Do Titanium Dioxide Particles Stimulate Macrophages to Release Proinflammatory Cytokines and Increase the Risk for Peri-implantitis?

PURPOSE: Titanium dioxide (TiO2) particles detached from titanium dental implants by tribocorrosion can be phagocytosed by macrophages, releasing various proinflammatory cytokines at the implant sites that may trigger peri-implantitis. The study objective was to measure the association between peri-implantitis and the presence of non-allergy-related proinflammatory cytokines associated with TiO2 particles.

METHODS: The investigators implemented a retrospective cross-sectional study and enrolled a sample of 60 subjects from a dental practice. Subjects were excluded if the plaque index was grade 3 (Silness and Löe). The predictor variable was a positive or negative TiO2 stimulation test, an in vitro macrophage proinflammatory response test. The outcome variable was peri-implantitis status defined as present or absent. Three groups were considered: control group with 20 patients without dental implants (group 1), 2 groups of patients with titanium dental implants, one without peri-implantitis (group 2), and the other with peri-implantitis (group 3) (n = 20 each). For patients with implants, depth of the gingival pockets of the implants were measured, and existing bleeding and suppuration were determined to assess peri-implantitis. Radiographs were taken if one or more factors applied to confirm the diagnosis of peri-implantitis. Further covariates were age, sex, duration of implant wear, and number of implants which were analyzed descriptively. Inferential analyses were undertaken using χ2 test, Kruskal-Wallis-, Wilcoxon-two-sample tests, and logistic regressions.

RESULTS: The sample was composed of 35 female and 25 male patients with a mean age of 54.2 years (standard deviation = 14.76). The overall TiO2 stimulation test positivity frequency was 28.3% and were 30.0%, 5.0%, and 50.0% in the control, implants without peri-implantitis, and implants with peri-implantitis groups. No statistically significant differences could be seen in the frequencies of the TiO2 stimulation test results between control group and combined groups 2 and 3 (P-value = .84). The risk for positive TiO2 patients with a titanium implant of developing peri-implantitis was statistically significant and higher compared to negative TiO2 patients (odds ratio, 19.0 with 95% confidence interval [2.12,170.38]; P-value< .01).

CONCLUSIONS: The data in this study showed a statistically significant relationship between a positive TiO2 stimulation test and peri-implantitis. Further studies with larger numbers of subjects are recommended to confirm this result.