Improvement of adhesion between epoxy resin-based fiber post and dental core resin using non-thermal atmospheric pressure nitrogen plasma treatment

Abstract

Fiber posts are widely used and accepted for the restoration of endodontically treated teeth as an alternative to cast post. Fiber post retention depends on the strength of the micro-mechanical and chemical interaction between material of fiber post and core resin. Theaim of the study was to evaluate and compare the adhesion between core resin and epoxy resin-based fiber post after non-thermal atmospheric pressure nitrogen plasma treatment and conventional treatments.The contact angles were measured with three different liquids (distilled water, diiodomethane and resin monomer mixture) before and after plasma treatment (0.5, 1, 3, 5, 7, and 9 minutes) on the epoxy resin surface (n=10). The contact angles also measured on the 1 minplasma treated epoxy resin surface after aging for 0, 1, 3, 5, and 7 days (n=10). The surface energy was determined by the Owens-Wendt method. X-ray photoelectron spectroscopy (XPS) was used to analyze the surface chemistry of the untreated and plasma treated epoxy resin. Shear bond strength between core resin and epoxy resin with plasma treated and untreated was measured using a universal testing machine(n=10). The shear bond strength also measured on the 1 min plasma treated epoxy resin after aging for 1, 3, 5, and 7 days (n=10). Push-out shear bond strength between core resin and plasma treated epoxy resin-based fiber post was measured and compared with conventional treatment (hydrofluoric acid etching or silane application) (n=10). Data were analyzed by using one-way ANOVA with Tukey test and independent t-test (p < 0.05).The contact angles decreased with increasing plasma treatment time in all liquids (p < 0.05), however, it increased with increasing aging time in all liquids (p < 0.05). The surface energy increased with increasing plasma treatment time (p < 0.05), however, it decreased with increasing aging time (p < 0.05). In the XPS spectra, C-O and C=O bonds identified and C-C bond decreased after plasma treatment. The amine groups and O=C bonds increased after plasma treatment. The shear bond strength value of plasma treated group was significantly higher than untreated group (p < 0.05). The shear bond strength value of plasma treated epoxy resin decreased with increasing aging time (p < 0.05). The push-out shear bond strength value of plasma treated group was significantly higher than only hydrofluoric acid or only silane treated groups (p < 0.05). There was no significant difference between hydrofluoric acid followed by silane treated group and plasma treated group (p > 0.05). The push-out shear bond strength values of only hydrofluoric acid or only silane treated groups were significantly higher than untreated group (p < 0.05).From the results of this study, non-thermal atmospheric pressure nitrogen plasma treatment favored the surface energy of the epoxy resin-based fiber post by modifying its surface chemically, consequently improved bond strength between core resin and epoxy resin-based fiber post.