The effect of 2 different diameter cast posts on tooth root fracture resistance in vitro.

Prosthetic treatment frequently involves the restoration of endodontically treated teeth (ETT), which in turn implies that there has been a reduction of the crown due to previous restorative treatment, trauma and/or endodontic manipulations. The prognosis of a restored ETT is very much dependent on pre-endodontic status of the tooth, the quality of the endodontic treatment, the amount remaining tooth structure and the bone support. The aim of this study is to measure fracture resistance of extracted premolar teeth restored with 2 different diameter posts. Extracted premolars were collected and stored in physiologic solution at 5 degrees C. The teeth were examined for fractures by direct and transillumination observation and 40 premolars were accepted for the study. The PC were modelled using the appropriate diameter plastic pattern for the post and Pattern Resin (GC) was used to model the core part of the PC. The PC patterns were invested and cast in cobalt chromium alloy and then cemented using zinc phosphate cement. Fracture resistances of the samples were tested in an "Instron 4301" (Instron Series IX Automated Material Testing System Version 5) with a loading speed of 0.5 mm/min. The data for each sample was recorded graphically. Both groups were analyzed using the t-test (p<0.01) in relationship to the mean value of that group. Post and cores significantly reduce the fracture resistance of the tooth and should be used only to secure retention and resistance form for full coverage crowns. Teeth with a larger diameter post have a reduced fracture resistance than teeth with a smaller diameter.