CHARACTERIZATION OF DENTURE ACRYLIC RESIN SURFACES MODIFIED BY GLOW-DISCHARGES

Resin samples prepared by compression molding using a poly(methyl meth acrylate) (PMMA) denture base material were exposed to radio-frequency (rf) glow discharges to improve the wettability of the material. Four ier transform infrared (FT-IR) reflectance, X-ray photoelectron spectr oscopy (XPS), and contact-angle measurements have been employed to cha racterize the changes introduced by the glow discharge plasma. FT-IR m easurements cannot detect any modification. XPS reveals an increase in the O/C atomic ratio. Contact angles of the plasma-treated samples ar e always lower when compared with untreated ones. The increased O atom ic concentration is attributed to formation of-COH groups on the surfa ce during plasma treatment. The O/C atomic ratio decreases upon heatin g the samples in vacuum to 100 degrees C for 1-2 min and exposing the samples to liquid CH2Cl2 for 1-2 min. Exposure to distilled water for prolonged periods causes a slight decrease during the initial 1-20 day s but levels off to a constant value up to a period of 60 days. Plasma treatment seems to offer a durable increase in the wettability for th ese materials left in air or distilled water.