Gingival recession is a common condition in which the gum tissue recedes, exposing the root surface of the tooth. This can lead to tooth sensitivity, higher risk of root decay, and aesthetic concerns. A commonly used surgical treatment is the coronally advanced flap combined with a connective tissue graft (CAF + SCTG), which aims to cover the exposed root and improve gum health.

Hyaluronic acid (HA) is a naturally occurring substance in the body that plays an important role in wound healing. It may help improve tissue repair, reduce inflammation, and enhance healing after surgery.

This study aims to evaluate whether the use of hyaluronic acid (hyaDENT BG®) in addition to standard surgical treatment improves clinical outcomes in patients with gingival recession. Participants will be randomly assigned to receive either standard treatment alone or standard treatment with hyaluronic acid.

The main outcome is the proportion of sites with complete root coverage after 12 months. Additional outcomes include healing, gum tissue improvement, patient-reported pain and discomfort, and aesthetic results.

The study also includes a laboratory component to investigate how hyaluronic acid affects cells involved in gum healing.

Gingival recession (GR) is a common mucogingival condition characterized by apical displacement of the gingival margin beyond the cemento-enamel junction, leading to root exposure, dentin hypersensitivity, increased risk of root caries, and aesthetic impairment. The coronally advanced flap combined with a subepithelial connective tissue graft (CAF + SCTG) is considered the gold standard for the treatment of single gingival recession defects, providing predictable root coverage and long-term stability. However, postoperative morbidity, donor-site discomfort, and incomplete root coverage may still occur.

Hyaluronic acid (HA) is a key component of the extracellular matrix with biological properties that promote wound healing, including stimulation of angiogenesis, cell migration, proliferation, and modulation of inflammatory responses. Cross-linked HA formulations exhibit prolonged bioactivity and may enhance soft tissue healing and regeneration in periodontal surgery.

This study is a prospective, randomized, controlled, post-market clinical follow-up (PMCF) trial designed to evaluate the clinical effectiveness and safety of adjunctive cross-linked hyaluronic acid (hyaDENT BG®) in combination with CAF + SCTG for the treatment of single RT1 and RT2 gingival recession defects. A total of 34 patients will be enrolled and randomly allocated in a 1:1 ratio to either the test group (CAF + SCTG with adjunctive HA) or the control group (CAF + SCTG alone). Randomization will be stratified by recession type (RT1 vs RT2), and outcome assessors will be blinded to treatment allocation.

The primary endpoint is complete root coverage (CRC) at 12 months, defined as recession depth equal to 0 mm relative to the cemento-enamel junction. Secondary endpoints include mean root coverage, recession reduction, clinical attachment level gain, probing depth reduction, keratinized tissue gain, early wound healing (Early Wound Healing Score), patient-reported outcomes (pain, discomfort, and oral health-related quality of life), and aesthetic outcomes assessed using the Root Coverage Esthetic Score (RES).

Clinical assessments will be performed at baseline and at predefined follow-up visits up to 12 months post-surgery using standardized protocols and calibrated examiners. Patient-reported outcomes will be collected using validated instruments, including visual analog scales (VAS) and the OHIP-14 questionnaire.

In parallel, an in vitro component will be conducted using primary human gingival fibroblasts isolated from connective tissue grafts obtained during surgery. These cells will be used to evaluate the effects of HA on cell viability, proliferation, migration, gene expression related to wound healing and inflammation, and activation of intracellular signaling pathways.

This combined clinical and translational approach aims to provide comprehensive evidence on both the clinical performance and biological mechanisms of action of hyaluronic acid in periodontal plastic surgery.

Inclusion Criteria:

• - Age ≥ 18 years, in good general health (ASA I or II)
• Presence of a single gingival recession defect classified as RT1 or RT2
• Recession depth ≥ 2 mm with identifiable cemento-enamel junction (CEJ)
• Presence of at least 1 mm of keratinized tissue at the defect site
• No active periodontal disease (probing depth ≤ 4 mm and no bleeding on probing at the selected tooth)
• Full-Mouth Plaque Score (FMPS ≤ 20%) and Full-Mouth Bleeding Score (FMBS ≤ 20%)
• Vital tooth without caries, cervical lesions, or defective restorations
• Good oral hygiene and motivation to maintain plaque control
• Ability and willingness to comply with study procedures
• Signed informed consent

Exclusion Criteria:

• Uncontrolled systemic diseases (e.g., uncontrolled diabetes, severe cardiovascular disease, immunodeficiency)
• Pregnant or breastfeeding women
• Autoimmune diseases or immunosuppressive therapy
• Known hypersensitivity to hyaluronic acid
• Heavy smokers (>10 cigarettes/day) or recent tobacco use
• Active periodontal disease at the study site
• Caries, root fractures, endodontic lesions, or defective restorations at the study tooth
• Previous mucogingival surgery at the study site
• Recent use of antibiotics, corticosteroids, or anti-inflammatory drugs
• Coagulation disorders or anticoagulant therapy contraindicating surgery
• Hormonal disorders affecting wound healing
• Acute oral infections
• Any condition that may interfere with study participation or follow-up

No final decision has been made regarding individual participant data sharing. Data sharing will be considered in accordance with applicable regulations and institutional policies.

Outcome assessors responsible for clinical measurements and evaluation of study endpoints are blinded to treatment allocation to minimize assessment bias. Standardized measurement protocols and calibrated examiners are used to ensure consistency across all time points.

The treating surgeon is not blinded due to the nature of the intervention, as the application of hyaluronic acid cannot be masked during the surgical procedure. Participants are not formally informed of their group allocation; however, complete blinding of participants cannot be guaranteed.