The relatively low elastic modulus of fiber posts reduces the risk of root fracture, but it also decreases composite core stabilization. To compensate for the lack of rigidity, larger post sizes can be necessary when restoring crownless teeth that have significant internal destruction of the root canal. This study evaluated the effectiveness of fiber posts with different emerging diameters and shapes on composite core stabilization as measured by fracture strength testing. Fracture strengths ranged from 262.6 ± 81 N to 422.8 ± 56 N. A one-way ANOVA test showed that fracture strength was affected by type of post (p<0.0001); single-tapered posts were weaker than double-tapered posts. Pearsons linear correlation test showed that the fracture strength results appear to have a direct correlation to the emerging diameter of the post (p<0.0001; r(2)=0.6191). The emerging diameter of fiber posts is important to stabilize the core. When restoring crownless teeth, it is advisable to use fiber posts with large emerging diameters; no additional preparation of the internal root dentin is necessary to enlarge the post diameter.
Purpose: This controlled clinical trial aimed to compare the 3-year outcomes of glass fiber posts and composite cores with gold alloy-based posts and cores for the restoration of endodontically treated teeth. Materials and Methods: One hundred forty-four patients in need of 205 restorations on endodontically treated teeth were selected and followed for 7 to 37 months (mean: 21 ± 9 months). The teeth were primarily stratified based on the remaining tissue available to restore the tooth core with or without a post. Then, randomization allocated the teeth to either test group 1 (prefabricated glass fiber posts), test group 2 (custom-made glass fiber posts), or test group 3 (composite cores without posts). The control group consisted of gold alloy-based posts and cores. All posts/cores were covered with all-ceramic single crowns. Failures were either absolute, such as root fractures or irreparable fractures of the post/core, or relative, such as loss of post retention or reparable fractures of the core. Success and survival probability lifetime curves, corrected for clustering, were drawn for the entire data set. Results: The recall rate at 3 years was 97.1%. Absolute failures consisted of two root fractures and one endodontic failure, while relative failures included three instances of retention loss of the post/core and one post fracture. Because of the low number of events, no statistical tests were performed. The success and survival probabilities over all groups together at 3 years amounted to 91.7% and 97.2%, respectively. Conclusions: After being followed for up to 3 years, both cast gold and composite post and core systems performed well clinically. Longer follow-up times are needed to detect possible significant differences. Int J Prosthodont 2011;24:363-372.
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