The goal of this study is to determine which method better increases the volume of soft tissues (gums) around dental implants: using the patient's own tissues or applying collagen matrices. The study also evaluates the safety of these methods and their impact on smile aesthetics.

The main questions it aims to answer:

Which method provides greater and more stable increase in gum thickness around the implant? Does the choice of material affect gum color (how well it matches adjacent areas)? What features of healing and cellular tissue structure are observed when using different materials?

Researchers will compare:

Autogenous connective tissue grafts (CTG) - the patient's own connective tissue grafts harvested from the palate or maxillary tuberosity Xenogeneic collagen matrices (XCM) - bioresorbable materials of animal origin (Fibro-Gide® and FibroMatrix®) that do not require harvesting the patient's own tissue

Participants will:

Undergo a surgical procedure to increase soft tissue volume in the area of implant placement (using one of four methods assigned randomly)

Attend clinic visits for follow-up examinations and assessments:

• Before surgery
• 3 months after surgery
• 6 months after surgery

Undergo additional examinations:

• 3D intraoral scanning to assess changes in tissue volume
• Cone-beam computed tomography (CBCT) to measure gum thickness
• Polarized-light photography to evaluate gum color
• Collection of a small tissue sample (biopsy) for laboratory analysis of tissue structure and cellular composition

Inclusion Criteria:

• Age between 21 and 75 years
• Requirement for single dental implant placement in the mandibular molar region (replacing no more than one tooth)
• Need for soft tissue augmentation to achieve peri-implant mucosal thickness ≥2 mm
• Signed voluntary informed consent for treatment and research participation
• Ability and willingness to attend all scheduled follow-up examinations for 12 months post-surgery
• Adequate oral hygiene and commitment to maintain it throughout the study period

Exclusion Criteria:

• Presence of systemic diseases in a decompensated stage (e.g., uncontrolled diabetes, severe cardiovascular disease)
• Current or prior use of immunosuppressants, bisphosphonates, or high-dose corticosteroids
• History of cancer, radiation therapy, or chemotherapy within 5 years prior to enrollment
• Need for concurrent bone grafting or immediate implant placement following tooth extraction
• Active periodontal disease or untreated oral infections at the time of surgery
• Heavy smoking (>10 cigarettes/day) or inability to abstain from smoking during the healing period
• Pregnancy or lactation
• Known allergy to collagen, porcine/bovine products, or materials used in the study (sutures, anesthetics)
• Participation in another clinical trial within 30 days prior to enrollment
• Refusal to participate in any stage of the study or inability to comply with study procedures
• Psychological or social conditions that, in the investigator's judgment, may compromise protocol adherence or data reliability

Individual participant data (IPD) will not be shared publicly. This decision is based on: (1) the single-center, academic nature of the study with a relatively small sample size, which increases re-identification risk even after de-identification; (2) the inclusion of detailed clinical, radiographic, and histological data that may contain sensitive personal health information; (3) ongoing secondary analyses and manuscript preparations by the investigative team; and (4) the absence of a dedicated infrastructure for secure, governed data sharing at this institution.