Assessment of Peri-Implant Bone Density Using Intraoral Periapical Radiographs: A Retrospective Observational Clinical Study

Background/Objectives: Osseointegration is essential for the long-term success of dental implants, and radiographic assessment may support the evaluation of peri-implant bone healing. This retrospective study evaluated peri-implant radiographic bone density (PIBD) as a potential indicator of osseointegration in patients who underwent successful implant-prosthetic rehabilitation. Methods: Patients with at least one endosseous dental implant and a minimum of two standardized periapical radiographs—one at placement (T0) and one during follow-up—were included. Digital radiographs were obtained using the paralleling technique and analyzed with ImageJ^®. Normalized bone density values were calculated for predefined areas of interest (AOIs). Marginal Bone Level (MBL) changes were also assessed. Statistical analyses included the Shapiro–Wilk test, Kruskal–Wallis test, and Dunn’s post hoc test with Bonferroni correction. Results: 88 implants in 64 patients were analyzed (198 radiographs; 1299 AOIs measurements). Normalized bone density showed significant temporal changes in several AOIs, mainly from 3 to 12 months, across coronal/middle/apical regions. PIBD decreased by approximately 8% between T0 and 3 months, followed by a significant increase at one year. MBL values were minimal and well below physiologic thresholds throughout follow-up. No significant correlation was found between MBL and normalized bone density. Conclusions: PIBD assessment may be a reliable, non-invasive tool for monitoring osseointegration during follow-up and supporting clinical decision-making in postoperative controls. The temporal pattern observed confirms three radiographic healing phases after implant placement: an initial decrease in PIBD during early remodeling, a subsequent increase reflecting osseointegration, and a final stabilization phase corresponding to tertiary implant stability.