Biopsies of the peri‐implant tissue were retrieved from 15 patients (aged 34 to 88 years, six males/nine females) with severe peri‐implantitis (eight ceramic implants, seven titanium implants) (see Table S1 in online Journal of Periodontology). The presence of macrophages, B‐Lymphocytes, T‐Lymphocytes, and plasma cells was identified in all samples. Micrographs illustrating peri‐implantitis lesions for both implant materials are presented in Figure 2. The predominant cell‐type in peri‐implantitis lesions around ceramic implants were plasma cells CD138 (mean 53%), followed by T‐lymphocytes CD3 (mean 32%), B‐lymphocytes CD20 (mean 10%) and macrophages CD68 (mean 5%) (Table 1). There was no significant difference regarding the total number of stained cells in peri‐implantitis lesions around ceramic implants in comparison with titanium implants (P > 0.05) (Fig. 3, see Table S2 in online Journal of Periodontology). In 249 of 300 (83%) ROI, there was a co‐appearance of CD3 and CD20 (see Figure S1 in online Journal of Periodontology).

Interestingly, a high interindividual variation regarding the prevalence of the cell‐type was observed in both materials. The range in the ceramic group was for CD3‐positive cells 20% to 70%, CD20‐positive cells 3% to 22%, CD68‐positive cells 2% to 10% and CD138‐positive cells 12% to 69% of all cells, whereas in the titanium group: CD3, 17% to 85%; CD20, 3% to 18%; CD68, 1% to 26%; CD138, 1% to 73% (see Table S2 in online Journal of Periodontology). Interindividual differences in the immunohistological cellular composition of the biopsies evaluated might also hint to an influence of the patient‐specific immune status rather than only the implant material used (Fig. 4).