Effects of build orientation induced surface modifications on the in vitro biocompatibility of electron beam melted Ti6Al4V

Abstract

Titanium and its alloys may be processed via additive manufacturing techniques such as electron beam melting (EBM).This field is receiving increased attention from various manufacturing sectors including the medical devices sector. While the economic and engineering potential of EBM for the manufacture of musculo-skeletal implants is clear, the impact on the biocompatibility of the materials has been less investigated. In this study, the effects of part orientation-induced surface modifications on the in vitro biocompatibility of the EBM Ti6Al4V alloy were investigated. The study assessed the suitability of three different Ti6Al4V surfaces produced via the EBM process as variables for proliferation and attachment of mouse fibroblast L929 cells. The three different surface topographies were obtained by orienting the parts in vertical, horizontal and inclined (55°) orientation in the EBM build chamber. The mouse fibroblasts were cultured in vitro on the Ti6Al4V alloy discs with three different surface finishes. Cell viability studies, fluorescent microscopy as well as scanning electron micrographs were used to assess the L929 cell attachment and proliferation. After 2 and 8 days of incubation, there was a higher vitality and proliferation of L929 cells on the vertical and inclined surfaces (R_a = 38 and 46 µm, respectively) than on the horizontal surfaces (R_a = 18 µm). On the vertical and inclined samples, the cells spread over a wider area, whereas on the horizontal samples cell spread was affected by the topographical features. The results showed that the implants produced by EBM meet basic biocompatibility requirements and also showed that part orientation of titanium during EBM can produce surfaces with different characteristics and these can affect cell growth.