Effects of Excimer Laser Treatment of Zirconia Disks on the Adhesion of L929 Fibroblasts

Abstract

The adhesion of zirconia and soft tissue is very important for the success of zirconia implants. The aim of this study was to characterize the effects of excimer laser treatment of zirconia on the adhesion of L929 fibroblasts. In this study, polished zirconia disks treated with an excimer laser were the experimental group and untreated zirconia disks were the control group. Surface roughness and contact angles of zirconia disks were measured. mRNA expression levels of integrin β1 and collagen type I α1 in L929 fibroblasts cultured on zirconia disks were measured using qRT-PCR. Cell morphology was evaluated using 3D laser microscopy and the expression of vinculin was characterized using confocal microscopy. There was no significant difference in the surface roughness of zirconia disks, but contact angles were significantly lower. mRNA expression of integrin β1 was significantly higher at 3, 6 and 24 h and of collagen type I α1 was significantly higher at 6 and 24 h. L929 fibroblasts tended to form elongated microspikes and vinculin colocalization in those microspikes. Furthermore, vinculin was strongly expressed in filopodia of L929 fibroblasts at 24 h. These results suggest that excimer laser treatment improves adhesion between zirconia disks and L929 fibroblasts.

Keywords: adhesion; excimer laser; fibroblast; implant surface; photofunctionalization; zirconia.

Figure 1

Surface roughness and surface wettability of zirconia disks. Macroscopically, there was no difference in the surface properties of the zirconia discs. In a 3D measuring laser microscope, the surface texture was smoother in the polished disks compared to the unpolished disks, but there was no difference in surface texture between the polished disks with or without the excimer laser treatment. There was no difference in surface wettability between the unpolished and polished disks, but the polished disks with the excimer laser treatment had an improved surface wettability compared to the polished disks without the excimer laser treatment.

Figure 2

Arithmetic surface roughness (Sa) of zirconia disks. The Sa value was significantly lower in polished disks and in polished disks irradiated with an excimer laser compared to unpolished disks. (n = 5).

Figure 3

Contact angle of zirconia disks. The contact angle of polished disks irradiated with the excimer laser was significantly lower than the unpolished disks and polished disks. (n = 5).

Figure 4

mRNA expression levels of Integrin β1 and Collagen type I α1. (a) The mRNA expression level of integrin β1 was significantly higher in the experimental group compared to the control group at 6 and 24 h. (n = 5) (b) The mRNA expression level of collagen type I α1 was significantly higher in the experimental group compared to the control group at 6 and 24 h. (n = 5).

Figure 5

Cell morphology assessed using a 3D measuring laser microscope. The cell morphology showed a trend toward slightly thicker microspike formation and spike elongation in the experimental group compared to the control group.

Figure 6

Immunocytochemistry of vinculin. Immunocytochemistry reveals vinculin expression within the elongated microspikes of fibroblasts. Furthermore, the elongation of vinculin-expressing thick spikes was observed at 24 h. (Vinculin: red, DAPI: blue, Phalloidin: green).