Thermal and cyclic loading of endodontic posts

The intent of this study was to determine pullout (shear) strength of carbo n and stainless steel serrated posts from teeth. The tooth-posts groups wer e controls, thermal-cycled, load-cycled (load applied at either a 45 degree s angle or along the long axis of the post), and thermal- and load-cycled. Human extracted third molars were embedded in denture acrylic. Post space w as prepared and the posts cemented with a resin cement according to manufac turer's instructions, The testing was in tension at a loading rate of 2 mm/ min. The pullout (shear) strengths (MPa +/- SD) for the carbon posts were: controls 6.1 +/- 3.3; load-cycled 4.3 +/- 2.2; and thermal-cycled 4.2 +/- 2 .2. The thermal-cycled and then load-cycled carbon posts all fractured duri ng testing and were unable to be evaluated for shear strength. The pullout (shear) strengths (MPa +/- SD) for the stainless steel posts were: controls 6.6 +/- 2.9; load-cycled 7.1 +/- 3.2; thermal-cycled 4.8 +/- 2.0; and ther mal load-cycled 6.8 +/- 3.5. The statistical analysis indicated no signific ant difference in the pullout (shear) strength between any of the post grou ps tested. Two different operators then prepared specimens using carbon pos ts abraded with 50 mu m alumina and non-abraded carbon posts. The alumina a brasion caused a decrease in the post bond strength with the alumina partic les impinging on the carbon fibers resulting in their fracture. The signifi cant difference between bond strengths was attributed to each operator's ye ars of clinical experience.