Effect of Clinically Relevant CAD/CAM Zirconia Polishing on Gingival Fibroblast Proliferation and Focal Adhesions

Abstract

Mucosal seal formation around dental abutments is critical to the successful integration of dental implants into the human oral cavity. No information exists for how clinically relevant polishing procedures for computer-aided design and computer-aided manufactured (CAD/CAM) zirconia abutments affects cellular responses important to mucosal seal formation. CAD/CAM zirconia was divided into four groups for clinically relevant polishing utilizing commercial polishing heads: control, coarse, coarse plus medium, and coarse plus medium plus fine. Surfaces were analyzed with scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical profilometry (OP). Subsequently, human gingival fibroblasts (HGFs) were seeded onto the zirconia surfaces. Proliferation was measured via a quantitative SEM technique and focal adhesion kinase (FAK) phosphorylation status was measured by an enzyme-linked immunosorbent assay (ELISA). Results showed an increase in proliferation on all polished surfaces as compared to the control. Phosphorylation of FAK at tyrosine 397 (Y397) was up-modulated on the control surfaces. The associated cell adaptation is discussed. In all cases, FAK phosphorylation was greater at 24 h than 48 h. These results suggest that clinicians should be mindful of the effects of abutment polishing methodology, as this may have an impact on early mucosal seal formation.

Keywords: abutment; dental implant; dental materials; gingival fibroblast; mucosal seal; zirconia.

Figure 1

Representative scanning electron micrographs of Zr surfaces at ×1800: (A) Control; (B) Group C (Course); (C) Group C+M (Course+Medium); (D) Group C+M+F (Course+Medium+Fine). See text for details on group definitions.

Figure 2

Optical profilometry-based measurement of R_a of control Zr surfaces and those following the C, C+M and C+M+F polishing steps. Bars indicate standard deviation. Same letter indicates no significant difference (p > 0.05).

Figure 3

Representative plan-view topographic atomic force micrographs (30 μm × 30 μm) of Zr surfaces. False color represents height from 0 (red/dark) to 0.9 μm (yellow/light): (A) Control; (B) Group C; (C) Group C+M; (D) Group C+M+F.

Figure 4

Atomic force microscopy-based measurement of R_a of control Zr surfaces and those following C, C+M and C+M+F polishing steps. Bars indicate standard deviation. Same letter indicates no significant difference (p > 0.05).

Figure 5

FAK phosphorylation of human gingival fibroblasts present on Zr following 24 h (solid color) and 48 h (cross-hatched) as measured by optical density. Bars indicate standard deviation. Same letter indicates no significant difference (p > 0.05).

Figure 6

Representative SEM micrographs of HGFs on Zr surfaces at ×200: (A) Control, 24 h incubation; (B) Group C, 24 h; (C) Group C+M, 24 h; (D) Group C+M+F, 24 h; (E) Control, 48 h; (F) Group C, 48 h; (G) Group C+M, 48 h; (H) Group C+M+F, 48 h.

Figure 7

Mean cell count of HGFs present on Zr following 24 h (solid color) and 48 h (cross-hatched). Bars indicate standard deviation. Same letter indicates no significant difference (p > 0.05).