Maximising the fracture resistance of dentine-bonded all-ceramic crowns.

Results of previous studies have indicated that the use of different ceramic materials and differing bonding/luting systems may affect resistance to fracture of teeth restored with dentine-bonded crowns. It is the purpose of this investigation to examine in vitro fracture resistance of dentine-bonded ceramic crowns, using materials in combination which have demonstrated increased fracture resistance when they are used individually. Ten sound maxillary premolar teeth were selected. These teeth were prepared for full crowns in a similar manner to previous, related studies. Standardised crowns were constructed in a leucite reinforced ceramic (Empress: Ivoclar-Vivadent, Liechten-stein) and placed using a dentine-bonding system and resin-composite luting system (3M; St. Paul, MN, USA). Compressive force was applied through a 4 mm diameter steel bar applied to the occlusal surface of the restored specimens. A mean fracturing force of 1.67 kN was recorded, statistical analysis indicating that this was significantly greater than any previously used combination of ceramic material and bonding/luting system, and greater than a group of sound, unrestored teeth. The fracture resistance of teeth restored in vitro by dentine bonded crowns may be enhanced by the combination of the materials described.