Tehran University of Medical Sciences Frontiers in Biomedical Technologies 2345-5837 13 1 2026 01 20 95 103 Baharan Ranjbar Omidi Dental Caries Prevention Research Center, Qazvin University of Medical Sciences, Qazvin, Iran Negar Soltanian Assistant Professor, Department of Operative Dentistry, Dentistry Faculty, Urmia University of Medical Sciences, Urmia, Iran Vahid Divanpour Assistant Professor, Department of Operative Dentistry, Boushehr University of Medical Sciences, Boushehr, Iran Monirsadat Mirzadeh Assistant Professor Community Medicine, Metabolic Diseases Research Center, Research Institute For Prevention Of Non-Communicable Diseases, Qazvin University Of Medical Sciences, Qazvin, Iran 2023 11 25 2024 06 30 Objectives: Repairing aged restorations is a common clinical process in Dental Operations. The aim of this study is to evaluate the effectiveness of different bonding systems in terms of different adhesive and surface treatment systems for repairing aged resin composites. Materials and Methods: Ninety resin composite discs were prepared and randomly assigned into three groups of 30, No surface preparation, Diamond milling roughness and Sandblasted. After 5000 heat cycles, each group was randomly divided into three subgroups of  Single Bond (3M), Composite primer (GC), and Schotch Bond Universal (3M) (n = 10). 180 composite cylinders of the new composite were prepared by squeezing the composite into a silicon tube. The samples were then subjected to 5000 heat cycles. Two-way ANOVA and Tukey tests were used for data analysis. Results: In the unprepared group, the universal bond and composite primer micro-shear bond strength were significantly higher than the single bond group (p < 0.05). In the milling group, the universal bond micro-shear bond strength was significantly higher than the composite primer and single bond group (p < 0.05). In single bond adhesive, micro-shear bond strength of milling was significantly greater than the sandblasted and unprepared groups (p < 0.05). In the universal adhesive group, micro-shear bond strength of milling group was significantly higher than the sandblasted and unprepared groups (p < 0.05). Conclusion: Micro-shear bond is affected by the surface preparation method and type of adhesive. Milling roughening with universal bond application showed the highest micro-shear bond strength. https://fbt.tums.ac.ir/index.php/fbt/article/view/889 https://fbt.tums.ac.ir/index.php/fbt/article/download/889/545