Influence of cement type on the fracture resistance of resin nanoceramic crowns over knife-edge margins: A pilot study

Abstract

Objective: To evaluate the influence of the type of cement on the fracture resistance of full-contour resin nanoceramic crowns cemented over preparations with knife-edge margins. Methods: A right lower premolar typodont model was prepared with a 1.5-mm axial reduction, a 2.0-mm occlusal reduction, and a knife-edge vertical margin. An anatomical crown was designed from the digital scanning of the preparation using CAD/CAM software. Then, 20 crowns were milled from resin nanoceramic CAD/CAM blocks (Cerasmart270TM) as well as a replica of the dental preparation in a cobalt-chrome alloy. The 20 crowns were randomly divided into two groups. Group 1 crowns were cemented with self-adhesive resin cement (G-CEM LinkAceTM) and group 2 crowns with resin-modified glass ionomer cement (FujiCEMTM 2). Subsequently, they were subjected to a loading test on an Instron universal testing machine until fracture occurred. The data were statistically analyzed using the parametric Student's t-test (a=0.05). Results: The type of cement was shown to have a statistically significant effect on the crowns' fracture resistance (p <0.001). Group 1 presented a mean of 1284.3±340.19 Newtons, much higher than the mean recorded in group 2, of 417.9±106.35 Newtons, with an increase of 207.3% in the fracture resistance after self-adhesive luting. Conclusions: Resin nanoceramic crowns cemented with self-adhesive resin cement showed considerably higher fracture resistance than those cemented with resin-modified glass ionomer cement.