Immunological Features of Peri-Implant Soft Tissue After Healing Abutment Dislodgement: A Comparative Human Study

Introduction and aims: Healing abutment dislodgement is a common clinical complication in dental implantology, yet its impact on peri-implant soft tissue immunity remains unclear. This exploratory pilot study aimed to investigate the immunological changes associated with different healing modes, which is essential for optimizing peri-implant tissue management. Methods: In this observational study, peri-implant soft tissues were collected from 12 patients and assigned to 4 groups: (A) sites with healing abutment dislodgement, (B) pre-implant recipient sites, (C) fully closed healing abutment sites, and (D) partially closed healing abutment sites. Histological and immunohistochemical analyses were performed to evaluate tissue morphology and the distribution of immune cell populations, including neutrophils, macrophages, T cells, B cells, and plasma cells. Results: Dislodgement of the healing abutment resulted in disruption of the epithelial barrier and pronounced infiltration of both innate and adaptive immune cells in peri-implant soft tissue. Compared to the fully and partially closed groups, the dislodgement group exhibited significantly higher densities of MPO⁺ neutrophils, CD68⁺ macrophages, CD3⁺ T cells, CD20⁺ B cells, and CD138⁺ plasma cells within both epithelial + superficial connective tissue region and deep connective tissue region. In contrast, intact healing abutments were associated with minimal immune cell infiltration and preserved tissue architecture. Notably, partially closed sites displayed localized immune cell aggregation at the deep connective tissue region (abutment-soft tissue interface). Conclusion: Disruption of the soft tissue barrier following healing abutment dislodgement is associated with persistent inflammatory responses and long-lasting immune cell infiltration. These findings highlight the importance of maintaining healing abutment stability and prompt restoration of the mucosal barrier to minimize immune activation and protect peri-implant tissue health. Clinical Relevance: Healing abutment dislodgement is a common but often under-recognized complication in implant dentistry. This study demonstrates that loss of the soft tissue seal following abutment dislodgement leads to persistent and pronounced immune cell infiltration and long-lasting inflammatory responses Clinically, these findings highlight the importance of maintaining healing abutment stability and prompt restoration of the mucosal barrier to minimize inflammation and protect peri-implant tissue health. Improved awareness and evidence-based management of abutment dislodgement may help prevent peri-implant complications and optimize long-term treatment outcomes.