Luting cements & Preparation Taper Influences on E.maxPress Crowns

Objectives: The purpose of this study was to determine the effect of different luting resin cements on the retentive strength of crowns prepared with 10-degree and 20-degree taper. Methods: Thirty-two freshly extracted sound human molars were divided into two main groups 1, 2 (n=16 teeth each) relative to the degree of preparation taper, group 1, 10-degrees taper and group 2, 20-degree taper. All ceramic crowns (e.max Press) were fabricated in a standardized manner for each tooth. Each group was further subdivided into two subgroups, A and B, (8 teeth each) relative to the type of resin cement used for bonding the crowns to the prepared teeth, either self-adhesive universal resin cement (Rely X Unicem, 3M/ESPE) or conventional resin cement with self-etching primer (Panavia F2.0., Kuraray). Retention was measured (MPa) by separating the crowns from the prepared teeth under tension on a universal testing machine. Analysis of variance was used to test the main effects on the retentive strength of the crowns. Results: Statistical analysis showed that the retentive bond strength was insignificantly affected by the type of the tested resin cement in group 1, while in group 2 the difference was significant. Conclusion: Increasing the taper of the preparation from 10 degree to 20- degrees did not affect the retention of crowns cemented with Panavia F 2.0. The crowns cemented with self adhesive cement (Unicem) resulted in significantly less retentive strength compared to the use of resin cement with separate self-etching prime.