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Atmospheric pressure plasma jet (APPJ) of N2 has been applied to promote adhesion between the epoxy resin post and composite core material due to the chemical active functional groups created. The APPJ was proved to be able to improve adhesive ability of the epoxy resin through the polar groups such as carbonyl group on its surface revealed by decreasing contact angle. The jet was generated from N2/Ar and N2/He gas mixture with ratio as low as 0.40–0.44 vol %, respectively. The optical emission spectrometry showed that the active species which could react with the substrate surface are nitrogen molecules and nitrogen molecules ion. The radial distribution functions (RDFs) calculations indicated that the most probable position of nitrogen active species reacting on the epoxy surface is at hydroxyl group with hydrogen bonding distance less than 35 nm.

Improvement of adhesion between epoxy based post and composite resin core materials by low temperature plasma is an on-going dental material development. To systematically investigate the effects of surface change on the material’s chemical and mechanical properties, three series of two component materials, epoxy/urethane dimethacrylate (UDMA), epoxy/polyethylene (PE), and epoxy/poly(methylmethacrylate) (PMMA), were compared with dental epoxy based post/composite resin core. Each dual-materials system was modeled at an atomistic level. A molecular dynamics (MD) method with COMPASS force field was employed to simulate the most probable functionalization and the materials physical properties changes. Material surface modification was modeled and optimized using quantum calculations based on experimental characterization. To validate calculation results, the effect of plasma treatment on the mechanical properties of the dental post materials were examined by tensile pull out test.