Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 18 0 2021 07 24 3128 3128 Sattar Kabiri Aja University of Medical Sciences, Tehran, Iran; Department of Orthodontics, School of Dentistry, Shahrekord University of Medical Sciences, Shahrekord, Iran Ammar Neshati Department of Prosthodontics, Faculty of Dentistry, Aja University of Medical Sciences, Tehran, Iran Bita Rohani Department of Oral Medicine, Faculty of Dentistry, Aja University of Medical Sciences, Tehran, Iran 2019 05 07 2020 10 08 Objectives: The aim of this study was to assess the shear bond strength (SBS) of zirconia ceramic to composite resin with various surface treatments following pressure changes. Materials and Methods: Totally, 135 zirconia blocks were prepared by computer-aided design/computer-aided manufacturing technology. The samples were divided into 9 groups (n=15). Three surface treatments including sandblasting, tribo-chemical preparation, and laser application were used. For each method, 45 samples were considered and tested under different pressure conditions. Z-Prime Plus primer was used for bonding of all samples to composite cylinders. All specimens were stored in water for 24 h, underwent thermocycling, and were then placed in a pressure chamber under normal-, high-, and low-pressure conditions. Then, the SBS test was performed for each sample. Data were analyzed by two-way and one-way ANOVA (α=0.05). Results: The SBS was significantly higher in sandblasting and tribochemical preparation compared with laser irradiation (P<0.05). There was no statistically significant difference in SBS of sandblasting and tribochemical preparation methods (P>0.05). Sandblasting, tribochemical preparation, and laser methods did not show a significant difference in SBS at different pressures (P>0.05). Conclusion: Sandblasting and tribochemical preparation yielded a higher SBS than laser. Different pressures had no effect on SBS, irrespective of surface preparation method.  https://fid.tums.ac.ir/index.php/fid/article/view/3128