Fracture resistance and failure mode of endodontically treated premolars reconstructed by different preparation approaches: Cervical margin relocation and crown lengthening with complete and partial ferrule with three different post and core systems

Purpose To assess the fracture resistance and failure mode of endodontically treated premolars reconstructed by different preparation approaches: cervical margin relocation (CMR) and crown lengthening (CL) with complete ferrule (CLF) and partial ferrule (CLPF) with three different post and core systems. Materials and Methods In this in vitro study, 100 maxillary premolars were assigned to the following 10 groups according to their preparation approach and type of post and core system (n = 10): (I) control (intact teeth), (II) prefabricated fiber post (PFP) and composite core with CMR (PFP‐CMR), (III) polyethylene fiber‐reinforced composite (PEFRC) with CMR (PEFRC‐CMR), (IV) casting post (CP) and core with CMR (CP‐CMR), (V) PFP‐CLPF, (VI) PEFRC‐CLPF, (VII) CP‐CLPF, (VIII) PFP‐CLF, (IX) PEFRC‐CLF, and (X) CP‐CLF. After thermomechanical loading, the fracture resistance and failure mode were assessed. Data were analyzed statistically (α = 0.05). Results In all post and core systems, the CLPF approach had lower fracture resistance than CMR (p 0.05). No significant difference was found in fracture resistance of different post and core systems with the same preparation approach (p > 0.05). CLPF showed the highest frequency of favorable, and CLF showed the highest frequency of unfavorable fractures. Conclusion CLPF yielded lower fracture resistance than CMR. The difference in fracture resistance was not significant between CLF and CMR but the frequency of unfavorable fractures was higher in CLF than in other groups.