Method: 3 commercial epoxy resin-based fiber posts (DT Light post, 2.2 mm diameter; Bisco Inc, Schaumburg, IL, U.S.A.) and a core resin (Luxacore; DMG, Hamburg, Germany) are used for this study. The non-thermal atmospheric pressure nitrogen plasma apparatus was provided by KwangWoon University and the nitrogen gas flow was 5 L/min, the voltage and current for operating the plasma was 15 kV and 13 mA. The distance of the specimen from the exit of the plasma jet was 5 mm. Experimental groups were composed as; no Tx (G1), plasma (G2), hydrofluoric acid (G3), silane (G4), and hydrofluoric acid and silane (G5). Each fiber post was uprightly placed on a base (2.2 mm in diameter) and a cylindrical mold (10 mm in diameter and 2 mm in height) paced on the base. The core resin was applied inside the mold and polymerized for 40 seconds with a LED curing unit. A total of 10 samples were prepared for each group. The specimens were stored at 37 °C for 24 hours. Push-out shear bond strength between epoxy resin-based fiber post and core resin was measured using a universal testing machine (5942, Instron, Norwood, MA, U.S.A.) at a cross-head speed of 1 mm/min. The results were statistically analyzed using one-way ANOVA.
Result: The mean and standard deviation of push-out shear bond strength (MPa) were G1: (19.36±1.06)a, G2: (26.36±0.97)c, G3: (21.86±1.17)b, G4: (22.66 ± 1.30)b, and G5: (26.83±2.76)c. G2 and G5 were the highest and there is no statistical difference between G2 and G5 (p>0/05).
Conclusion: Non-thermal atmospheric pressure nitrogen plasma treatment was effective to enhance bond strength between core resin and epoxy resin-based fiber post.