Effect of intermediate fiber layer on the fracture load and failure mode of maxillary incisors restored with laminate veneers.

This study evaluated the fracture load and failure mode of various veneer materials cemented with or without the addition of a fiber-reinforced composite (FRC) layer at the adhesive interface. Sixty intact incisors were randomly divided into three groups. Group 1 was fabricated with the heat-press technique (IPS Empress 2); Group 2 with the copy milling technique (ZirkonZahn); and Group 3 with the direct or indirect composite technique (Z250)--and specimens were cemented either with or without FRC at the adhesive interface. The specimens were thermocycled and tested with a universal testing machine. No significant differences in fracture load (p>0.05) were found among the various veneer materials. The addition of FRC at the adhesive layer did not lead to significant differences in the fracture load (p>0.05) but resulted in differences in the failure mode. Laminate veneers made of composite, zirconia, and Empress 2 showed comparable mean fracture loads. However, the use of FRC at the interface changed their failure modes.