Cold Plasma Induced Surface Modification Of Heat-polymerized Acrylic Resin

Heat-polymerized acrylic resin is the most commonly used denture base resin. Plasma is the fourth state of matter, which is general produced by ionizing the gas. Cold plasma is widely used in biomedical research, such as sterilization, cancer therapy, teeth whitening and surface modification.Object:To study the changes of water contact angle, surface roughness, microhardness, flexural strength, elastic modulus and the early adherence of Candida albicans after heat-polymerized acrylic resin were treated by cold plasma, and explore the preliminary mechanism.Method:Contact angle measurement instrument was employed to detect the contact angle before and after treatment; profilometer was used to test the surface roughness; Vicker’s Microhardness Testers was employed to detect the microhardness; flexural strength and elasticity modulus were tested by an electronic universal testing machine; Colony Forming Units (CFU) counting, Scanning Electron Microscopy (SEM) were employed to observe the early adherence of Candida albicans; plasma components were analyzed by the optical emission spectroscopy (OES); elemental composition and chemical bond changes were measured by X-ray photoelectron spectroscopy analysis (XPS). SPSS18.0was used for data analysis.Result:After cold plasma treatment, the hydrophilic improved; the early adherence of Candida albicans reduced significantly in CFU values; the microhardness increase significantly; there are no significant differences detected in surface roughness, flexural strength and elasticity modulus. There existed plenty of atomic oxygen, hydroxyl radicals, singlet oxygen and free electrons in the plasma components according to the OES result. XPS analysis result indicated reduction of C and O proportion, and a new hydrophilic group C-OH was generated after plasma treatment.Conclusion:As a promising strategy, plasma treatment could improve the surface wettability of denture base, and reduce significantly the early Candida albicans adherence, thus offering a valuable tool for surface modification of the acrylic resin without obstructing the strength properties and providing a potential approach to prevent denture stomatitis.