Histological Outcomes of Alveolar Ridge Preservation Versus Spontaneous Healing Following Tooth Extraction: A Systematic Review and Meta-Analysis

<b>Objectives:</b> This systematic review and meta-analysis aimed to evaluate histological outcomes of alveolar ridge preservation (ARP) compared to spontaneous healing after tooth extraction, focusing on the percentage of new bone formation and residual graft material. <b>Materials and Methods</b>: Randomized controlled trials (RCTs) assessing histomorphometric outcomes in humans were included. Eligible studies compared ARP using various graft materials to unassisted socket healing. Primary outcome was new bone formation (%); secondary outcome was residual graft material (%). Random-effects meta-analyses and subgroup analyses were conducted based on graft material type, membrane application, and healing duration. Risk of bias and certainty of evidence were assessed using the Cochrane RoB 2.0 tool and GRADE, respectively. <b>Results</b>: Twenty-two RCTs (816 patients) met inclusion criteria. Overall, ARP did not result in significantly greater new bone formation compared to spontaneous healing (mean difference -5.86%, 95% CI: -13.84% to 2.11%, <i>p</i> = 0.15; I² = 98%), revealing a paradoxical trend: while ARP maintains ridge volume, histologically it may yield slightly lower proportions of vital bone compared to unassisted healing. However, autologous biomaterials (e.g., PRF/CGF) and xenografts with collagen membranes showed significantly new bone formation (mean differences +16.28% and -22.47%; <i>p</i>< 0.001 and <i>p</i> = 0.003, respectively). Residual graft content was highest in relation to xenografts and allografts, particularly without membranes. Long-term studies demonstrated a statistically significant benefit for ARP following excluding high-risk trials. <b>Conclusions:</b> Histological advantage of ARP is biomaterial-dependent. Autologous platelet concentrates and xenografts with membranes yielded the most consistent bone regeneration outcomes. Clinical Relevance: Although ARP preserves socket volume, its histological superiority over natural healing is not universal. Therefore, the selection of biomaterials and determination of and appropriate healing period are critical parameters.