Fracture strength of direct versus indirect laminates with and without fiber application at the cementation interface

Objectives This study compared the fracture strength of direct and indirect resin composite laminate veneers and evaluated the effect of a bidirectional E-glass woven fiber application at different locations at the cementation interface. Methods Standard preparations on canines (N = 50, 10 per group) were made using a depth cutting bur (0.7 mm depth) designed for laminate veneer restorations. Forty indirect laminates using a highly filled polymeric material (Estenia) and 10 direct laminates (Quadrant Anterior Shine) were prepared according to the manufacturerʹs instructions. Bidirectional E-glass woven-fiber sheet (0.06 mm) (Everstick) was applied at different locations at the cementation interface. The control group received no fibers. The specimens were stored in water at 37 °C for 1 month prior to fracture testing performed in a universal testing machine where the load was applied from the incisal direction at 137° (1 mm/min). Results No significant differences were found between the five groups (P > 0.01) (one-way ANOVA). While indirect laminate veneers showed mean fracture strength of 247 ± 47 N, direct laminate veneers revealed 239 ± 104 N. The use of E-glass fibers at the cementation interface at different locations did not increase the fracture strength significantly (286–313 N) (P > 0.01). Failure analysis showed mainly cohesive fracture of the veneer restoration (20/50) and adhesive failure between the cementation interface and the laminate with fiber exposure (19/50) covering more than half of the restorations. Significance Direct and indirect resin composite laminate veneers showed comparable mean fracture strengths. The use of E-glass woven-fiber sheet at the cementation interface did not increase the fracture strength of the polymeric laminate veneers.