Influence of timing of coronal preparation on retention of two types of post cores

PURPOSE: To compare the effect of coronal preparation on retention of cemented cast (Cr-Ni) and IPS post core systems. METHODS: Cr-Ni and IPS post and cores were placed in 48 extracted single rooted human teeth with two different cements (dual-cure resin and glass-ionomer cement) and randomly divided into four groups of 12 specimens each. twelve of each post-core system were cemented with dual-cure cement and the other 12 of each system were cemented with glass-ionomer cement. Twelve specimens of each post core system were subjected to an axially directed removal force using a universal testing machine. Four groups of 12 specimens were divided into subgroups and subjected to preparation of their cores at 15 minutes and 24 hours after cementation. The specimens were tested at 24 hours having been stored in water at 37 degrees C for the waiting period. The forces required for dislodgement of the posts from their prepared spaces were recorded. Data were statistically analyzed using ANOVA and the Newman-Keuls multiple comparison test. RESULTS: Retention generally increased with time following cementation for both groups. The specimens cemented with glass-ionomer cement revealed less retention compared with specimens cemented with resin cement. Preparation of cemented post cores using a high speed handpiece had a significantly negative effect on retention when carried out 15 minutes and 24 hours after cementation.