Effects of plasma-induced grafting modification on the adhesive strength and mechanical properties of fiber posts.

This study aimed to assess the effects of plasma grafting modification on the micro-push-out adhesive strength and mechanical properties of fiber posts and to assess the stability of these treatment effects.Glass-fiber posts were divided into four groups based on the treatment methods used, as follows: (1) Group NT: no treatment; (2) Group PT: Helium (He) plasma treatment; (3) Group PIG: He-plasma-induced post-irradiation grafting; and (4) Group SIG: He-plasma-induced syn-irradiation grafting. The treated fiber posts were bonded using self-adhesive resin cement exposure to air for 0, 1, 6 or 12 hours separately after surface treatment. Micro-push-out adhesive strength, flexural modulus, and flexural strength were measured.Plasma treatment, post-irradiation grafting, and syn-irradiation grafting improved adhesive strength at the 0-hours level. However, the improved adhesive strength disappeared in group PT after exposure for one or more hours. In group PIG, the adhesive strength after 1-hour exposure was 20.5% lower than that of 0-hour exposure (adhesive immediately after treatment), and no statistically significant differences in adhesive strength were observed between the 1, 6, and 12-hour exposure. In group SIG, no statistically significant differences in adhesive strength were observed among the 0, 1, and 6-hour exposure. Although the adhesive strength was 23% lower at the 12-hour exposure than that of 0-hour exposure in group SIG, the adhesive strength of fiber posts received syn-irradiation grafting still presented the best adhesive strength compared with the other treatment methods. The three-point flexural modulus and strength remained unaffected by the treatment methods used.Plasma-induced syn-irradiation grafting provided the ideal improvement and stability in adhesive strength in fiber posts. In addition, plasma-induced grafting modification successfully overcame the surface aging effect caused by plasma treatment alone without affecting the bulk mechanical properties of fiber posts.