Shear bond strength of CAD/CAM resin-based composite specimens to human dentin in comparison to CAD/CAM lithium disilicate ceramic specimens in vitro.

OBJECTIVES: The aim of this in vitro study was to compare the shear bond strength of a CAD/CAM resin-based composite restoration material with a lithium-disilicate-ceramic restoration material on human dentin. In addition, the influence of the chosen adhesive system should be investigated. METHOD AND MATERIALS: Thirty cylindrical specimens each were fabricated from the composite resin-based material Grandio Blocs (GB) and the ceramic IPS e.max CAD (IEM). In each case, 15 specimens were bonded to human dentin samples using the adhesive system recommended and provided by the manufacturer. For 15 additional specimens, the adhesive systems were interchanged. After water storage (4 weeks) and thermocycling (5,000 cycles between 5 degrees C and 55 degrees C), the shear bond strength, the fracture modes, and the Adhesive Remnant Index (ARI) were determined. All data were statistically evaluated (Kruskal-Wallis test; P < .05). RESULTS: The shear bond strength of IEM in combination with the manufacturer's recommended adhesive system was statistically significantly higher than in those of all other groups (P < .05), resulting in 39.24 +/- 7.73 N/mm2. For IEM, adhesive fracture mode was the only mode found, while adhesive and mixed fracture modes occurred in both GB groups. Significantly more adhesive/restoration material remnants (ARI) remained on the dentin surfaces in both GB groups (P < .05). CONCLUSION: For IEM the adhesive system recommended by the manufacturer should be used. For the GB samples, the choice of adhesive system had no influence on the shear bond strength. With GB, fracture may occur partly within the material under heavy load.