Retention and shear bond strength of two post systems

The purpose of this study was to compare the retention and shear strength o f teeth restored with the Para Plus post (P) and the C post (C1 and C2) sys tems, Twenty-four P, C1, and C2 posts each were placed 7 mm into recently e xtracted and endodontically treated maxillary anterior roots and luted with Ketac-Cem and Bis-Core respectively. In addition, 13 samples of each post type had a Bis-Core composite core placed. The tensile retention strength o f the post and the shear strength of the post and core restorations when th e core was loaded buccolingually at 45 degrees to the roots' long axis were determined at a strain rate of 1.3 mm/min. The C2 posts required significa ntly more tensile force (P < 0.0001) to remove them than the P or C1 posts. The shear strength of the post/core restorations was not significantly dif ferent (P < 0.04). The C1 restorations had 12 root fractures, the C2 restor ations had 11 root fractures, and the P samples had six root fractures. It was concluded that the lack of stiffness of the C posts adversely affected the success of these restorations.