Cell Accelerated Corrosion (CAC) on the Dental Implant: An Exploratory Study with Gingival Fibroblasts and Macrophages

A growing body of research in orthopedic literature suggests that the host cells surrounding the implant may promote corrosion. This factor is termed Cell Accelerated Corrosion-(CAC). The dental literature on CAC is very limited. Thus, this work aimed to ascertain how the Ti corrosion processes were affected when gingival fibroblasts (FB) and macrophages (MP) were exposed to Ti ions and particles. Electrochemical tests were performed on commercially pure Ti-grade-IV polished discs. Based on potentiodynamic data FB cells challenged with Ti ions or particles have higher i_corr when compared with MP-Ti particles followed by the MP-Ti ion group. The study found that spent cell culture media of FB and MP cells challenged with Ti particles or Ti ions increased the corrosion rate. Ti ions were harmful to both FB and MP cells, whereas Ti particles exhibited negligible toxicity. Gene expression assay by RT-PCR revealed that treating FB cells to Ti ions increased the expression of TNF and relatively increased the expression of iNos-2. Ti ions increased the expression of IL-6, Tnf, and Cox in MP cells. Concerning Ti particles, IL-6 was upregulated in MP cells. Ti ions enhanced the pro-inflammatory cytokines IL-6, TNF, and COX while decreasing IL-1β. In summary, this study clearly explains about Ti corrosion process in cell accelerated environment, which may contribute to dental implant failures.