Differential cytokine expressions affect the severity of peri‐implant disease

Objective: This study assessed gene expression by quantitative polymerase chain reaction of inflammatory‐ [interleukin (IL)‐12, tumor necrosis factor‐α (TNF‐α), IL‐4, and IL‐10] and osteoclastogenesis‐related factors [receptor activator of NF‐κB ligand (RANKL) and osteoprotegerin (OPG)] in sites exhibiting different severities of peri‐implant disease. Material and methods: Peri‐implant soft tissue biopsies ( n =48) were harvested from healthy implant (HI), mucositis (MC), initial peri‐implantitis (IP) and severe peri‐implantitis (SP) sites. Results: IL‐12 and TNF‐α mRNA levels were higher in SP, followed by IP and MC ( P <0.05). IL‐4 was higher in HI, followed by MC, SP and IP ( P <0.05). IL‐10 was the lowest in HI, while no differences were detected among the diseased groups ( P >0.05). OPG mRNA levels were higher in HI, followed by IP, SP and MC, whereas RANKL was increased as the peri‐implantitis severity increased ( P <0.05). The highest OPG/RANKL ratio was observed in HI and the lowest in SP ( P <0.01). Conclusion: These findings suggest that expressions of inflammatory‐ and osteoclastogenesis‐related factors may play an important role in the onset and severity of the peri‐implant diseases.