Influence of film thickness on joint bend strength of a ceramic/resin composite joint

Objectives. The purpose of this study was to evaluate the influence of different film thicknesses of resin composite luting agents on the joint bend strength of a ceramic/resin interface. Methods. Mirage FLC (Chamelon Dental Products) and Vita Cerec (Coltène AG) duo cement were used in combination with the ceramic materials, Mirage and Vita Cerec blocks. Cement layers with thicknesses of 20 μm, 50 μm, 100 μm and 200 μm were light-cured with a high-intensity curing light. Ten specimens of each ceramic/cement combination and thickness provided a total of 80 complete test specimens. Each specimen was placed in a four-point bending jig mounted in a universal tensile testing machine and underwent loading. A paired two-tailed Studentʹs t-test was used to evaluate differences between different series of film thicknesses and resin cement combinations. Results. Within each ceramic-cement combination, the bond strength values were significantly lower for the 20 μm film than the thicker films. Significance. Taking into account the physical and clinical properties of resin-based luting agents, available knowledge indicates that a marginal gap on the order of 50–100 μm seems to optimize performance.