Inflammatory Response of Peri-implant Cells to Piezoelectric Ceramic Composite Implant Surfaces – In Vitro Study

Osseointegration is the major success factor for dental implants. In order to optimize the biological response, several strategies have been investigated. Due to its piezoelectric properties similar to bone electric potentials generated in loading function, barium titanate (BaTiO3) piezoelectric ceramic is a potential approach for promoting osteogenic proliferation and differentiation and, consequently, accelerating osseointegration. However, the potential inflammatory effects in peri-implant cells and tissues are not defined. The aim of this in vitro study was to evaluate the inflammatory response of gingival fibroblasts and human fetal osteoblasts in contact with BaTiO3-functionalized zirconia implant surfaces with piezoelectric properties. Composite discs with 5 wt.% BaTiO3 in Yttria-stabilized zirconia (YSZ) were prepared through press-and-sintering technique (n=15). Contact poling was carried out in silicon oil bath under DC 2 kV/mm electric field at 130 °C for 30 min followed with field cooling. Reference samples of YSZ were processed parallel to the composites. Human gingival fibroblasts (hTERT) and fetal osteoblasts (hFOB1.19) were cultured on discs for 14 and 7 days, respectively, by previously described methods. Cell viability was evaluated at 1, 3, 7 and 14 days using a commercial resazurin-based method. IL-1b and IL-6 were evaluated at 1 and 3 days in each fibroblast and osteoblast culture and osteopontin was measured in osteoblast cell culture at 3- and 7-days using ELISA. Osteoblasts alkaline phosphatase (ALP) activity was measured using an enzymatic colorimetric assay at 7 and 14 days. All results were presented as mean ± confidence interval (CI). Group comparisons were based on one-way ANOVA repeated measures or Kruskal-Wallis and Tukey’s post-hoc using appropriate statistical software and significance was set at p<0.05. Cell viability increased over time for all groups in both cell cultures. However, in osteoblasts was significantly lower in non-poled group at 14 days comparing to poled group. No significant differences in fibroblasts viability were observed between groups. Although a trend towards ALP activity significantly higher in poled group at 7 days (1.18±0.49 umol/min/mL) and YSZ group (2.22±0.17 umol/min/mL) at 14 days comparing to non-poled group (p<0.05), no significant differences in osteopontin secretion were observed between groups. Regarding osteoblasts inflammatory markers, IL-1b remains constant and a notorious increase from 1 to 3 days in IL-6 were observed in poled group, but without statistically significant differences between groups. Fibroblasts IL-1b secretion was similar to osteoblasts, with constant values over time and no significant differences between groups. However, IL-6 secretion decreased from 1 to 3 days in all study groups and repeated measures analysis revealed significant lower values in non-poled group (20.93±3.00 pg/mL) comparing to YSZ (43.79±13.77 pg/mL) at 3 days (p<0.05). Our results suggest that the Zirconia composite surfaces with the addition of BaTiO3 is not cytotoxic to peri-implant tissues cells. Additionally, samples with or without piezoelectric properties do not affect cellular differentiation and inflammatory profile. Nevertheless, the addition of non-poled BaTiO3 to YSZ may have a potential reduction effect in IL-6 mediated—inflammatory activity in fibroblasts.