Buccal Graft + Collagen Matrix Versus Free Gingival Graft for Keratinized Mucosa Augmentation at Implant Sites

Inclusion Criteria: * Age ≥ 18 years, * Periodontally and systemically healthy, * Full-mouth plaque score and full-mouth bleeding ≤ 20% (measured at four sites per tooth), * Presence of at least one dental implant with \< 2 mm of KM and lack of firm/adherent mucosa, * Presence of at least 4 mm of keratinized gingiva in two or more teeth nonadjacent to the implant to be treated, * Implants diagnosed as healthy (Berglundh et al. 2018), * The patient must be able to perform good oral hygiene. Exclusion criteria: * Contraindications for surgery, * Systemic condition (e.g. diabetes mellitus, HIV, cancer, etc) that could compromise wound healing, * Patients pregnant or attempting to get pregnant (self-reported), * Untreated periodontitis, * Untreated peri-implant mucositis or peri-implantitis (Berglundh et al. 2018), * Smoking, * Allergy to collagen-based medical products or iodine, * Previous free gingival graft procedure at the target site.