Influence of preparation height and luting agent type on crown retention in molars

Aim: Mechanical characteristics of the preparation along with luting agent are significant elements on the maintenance of fixed prostheses. This study aimed at assessing the retention of metal complete crowns luted with two different luting agents under different preparation height.
Methods: Forty human third molars were selected and prepared to receive total crowns, and were randomly divided in 4 groups: (1) 5-mm preparation height (PH) and RelyX U100 self-adhesive resin cement (SA); (2) 5-mm PH and zinc phosphate (ZP); (3) 3-mm PH and SA; and (4) 3-mm PH and ZP. Crowns were cast in nickel-chromium alloy. The tensile strength was tested in a universal testing machine.
Results: Mean tensile strength values to crown displacement (kgf) and standard deviation were 39.6 (13.0) for group 1; 16.9 (8.1) for group 2; 32.2 (7.9) for group 3; and 10.6 (3.2) for group 4. Overall, the crowns cemented with SA presented significantly higher mean tensile strength values than ZP, and the 5-mm PH presented significantly higher mean tensile strength values than 3-mm PH.
Conclusions: The self-adhesive resin cement and higher preparation height improved crown retention.