Accelerated Osteogenic Differentiation and Bone Formation on Zirconia with Surface Grooves Created with Fiber Laser Irradiation.

Abstract

Modification of the surface topography of biomaterials is a critical factor for the proliferation and differentiation of osteoblasts. Elucidating the biological response to surface roughening is necessary for clinical application of zirconia implants. To investigate the effects of fiber laser-induced zirconia surface roughening on cultured osteoblast-like cell morphology, proliferation, differentiation, and calcification, and on in vivo bone formation. Sixty-six machine-surfaced yttria-tetragonal zirconia polycrystal plates (S-Zr) and 16 machine-surfaced implants were used as controls. We prepared 66 rough plates (R-Zr) and 16 rough implants by surface treatment using a fiber laser. MC3T3-E1 cells spread well in all directions on S-Zr, whereas elongated cells with poorly organized actin stress fibers were observed on R-Zr. Cell proliferation was significantly greater on R-Zr than on S-Zr. The Runx2 mRNA level increased time dependently in osteogenic culture condition. Alkaline phosphatase activity and osteocalcin mRNA levels were higher on R-Zr compared with S-Zr. Alizarin red S staining revealed greater calcification on R-Zr than on S-Zr. Laser treatment of zirconia implant bodies placed in rat tibiae increased the bone-implant contact ratio and removal torque considerably. Our results suggest that fiber laser irradiation produces adequate surface roughening of zirconia ceramics to support osseointegration.