Xenogenic Materials for Alveolar Ridge Preservation: A Systematic Review of Randomized Controlled Trials

Background/Objectives: Alveolar ridge atrophy following tooth extraction complicates subsequent prosthetic rehabilitation and implant placement. This systematic review seeks to provide a comprehensive evaluation of existing evidence regarding the effectiveness of xenogeneic bone graft materials in socket preservation, particularly emphasizing their influence on the adjacent soft tissues. Methods: A systematic literature search was carried out across the CENTRAL, Embase, MEDLINE, PubMed, and Scopus databases. The search targeted randomized controlled trials (RCTs) published in English between January 2015 and September 2025 that examined xenogenic bone grafts used for ridge preservation in comparison either to spontaneous socket healing or to other types of grafting materials. The primary outcomes of interest were bone regeneration and alterations in soft tissues. Multiple independent reviewers performed study screening, data extraction, and risk of bias evaluation using the RoB 2 tool. Results: From 2242 initial records, 4 RCTs (138 patients) met the inclusion criteria. Studies compared xenografts (deproteinized bovine bone mineral with/without collagen), often combined with membranes, to unassisted healing. Augmentation techniques consistently showed a trend toward reduced horizontal and vertical ridge contraction compared to controls, though differences often lacked statistical significance (p > 0.05). Histological analysis revealed significantly less vital bone formation and residual graft particles in xenograft sites versus controls, suggesting volume maintenance is largely graft-dependent. Soft tissue contour changes were evaluated using 3D model scanning. Risk of bias varied, with concerns regarding randomization and reported outcomes in some studies. Conclusions: Xenogenic materials demonstrate comparable clinical effectiveness in preserving alveolar ridge dimensions, though radiographic volume stability may be partially attributed to the slow resorption of the graft material itself rather than new bone formation.