Hamadan University of Medical Sciences Avicenna Journal of Dental Research 2423-7582 12 1 2020 03 30 Evaluation of Surface Preparations Combined With Different Generations of Bonding on the Bond Strength of Resin Composite Repair: An Original Article 2 7 10.34172/ajdr.2020.02 EN Azam Valian https://orcid.org/0000-0001-5363-9762 Marzieh Nejatifard https://orcid.org/0000-0001-8486-1489 Elham Moravej Salehi Fatemeh Jamali Journal Article 10.34172/ajdr.2020.02 2020 02 08 2020 03 18 Background: This study evaluated the effect of different mechanical surface preparation methods, as well as different adhesives including universal bonding agents, on the shear bond strength of composite repairs. Methods: This study was experimentally performed on 64 Z250 composite discs (3M, ESPE) with 6 mm diameter and 2 mm height. A total of 60 samples were randomly divided into 6 groups as follows: Group A) diamond milling + Adper Single Bond 2, group B) diamond milling + Single Bond Universal, group C) diamond milling + All Bond Universal, group D) sandblast + Adper Single Bond 2, group E) sandblast + Single Bond Universal, group F) sandblast + All Bond Universal. Then, the new composite was placed on the bonding layer, cured, and underwent aging again. The samples were assessed for shear bond strength by universal testing machine and their failure mode was investigated under the light microscope (20x and 100x). Finally, 4 remaining samples, which were surface-prepared by diamond milling and sandblasting, were evaluated for qualitative analysis of surface roughness using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Data were analyzed by oneway ANOVA and Fisher’s exact tests. Results: There was no statistically significant difference in shear bond strength and failure mode among the groups (P> 0.05). However, diamond milling + Single Bond Universal group showed the highest and Adper Single Bond 2 had the lowest bond strength. Conclusions: There was no significant difference in bond strength using different methods. Therefore, diamond milling + Single Bond Universal was suggested as the best and most available method compared to sandblasting.