L-PRF Block vs Composite Graft for Horizontal Ridge Augmentation

Background and Biological Rationale:

Tooth extraction initiates a physiological healing cascade accompanied by significant dimensional loss of the alveolar process, with horizontal bone loss averaging 3.87 mm. In the anterior maxilla, the facial bone wall is thin (<1 mm in up to 90% of cases) and composed primarily of tooth-dependent bundle bone, rendering it highly susceptible to post-extraction resorption. Guided bone regeneration (GBR) is widely utilized to restore horizontal ridge width prior to implant placement. The combination of autogenous bone (AB) and deproteinized bovine bone mineral (DBBM) in a 1:1 ratio provides both osteogenic cells/growth factors and an osteoconductive scaffold with low turnover, demonstrating predictable horizontal bone gains of 4 to 5 mm. However, autogenous bone collection requires a secondary surgical site (e.g., mandibular symphysis or ramus), increasing operative time, postoperative pain, and complication risk. Leukocyte- and platelet-rich fibrin (L-PRF) blocks have emerged as a biomaterial alternative that eliminates donor site harvesting. In this technique, DBBM particles are bound within a polymerized autogenous fibrin matrix enriched with blood-derived platelets, leukocytes, and growth factors (including PDGF, VEGF, TGF-beta, and BMPs). Liquid fibrinogen facilitates cohesive molding into a form-stable block that aids graft adaptation and space maintenance while promoting local angiogenesis and cell recruitment. Study Objectives and Hypothesis:

The main objective is to evaluate whether horizontal ridge augmentation using an L-PRF Block provides non-inferior horizontal bone gain compared to a conventional autogenous bone/DBBM composite graft. The primary null hypothesis ($H_0$) states that the L-PRF Block is inferior to the autogenous bone/DBBM composite graft, with a difference in horizontal bone gain exceeding the predefined non-inferiority margin of 1 mm. The alternative hypothesis ($H_1$) states that the L-PRF Block is non-inferior. Study Methodology and Timeline:Preoperative Phase ($T_0$):Clinical and periodontal assessment (FMPS $\le 20\%$, FMBS $\le 20\%$). Preoperative CBCT scan ($T_0$) to measure baseline ridge dimensions. Professional oral hygiene therapy and instruction. Surgical Augmentation Phase ($T_1$):Full-thickness mucoperiosteal flap elevation and cortical perforations (decortication) at the recipient site. Control Group: Autogenous bone harvested from the mandibular symphysis via trephine bur, mixed 1:1 with DBBM, adapted to the defect, and covered with a native collagen membrane. Test Group: Venous blood collection (red-cap and white-cap tubes) centrifuged to produce L-PRF membranes and liquid fibrinogen. Fragmented L-PRF membranes and DBBM (50:50) mixed with liquid fibrinogen to form a cohesive L-PRF Block, adapted to the defect, and covered with a resorbable collagen membrane. Primary tension-free wound closure. Immediate postoperative CBCT scan ($T_1$) for baseline augmented graft volume. Postoperative Assessment \& Healing (2 Weeks to 6 Months):Patient-reported pain intensity (VAS 0-10) and analgesic consumption recorded at Days 3 and 7. Suture removal and wound healing evaluation at 2 weeks. Implant Placement \& Biopsy Harvesting ($T_2$, 6 Months):Follow-up CBCT scan ($T_2$) to evaluate horizontal bone gain and graft dimensional stability via digital DICOM superimposition. Prior to osteotomy, a 2 mm diameter $\times$ 6 mm depth bone core biopsy harvested along the planned implant axis using a trephine bur. Biopsies processed for H\&E and Masson's Trichrome staining to quantify newly formed bone (%), residual graft material (%), and connective tissue/marrow spaces (%). Dental implant placement and measurement of primary stability using Osstell resonance frequency analysis (ISQ). Second-Stage Surgery ($T_3$, 9 Months):Implant uncovery, healing abutment connection, and measurement of secondary stability (ISQ). Restoration \& Final Evaluation ($T_4$, 15 Months / 6 Months Post-Restoration):Delivery of final implant restoration. Final CBCT scan ($T_4$) to quantify buccal bone plate thickness surrounding the implant. Evaluation of patient satisfaction with esthetics (white and pink score) and masticatory function using a VAS questionnaire