Objective:To investigate the effects of plasma treatment on the surface element,wettability and adhesion properties of aged denture base resin.Methods:42 pieces of 10 mm × 10 mm × 1 mm and 100 cubes of 8 mm × 10 mm × 30 mm polymethyl methacrylate specimens were prepared and thermocycled at 5-55 ℃ for 5 000 cycles.40 pieces were used for surface contact angle measurement and 2 for X-ray photoelectron spectroscopy analysis.The 100 cubes were randomly divided into 5 groups:Control(A) and 4 experimental groups in which the samples were exposed to plasma for 1 min (B),2 min (C),3 min (D) and 4 min (E) (n =20) respectively.After plasma treatment,silicone-based soft liner (3 mm) was packed against 2 resin cubes.Thus,50 tensile test specimens were obtained(n =10),and the tensile bond strength was tested by a universal testing machine.Results:The contact angle (°) of group A,B,C,D,E was 63.60 ± 10.81,46.79 ± 5.08,44.13 ± 4.17,40.11 ± 6.01 and 41.03 ± 8.61 respectively (A vs B,C,D or E,P ＜ 0.05).After plasma treatment,the contents of O =C-O and C-O in the samples were increased from 14.17％ and 20.58％ to 18.32％ and 29.32％,respectively.The tensile bond strength(MPa) of group A,B,C,D and E was 0.884 ±0.130,1.281 ±0.086,1.419 ±0.103,1.871 ± 0.248 and 1.904 ± 0.223 respectively (A vs B,C,D or E,P ＜ 0.05;B or C vs D or E,P ＜ 0.05;B vs C,P ＞ 0.05;D vs E,P ＞ 0.05).Conclusion:Plasma treatment can improve the wettability and adhesion properties of aged denture base resin.