Objectives: This study investigated the load fatigue performance of new prefabricated post-core systems in endodontically treated teeth with complete crowns and minimal ferrule. Failure mode of the luting cements was also analysed. Methods: 50 human mandibular premolars were randomly assigned to five groups (n=10), and restored with five post-core systems. Groups 1-4 posts were cemented with Post Hi-X Cement, and group 5 posts with Variolink II. Cores were built-up with Biscore. Final preparation height was 6-mm, (including 1-mm ferrule). Following crown cementation with Panavia-F, specimens were subjected to fatigue loading of 6-kg, at 45°, 1.2 Hz till preliminary failure was detected from lingual strain gauge output. Specimens were sectioned bucco-lingually and observed under 10x magnification. Results: The mean number of load cycles to preliminary failure were:
|
Groups |
Diameter |
Load Cycles x103 |
|
1-Parapost/Titanium |
1.25 mm |
62.96 (8.2)a |
|
2-C-Post/Carbon Fibre |
1.4/1.0 mm |
31.18 (2.9)b |
|
3-Aestheti Plus Post/Quartz Fibre |
1.4/1.0 mm |
14.17 (3.2)c |
|
4-Light Post/Quartz Fibre |
1.4/1.0 mm |
5.72 (1.8)d |
|
5-Cosmopost/Zirconium Oxide |
1.4 mm |
45.43 (3.5)e |
(*superscript letters indicate statistical subsets; SD in parentheses)
ANOVA showed significant differences (p<0.5) in mean load cycles to preliminary failure between groups. Tukey HSD post hoc test confirmed that all groups were significantly different (p<0.5). Groups 2-5 showed adhesive failure of crown cement at core/cement interface. Group 1 showed adhesive failure at core/cement interface near cervical half of crown, and at cement/crown interface near occlusal half. Conclusions: Bonded posts with higher Shear Modulus had greater mean load cycles to preliminary failure. Young's Modulus of the post appears to affect flexion of core during loading. Inadequate bonding of zirconia post to resin cement or core may have affected its results. In teeth with 1-mm ferrule, the Parapost appears to be the system of choice. The use of Aestheti Plus Post and Light Post are contraindicated.