The effect of plasma surface treatment on the bioactivity of titanium implant materials (in vitro)

Abstract

Background: The surface of an implantable biomaterial plays a very important role in determining the biocompatibility, osteoinduction, and osteointegration of implants because it is in intimate contact with the host bone and soft tissues.

Objective: This study was aimed to assess the effect of plasma surface treatment on the bioactivity of titanium alloy (Ti-6Al-4V).

Materials and methods: Fifteen titanium alloy samples were used in this study. The samples were divided into three groups (with five samples in each group). Five samples were kept untreated and served as control (group A). Another five plasma samples were sprayed for nitrogen ion implantation on their surfaces (group B) and the last five samples were pre-etched with acid before plasma treatment (group C). All the investigated samples were immersed for 7 days in Hank's balanced salt solution (HBSS) which was used as a simulating body fluid (SBF) at pH 7.4 and 37°C. HBSS was renewed every 3 days. The different surfaces were characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDXA), and Fourier Transformation Infrared Spectroscopy (FTIR).

Results: Nitriding of Ti-alloy samples via plasma nitrogen ion implantation increased the bioactivity of titanium. Moreover, the surface topography affected the chemical structure of the formed apatite. Increasing the surface roughness enhanced the bioactivity of the implant material.

Conclusions: Nitridation can be exploited as an effective way to promote the formation of bone-like material on the implant surface.

Keywords: Bioactivity; nitridation; nitrogen ion implantation; plasma; plasma surface treatment; surface roughness; surface treatment.

Figure 1

X-ray diffraction pattern of all investigated groups

Figure 2

AF micrographs (3D) of the investigated groups a, b and c. (a) Control group. (b) Plasma treated group. (c) Plasma treated with acid etch group

Figure 3

Mean values of surface roughness (Ra) of the investigated groups

Figure 4

SE micrographs of groups a, b, and c before and after immersion in Hank's solution. (i) Before immersion in Hank's solution. (ii) After immersion in Hank's solution

Figure 5

EDX spectrum of the investigated groups a, b and c after immersion in Hank's solution

Figure 6

FTIR spectra of the investigated groups A, B and C after immersion in Hank's solution