Investigation of the effect of different polishing methods on the microorganism adhesion and surface roughness of denture base materials

Material and Methods: 60 specimens were prepared for each of conventional heat polymerized PMMA (G), injection heat-polymerized PMMA (E) and pre polymerized CAD/CAM PMMA (CAD/CAM) denture base materials. All specimens were wet grounded with 800, 1000, 1200 and 2500 - grit silicone carbide abrasive paper. The prepared specimens were divided into 3 sub-groups (n=20) for different polishing procedures. Mechanical polishing (M) was applied to the first group and the other two groups were chemically polished with photo-activating glazes [Palaseal (Ps), Optiglaze color (Og)]. A profilometer was used to evaluate the surface roughness. Bacterial colonization after one day were evaluated by colony counting technique. A multi comparison of variance was used to statistically analyze the result data and the average value was used compared by Bonferroni Correction Test (p=0.05). The Pearson Rank Correlation test was used to evaluate the relationship between surface roughness and bacterial colonization. To determine the relationship between them, Regression Analysis were used. Results: In general, when PMMA base materials were compared, the lowest average surface roughness (Ra) values and bacterial colonization values were obtained in CAD/CAM group. When the polishing methods were compared, the lowest average surface roughness (Ra) values were obtained in the M group. As a result of bacterial colonization measurement, lower colonization values were obtained with M compared to other groups. Conclusions: When the different types of PMMA base materials that used in our study were compared in terms of surface roughness, no statistically significant difference was found between them, but significant differences were found in bacterial colonization. As a result of our study, it has been observed that mechanical polishing generally provides better results than light-activated glazing agents. Key Words: CAD/CAM PMMA, surface roughness, polymethylmethacrylate (PMMA), digital CAD/CAM dentures, mechanical polishing, chemical polishing