Erythritol vs Ultrasonic Scaler Prophylaxis Systems on Dental Implants With Crowns Made by Different Materials

The aim of the study is to assess which prophylaxis methods is the most suitable for peri-implant hygiene between erythritol and ultrasonic scaler with peek inserts. A randomized clinical trial will be conducted on the patient. Patients will be randomly divided into two groups: * Erythritol group: erythritol with a particle size of \~14 µm will be used for 5 seconds (AIRFLOW® PLUS EMS) * Ultrasonic scaler group: a piezoelectric handpiece with peek inserts (Mini Piezon EMS; PI EMS) will be used. Different subgroups will be defined according to the material of the dental crown of the related implant: feldspathic ceramic, zirconia and lithium disilicate. The oral hygiene session will be carried out every 6 months (2-years follow-up; 6 sessions), after instruction and motivation of the patient, completion of the clinical chart with the recording of the Probing Depth (evaluation in mm of the peri-implant sulcus taken by a periodontal probe; 4 surfaces of the gingival margin are detected: vestibular, palatal/lingual, mesial, distal), Bleeding on Probing and Plaque Index.