Five-Year Retrospective Radiographic Analysis of Peri-Implant Bone Stability: A Comparison Between Two Socket Preservation Protocols and Spontaneous Healing

Objectives: The primary objective of this retrospective pilot study was to evaluate the long-term radiographic stability of peri-implant marginal bone levels (MBLs) at a five-year follow-up, comparing two different socket preservation protocols against spontaneous healing. Materials and Methods: A total of 24 patients who underwent tooth extraction followed by delayed implant placement were divided into three groups of 8 subjects each. Test Group 1 was treated with a heterologous cortico-cancellous bone graft covered by a slow-resorbing bovine pericardium membrane. Test Group 2 received the same bone graft but covered by a rapidly resorbing native porcine collagen membrane. The Control Group was left to heal spontaneously. Marginal bone loss (MBL) was calculated radiographically by measuring the difference in bone levels between the time of osseointegration (T0) and the 5-year follow-up (T1). For each implant, mesial and distal MBL values were averaged to obtain a single mean per-implant MBL value for group-level analysis. Results: The 5-year implant survival rate was 100% across all analyzed groups. Test Group 1 demonstrated the highest peri-implant bone stability, recording a mean MBL of 0.17±0.20 mm. In contrast, Test Group 2 and the Control Group exhibited greater resorption, with mean MBL values of 0.46±0.12 mm and 0.45±0.27 mm, respectively. Descriptive analysis indicated a trend toward improved peri-implant bone preservation in the group treated with biomaterial and a slow-resorbing pericardium membrane compared to both the short-resorbing collagen membrane group and the spontaneous healing control group. Conclusions: Within the limitations of this pilot study, the results suggest that the choice of barrier membrane in socket preservation procedures could affect 5-year marginal bone stability. The application of a slow-resorbing membrane provided a prolonged barrier action and showed a descriptive trend of lower mean marginal bone loss. However, the extremely small sample size precludes establishing clinical superiority over standard collagen membranes or spontaneous healing. Further randomized clinical trials with larger cohorts are necessary to confirm these long-term findings.