Fracture strength and survival rate of endodontically treated maxillary incisors with approximal cavities after restoration with different post and core systems: an in-vitro study

Objectives: This study compared the fracture strength and survival rate of endodontically treated crowned maxillary incisors with approximal class III cavities and different core build-ups. Methods: Sixty-four caries free human maxillary central incisors were selec ted for standardized size and quality, endodontically treated and prepared with approximal cavities 3 mm in diameter. Group 1 was restored with titani um posts, group 2 received zirconia posts, in group 3 the root canal was pa rtially filled with a hybrid composite. In the control group, only the acce ss opening was restored. All teeth were prepared for and restored with full cast metal alloy crowns and subsequently exposed to 1.2 million cycles in a computer-controlled chewing simulator with simultaneous thermocycling. In addition, the samples were loaded until fracture in a static testing devic e. Results: One specimen with composite reinforced root canal did not survive the dynamic load test. The following median fracture strengths in Newtons f or the different groups were: titanium post 1038, zirconia 1057, composite resin 750, control (no post) 1171. The fracture load in group 3 (composite resin) was significantly lower (P < 0.05) than in the other groups. Conclusions: The reconstruction of endodontically treated single rooted tee th with approximal cavities can be successfully performed by closure of the endodontic and additional cavities with composite. Cementation of endodont ic posts offers comparable but no advantageous fracture resistance. Enlarge ment of the root canal space after completion of endodontic treatment shoul d be avoided and cannot be compensated for by injection of composite resin. Less catastrophic failures were observed without post reconstruction. (C) 2001 Elsevier Science Ltd. All rights reserved.