Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 20 0 2023 03 12 1 6 EN Sara Tavakolizadeh Assistant Professor, Department of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Najmeh Yazdani Dentist, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Rahab Ghoveizi Assistant Professor, Department of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Abolghasem Mohammadi Assistant Professor, Department of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Elaheh Beyabanaki Assistant Professor, Department of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Soudabeh Koulivand post graduate student of medical science 2021 09 17 2022 08 19 Objectives: This study assessed the fracture resistance of zirconia crowns with four framework designs, fabricated by computer-aided design/computer-aided manufacturing (CAD/CAM) technology. Materials and Methods: In this experimental study, a maxillary central incisor was prepared and scanned with a CAD/CAM scanner, and 40 frameworks with 4 designs (N=10) were fabricated as follows: simple core, dentine core with a design similar to dentine, 3mm trestle design collar in the lingual aspect with proximal buttresses, and monolithic or full-contour. After porcelain applying and 20h immersion in distilled water (37°C), crowns were cemented on metal dies using zinc phosphate cement. Fracture resistance was measured by a universal testing machine. Data were analyzed with one-way ANOVA (alpha=0.05). Results: Fracture resistance was maximum in the monolithic group, followed by the dentine core, trestle design, and simple core groups, respectively. The mean fracture resistance of the monolithic group was significantly higher than that of the simple core group (P<0.005). Conclusion: Zirconia restorations with frameworks that provided higher and more support for porcelain, showed increased fracture resistance https://fid.tums.ac.ir/index.php/fid/article/view/4195