20 consecutive adult implant patients, presenting the signs of peri-implant mucositis (probing depth ≥4 mm combined with bleeding and/or pus on probing) or initial peri-implantitis (probing depth ≥4 mm, bleeding and suppuration plus radiographic loss of supporting bone ≤30% compared with the situation after implant placement) will be included.

Sites will be treated by ultrasonic debridement of the pocket, performed using a piezoceramic ultrasonic device. For the purpose, a Tip will be connected to the Handpiece Led (5 minutes/pocket) . Then, it will be followed by the subgingival use of erythritol powder applied by the use of Handpiece connected to an airflow unit 2x5 seconds/pocket. At this time the subgingival delivery of metronidazole gel will be provided. After instrumentation, patients will rinse with chlorhexidine 0.20% 3 times/day for 2 weeks.

At baseline, 1 month, 3 months and 6 months the following parameters will be evaluated: Probing Pocket depth (PPD), Bleeding on Probing (BoP), Clinical Attachment Level (CAL).

Inclusion Criteria:

• adult patients suffering from peri-implant mucositis or peri-implantitis

Exclusion Criteria:

• Heavy smokers current pregnant history of malignancy long-term steroidal or antibiotic therapy