In vitro comparison of the shear bond strength for glass ceramic laminate veneer material by the using of two different adhesive systems

The aim of this in vitro study is to evaluate the shear bond strength of the glass-ceramic laminate veneer material cemented to prepared enamel, enamel- dentin complex, and dentin surfaces with the use of two different luting systems. Sixty sound human premolar teeth were selected, and the teeth were divided randomly into 3 groups (n = 20). The teeth were prepared as three levels for bonding surfaces of enamel (E), dentine (D), and enamel–dentine complex (E–D). The glass-ceramic ( GC li si press, GC Co.) was prepared into discs of 4 mm in diameter and 1.5 ± 0.2 mm high. The discs were grounded with the adhesive paper to reaches 1.2 ± 0.1 mm. Each bonding surface was divided into two subgroups (n=10). The ceramic discs were adhesively luted by using light-curing cement (GC VENEER [V], GC Co) and dual curing cement (GC Linkforce [LF], GC Co) according to the manufacture's instructions. The samples were subjected to thermocycling with 5000 cycles (50C-150C) with 15 second dwell time, shear bond strength testing by using an Instron machine with a crosshead speed of 0.5mm/minute, and failure mode analysis using a stereomicroscope. Fir statistical analysis, the One-way ANOVA test, and Student's t-tests were used and the significance was evaluated at the p < 0.05 level. There was a statistically significant difference between the three groups, with the higher shear bond strength value in the (E) group (32,49 MPa ± 6,95), followed by the (ED) group (22,02 MPa ±3,43) and the lowest value in the (D) group (16,78 MPa ±2,46). There were no statistically significant differences between the two types of resin cement within the groups of the same adhesion surface, The mean shear bond strength values of the (GC-V) cement groups were equal to 23,14 MPa ±7,7, and for the (GC- LF) cement groups were equal to 24,39 MPa ±8,45. The shear bond strength of porcelain laminate veneers to 3 distinct tooth structures (enamel, dentine, and enamel–dentine complex) was impacted by the type of tooth structure. Keywords: Porcelain laminate veneers, ceramic discs, Dentine exposure, Adhesives, shear bond strength.