Thesis (Ph.D.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Prosthodontics

Objective: To assess the fracture resistance and stress analysis of endodontically treated teeth restored using hybrid ceramic or resin nano-ceramic endocrowns compared to fiber post crown. Materials and methods: Twenty-four extracted maxillary central incisors were selected, decapitated, endodontically treated and randomly assigned to three groups (n=8) according to the restorative technique used (Group I: Hybrid ceramic endocrowns, Group II: Resin-nano ceramic endocrowns and Group III: Glass fiber post, composite core and hybrid ceramic crown). All restorations were fabricated using cerec inLab system, finished, polished and cemented using dual cured self-adhesive resin cement. Specimens were subjected to thermocycling and mechanical fatigue loading then tested for fracture resistance. The obtained data from were statistically analyzed by 1-way ANOVA and Tukey{u2019}s test. The failed specimens were evaluated to determine the mode of failure. Using sophisticated finite element analysis software different types of stresses (1st principal stress, 3rd principal stress, von Mises stress) were assessed. Results: All specimens survived thermocycling. After mechanical fatigue loading, two samples in Group I, four samples in Group II (half the sample size) failed, while none of the samples of Group III failed. After fracture resistance test, Group III showed the highest mean value (394.71 MPa±85.5) followed by Group I (261.7 MPa±28.8), while Group II (153.29 MPa±12.7) showed the lowest results. The results were statistically significant difference between the tested groups (P-value <0.001). All failures in Group I were favorable. Two specimens in Group II, two specimens in Group III, showed unfavorable failure. After FEA, the highest stresses were seen at the area of load application

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