Effect of different preparation heights and luting agents on tensile bond strengths in Nickel Chromium crown – a comparative in- vitro study

Aim: Mechanical characteristics of tooth preparation along with luting agents are significant entities on the maintenance of fixed dental prostheses. This study aimed at assessing the retention of complete metal crowns luted with two different luting agents using two different preparation height. Methods: Forty human maxillary premolars were selected and prepared to receive complete metal crowns, and were randomly divided in 4 groups: Group A: 7-mm preparation height (PH) and glass ionomer cement (GIC); Group B: 7-mm PH and RelyX U200 self-adhesive resin cement (SA); Group C: 4-mm PH and glass ionomer cement (GIC); and Group D: 4-mm PH and RelyX U200 self-adhesive resin cement (SA). Crowns were casted in nickel-chromium alloy. The tensile strength was tested in a universal testing machine. Results: Mean tensile strength for group Group A: 519.91 ± 155.06; for Group B: 643.81 ± 142.65; for Group C: 260.35 ± 76.11and Group D: 627.95 ± 209.34.Overall, the crowns cemented with RelyX U200 self-adhesive resin cement presented significantly higher mean tensile strength values than GIC, and the 7-mm PH presented significantly higher mean tensile strength values than 4-mm PH. Conclusions: The self-adhesive resin cement and 7mm preparation height improved crown retention.