The cellular composition of tissue with peri‐implantitis around zirconia‐based implants has never been explored before. The specific interaction of inflammatory cells in tissue with peri‐implantitis and their impact on peri‐implant osseous breakdown with regard to the implant material is still unknown. The present pilot study demonstrated that there is a similar histological appearance of peri‐implantitis lesions around ceramic and titanium implants in the soft tissue. The most predominant cells found for both materials were plasma cells (CD138) followed by T‐lymphocytes (CD3). The mean distribution of cells observed in this study is in accordance with the results Carcuac and Berglundh presented for peri‐implantitis around titanium implants (mean CD138, 33%; CD3, 21%; CD68, 11%; CD 20, 7%). However, the latter authors provided mean values and analyzed solely titanium samples. Information regarding individual variations of the patients’ immune response was not reported. In the present study, an interindividual distinction regarding cell‐type frequency on the patient level was seen irrespective of the implant material. The current results may suggest that an immune response is associated with patient‐specific parameters rather than with implant materials.

The present immunohistological data display the late phase of peri‐implantitis (with indication of implant removal) with the differentiation of B cells and the existence of antibody‐secreting cells (plasma cells) verified by CD138 staining. Antibody‐secreting cells are fundamental in humoral immunity by secreting antibodies which prevent bacterial adherence, promote phagocytosis, and activate the complement system. Interestingly, the T‐cell arm of the immune response is activated in this stadium of peri‐implantitis as well, demonstrated by the amount of expressed CD3‐positive T cells. T cells are able to differentiate into various different subsets. Basically, CD8‐positive T cells showed a cytotoxic potential acting to kill cells that have been infected with intracellular microbes and tumors. CD4‐positive T cells are designated as helper cells as they are responsible to regulate the cellular (B‐cell help) and humoral immune responses (delayed‐type hypersensitivity). Since the aim of the present study was a general overview of inflammatory cell appearance in peri‐implant tissue around two implant materials, a T‐cell subset characterization was not performed. A detailed lymphocyte characterization should be performed in future studies to discriminate this lymphocyte‐driven inflammation process.