Gingival recession is the exposure of the root surface due to the gum margin moving away from the crown of the tooth. It's common in adults and becomes more prevalent and severe with age. About 50% of people aged 18-64 and up to 88% of those over 65 have at least one site with gingival recession. The causes are multifactorial, including factors like aggressive brushing, thin gum tissue, orthodontic treatments, and more.

A systematic review found that untreated gingival recessions tend to worsen over time, with a significant increase in both the number of sites and the depth of the recession. A new classification system for gingival recessions has been proposed, categorizing them based on the detection of the cementoenamel junction (CEJ) and interproximal attachment loss.

Surgical techniques aim to restore the gum margin to its original position with minimal probing depths and good aesthetic results. The standard treatment involves a connective tissue graft from a donor site, but newer methods using substitutes like collagen matrices and platelet concentrates have shown comparable results.

Acellular Dermal Matrix (ADM) is a processed dermal tissue used as a substitute for connective tissue in root coverage and implant soft tissue corrections. It has shown favorable results, especially in reducing patient morbidity and thickening the gingival phenotype. ADM can be combined with a coronally positioned flap or tunnel technique for effective root coverage.

The use of platelet concentrates, such as Leukocyte and Platelet-Rich Fibrin (L-PRF), has also become an important alternative. These concentrates improve healing by providing growth factors and cytokines, aiding in the development of microvascularization.

The objective is to assess whether combining Acellular Dermal Matrix (ADM) with Leukocyte and Platelet-Rich Fibrin (L-PRF) yields better or comparable results to ADM alone in terms of complete root coverage, percentage of root coverage (PRC), recession reduction (RecRED), gain of keratinized gingiva (KGG), height of the interdental papilla (IDH), and increased gingival thickness (GT) after 6 months.

Inclusion Criteria:

• adult patients with ≥18 years of age. ability to understand all the study procedures and to comply with them throughout the entire study period. Ability and willingness to give written informed consent.

an adequate level of oral hygiene (plaque index ≤ 25%) (O'Leary et al., 1972).

an adequate general bleeding on probing (≤ 20%) treated periodontal disease. presence of two or more adjacent Cairo type I or II gingival recessions, with ≥1mm of keratinized gingiva in all the deffects.

Exclusion Criteria:

• untreated periodontitis.
• smokers > 5 cigarettes per day.
• local or systemic diseases that would interfere with routine periodontal therapy (i.e., uncontrolled diabetes mellitus, cancer, HIV, chronic high-dose steroid therapy, metabolic bone disease, radiation, immunosuppressive disease, hepatic dysfunction, immunosuppressive disease, autoimmune disease).
• treatment with anticoagulants or bisphosphonates.
• pregnant or lactating women.
• radiographic interproximal bone loss.
• tooth Mobility. If present, splinting should be performed prior to treatment.
• Active orthodontic treatment
• allergy or intolerance to study medication
• use of systemic antibiotics during the last 3 months
• use of systemic antibiotics for endocarditis prophylaxis
• patients with intentions to change residence that prevent follow-up

The randomization sequence will be carried out using a computer-generated list (StataⓇ v15.1) with a 1:1 allocation ratio according to a block randomization procedure. Allocation concealment will be kept by means of opaque-sealed envelopes that will be opened immediately after the anesthesia.