Machined titanium dental implant corrosion under inflammatory and hyperglycemic conditions

Objectives: Many patients who receive endosseous dental implants are hyperglycemic secondary to diabetes or metabolic syndrome. Hyperglycemia exposes nearly all cells to chronically high levels of glucose, leading to altered cell function and inflammatory stress. The effects of hyperglycemia, altered cell function, or inflammatory mediators on implant corosion are not well studied, yet these effects are critical to implant biocompatibility and osseointegration. Therefore, in the current study, we used electrochemical techniques to test a hypothesis that cellular and electrolytic changes that accompany hyperglycemia will alter titanium-based implant corrosion. Methods: The corrosion of commercially-pure (Nobel Biocare Branemark Mark II, machined, grade 2) titanium endosseous implants was estimated (n = 3) by open circuit potentials, linear polarization resistance, electrical impedance spectroscopy (EIS), and cyclic polarization in phosphate-buffered saline (control condition), complete cell-culture medium (10% serum), and media with human THP1-monocytic cells, all with or without increased dextrose (15 mM). In selected samples, THP1 were activated for 2 h with lipopolysaccharide prior to implant exposure, and IL-1ß secretion was measured to determine if implants triggered IL-1ß secretion from monocytes. Results: Implants under conditions of inflammatory stress exhibited more negative (145 to 190 mV lower, p< 0.05)-Ecorr values, suggesting an increased risk of corrosion. Linear polarization detected significantly higher rates of corrosion when dextrose concentrations were elevated (2.3-2.7 fold, p< 0.05). EIS measurements suggested that implants were passivated, which may have limited corrosion rates over the short-term of this test. This latter result was supported by cyclic polarization tests. IL-1ß secretion was not altered by implant exposure. Conclusions: Our results suggest that inflammatory stress and hyperglycemia increase the corrosion of dental endosseous titanium-based implants, but that longer, more aggressive electrochemical conditions may be necessary to fully assess these effects.