Methods: Y-TZP ceramic specimens were divided in three groups (n=48). In group 1 zirconia ceramic discs were industrially fabricated using ceramic injection moulding (CIM, gapless, D), in group 2 specimens were milled with a Lava machine (L, 3M Espe, D) and subsequently sintered, and in group 3 specimens consisted of hipped zirconia ceramic (DC-Zirkon, Metoxit, CH), and were milled after finishing the hip-treatment. Hollow plastic screws filled with composite resin were bonded to the zirconia ceramic discs, half and half with a conventional composite resin (V, Variolink II) and with a phosphate monomer-containing resin (P, Panavia 21). TBS was measured in a universal testing machine after 24 hours, and after 150 days aging in Ringer's solution. Failure modes were examined under magnification. ANOVA was used to test the effects of the manufacturing processes, the luting materials and the aging procedure on bond strength. Multiple comparisons of least-square means were done for the pair-wise comparisons adjusted by Tukey-Kramer.
Results: With both resins tested CIM ceramic revealed significantly higher TBS compared to the other tested ceramic materials. Using the conventional composite resin, additionally L ceramic showed significantly higher TBS compared to DC ceramic. Mean bond strength values of 37.4MPa (±1.7) and 33.9MPa (±1.7) for P, and 36.1MPa (±2.2) and 27.8MPa (±2.2) for V were measured after 24h and after 150d, respectively. Influence of aging was significant for V only (p≤0.002). Fracture mode was basically mixed cohesive/adhesive.
Conclusion: Tensile bond strength between zirconia ceramic and composite luting materials is influenced by the manufacturing process of the ceramic work piece, and the luting material used.