Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 17 0 2021 01 19 3537 3537 Fatemeh Darvishi Department of Operative Dentistry, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran Parnian Alizadeh Oskoee Dental and Periodontal Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Mohammad Esmaeel Ebrahimi Chaharom Department of Operative Dentistry, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran Amir Ahmad Ajami Department of Operative Dentistry, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran Soodabeh Kimyai Dental and Periodontal Research Center, Tabriz University of Medical Sciences, Tabriz, Iran 2020 04 13 2020 09 29 Objectives: This study aimed to evaluate the fracture resistance of over flared endodontically treated bovine central incisors restored with prefabricated and custom-made glass fiber posts, using the multi-post approach.  Materials and Methods: Sixty-eight crownless over flared endodontically treated incisors were used for this study. The depth of prepared post space was 10 mm, and the remaining dentin thickness of the roots was 1 mm. The samples were randomly divided into four groups (n=17): Group 1: two prefabricated glass fiber posts; group 2: prefabricated glass fiber post + braided glass fiber; group 3: braided glass fiber; group 4: no post. Static load was applied at a crosshead speed of 0.5 mm/min at 135º angle relative to the root longitudinal axis until fracture. The data were analyzed using one-way ANOVA and post hoc Tukey’s test at a significance level of P<0.05. Results: Groups 3 and 4 exhibited the maximum (981 N) and minimum (461 N) fracture strength values, respectively. The differences between group 4 and other groups were significant (P<0.001), but the differences between groups 1, 2, and 3 were not significant (P>0.05). Conclusion: Multiple prefabricated and custom-made glass fiber posts significantly increased the fracture resistance of crownless endodontically treated central incisors with over flared root canals. https://fid.tums.ac.ir/index.php/fid/article/view/3537 https://fid.tums.ac.ir/index.php/fid/article/download/3537/1833