“…Titanium particles have been reported to cause degenerative changes in peri-implant tissue where they are phagocytosed by macrophages and neutrophils activated as part of the biological response (Fage et al, 2016;Noronha Oliveira et al, 2018;Thomas et al, 2013). Although recent studies have demonstrated a potential of titanium particles to cause inflammatory reactions in peri-implant tissue, hard evidence for a causal relationship is yet to be provided (Fretwurst, Nelson, Tarnow, Wang, & Giannobile, 2018;Mombelli, Hashim, & Cionca, 2018). Whether zirconia implants may cause immunological reactions similar to titanium (Cionca, Hashim, Cancela, Giannopoulou, & Mombelli, 2016) or no such effects (Siddiqi, Duncan, De Silva, & Zafar, 2016) continues to be debated.…”