COMPARISON OF TWO METHODS FOR TESTING RESTORED TOOTH FAILURE RESISTANCE.

Purpose: The aim of this study is to investigate the influence of loading test type on the results of failure resistance investigations of teeth restored with post and cores. Methods: Two experimental set-ups were used to compare the failure resistance and failure mode of teeth restored with glass fiber posts and resin core (fiber specimens) with those of teeth restored with cast post and core (cast specimens). In the first experimental set-up, 10 fiber and 10 cast specimens underwent a fatigue test: 2-kg load was buccolingually applied for 900,000 cycles in a wet environment, using a lever-type device. Since specimens did not fail, an additional quasi-static bending test (static test) was performed until failure of the post-tooth complex. In the second experimental set-up, the same number of teeth was identically prepared and restored, but they were submitted to the static test only. Results: Failure resistance and failure mode were separately investigated by the two testing methods. While post type was found to significantly affect failure resistance by both testing methods (t-test, p < 0.05), post type significantly influenced failure mode only in the fatigue test (Fisher's exact probability test, p < 0.05). Conclusions: If failure resistance is the outcome of interest, testing of teeth restored with posts and cores by a quasi-static bending test alone might be sufficient to predict fracture behavior of restored teeth after an estimated period of 3-4 years of simulated oral function. Conversely, to investigate the influence of dental material aging on failure mode of post-restored teeth, testing under dynamic conditions in wet environment is recommended. [ABSTRACT FROM AUTHOR]