ABSTRACT
Objective:To evaluate the effects of various tapers of canal preparations on the retention of cast posts in endodontically treated upper incisors in vitro.Methods: Forty human central or lateral maxillary incisors were prepared by removing the clinical crown at 1 mm above the approximal CEJ and treated the canals with instruments of varying tapers. The groups comprising 10 teeth of each group were divided as follows: Taper 0.02 /15~40#SS (stainless steel K-files) with step-back technique as control, PF (ProFile)OS 3#/0.06 with taper 0.06/PF 25#/ in apical third, PF OS 4#/0.07 with taper PF 0.06/30# in apical third, PF OS 5#/0.08 with PF taper 0.06/35# in apical third. Then, canals were filled with gutta percha and AH Plus sealer using vertical condensation technique with a level of 5 mm of gutta-percha left in the apical segment of the root. Metal cast posts were made by direct method and then the post was cemented with HY-BOND GLASIONMER CX (Shofu,Inc)cement. The roots were fixed in copper rings with mounting plaster and mounted on a WD-5A machine.The posts were subjected to gradually increasing vertical tensile force until dislodgment of the post occurred. Force (N) required to dislodge the post was obtained for each tooth, and the average force of the groups was compared using a one-way ANOVA and SNK multiple comparisons with SAS V8.1. Results:The highest resistance to dislodgment was obtained with PF OS 4#/0.07, whereas the lowest was obtained by the PF OS 3#/0.06. Nonstatistical difference was found between Taper 0.02 /15~40# and PF OS 3#/0.06. PF OS 4#/0.07 was statistically superior to Taper 0.02 /15~40# and PF OS 3#/0.06 but not PF OS 5#/0.08. Conclusion: The retention of posts is affected strongly with the increase in the diameter than with the increase in the taper angle. PF OS 4#/0.07 with taper PF 0.06/30# in apical third seems to be the best taper for maximal resistance to post dislodgment.