The objective of this study was to compare the efficacy of Coronal Advanced Flap (CAF) alone versus CAF combined with Leukocyte-Platelet-Rich Fibrin (L-PRF) to achieve root coverage in patients with gingival recession. This was assessed by measuring the percentage of root coverage at six months post-surgery. By focusing on the root coverage level, the study aimed to determine whether adding L-PRF to CAF significantly improved over using CAF alone.

The other objective was to provide a comprehensive assessment of the outcomes related to root coverage and overall patient satisfaction. Moreover, different outcomes of recession coverage were assessed, including the percentage of complete root coverage and mean root coverage. These evaluations were intended to offer a more detailed understanding of the possible success of each surgical technique. Additionally, the difference in gingival tissue thickness between the two groups was attempted to measure at six months post-surgery to determine whether the addition of L-PRF to CAF improved tissue quality and stability.

The study also aimed to determine the overall volume gain in gingival tissue in the specific area of recession covered by both techniques, providing information on their regenerative capabilities and the three-dimensional changes in tissue structure.

Furthermore, it sought to analyze the healing and recovery processes by comparing postoperative complications, patient discomfort, and overall recovery time between the two groups. Finally, another goal was to investigate the patient's satisfaction with the aesthetic and functional outcomes of the procedures, evaluating their perceptions of the success of treatment and the quality of life after surgery. This comprehensive approach was designed to ensure that all relevant outcomes were considered, offering a robust evaluation of the effectiveness and benefits of combining CAF with L-PRF and providing comparability with previous and future studies.

The positive hypothesis raised was: CAF combined with L-PRF will: (a) result in significantly greater root coverage compared to CAF alone at six months post-surgery; (b) lead to thicker gingival tissue and better tissue quality compared to CAF alone; (c) will have a faster healing and recovery, with fewer complications in the CAF with L-PRF group compared to the CAF alone group; (d) will report higher satisfaction levels with the treatment outcomes compared to those undergoing CAF alone.

A clinician not involved with the care of participants assessed eligibility and filled out the data form, and after receiving the allocation information from the randomization unit, the surgeon, a clinician not involved in data collection, started the protocolized procedure.

BLOOD COLLECTION: If a patient was assigned to the test group (L-PRF), a designed nurse proceeded to the blood collection to obtain L-PRF. A vein (basilica, cephalic, or median), usually on the inside of the elbow or the back of the hand, was the source of blood. The area where the puncture occurred was cleaned with an antiseptic. An elastic band or pressure cuff was wrapped around the forearm to squeeze the vein and make it more noticeable under the band. This helped the needle find the vein more easily.

As soon as that was done, a needle was placed in the vein, and blood was collected in a clean and sealed plastic tube (Intra Spin™ - Intra-Lock), between 4 and 6 tubes, without anticoagulant. During the process, the band was removed to allow blood to flow normally, and after the blood was collected, the needle was removed, and the puncture site was covered to prevent bleeding. The L-PRF membranes were prepared according to the technique described by Choukroun et al. (2001). Tubes were centrifuged immediately at 2700 rpm for 12 minutes on the centrifugation machine (Intraspin™, Intra-lock®, Florida, USA).

After centrifugation, the gelatinous portion obtained from each tube was removed and separated from the red part with tweezers. The membranes obtained were placed on a sterile metal surface.

The light metal plate and cover of the compression box (e.g., Xpression™ Intra-Lock, Boca Raton, FL, USA) were used to gently compress the L-PRF clots by gravity. After five minutes, the L-PRF membranes could be used.

A protocol of 2700RPM for 12 minutes (RCF-clot = 408g) was used to produce L-PRF membranes with leukocytes and platelets. L-PRF membranes were produced utilizing an Intraspin™ centrifugation device (33° rotor angulation, 50mm radius at the clot, 80mm at the max, Intra-Lock, Boca Raton, Florida, USA) utilizing 9mL glass-coated plastic tubes (Intra-Lock).

SURGICAL PROCEDURE: In case of CEJ undetectable or with 'step,' CEJ restoration was performed prior to the surgical procedure and digital scan (T0).

The coronally advanced flap (CAF) technique for multiple gingival recessions, as described by de Sanctis and Zucchelli, is a minimally invasive surgical procedure with intrasulcular incisions around the affected teeth and horizontal incisions in the interdental areas, preserving the papillae. A split-full-split thickness envelope flap is then elevated, with split-thickness dissection in the papillae and beyond the mucogingival junction and full-thickness at the recession level. This technique avoids vertical releasing incisions, contributing to better blood supply, improved esthetics, and a more comfortable postoperative experience for the patient.

SURGICAL STEP BY STEP: The anesthetic was applied to the intervened area, and a coronal advance flap was created. After local anesthesia, a horizontal incision was made, delimitating the coronal part of the flap. This horizontal incision of the envelope flap consists of an oblique submarginal incision in the interdental areas that creates a surgical papilla. The incisions continue with the intrasulcular incision in the recession defects and are extended to form an envelope flap between the central and molar. This design facilitates the planned coronal repositioning of the flap tissue on the exposed root surfaces.

The envelope flap is raised with a split-full-split approach in the coronal-apical direction, and the oblique interdental incisions are performed, keeping the blade parallel to the long axis of the teeth to dissect the surgical papilla in a split-thickness manner.

The apical gingival tissue at root exposures is raised to a full thickness to provide the critical part of the flap for root coverage with more thickness. Finally, the most apical portion of the flap is elevated in a split-thickness to facilitate coronal displacement of the flap. At the limit of the flap (central and molar), a hemi-utilization was performed to ensure the release of tension and better mobilization of the flap at extremities.

Then, a sharp dissection was performed in the mucosa of the vestibular lining to eliminate muscle tension. It must be considered that the "adequate" coronal displacement of the flap results from eliminating muscle and lip tensions in the apical part of the flap. This way, the flap design incorporates a wide base to ensure adequate blood supply, with the base of the flap being wider than the coronal portion to promote better vascularization and healing. The flap's length should be sufficient to cover the recession defects fully and extend coronally beyond the CEJ of the involved teeth, ensuring complete coverage of the exposed roots and promoting optimal healing.

The epithelium is removed from the anatomical papillae to allow them to fit the surgical papillae at the time of suture. Then, root cleaning is performed with manual Mini-Gracey curettes (LM®, Finland).

In the CAF+L-PRF group, ideal 6 (minimum 4) L-PRF membranes (with dimensions of receptor bed) are fixed together, with resorbable suture six zeros (Novosyn®, BBraun, Melsungen, Germany) and adapted to the root surface at CEJ level with the face of the inner membrane towards the recession.

The flap is then repositioned. Each surgical papilla that was dislocated surgically (concerning the anatomic papilla by the oblique submarginal interdental incisions) is now placed over the de-epithelialized papilla, promoting a rotation of the flap toward the canine and in a coronal direction. One of the key factors for recession coverage techniques is ensuring that the flap can be advanced coronally without any tension. So, if considered necessary, when verifying the reposition of the flap, additional partial-thickness dissection was performed apically to relieve tension and allow for proper positioning of the flap before suture.

After repositioning the flap, it was stabilized with a suspended suture. Sling sutures with 6/0 PTFE (Elasyn®, BBraun, Melsungen, Germany) were used to precisely adapt the buccal flap on the exposed root surfaces and stabilize every surgical papilla.

To ensure standardization of the technique and less variability, the flap was always performed from central to first molar (no vertical incisions), even if there was no recession at the lateral or central level.

Inclusion criteria:

• People over 18 years of age
• Nonsmokers or smokers with less than ten cigarettes (self-reported)
• No medical pathology that prevents the application of treatments affects the response of these and the healing process: protein and vitamin deficiency, therapeutic radiation, metabolic disorders (diabetes, hypercalcemia, and others.), drug disorders (antimetabolic, immunosuppressive) and hormonal, allergy to some component of the treatments applied in the study.
• Not be pregnant.
• The presence of oral health with the plaque control record (PCR) and bleeding on probing (BOP)is less than 25%
• At least, the presence of two or more neighboring, or not, gingival recessions Miller class 1 in the anterior upper jaw (central and lateral incisors, canine, first and second premolars.

Exclusion criteria:

• not accepted participation in the study

• not signed the informed consent

• recession greater than Miller's class1 or RT-1

• presence of any non-controlled disease. 4) Gingival recessions present a minimal amount (>1,5 mm) of keratinized tissue (KT) apical to the recession area.

  5) Pocket depth (PD) </=3 mm and CAL interproximal </ = 0 6) Absence of carious lesions, occlusal trauma, or previous root cover procedures.

  7) Absence of a prosthetic crown on experimental teeth.