Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 14 2 2017 08 06 69 75 EN Negin Nasoohi Associate Professor, Department of Restorative and Cosmetic Dentistry, Islamic Azad University, Tehran, Iran Maryam Hoorizad Associate Professor, Department of Restorative and Cosmetic Dentistry, Islamic Azad University, Tehran, Iran Seyedeh Farnaz Tabatabaie Postgraduate Student of Restorative and Cosmetic Dentistry, Department of Restorative and Cosmetic Dentistry, Islamic Azad University, Tehran, Iran 2017 01 25 2017 03 30 Objectives: This study aimed to assess the effect of wet and dry finishing and polishing on microhardness and roughness of microhybrid and nanohybrid composites. Materials and Methods: Thirty samples were fabricated of each of the Polofil Supra and Aelite Aesthetic All-Purpose Body microhybrid and Grandio and Aelite Aesthetic Enamel nanohybrid composite resins. Each group (n=30) was divided into three subgroups of D, W and C (n=10). Finishing and polishing were performed dry in group D and under water coolant in group W. Group C served as the control group and did not receive finishing and polishing. Surface roughness of samples was measured by a profilometer and their hardness was measured by a Vickers hardness tester. Data were analyzed using two-way ANOVA (P<0.05). Results: The smoothest surfaces with the lowest microhardness were obtained under Mylar strip without finishing/polishing for all composites (P<0.0001). The highest surface roughness was recorded for dry finishing/polishing for all composites (P<0.0001). Dry finishing/polishing increased the microhardness of all composites (P<0.0001). Conclusions: Dry finishing and polishing increases the microhardness and surface roughness of microhybrid and nanohybrid composite resins.   https://fid.tums.ac.ir/index.php/fid/article/view/1713 https://fid.tums.ac.ir/index.php/fid/article/download/1713/939