This study evaluated the failure load and the shear bond strength of 4 block materials indicated for computer-aided design/computer-aided manufacturing (CAD/CAM) of dental veneers: lithium disilicate, feldspathic ceramic, polymer-infiltrated ceramic, and nanohybrid composite. The tested hypothesis was that the material that combined an elastic modulus similar to that of enamel with the highest bond strength values would present the highest failure load. From prefabricated CAD/CAM blocks, disc-shaped specimens (6.0 × 0.7 mm; n = 10) and cylinders (2.4 × 2.5 mm; n = 10) were fabricated for load-to-failure and shear bond strength tests, respectively. Materials were adhesively bonded to flattened bovine enamel surfaces, stored in distilled water at 37°C for 90 days, and subjected to thermocycling (2000 cycles of 5°C to 55°C). Discs of restorative material were bonded to enamel and subjected to an increasing load that was applied perpendicular to the bonding interface until catastrophic failure occurred. A chisel was used to apply an increasing load parallel to the adhesive interface between the enamel and a cylinder of restorative material to measure shear bond strength. Data were subjected to a Weibull analysis and 1-way analysis of variance followed by a Tukey post hoc test (α = 0.05). The type of restorative material significantly affected the (mean [SD]) failure load when bonded to enamel (P = 0.006): polymer-infiltrated ceramic (1167.9 [310.2] N) = feldspathic ceramic (1115.0 [382.0] N) = nanohybrid composite (1067.3 [251.0] N) > lithium disilicate (786.2 [304.5] N). The type of restorative material also significantly affected the (mean [SD]) bond strength to enamel (P < 0.001): lithium disilicate (32.81 [11.19] MPa) = polymer-infiltrated ceramic (27.04 [7.65] MPa) > feldspathic ceramic (21.11 [9.16] MPa) > nanohybrid composite (9.08 [3.66] MPa). The polymer-infiltrated ceramic presented the best performance when bonded to enamel.
Keywords: aging; ceramic; composite resins; dental enamel; failure load; shear bond strength.