Cyclic Loading of Incisors Restored with Different Post Systems

Objective: To evaluate the fatigue resistance of different post systems by submitting them to cyclic loading. Methods: Human maxillary central incisors of similar dimensions were decapitated, root filled and embedded in acrylic blocks with simulated periodontal ligaments. Post spaces were prepared to a depth of 8 mm and restored with one of the following prefabricated posts: a 1.5 mm diameter titanium post (Mooser) (A), a 1.7 mm diameter zirconia ceramic post (Cosmopost) (B), a 1.4 diameter quartz fiber post (Aestheti-Plus) (C), and glass fiber posts (FRC Postec) of 1.5 mm (D) and 2.0 mm in diameter (E). All the posts were covered with metal copings, stored in 37°C water for 48 h, and then cyclically loaded with 25 N peak load at a 45° angle to the axial direction in a loading machine (Zwick 1465). Every 250 cycles (0.2 Hz frequency), the peak load was increased by 25 N until failure occurred. The equivalent load was calculated with the formula: eq 1 P ( )/1000 = = ⋅ ∑ n ii i PN , where Pi is the peak load, which is repeated for Ni cycles. Results: Failure modes were yielding (A) and post fracture (B-E). ANOVA post hoc Tukey test showed significantly higher mean loading cycles and mean equivalent loads for (A) than for the other post groups (p 0.05). Conclusion: For severely damaged upper incisors without ferrule, metal posts demonstrated higher fatigue resistance than fiber-reinforced composite or zirconia posts and thus may be preferable over non-metal posts.