RESUMEN
<p><b>OBJECTIVE</b>To explore the working parameters of the microwave plasma for surface modification of denture base resins.</p><p><b>METHODS</b>Using orthogonal test method, 80 specimens of denture material were divided into 16 groups for testing. At the gas flow of 13.7 cm3/min, the specimens were tested under the working condition of different microwave powers (100, 150, 200 and 250 W), different gasses (oxygen, air, argon, oxygen and argon mixture), different gas pressure (0.4, 0.6, 0.8, and 1 kPa), and varying processing time (1, 2, 5, and 8 min). Each group of specimens was treated with the microwave plasma and the contact angles were confirmed by scanning electron microscopy.</p><p><b>RESULTS</b>The pictures of instantaneous droplet morphology were obtained from each group of samples, and the values of contact angle were measured. The contact angle was 68.86 degrees in the untreated group, and the angles of several treated groups were 48.15 degrees , 40.7 degrees and 32.76 degrees, showing a statistically significant variation of the contact angle after the treatment.</p><p><b>CONCLUSION</b>Processing time of 8 min, microwave power at 100 W, total pressure in the chamber at 0.8 kPa, and the presence of oxygen constitute the optimal condition of microwave plasma for surface modification of denture base resins. Under these conditions, the smallest contact angle of the denture base resins is 34.58 degrees, suggesting a good effect of surface modification.</p>