Fracture strength of endodontically-treated teeth restored with post and cores and composite cores only

This study compared the fracture strength of different conditioned metallic posts, fiber-reinforced-composite posts and composite cores only in teeth without coronal tooth structure and determined failure modes after the fracture test. Post spaces were prepared in the root canals, and the teeth were randomly divided into seven experimental groups: Gr1: Titanium posts (ParaPost) + Silano-Pen (Bredent) + silane; Gr2: Titanium posts + 30 microm CoJet-Sand (3M ESPE) + silane; Gr3: Titanium posts + 50 microm Al2O3 + V-primer (Sun Medical); Gr4: Titanium posts + 50 microm Al2O3 + Alloy primer (Kuraray); Gr5: E-glass FRC post (EverStick); Gr6: Polyethylene fiber (Ribbond) + Resin impregnation and Gr7: Resin composite core only, with no posts. The posts were cemented using Panavia F 2.0 (Kuraray); coronal parts of the roots were etched, primed, bonded and composite cores were built-up. After thermocycling (5 degrees C-55 degrees C, 6000x), the fracture strength test was performed. The fracture strength of titanium posts (408 +/- 122 - 550 +/- 149 N) was significantly higher (p<0.05) than that of FRC posts (321 +/- 131 and 267 +/- 108 N for Everstick and Ribbond, respectively) or the group without posts (175 +/- 70 N) (Gr7) (ANOVA, Tukey's test). The group without posts resulted in complete core detachment (100%). In the E-glass FRC group, 60% adhesive core fracture occurred, covering >1/3 of the core and, in the polyethylene FRC group, 100% post-core detachment at the canal opening was observed. In all the titanium post applied groups (Gr1-Gr4), the posts remained in place with partial detachment of the core material from the post surface at varying degrees, depending on the conditioning method used. When no coronal tooth structure exist, the metal posts showed higher fracture strength values as opposed to the FRC post or no-post approach.