MICRO-SURG: Subgingival Microbiome in Peri-Implantitis, Regenerative, and Resective Periodontal Surgery

Inclusion Criteria: * Age 18 years or older * Confirmed diagnosis of Peri-implantitis (for the peri-implantitis surgery arm), or Stage III/IV periodontitis (for the periodontal surgery arms) * Indication for surgical therapy corresponding to the assigned study arm * Ability to understand the study procedures and provide written informed consent * Adequate oral hygiene (API/SBI according to the clinician's judgment) * Willingness and ability to attend all follow-up visits * Willingness to provide salivary and subgingival plaque samples for microbiome analyses (NGS, SMDI) Exclusion Criteria: * Systemic conditions contraindicating oral surgical procedures * Severe systemic diseases (e.g., uncontrolled diabetes mellitus, immunosuppressive disorders) * Use of systemic antibiotics within the previous 3 months * Active COVID-19 infection at the time of surgery * Pregnancy or breastfeeding * Drug or alcohol abuse * Smoking more than 10 cigarettes per day * Known allergies to materials used in the assigned intervention (e.g., local anesthetics, sutures, membranes, bone grafting materials) * Participation in another clinical study within the previous 30 days * Acute oral infections that contraindicate participation * Inability or unwillingness to comply with all follow-up appointments Lack of capacity to provide informed consent