Effect of eluates from zirconia-modified glass ionomer cements on DNA double-stranded breaks in human gingival fibroblast cells

Objective

To formulate novel glass ionomer cements (GICs) containing zirconia (nanoparticles (NPs) and micro-particles (MPs)) and investigate the genotoxic effect of their eluates on DNA double-strand breaks of human gingival fibroblasts (HGFs) in vitro using a γ-H2AX fluorescent assay.

Methods

GIC (control, C), 10%ZrO₂NPsGIC (T1) and 10%ZrO₂MPsGIC (T2) were prepared per the manufacturer’s instructions (hand-mixed, P/L = 3.4:1 w/w%). Dulbecco’s modified Eagle’s medium (DMEM) was used as the culture medium for HGFs and for eluate preparation. Eluates were collected from all specimens (n = 5/g, 5 × 2 mm) after 24 h and used for XTT to obtain the EC₅₀ using Graph Pad Prism4. A γ-H2AX immunofluorescence assay was performed to detect DSBs in HGFs. The mean foci per cells and percentage of free foci cells were statistically compared (one-way ANOVA with Tamhane’s post hoc and Chi-square respectively) (p < 0.05).

Results

(1) EC₅₀ ranged from 31 to 36%. 5% and 20% eluate concentrations were selected for the genotoxicity test. (2) Cells exposed to eluates from T1 had lower mean foci per cell than cells in T2 and C eluates (p < 0.05). Only cells in T1 at 5% had lower mean foci cell than medium (p < 0.05). (3) T1 and C at both concentration showed a higher, but not significant, percentage of free foci cells than negative control (medium). At 20% eluate concentration T2 had a lower percentage of free foci cells than C (p < 0.05).

Significance

Nano-zirconia GIC and micro-zirconia GIC were formulated. GIC and both zirconia modified GICs had no genotoxic effect on HGFs in vitro. Further studies related to physical properties should be performed to determine the future clinical applications for these novel nanomaterials.