Bonding to a High-strength Ceramic Core Material: The Durability of Different Adhesion Systems

Objectives: Modern adhesive technologies have made it possible to provide retention for dental ceramic restorations in cases were retention cannot be governed by the geometry of the tooth preparation. Resins do, however, not exhibit natural affinity for bonding to densely sintered high-strength alumina ceramics without some kind of surface treatment of the ceramic. The objectives of the present study were to investigate if sufficient bond strength can be established between densely sintered high-strength alumina ceramics and a bonding agent. Methods: 120 specimens were made by bonding composite cylinders to densely sintered high-strength alumina ceramic discs (Procera® All-Ceram). The surface of the discs were sandblasted with 110µm Al2O3 and the cylinders were subsequently bonded to the discs by using one of six different bonding systems, all according to the manufacturer's adhesion protocol. Groups of 20 specimens were then divided into subgroups. Ten were stored one week in distilled water (37°C) and the other 10 were stored one week in distilled water (37°C) and during this week subjected to 5000 thermocycles (5-55°) in order to stress the bond interface. Finally the specimens were loaded until fracture. The loads were registered and any statistical differences between the different groups were tested with t-test. Results: The bond strengths were: (1) Variolink II:27/34MPa (H2O-stored/thermocycled), (2) Bisco-Choice:14/11MPa, (3) Bisco-Illusion:10/9MPa, (4) Nexus 2:10/5MPa, (5) Rely X Veneer:4/2MPa, (6) Panavia F:31/36 MPa. Groups 1 and 6 were significantly (P<0.0001) stronger than 2, 3, 4 and 5 irrespective of treatment. There was no significant difference between 1 and 6. Conclusions: Adhesive bonding techniques can be used to establish sufficient bond to densely sintered high-strength alumina ceramics. The results of this study indicate, however, that the choice of bonding technique and materials could be crucial for the treatment outcome.