This two-arm, single-blinded, monocentric, controlled, randomised clinical study is designed to examine the effect of professional submucosal treatment by means of ultrasonics with plastic tip (test group), as compared to no professional submucosal instrumentation (control group), in the treatment of peri-implant mucositis (PIM). Both groups will have oral hygiene instruction/reinforcement (OHI) at baseline and repeated at 3 months. In the study, 50 participants will be enrolled (25 per group), with each patient contributing one implant with PIM. Peri-implant sulcus fluid (PISF) samples will be obtained at baseline, 3- and 6-months to analyse the change of relevant biomarkers over the course of PIM treatment. Intraoral scans will be performed at baseline, 3- and 6-months to analyse potential soft-tissue volumetric changes according to treatment.

Inclusion Criteria:

• Subject must be ≥ 20 years
• Subject must have one implant presenting PIM as defined according to the World Workshop 2017 criteria (presence of BoP and/or suppuration (SoP), without bone loss exceeding 0.5 mm beyond crestal bone level changes resulting from initial remodeling, regardless of PPD. In absence of baseline radiographs (i.e., 0-1 year after loading) a bone level of <2mm from the top of the intraosseous part of the implant is considered as the reference threshold)
• Cleansable prosthesis (an interproximal brush must be able to pass from side to side at interproximal aspects tangential to the peri-implant sulcus, and a brush has to be able to reach the buccal and palatal/lingual sulcus).
• No evidence of occlusal overload
• No cement remnants identified on radiographs or clinically
• Implant-supported fixed restoration inserted at least 6 months before patient enrolment and not interfering with assessment of clinical parameters at more than 3/6 sites
• Periodontally healthy subjects or treated periodontitis (no residual site with PPD ≥ 5 mm)
• Full-mouth plaque (FMPS) and bleeding (FMBS) score ≤ 20%¬¬¬¬¬¬¬ at screening visit
• Non-smokers or light-smokers (<10 cigarettes per day)
• Competent to give consent

Exclusion Criteria:

• Previous radiotherapy, current use of chemotherapy, systemic long-term corticosteroid treatment
• Hematologic disorders
• Pregnant subjects
• Patients classified as > class 2 according to the ASA (American Society of Anesthesiologists) physical status classification
• No systemic antibiotic treatment within 3 months prior to intervention

IPD will be available for other researchers upon reasonable request and as long as in accordance with ethical committee and national GDPR rules.

Investigator-blinded