The effect of nitrogen plasma treatment on adhesive properties of PEEK

The purpose of this study is to investigate the effect of nitrogen plasma treatment on the shear bonding strength (SBS) of polyetheretherketone (PEEK) to resin cements. A total of 240 PEEK specimens were subjected to different duration of nitrogen plasma treatment for 0 min, 15 min, 25 min, 35 min respectively. The surface topography was observed by a scanning electron microscope (SEM). In addition, X-ray photoelectron spectroscopy (XPS) was applied to study the surface element content changes before and after treatment. The adhesive specimens were bonded with Variolink in all groups. Afterwards, each group was divided into three subgroups (n = 20/group), (a) water storage for 56 h at 37 °C, (b) thermal cycling for 5000 times, (c) thermal cycling for 10000 times. Following storage shear bond strength (SBS) was tested in a universal testing machine and the failure modes were observed by stereoscopic microscope. After plasma treatment, the bonding strength between PEEK and Variolink was significantly increased. Among them, the 25 min group achieved the highest bonding strength. After thermal cycling, the SBS values were significantly decreased, compared with the group in water storage. Nitrogen low temperature plasma treatment improves SBS between PEEK and resin, and a duration of 25 min treatment group seems to be the best.