fracture resistance and failure mode of endodontically treated premolars restored with different adhesive restorations

introduction: the restoration of endodontically treated teeth is a topic that has been studied extensively but it is still a challenge for dental practitioners. the aim of this study was to evaluate fracture resistance, fracture patterns and fracture location of endodontically treated human maxillary premolars restored with direct and indirect composite resin and ceramic restoration. methods: eighty non-carious maxillary premolars were selected and divided into four groups (n=20). endodontic treatment and mesio-occluso-distal preparations were carried out in all the groups except for the control group (group i). subsequently, the prepared teeth were restored as follows: group ii: indirect composite restoration; group iii: ceramic restoration; group iv: direct composite restoration. the specimens were subjected to compressive axial loading until fracture occurred. the mode of failure was also recorded. results: group i had higher fracture resistance (1196.82±241.74) than the other groups (p< 0.05) and group iv exhibited significantly higher values (962.10±165.52) compared to groups ii (731.21±85.89) and iii (758.18±108.10) (p< 0.05). the fracture patterns were significantly different between the composite resin groups and the ceramic group (p< 0.05). the most prevalent fracture pattern in the groups ii and iv was mixed fracture and in the group iii, restoration cohesive fracture was the predominant pattern. with regard to fracture location, the direct composite restorations exhibited more fractures below the cej compared to the indirect restorations (p< 0.05). conclusions: use of direct composite restorations resulted in higher resistance against fracture, but their failure modes may be unfavorable