The purpose of this study was to evaluate the effects of fiber posts and different restorations on the fracture
resistance of endodontically treated maxillary premolars with cervical cavities. In forty extracted human first maxillary
premolars, cervical cavities were prepared simulating cervical lesions and randomly divided into four groups (n=10):
COM-NP, endodontically treated teeth (ETT) restored with resin composite without fiber posts; ON-NP, ETT restored
with CAD/CAM ceramic onlays without fiber posts; COM-P, ETT restored with resin composite and fiber posts; and
CR-P, ETT restored with CAD/CAM ceramic crowns and fiber posts. After the fiber posts and restorations had been
cemented with resin cement, all specimens were loaded onto the long axis in a universal testing machine until
fracture at a speed of 0.5 mm/min. Fracture load (N) and fracture modes were evaluated in all specimens. The
mode of failure was determined by visual inspection. Data were analyzed with Welch’s ANOVA and Games-Howell tests
(p<0.05). Fracture load for all groups were (N): COM-NP (933.48±242.53); ON-NP (1871.45±313.59); COM-P
(1510.17±251.87); and CR-P (2189.97±600.38). COM-NP had the lowest fracture resistance, significantly different from
those of the other groups (p≤0.05). Statistically significant differences were observed among groups (p≤0.05), except
in the ON-NP to CR-P groups (p=0.471). All groups showed the non-restorable fracture mode. Cuspal-coverage
restorations significantly enhanced the fracture resistance of endodontically treated maxillary premolars with cervical
cavities. Placement of fiber posts improved the fracture resistance of endodontically treated teeth but did not
make the failure restorable.