have at least one implant (Renvert et al. 2009),
• with bleeding on probing using a 0.2N probing force or spontaneous bleeding with local swelling (code 1, 2 or 3 as described in Corbella et al. 2011) and with bone resorption of no more of 1 mm (preferably no bone loss visible on radiographs) as evaluated through the use of standardized radiographs, taken with the use of an individualized radiograph holder in comparison with findings from radiographs taken immediately following placement of the implant prosthesis (similar to Renvert et al. 2009 and Algraffee et al. 2011).
• females and males 35 to 65 years old; (IV) full mouth bleeding score % lower than 20%.

Exclusion Criteria:

• systemic diseases that could affect the immune response or that could condition the bacterial colonization
• use of anti-inflammatory prescription medications, or antibiotics within the preceding respectively 1 week and 3 months or during the study,
• full-mouth plaque score (FMPS) >20%;
• full-mouth bleeding score (FMBS) >20%,
• smokers of more than 5 cigarettes a day,
• Documented allergy or intolerance towards the components of the products used in the study,
• Presence of active infection with suppuration.
• Absence of periodontitis in the rest of the mouth
• Pregnancy (certified by auto-declaration)
• Patients suffering from upper respiratory tract infections, from chronic bronchitis
• endocarditis, breast feeding, contagious disease, immune deficiency (neutropenia, angranulocytosis, diabetes, hemophilia), patients under treatment (radiotherapy, chemotherapy, antibiotics).

The investigators planned to share anonymized IPD after the end of the study