Dysregulation of the Immune System in Advanced Periimplantitis: Systemic Implications and Inflammatory Mechanisms—A Hematological and Immunological Study

<b>Objectives:</b> This study aimed to assess the systemic and local inflammatory responses in patients with periimplantitis, focusing on key immune markers and clinical parameters. The study further explores the relationship between inflammatory markers, clinical indices, and immune dysregulation, particularly regarding T-cell exhaustion and systemic inflammation. <b>Methods:</b> A cohort of patients with periimplantitis, classified into moderate and advanced stages, was compared to a control group of healthy individuals with dental implants. Clinical parameters, including plaque index (API), bleeding on probing (BoP), probing pocket depth (PPD), and peri-implant sulcus depth (PSI), were recorded. Hematological, immunological, and biochemical analyses were performed, with a focus on immune cell populations (NK cells, T-cells, and their exhaustion markers PD-1 and PD-L1). <b>Results:</b> Patients with periimplantitis exhibited significantly higher clinical indices (API, BoP, PSI, and PPD) than the control group, with the most pronounced differences in the advanced periimplantitis group. Hematological analysis revealed increased leukocyte and neutrophil counts, whereas NK cell levels were significantly reduced. Immunological profiling indicated elevated PD-1 and PD-L1 expression on T-cells, suggesting T-cell exhaustion and immune dysregulation. Furthermore, strong correlations were found between increased PPD values and elevated inflammatory marker levels, highlighting the relationship between peri-implant pocket depth and systemic inflammation. <b>Conclusions:</b> The findings confirm that immune dysregulation plays a central role in periimplantitis progression. The association between increased inflammatory markers, immune alterations, and clinical indices emphasizes the need for a multifactorial diagnostic and treatment approach. Integrating immune modulation strategies, clinical assessments, and lifestyle modifications, such as improved oral hygiene and smoking cessation, could improve disease management and reduce recurrence.