INTRODUCTION:A direct link was found between surface roughness, the accumulation of plaque and the adherence of microorganisms concerning acrylic resins. However, the surface properties of the new thermoplastic materials remain questionable especially after using the conventional finishing and polishing techniques. Studying surface properties of each material makes the recommendation of the proper techniques easier. OBJECTIVES: This in vitro study intended to compare three types of denture base materials in regarding to the effect of different polishing techniques on their surface roughness. MATERIALS AND METHODS: 36 specimens were incorporated in this study. 12 specimens were in each group. 3 groups were formed: Group A: Heat cured Polymethylmethacrylate (PMMA). Group B: Thermoplastic Polyamides. Group C: Thermoplastic Acetal. Dimensions of specimens were (20×20×3 mm) with projection at the side. Statistical analysis was carried out using two way analysis of variance (ANOVA). Statistical significance was defined at P≤0.05. RESULTS: Technique no. 1 showed a high significant value in compared to technique no.2 for polishing the tested materials. CONCLUSIONS: PMMA was the highest affected group followed by thermoplastic acetal and the last affected group was thermoplastic polyamide. Prepolishing rubberizing with rubber bur improves the polishing procedure. RESULTS: Remarkable improvement in the histology and the ultrastructure of the alveolar bone of rats in Group III was observed. Moreover, hematological values revealed significant decrease in the inflammatory condition of rats with induced RA after fish oil treatment. CONCLUSIONS: Rheumatoid arthritis is an important risk factor for alveolar bone loss. The treatment of the RA induced rats with fish oil not only prevented the alveolar bone resorption and stimulated new bone formation, but also reduced relatively the level of rheumatoid factor in the blood.