Domiciliary Use of Hyaluronic Acid Gel Solutions vs Domiciliary Use of Chlorhexidine Mouthwash 0,20% for the Management of Peri-implant Mucositis Sites

This is a randomized controlled clinical trial (RCT). After signing the informed consent, patients satisfying the inclusion criteria will undergo supragingival and subgingival professional oral hygiene of both arches performed with ultrasonic instrumentation with PEEK inserts, manual instrumentation with PEEK curettes and air polishing with glycine powder. After that, the sample will be randomly divided into 2 groups based on the domiciliary assigned treatment: * Aftoral® Oral Gel solution with Hyaluronic Acid, Xylitol and glycerophosphoinositol for the domiciliary use for 15 days for 2 peri-implant mucositis sites. * Unidea® Chlorhexidine digluconate Mouthwash 0,20% administration for the domiciliary application for 15 days for 2 peri-implant sites. The study will last 6 months. Patients will be visited at: T0, after 1 month from T0 (T1), after 3 months (T2), after 6 months (T3), after 9 months (T4) and after 12 months (T5). Professional hygiene will be performed again at T3. At each recall session were collected a satisfaction questionnaire of the products (taste, smell, consistency, persistence and ease of application) and the following periodontal clinical indices, using a PEEK probe on each peri-implant site: * conditions of the marginal mucosa (swelling and erythema), * migration of the marginal mucosa, * PPD (Probing Pocket Depth), * BOP% (Bleeding on Probing), * BS (Bleeding Score), * Suppuration, * PCR% (Plaque Control Record),